NCI: trybot test for sqlite 3.17 import.

third_party/sqlite/amalgamation/sqlite3.07.c

+/************** Begin file fts3.c ********************************************/
+/*
+** 2006 Oct 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This is an SQLite module implementing full-text search.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+**     * The FTS3 module is being built as an extension
+**       (in which case SQLITE_CORE is not defined), or
+**
+**     * The FTS3 module is being built into the core of
+**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+*/
+
+/* The full-text index is stored in a series of b+tree (-like)
+** structures called segments which map terms to doclists.  The
+** structures are like b+trees in layout, but are constructed from the
+** bottom up in optimal fashion and are not updatable.  Since trees
+** are built from the bottom up, things will be described from the
+** bottom up.
+**
+**
+**** Varints ****
+** The basic unit of encoding is a variable-length integer called a
+** varint.  We encode variable-length integers in little-endian order
+** using seven bits * per byte as follows:
+**
+** KEY:
+**         A = 0xxxxxxx    7 bits of data and one flag bit
+**         B = 1xxxxxxx    7 bits of data and one flag bit
+**
+**  7 bits - A
+** 14 bits - BA
+** 21 bits - BBA
+** and so on.
+**
+** This is similar in concept to how sqlite encodes "varints" but
+** the encoding is not the same.  SQLite varints are big-endian
+** are are limited to 9 bytes in length whereas FTS3 varints are
+** little-endian and can be up to 10 bytes in length (in theory).
+**
+** Example encodings:
+**
+**     1:    0x01
+**   127:    0x7f
+**   128:    0x81 0x00
+**
+**
+**** Document lists ****
+** A doclist (document list) holds a docid-sorted list of hits for a
+** given term.  Doclists hold docids and associated token positions.
+** A docid is the unique integer identifier for a single document.
+** A position is the index of a word within the document.  The first 
+** word of the document has a position of 0.
+**
+** FTS3 used to optionally store character offsets using a compile-time
+** option.  But that functionality is no longer supported.
+**
+** A doclist is stored like this:
+**
+** array {
+**   varint docid;          (delta from previous doclist)
+**   array {                (position list for column 0)
+**     varint position;     (2 more than the delta from previous position)
+**   }
+**   array {
+**     varint POS_COLUMN;   (marks start of position list for new column)
+**     varint column;       (index of new column)
+**     array {
+**       varint position;   (2 more than the delta from previous position)
+**     }
+**   }
+**   varint POS_END;        (marks end of positions for this document.
+** }
+**
+** Here, array { X } means zero or more occurrences of X, adjacent in
+** memory.  A "position" is an index of a token in the token stream
+** generated by the tokenizer. Note that POS_END and POS_COLUMN occur 
+** in the same logical place as the position element, and act as sentinals
+** ending a position list array.  POS_END is 0.  POS_COLUMN is 1.
+** The positions numbers are not stored literally but rather as two more
+** than the difference from the prior position, or the just the position plus
+** 2 for the first position.  Example:
+**
+**   label:       A B C D E  F  G H   I  J K
+**   value:     123 5 9 1 1 14 35 0 234 72 0
+**
+** The 123 value is the first docid.  For column zero in this document
+** there are two matches at positions 3 and 10 (5-2 and 9-2+3).  The 1
+** at D signals the start of a new column; the 1 at E indicates that the
+** new column is column number 1.  There are two positions at 12 and 45
+** (14-2 and 35-2+12).  The 0 at H indicate the end-of-document.  The
+** 234 at I is the delta to next docid (357).  It has one position 70
+** (72-2) and then terminates with the 0 at K.
+**
+** A "position-list" is the list of positions for multiple columns for
+** a single docid.  A "column-list" is the set of positions for a single
+** column.  Hence, a position-list consists of one or more column-lists,
+** a document record consists of a docid followed by a position-list and
+** a doclist consists of one or more document records.
+**
+** A bare doclist omits the position information, becoming an 
+** array of varint-encoded docids.
+**
+**** Segment leaf nodes ****
+** Segment leaf nodes store terms and doclists, ordered by term.  Leaf
+** nodes are written using LeafWriter, and read using LeafReader (to
+** iterate through a single leaf node's data) and LeavesReader (to
+** iterate through a segment's entire leaf layer).  Leaf nodes have
+** the format:
+**
+** varint iHeight;             (height from leaf level, always 0)
+** varint nTerm;               (length of first term)
+** char pTerm[nTerm];          (content of first term)
+** varint nDoclist;            (length of term's associated doclist)
+** char pDoclist[nDoclist];    (content of doclist)
+** array {
+**                             (further terms are delta-encoded)
+**   varint nPrefix;           (length of prefix shared with previous term)
+**   varint nSuffix;           (length of unshared suffix)
+**   char pTermSuffix[nSuffix];(unshared suffix of next term)
+**   varint nDoclist;          (length of term's associated doclist)
+**   char pDoclist[nDoclist];  (content of doclist)
+** }
+**
+** Here, array { X } means zero or more occurrences of X, adjacent in
+** memory.
+**
+** Leaf nodes are broken into blocks which are stored contiguously in
+** the %_segments table in sorted order.  This means that when the end
+** of a node is reached, the next term is in the node with the next
+** greater node id.
+**
+** New data is spilled to a new leaf node when the current node
+** exceeds LEAF_MAX bytes (default 2048).  New data which itself is
+** larger than STANDALONE_MIN (default 1024) is placed in a standalone
+** node (a leaf node with a single term and doclist).  The goal of
+** these settings is to pack together groups of small doclists while
+** making it efficient to directly access large doclists.  The
+** assumption is that large doclists represent terms which are more
+** likely to be query targets.
+**
+** TODO(shess) It may be useful for blocking decisions to be more
+** dynamic.  For instance, it may make more sense to have a 2.5k leaf
+** node rather than splitting into 2k and .5k nodes.  My intuition is
+** that this might extend through 2x or 4x the pagesize.
+**
+**
+**** Segment interior nodes ****
+** Segment interior nodes store blockids for subtree nodes and terms
+** to describe what data is stored by the each subtree.  Interior
+** nodes are written using InteriorWriter, and read using
+** InteriorReader.  InteriorWriters are created as needed when
+** SegmentWriter creates new leaf nodes, or when an interior node
+** itself grows too big and must be split.  The format of interior
+** nodes:
+**
+** varint iHeight;           (height from leaf level, always >0)
+** varint iBlockid;          (block id of node's leftmost subtree)
+** optional {
+**   varint nTerm;           (length of first term)
+**   char pTerm[nTerm];      (content of first term)
+**   array {
+**                                (further terms are delta-encoded)
+**     varint nPrefix;            (length of shared prefix with previous term)
+**     varint nSuffix;            (length of unshared suffix)
+**     char pTermSuffix[nSuffix]; (unshared suffix of next term)
+**   }
+** }
+**
+** Here, optional { X } means an optional element, while array { X }
+** means zero or more occurrences of X, adjacent in memory.
+**
+** An interior node encodes n terms separating n+1 subtrees.  The
+** subtree blocks are contiguous, so only the first subtree's blockid
+** is encoded.  The subtree at iBlockid will contain all terms less
+** than the first term encoded (or all terms if no term is encoded).
+** Otherwise, for terms greater than or equal to pTerm[i] but less
+** than pTerm[i+1], the subtree for that term will be rooted at
+** iBlockid+i.  Interior nodes only store enough term data to
+** distinguish adjacent children (if the rightmost term of the left
+** child is "something", and the leftmost term of the right child is
+** "wicked", only "w" is stored).
+**
+** New data is spilled to a new interior node at the same height when
+** the current node exceeds INTERIOR_MAX bytes (default 2048).
+** INTERIOR_MIN_TERMS (default 7) keeps large terms from monopolizing
+** interior nodes and making the tree too skinny.  The interior nodes
+** at a given height are naturally tracked by interior nodes at
+** height+1, and so on.
+**
+**
+**** Segment directory ****
+** The segment directory in table %_segdir stores meta-information for
+** merging and deleting segments, and also the root node of the
+** segment's tree.
+**
+** The root node is the top node of the segment's tree after encoding
+** the entire segment, restricted to ROOT_MAX bytes (default 1024).
+** This could be either a leaf node or an interior node.  If the top
+** node requires more than ROOT_MAX bytes, it is flushed to %_segments
+** and a new root interior node is generated (which should always fit
+** within ROOT_MAX because it only needs space for 2 varints, the
+** height and the blockid of the previous root).
+**
+** The meta-information in the segment directory is:
+**   level               - segment level (see below)
+**   idx                 - index within level
+**                       - (level,idx uniquely identify a segment)
+**   start_block         - first leaf node
+**   leaves_end_block    - last leaf node
+**   end_block           - last block (including interior nodes)
+**   root                - contents of root node
+**
+** If the root node is a leaf node, then start_block,
+** leaves_end_block, and end_block are all 0.
+**
+**
+**** Segment merging ****
+** To amortize update costs, segments are grouped into levels and
+** merged in batches.  Each increase in level represents exponentially
+** more documents.
+**
+** New documents (actually, document updates) are tokenized and
+** written individually (using LeafWriter) to a level 0 segment, with
+** incrementing idx.  When idx reaches MERGE_COUNT (default 16), all
+** level 0 segments are merged into a single level 1 segment.  Level 1
+** is populated like level 0, and eventually MERGE_COUNT level 1
+** segments are merged to a single level 2 segment (representing
+** MERGE_COUNT^2 updates), and so on.
+**
+** A segment merge traverses all segments at a given level in
+** parallel, performing a straightforward sorted merge.  Since segment
+** leaf nodes are written in to the %_segments table in order, this
+** merge traverses the underlying sqlite disk structures efficiently.
+** After the merge, all segment blocks from the merged level are
+** deleted.
+**
+** MERGE_COUNT controls how often we merge segments.  16 seems to be
+** somewhat of a sweet spot for insertion performance.  32 and 64 show
+** very similar performance numbers to 16 on insertion, though they're
+** a tiny bit slower (perhaps due to more overhead in merge-time
+** sorting).  8 is about 20% slower than 16, 4 about 50% slower than
+** 16, 2 about 66% slower than 16.
+**
+** At query time, high MERGE_COUNT increases the number of segments
+** which need to be scanned and merged.  For instance, with 100k docs
+** inserted:
+**
+**    MERGE_COUNT   segments
+**       16           25
+**        8           12
+**        4           10
+**        2            6
+**
+** This appears to have only a moderate impact on queries for very
+** frequent terms (which are somewhat dominated by segment merge
+** costs), and infrequent and non-existent terms still seem to be fast
+** even with many segments.
+**
+** TODO(shess) That said, it would be nice to have a better query-side
+** argument for MERGE_COUNT of 16.  Also, it is possible/likely that
+** optimizations to things like doclist merging will swing the sweet
+** spot around.
+**
+**
+**
+**** Handling of deletions and updates ****
+** Since we're using a segmented structure, with no docid-oriented
+** index into the term index, we clearly cannot simply update the term
+** index when a document is deleted or updated.  For deletions, we
+** write an empty doclist (varint(docid) varint(POS_END)), for updates
+** we simply write the new doclist.  Segment merges overwrite older
+** data for a particular docid with newer data, so deletes or updates
+** will eventually overtake the earlier data and knock it out.  The
+** query logic likewise merges doclists so that newer data knocks out
+** older data.
+*/
+#define CHROMIUM_FTS3_CHANGES 1
+
+/************** Include fts3Int.h in the middle of fts3.c ********************/
+/************** Begin file fts3Int.h *****************************************/
+/*
+** 2009 Nov 12
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+*/
+#ifndef _FTSINT_H
+#define _FTSINT_H
+
+#if !defined(NDEBUG) && !defined(SQLITE_DEBUG) 
+# define NDEBUG 1
+#endif
+
+/* FTS3/FTS4 require virtual tables */
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+# undef SQLITE_ENABLE_FTS3
+# undef SQLITE_ENABLE_FTS4
+#endif
+
+/*
+** FTS4 is really an extension for FTS3.  It is enabled using the
+** SQLITE_ENABLE_FTS3 macro.  But to avoid confusion we also all
+** the SQLITE_ENABLE_FTS4 macro to serve as an alisse for SQLITE_ENABLE_FTS3.
+*/
+#if defined(SQLITE_ENABLE_FTS4) && !defined(SQLITE_ENABLE_FTS3)
+# define SQLITE_ENABLE_FTS3
+#endif
+
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* If not building as part of the core, include sqlite3ext.h. */
+#ifndef SQLITE_CORE
+/* # include "sqlite3ext.h"  */
+SQLITE_EXTENSION_INIT3
+#endif
+
+/* #include "sqlite3.h" */
+/************** Include fts3_tokenizer.h in the middle of fts3Int.h **********/
+/************** Begin file fts3_tokenizer.h **********************************/
+/*
+** 2006 July 10
+**
+** The author disclaims copyright to this source code.
+**
+*************************************************************************
+** Defines the interface to tokenizers used by fulltext-search.  There
+** are three basic components:
+**
+** sqlite3_tokenizer_module is a singleton defining the tokenizer
+** interface functions.  This is essentially the class structure for
+** tokenizers.
+**
+** sqlite3_tokenizer is used to define a particular tokenizer, perhaps
+** including customization information defined at creation time.
+**
+** sqlite3_tokenizer_cursor is generated by a tokenizer to generate
+** tokens from a particular input.
+*/
+#ifndef _FTS3_TOKENIZER_H_
+#define _FTS3_TOKENIZER_H_
+
+/* TODO(shess) Only used for SQLITE_OK and SQLITE_DONE at this time.
+** If tokenizers are to be allowed to call sqlite3_*() functions, then
+** we will need a way to register the API consistently.
+*/
+/* #include "sqlite3.h" */
+
+/*
+** Structures used by the tokenizer interface. When a new tokenizer
+** implementation is registered, the caller provides a pointer to
+** an sqlite3_tokenizer_module containing pointers to the callback
+** functions that make up an implementation.
+**
+** When an fts3 table is created, it passes any arguments passed to
+** the tokenizer clause of the CREATE VIRTUAL TABLE statement to the
+** sqlite3_tokenizer_module.xCreate() function of the requested tokenizer
+** implementation. The xCreate() function in turn returns an 
+** sqlite3_tokenizer structure representing the specific tokenizer to
+** be used for the fts3 table (customized by the tokenizer clause arguments).
+**
+** To tokenize an input buffer, the sqlite3_tokenizer_module.xOpen()
+** method is called. It returns an sqlite3_tokenizer_cursor object
+** that may be used to tokenize a specific input buffer based on
+** the tokenization rules supplied by a specific sqlite3_tokenizer
+** object.
+*/
+typedef struct sqlite3_tokenizer_module sqlite3_tokenizer_module;
+typedef struct sqlite3_tokenizer sqlite3_tokenizer;
+typedef struct sqlite3_tokenizer_cursor sqlite3_tokenizer_cursor;
+
+struct sqlite3_tokenizer_module {
+
+  /*
+  ** Structure version. Should always be set to 0 or 1.
+  */
+  int iVersion;
+
+  /*
+  ** Create a new tokenizer. The values in the argv[] array are the
+  ** arguments passed to the "tokenizer" clause of the CREATE VIRTUAL
+  ** TABLE statement that created the fts3 table. For example, if
+  ** the following SQL is executed:
+  **
+  **   CREATE .. USING fts3( ... , tokenizer <tokenizer-name> arg1 arg2)
+  **
+  ** then argc is set to 2, and the argv[] array contains pointers
+  ** to the strings "arg1" and "arg2".
+  **
+  ** This method should return either SQLITE_OK (0), or an SQLite error 
+  ** code. If SQLITE_OK is returned, then *ppTokenizer should be set
+  ** to point at the newly created tokenizer structure. The generic
+  ** sqlite3_tokenizer.pModule variable should not be initialized by
+  ** this callback. The caller will do so.
+  */
+  int (*xCreate)(
+    int argc,                           /* Size of argv array */
+    const char *const*argv,             /* Tokenizer argument strings */
+    sqlite3_tokenizer **ppTokenizer     /* OUT: Created tokenizer */
+  );
+
+  /*
+  ** Destroy an existing tokenizer. The fts3 module calls this method
+  ** exactly once for each successful call to xCreate().
+  */
+  int (*xDestroy)(sqlite3_tokenizer *pTokenizer);
+
+  /*
+  ** Create a tokenizer cursor to tokenize an input buffer. The caller
+  ** is responsible for ensuring that the input buffer remains valid
+  ** until the cursor is closed (using the xClose() method). 
+  */
+  int (*xOpen)(
+    sqlite3_tokenizer *pTokenizer,       /* Tokenizer object */
+    const char *pInput, int nBytes,      /* Input buffer */
+    sqlite3_tokenizer_cursor **ppCursor  /* OUT: Created tokenizer cursor */
+  );
+
+  /*
+  ** Destroy an existing tokenizer cursor. The fts3 module calls this 
+  ** method exactly once for each successful call to xOpen().
+  */
+  int (*xClose)(sqlite3_tokenizer_cursor *pCursor);
+
+  /*
+  ** Retrieve the next token from the tokenizer cursor pCursor. This
+  ** method should either return SQLITE_OK and set the values of the
+  ** "OUT" variables identified below, or SQLITE_DONE to indicate that
+  ** the end of the buffer has been reached, or an SQLite error code.
+  **
+  ** *ppToken should be set to point at a buffer containing the 
+  ** normalized version of the token (i.e. after any case-folding and/or
+  ** stemming has been performed). *pnBytes should be set to the length
+  ** of this buffer in bytes. The input text that generated the token is
+  ** identified by the byte offsets returned in *piStartOffset and
+  ** *piEndOffset. *piStartOffset should be set to the index of the first
+  ** byte of the token in the input buffer. *piEndOffset should be set
+  ** to the index of the first byte just past the end of the token in
+  ** the input buffer.
+  **
+  ** The buffer *ppToken is set to point at is managed by the tokenizer
+  ** implementation. It is only required to be valid until the next call
+  ** to xNext() or xClose(). 
+  */
+  /* TODO(shess) current implementation requires pInput to be
+  ** nul-terminated.  This should either be fixed, or pInput/nBytes
+  ** should be converted to zInput.
+  */
+  int (*xNext)(
+    sqlite3_tokenizer_cursor *pCursor,   /* Tokenizer cursor */
+    const char **ppToken, int *pnBytes,  /* OUT: Normalized text for token */
+    int *piStartOffset,  /* OUT: Byte offset of token in input buffer */
+    int *piEndOffset,    /* OUT: Byte offset of end of token in input buffer */
+    int *piPosition      /* OUT: Number of tokens returned before this one */
+  );
+
+  /***********************************************************************
+  ** Methods below this point are only available if iVersion>=1.
+  */
+
+  /* 
+  ** Configure the language id of a tokenizer cursor.
+  */
+  int (*xLanguageid)(sqlite3_tokenizer_cursor *pCsr, int iLangid);
+};
+
+struct sqlite3_tokenizer {
+  const sqlite3_tokenizer_module *pModule;  /* The module for this tokenizer */
+  /* Tokenizer implementations will typically add additional fields */
+};
+
+struct sqlite3_tokenizer_cursor {
+  sqlite3_tokenizer *pTokenizer;       /* Tokenizer for this cursor. */
+  /* Tokenizer implementations will typically add additional fields */
+};
+
+int fts3_global_term_cnt(int iTerm, int iCol);
+int fts3_term_cnt(int iTerm, int iCol);
+
+
+#endif /* _FTS3_TOKENIZER_H_ */
+
+/************** End of fts3_tokenizer.h **************************************/
+/************** Continuing where we left off in fts3Int.h ********************/
+/************** Include fts3_hash.h in the middle of fts3Int.h ***************/
+/************** Begin file fts3_hash.h ***************************************/
+/*
+** 2001 September 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the header file for the generic hash-table implementation
+** used in SQLite.  We've modified it slightly to serve as a standalone
+** hash table implementation for the full-text indexing module.
+**
+*/
+#ifndef _FTS3_HASH_H_
+#define _FTS3_HASH_H_
+
+/* Forward declarations of structures. */
+typedef struct Fts3Hash Fts3Hash;
+typedef struct Fts3HashElem Fts3HashElem;
+
+/* A complete hash table is an instance of the following structure.
+** The internals of this structure are intended to be opaque -- client
+** code should not attempt to access or modify the fields of this structure
+** directly.  Change this structure only by using the routines below.
+** However, many of the "procedures" and "functions" for modifying and
+** accessing this structure are really macros, so we can't really make
+** this structure opaque.
+*/
+struct Fts3Hash {
+  char keyClass;          /* HASH_INT, _POINTER, _STRING, _BINARY */
+  char copyKey;           /* True if copy of key made on insert */
+  int count;              /* Number of entries in this table */
+  Fts3HashElem *first;    /* The first element of the array */
+  int htsize;             /* Number of buckets in the hash table */
+  struct _fts3ht {        /* the hash table */
+    int count;               /* Number of entries with this hash */
+    Fts3HashElem *chain;     /* Pointer to first entry with this hash */
+  } *ht;
+};
+
+/* Each element in the hash table is an instance of the following 
+** structure.  All elements are stored on a single doubly-linked list.
+**
+** Again, this structure is intended to be opaque, but it can't really
+** be opaque because it is used by macros.
+*/
+struct Fts3HashElem {
+  Fts3HashElem *next, *prev; /* Next and previous elements in the table */
+  void *data;                /* Data associated with this element */
+  void *pKey; int nKey;      /* Key associated with this element */
+};
+
+/*
+** There are 2 different modes of operation for a hash table:
+**
+**   FTS3_HASH_STRING        pKey points to a string that is nKey bytes long
+**                           (including the null-terminator, if any).  Case
+**                           is respected in comparisons.
+**
+**   FTS3_HASH_BINARY        pKey points to binary data nKey bytes long. 
+**                           memcmp() is used to compare keys.
+**
+** A copy of the key is made if the copyKey parameter to fts3HashInit is 1.  
+*/
+#define FTS3_HASH_STRING    1
+#define FTS3_HASH_BINARY    2
+
+/*
+** Access routines.  To delete, insert a NULL pointer.
+*/
+SQLITE_PRIVATE void sqlite3Fts3HashInit(Fts3Hash *pNew, char keyClass, char copyKey);
+SQLITE_PRIVATE void *sqlite3Fts3HashInsert(Fts3Hash*, const void *pKey, int nKey, void *pData);
+SQLITE_PRIVATE void *sqlite3Fts3HashFind(const Fts3Hash*, const void *pKey, int nKey);
+SQLITE_PRIVATE void sqlite3Fts3HashClear(Fts3Hash*);
+SQLITE_PRIVATE Fts3HashElem *sqlite3Fts3HashFindElem(const Fts3Hash *, const void *, int);
+
+/*
+** Shorthand for the functions above
+*/
+#define fts3HashInit     sqlite3Fts3HashInit
+#define fts3HashInsert   sqlite3Fts3HashInsert
+#define fts3HashFind     sqlite3Fts3HashFind
+#define fts3HashClear    sqlite3Fts3HashClear
+#define fts3HashFindElem sqlite3Fts3HashFindElem
+
+/*
+** Macros for looping over all elements of a hash table.  The idiom is
+** like this:
+**
+**   Fts3Hash h;
+**   Fts3HashElem *p;
+**   ...
+**   for(p=fts3HashFirst(&h); p; p=fts3HashNext(p)){
+**     SomeStructure *pData = fts3HashData(p);
+**     // do something with pData
+**   }
+*/
+#define fts3HashFirst(H)  ((H)->first)
+#define fts3HashNext(E)   ((E)->next)
+#define fts3HashData(E)   ((E)->data)
+#define fts3HashKey(E)    ((E)->pKey)
+#define fts3HashKeysize(E) ((E)->nKey)
+
+/*
+** Number of entries in a hash table
+*/
+#define fts3HashCount(H)  ((H)->count)
+
+#endif /* _FTS3_HASH_H_ */
+
+/************** End of fts3_hash.h *******************************************/
+/************** Continuing where we left off in fts3Int.h ********************/
+
+/*
+** This constant determines the maximum depth of an FTS expression tree
+** that the library will create and use. FTS uses recursion to perform 
+** various operations on the query tree, so the disadvantage of a large
+** limit is that it may allow very large queries to use large amounts
+** of stack space (perhaps causing a stack overflow).
+*/
+#ifndef SQLITE_FTS3_MAX_EXPR_DEPTH
+# define SQLITE_FTS3_MAX_EXPR_DEPTH 12
+#endif
+
+
+/*
+** This constant controls how often segments are merged. Once there are
+** FTS3_MERGE_COUNT segments of level N, they are merged into a single
+** segment of level N+1.
+*/
+#define FTS3_MERGE_COUNT 16
+
+/*
+** This is the maximum amount of data (in bytes) to store in the 
+** Fts3Table.pendingTerms hash table. Normally, the hash table is
+** populated as documents are inserted/updated/deleted in a transaction
+** and used to create a new segment when the transaction is committed.
+** However if this limit is reached midway through a transaction, a new 
+** segment is created and the hash table cleared immediately.
+*/
+#define FTS3_MAX_PENDING_DATA (1*1024*1024)
+
+/*
+** Macro to return the number of elements in an array. SQLite has a
+** similar macro called ArraySize(). Use a different name to avoid
+** a collision when building an amalgamation with built-in FTS3.
+*/
+#define SizeofArray(X) ((int)(sizeof(X)/sizeof(X[0])))
+
+
+#ifndef MIN
+# define MIN(x,y) ((x)<(y)?(x):(y))
+#endif
+#ifndef MAX
+# define MAX(x,y) ((x)>(y)?(x):(y))
+#endif
+
+/*
+** Maximum length of a varint encoded integer. The varint format is different
+** from that used by SQLite, so the maximum length is 10, not 9.
+*/
+#define FTS3_VARINT_MAX 10
+
+/*
+** FTS4 virtual tables may maintain multiple indexes - one index of all terms
+** in the document set and zero or more prefix indexes. All indexes are stored
+** as one or more b+-trees in the %_segments and %_segdir tables. 
+**
+** It is possible to determine which index a b+-tree belongs to based on the
+** value stored in the "%_segdir.level" column. Given this value L, the index
+** that the b+-tree belongs to is (L<<10). In other words, all b+-trees with
+** level values between 0 and 1023 (inclusive) belong to index 0, all levels
+** between 1024 and 2047 to index 1, and so on.
+**
+** It is considered impossible for an index to use more than 1024 levels. In 
+** theory though this may happen, but only after at least 
+** (FTS3_MERGE_COUNT^1024) separate flushes of the pending-terms tables.
+*/
+#define FTS3_SEGDIR_MAXLEVEL      1024
+#define FTS3_SEGDIR_MAXLEVEL_STR "1024"
+
+/*
+** The testcase() macro is only used by the amalgamation.  If undefined,
+** make it a no-op.
+*/
+#ifndef testcase
+# define testcase(X)
+#endif
+
+/*
+** Terminator values for position-lists and column-lists.
+*/
+#define POS_COLUMN  (1)     /* Column-list terminator */
+#define POS_END     (0)     /* Position-list terminator */ 
+
+/*
+** This section provides definitions to allow the
+** FTS3 extension to be compiled outside of the 
+** amalgamation.
+*/
+#ifndef SQLITE_AMALGAMATION
+/*
+** Macros indicating that conditional expressions are always true or
+** false.
+*/
+#ifdef SQLITE_COVERAGE_TEST
+# define ALWAYS(x) (1)
+# define NEVER(X)  (0)
+#elif defined(SQLITE_DEBUG)
+# define ALWAYS(x) sqlite3Fts3Always((x)!=0)
+# define NEVER(x) sqlite3Fts3Never((x)!=0)
+SQLITE_PRIVATE int sqlite3Fts3Always(int b);
+SQLITE_PRIVATE int sqlite3Fts3Never(int b);
+#else
+# define ALWAYS(x) (x)
+# define NEVER(x)  (x)
+#endif
+
+/*
+** Internal types used by SQLite.
+*/
+typedef unsigned char u8;         /* 1-byte (or larger) unsigned integer */
+typedef short int i16;            /* 2-byte (or larger) signed integer */
+typedef unsigned int u32;         /* 4-byte unsigned integer */
+typedef sqlite3_uint64 u64;       /* 8-byte unsigned integer */
+typedef sqlite3_int64 i64;        /* 8-byte signed integer */
+
+/*
+** Macro used to suppress compiler warnings for unused parameters.
+*/
+#define UNUSED_PARAMETER(x) (void)(x)
+
+/*
+** Activate assert() only if SQLITE_TEST is enabled.
+*/
+#if !defined(NDEBUG) && !defined(SQLITE_DEBUG) 
+# define NDEBUG 1
+#endif
+
+/*
+** The TESTONLY macro is used to enclose variable declarations or
+** other bits of code that are needed to support the arguments
+** within testcase() and assert() macros.
+*/
+#if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
+# define TESTONLY(X)  X
+#else
+# define TESTONLY(X)
+#endif
+
+#endif /* SQLITE_AMALGAMATION */
+
+#ifdef SQLITE_DEBUG
+SQLITE_PRIVATE int sqlite3Fts3Corrupt(void);
+# define FTS_CORRUPT_VTAB sqlite3Fts3Corrupt()
+#else
+# define FTS_CORRUPT_VTAB SQLITE_CORRUPT_VTAB
+#endif
+
+typedef struct Fts3Table Fts3Table;
+typedef struct Fts3Cursor Fts3Cursor;
+typedef struct Fts3Expr Fts3Expr;
+typedef struct Fts3Phrase Fts3Phrase;
+typedef struct Fts3PhraseToken Fts3PhraseToken;
+
+typedef struct Fts3Doclist Fts3Doclist;
+typedef struct Fts3SegFilter Fts3SegFilter;
+typedef struct Fts3DeferredToken Fts3DeferredToken;
+typedef struct Fts3SegReader Fts3SegReader;
+typedef struct Fts3MultiSegReader Fts3MultiSegReader;
+
+typedef struct MatchinfoBuffer MatchinfoBuffer;
+
+/*
+** A connection to a fulltext index is an instance of the following
+** structure. The xCreate and xConnect methods create an instance
+** of this structure and xDestroy and xDisconnect free that instance.
+** All other methods receive a pointer to the structure as one of their
+** arguments.
+*/
+struct Fts3Table {
+  sqlite3_vtab base;              /* Base class used by SQLite core */
+  sqlite3 *db;                    /* The database connection */
+  const char *zDb;                /* logical database name */
+  const char *zName;              /* virtual table name */
+  int nColumn;                    /* number of named columns in virtual table */
+  char **azColumn;                /* column names.  malloced */
+  u8 *abNotindexed;               /* True for 'notindexed' columns */
+  sqlite3_tokenizer *pTokenizer;  /* tokenizer for inserts and queries */
+  char *zContentTbl;              /* content=xxx option, or NULL */
+  char *zLanguageid;              /* languageid=xxx option, or NULL */
+  int nAutoincrmerge;             /* Value configured by 'automerge' */
+  u32 nLeafAdd;                   /* Number of leaf blocks added this trans */
+
+  /* Precompiled statements used by the implementation. Each of these 
+  ** statements is run and reset within a single virtual table API call. 
+  */
+  sqlite3_stmt *aStmt[40];
+  sqlite3_stmt *pSeekStmt;        /* Cache for fts3CursorSeekStmt() */
+
+  char *zReadExprlist;
+  char *zWriteExprlist;
+
+  int nNodeSize;                  /* Soft limit for node size */
+  u8 bFts4;                       /* True for FTS4, false for FTS3 */
+  u8 bHasStat;                    /* True if %_stat table exists (2==unknown) */
+  u8 bHasDocsize;                 /* True if %_docsize table exists */
+  u8 bDescIdx;                    /* True if doclists are in reverse order */
+  u8 bIgnoreSavepoint;            /* True to ignore xSavepoint invocations */
+  int nPgsz;                      /* Page size for host database */
+  char *zSegmentsTbl;             /* Name of %_segments table */
+  sqlite3_blob *pSegments;        /* Blob handle open on %_segments table */
+
+  /* 
+  ** The following array of hash tables is used to buffer pending index 
+  ** updates during transactions. All pending updates buffered at any one
+  ** time must share a common language-id (see the FTS4 langid= feature).
+  ** The current language id is stored in variable iPrevLangid.
+  **
+  ** A single FTS4 table may have multiple full-text indexes. For each index
+  ** there is an entry in the aIndex[] array. Index 0 is an index of all the
+  ** terms that appear in the document set. Each subsequent index in aIndex[]
+  ** is an index of prefixes of a specific length.
+  **
+  ** Variable nPendingData contains an estimate the memory consumed by the 
+  ** pending data structures, including hash table overhead, but not including
+  ** malloc overhead.  When nPendingData exceeds nMaxPendingData, all hash
+  ** tables are flushed to disk. Variable iPrevDocid is the docid of the most 
+  ** recently inserted record.
+  */
+  int nIndex;                     /* Size of aIndex[] */
+  struct Fts3Index {
+    int nPrefix;                  /* Prefix length (0 for main terms index) */
+    Fts3Hash hPending;            /* Pending terms table for this index */
+  } *aIndex;
+  int nMaxPendingData;            /* Max pending data before flush to disk */
+  int nPendingData;               /* Current bytes of pending data */
+  sqlite_int64 iPrevDocid;        /* Docid of most recently inserted document */
+  int iPrevLangid;                /* Langid of recently inserted document */
+  int bPrevDelete;                /* True if last operation was a delete */
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
+  /* State variables used for validating that the transaction control
+  ** methods of the virtual table are called at appropriate times.  These
+  ** values do not contribute to FTS functionality; they are used for
+  ** verifying the operation of the SQLite core.
+  */
+  int inTransaction;     /* True after xBegin but before xCommit/xRollback */
+  int mxSavepoint;       /* Largest valid xSavepoint integer */
+#endif
+
+#ifdef SQLITE_TEST
+  /* True to disable the incremental doclist optimization. This is controled
+  ** by special insert command 'test-no-incr-doclist'.  */
+  int bNoIncrDoclist;
+#endif
+};
+
+/*
+** When the core wants to read from the virtual table, it creates a
+** virtual table cursor (an instance of the following structure) using
+** the xOpen method. Cursors are destroyed using the xClose method.
+*/
+struct Fts3Cursor {
+  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
+  i16 eSearch;                    /* Search strategy (see below) */
+  u8 isEof;                       /* True if at End Of Results */
+  u8 isRequireSeek;               /* True if must seek pStmt to %_content row */
+  u8 bSeekStmt;                   /* True if pStmt is a seek */
+  sqlite3_stmt *pStmt;            /* Prepared statement in use by the cursor */
+  Fts3Expr *pExpr;                /* Parsed MATCH query string */
+  int iLangid;                    /* Language being queried for */
+  int nPhrase;                    /* Number of matchable phrases in query */
+  Fts3DeferredToken *pDeferred;   /* Deferred search tokens, if any */
+  sqlite3_int64 iPrevId;          /* Previous id read from aDoclist */
+  char *pNextId;                  /* Pointer into the body of aDoclist */
+  char *aDoclist;                 /* List of docids for full-text queries */
+  int nDoclist;                   /* Size of buffer at aDoclist */
+  u8 bDesc;                       /* True to sort in descending order */
+  int eEvalmode;                  /* An FTS3_EVAL_XX constant */
+  int nRowAvg;                    /* Average size of database rows, in pages */
+  sqlite3_int64 nDoc;             /* Documents in table */
+  i64 iMinDocid;                  /* Minimum docid to return */
+  i64 iMaxDocid;                  /* Maximum docid to return */
+  int isMatchinfoNeeded;          /* True when aMatchinfo[] needs filling in */
+  MatchinfoBuffer *pMIBuffer;     /* Buffer for matchinfo data */
+};
+
+#define FTS3_EVAL_FILTER    0
+#define FTS3_EVAL_NEXT      1
+#define FTS3_EVAL_MATCHINFO 2
+
+/*
+** The Fts3Cursor.eSearch member is always set to one of the following.
+** Actualy, Fts3Cursor.eSearch can be greater than or equal to
+** FTS3_FULLTEXT_SEARCH.  If so, then Fts3Cursor.eSearch - 2 is the index
+** of the column to be searched.  For example, in
+**
+**     CREATE VIRTUAL TABLE ex1 USING fts3(a,b,c,d);
+**     SELECT docid FROM ex1 WHERE b MATCH 'one two three';
+** 
+** Because the LHS of the MATCH operator is 2nd column "b",
+** Fts3Cursor.eSearch will be set to FTS3_FULLTEXT_SEARCH+1.  (+0 for a,
+** +1 for b, +2 for c, +3 for d.)  If the LHS of MATCH were "ex1" 
+** indicating that all columns should be searched,
+** then eSearch would be set to FTS3_FULLTEXT_SEARCH+4.
+*/
+#define FTS3_FULLSCAN_SEARCH 0    /* Linear scan of %_content table */
+#define FTS3_DOCID_SEARCH    1    /* Lookup by rowid on %_content table */
+#define FTS3_FULLTEXT_SEARCH 2    /* Full-text index search */
+
+/*
+** The lower 16-bits of the sqlite3_index_info.idxNum value set by
+** the xBestIndex() method contains the Fts3Cursor.eSearch value described
+** above. The upper 16-bits contain a combination of the following
+** bits, used to describe extra constraints on full-text searches.
+*/
+#define FTS3_HAVE_LANGID    0x00010000      /* languageid=? */
+#define FTS3_HAVE_DOCID_GE  0x00020000      /* docid>=? */
+#define FTS3_HAVE_DOCID_LE  0x00040000      /* docid<=? */
+
+struct Fts3Doclist {
+  char *aAll;                    /* Array containing doclist (or NULL) */
+  int nAll;                      /* Size of a[] in bytes */
+  char *pNextDocid;              /* Pointer to next docid */
+
+  sqlite3_int64 iDocid;          /* Current docid (if pList!=0) */
+  int bFreeList;                 /* True if pList should be sqlite3_free()d */
+  char *pList;                   /* Pointer to position list following iDocid */
+  int nList;                     /* Length of position list */
+};
+
+/*
+** A "phrase" is a sequence of one or more tokens that must match in
+** sequence.  A single token is the base case and the most common case.
+** For a sequence of tokens contained in double-quotes (i.e. "one two three")
+** nToken will be the number of tokens in the string.
+*/
+struct Fts3PhraseToken {
+  char *z;                        /* Text of the token */
+  int n;                          /* Number of bytes in buffer z */
+  int isPrefix;                   /* True if token ends with a "*" character */
+  int bFirst;                     /* True if token must appear at position 0 */
+
+  /* Variables above this point are populated when the expression is
+  ** parsed (by code in fts3_expr.c). Below this point the variables are
+  ** used when evaluating the expression. */
+  Fts3DeferredToken *pDeferred;   /* Deferred token object for this token */
+  Fts3MultiSegReader *pSegcsr;    /* Segment-reader for this token */
+};
+
+struct Fts3Phrase {
+  /* Cache of doclist for this phrase. */
+  Fts3Doclist doclist;
+  int bIncr;                 /* True if doclist is loaded incrementally */
+  int iDoclistToken;
+
+  /* Used by sqlite3Fts3EvalPhrasePoslist() if this is a descendent of an
+  ** OR condition.  */
+  char *pOrPoslist;
+  i64 iOrDocid;
+
+  /* Variables below this point are populated by fts3_expr.c when parsing 
+  ** a MATCH expression. Everything above is part of the evaluation phase. 
+  */
+  int nToken;                /* Number of tokens in the phrase */
+  int iColumn;               /* Index of column this phrase must match */
+  Fts3PhraseToken aToken[1]; /* One entry for each token in the phrase */
+};
+
+/*
+** A tree of these objects forms the RHS of a MATCH operator.
+**
+** If Fts3Expr.eType is FTSQUERY_PHRASE and isLoaded is true, then aDoclist 
+** points to a malloced buffer, size nDoclist bytes, containing the results 
+** of this phrase query in FTS3 doclist format. As usual, the initial 
+** "Length" field found in doclists stored on disk is omitted from this 
+** buffer.
+**
+** Variable aMI is used only for FTSQUERY_NEAR nodes to store the global
+** matchinfo data. If it is not NULL, it points to an array of size nCol*3,
+** where nCol is the number of columns in the queried FTS table. The array
+** is populated as follows:
+**
+**   aMI[iCol*3 + 0] = Undefined
+**   aMI[iCol*3 + 1] = Number of occurrences
+**   aMI[iCol*3 + 2] = Number of rows containing at least one instance
+**
+** The aMI array is allocated using sqlite3_malloc(). It should be freed 
+** when the expression node is.
+*/
+struct Fts3Expr {
+  int eType;                 /* One of the FTSQUERY_XXX values defined below */
+  int nNear;                 /* Valid if eType==FTSQUERY_NEAR */
+  Fts3Expr *pParent;         /* pParent->pLeft==this or pParent->pRight==this */
+  Fts3Expr *pLeft;           /* Left operand */
+  Fts3Expr *pRight;          /* Right operand */
+  Fts3Phrase *pPhrase;       /* Valid if eType==FTSQUERY_PHRASE */
+
+  /* The following are used by the fts3_eval.c module. */
+  sqlite3_int64 iDocid;      /* Current docid */
+  u8 bEof;                   /* True this expression is at EOF already */
+  u8 bStart;                 /* True if iDocid is valid */
+  u8 bDeferred;              /* True if this expression is entirely deferred */
+
+  /* The following are used by the fts3_snippet.c module. */
+  int iPhrase;               /* Index of this phrase in matchinfo() results */
+  u32 *aMI;                  /* See above */
+};
+
+/*
+** Candidate values for Fts3Query.eType. Note that the order of the first
+** four values is in order of precedence when parsing expressions. For 
+** example, the following:
+**
+**   "a OR b AND c NOT d NEAR e"
+**
+** is equivalent to:
+**
+**   "a OR (b AND (c NOT (d NEAR e)))"
+*/
+#define FTSQUERY_NEAR   1
+#define FTSQUERY_NOT    2
+#define FTSQUERY_AND    3
+#define FTSQUERY_OR     4
+#define FTSQUERY_PHRASE 5
+
+
+/* fts3_write.c */
+SQLITE_PRIVATE int sqlite3Fts3UpdateMethod(sqlite3_vtab*,int,sqlite3_value**,sqlite3_int64*);
+SQLITE_PRIVATE int sqlite3Fts3PendingTermsFlush(Fts3Table *);
+SQLITE_PRIVATE void sqlite3Fts3PendingTermsClear(Fts3Table *);
+SQLITE_PRIVATE int sqlite3Fts3Optimize(Fts3Table *);
+SQLITE_PRIVATE int sqlite3Fts3SegReaderNew(int, int, sqlite3_int64,
+  sqlite3_int64, sqlite3_int64, const char *, int, Fts3SegReader**);
+SQLITE_PRIVATE int sqlite3Fts3SegReaderPending(
+  Fts3Table*,int,const char*,int,int,Fts3SegReader**);
+SQLITE_PRIVATE void sqlite3Fts3SegReaderFree(Fts3SegReader *);
+SQLITE_PRIVATE int sqlite3Fts3AllSegdirs(Fts3Table*, int, int, int, sqlite3_stmt **);
+SQLITE_PRIVATE int sqlite3Fts3ReadBlock(Fts3Table*, sqlite3_int64, char **, int*, int*);
+
+SQLITE_PRIVATE int sqlite3Fts3SelectDoctotal(Fts3Table *, sqlite3_stmt **);
+SQLITE_PRIVATE int sqlite3Fts3SelectDocsize(Fts3Table *, sqlite3_int64, sqlite3_stmt **);
+
+#ifndef SQLITE_DISABLE_FTS4_DEFERRED
+SQLITE_PRIVATE void sqlite3Fts3FreeDeferredTokens(Fts3Cursor *);
+SQLITE_PRIVATE int sqlite3Fts3DeferToken(Fts3Cursor *, Fts3PhraseToken *, int);
+SQLITE_PRIVATE int sqlite3Fts3CacheDeferredDoclists(Fts3Cursor *);
+SQLITE_PRIVATE void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *);
+SQLITE_PRIVATE int sqlite3Fts3DeferredTokenList(Fts3DeferredToken *, char **, int *);
+#else
+# define sqlite3Fts3FreeDeferredTokens(x)
+# define sqlite3Fts3DeferToken(x,y,z) SQLITE_OK
+# define sqlite3Fts3CacheDeferredDoclists(x) SQLITE_OK
+# define sqlite3Fts3FreeDeferredDoclists(x)
+# define sqlite3Fts3DeferredTokenList(x,y,z) SQLITE_OK
+#endif
+
+SQLITE_PRIVATE void sqlite3Fts3SegmentsClose(Fts3Table *);
+SQLITE_PRIVATE int sqlite3Fts3MaxLevel(Fts3Table *, int *);
+
+/* Special values interpreted by sqlite3SegReaderCursor() */
+#define FTS3_SEGCURSOR_PENDING        -1
+#define FTS3_SEGCURSOR_ALL            -2
+
+SQLITE_PRIVATE int sqlite3Fts3SegReaderStart(Fts3Table*, Fts3MultiSegReader*, Fts3SegFilter*);
+SQLITE_PRIVATE int sqlite3Fts3SegReaderStep(Fts3Table *, Fts3MultiSegReader *);
+SQLITE_PRIVATE void sqlite3Fts3SegReaderFinish(Fts3MultiSegReader *);
+
+SQLITE_PRIVATE int sqlite3Fts3SegReaderCursor(Fts3Table *, 
+    int, int, int, const char *, int, int, int, Fts3MultiSegReader *);
+
+/* Flags allowed as part of the 4th argument to SegmentReaderIterate() */
+#define FTS3_SEGMENT_REQUIRE_POS   0x00000001
+#define FTS3_SEGMENT_IGNORE_EMPTY  0x00000002
+#define FTS3_SEGMENT_COLUMN_FILTER 0x00000004
+#define FTS3_SEGMENT_PREFIX        0x00000008
+#define FTS3_SEGMENT_SCAN          0x00000010
+#define FTS3_SEGMENT_FIRST         0x00000020
+
+/* Type passed as 4th argument to SegmentReaderIterate() */
+struct Fts3SegFilter {
+  const char *zTerm;
+  int nTerm;
+  int iCol;
+  int flags;
+};
+
+struct Fts3MultiSegReader {
+  /* Used internally by sqlite3Fts3SegReaderXXX() calls */
+  Fts3SegReader **apSegment;      /* Array of Fts3SegReader objects */
+  int nSegment;                   /* Size of apSegment array */
+  int nAdvance;                   /* How many seg-readers to advance */
+  Fts3SegFilter *pFilter;         /* Pointer to filter object */
+  char *aBuffer;                  /* Buffer to merge doclists in */
+  int nBuffer;                    /* Allocated size of aBuffer[] in bytes */
+
+  int iColFilter;                 /* If >=0, filter for this column */
+  int bRestart;
+
+  /* Used by fts3.c only. */
+  int nCost;                      /* Cost of running iterator */
+  int bLookup;                    /* True if a lookup of a single entry. */
+
+  /* Output values. Valid only after Fts3SegReaderStep() returns SQLITE_ROW. */
+  char *zTerm;                    /* Pointer to term buffer */
+  int nTerm;                      /* Size of zTerm in bytes */
+  char *aDoclist;                 /* Pointer to doclist buffer */
+  int nDoclist;                   /* Size of aDoclist[] in bytes */
+};
+
+SQLITE_PRIVATE int sqlite3Fts3Incrmerge(Fts3Table*,int,int);
+
+#define fts3GetVarint32(p, piVal) (                                           \
+  (*(u8*)(p)&0x80) ? sqlite3Fts3GetVarint32(p, piVal) : (*piVal=*(u8*)(p), 1) \
+)
+
+/* fts3.c */
+SQLITE_PRIVATE void sqlite3Fts3ErrMsg(char**,const char*,...);
+SQLITE_PRIVATE int sqlite3Fts3PutVarint(char *, sqlite3_int64);
+SQLITE_PRIVATE int sqlite3Fts3GetVarint(const char *, sqlite_int64 *);
+SQLITE_PRIVATE int sqlite3Fts3GetVarint32(const char *, int *);
+SQLITE_PRIVATE int sqlite3Fts3VarintLen(sqlite3_uint64);
+SQLITE_PRIVATE void sqlite3Fts3Dequote(char *);
+SQLITE_PRIVATE void sqlite3Fts3DoclistPrev(int,char*,int,char**,sqlite3_int64*,int*,u8*);
+SQLITE_PRIVATE int sqlite3Fts3EvalPhraseStats(Fts3Cursor *, Fts3Expr *, u32 *);
+SQLITE_PRIVATE int sqlite3Fts3FirstFilter(sqlite3_int64, char *, int, char *);
+SQLITE_PRIVATE void sqlite3Fts3CreateStatTable(int*, Fts3Table*);
+SQLITE_PRIVATE int sqlite3Fts3EvalTestDeferred(Fts3Cursor *pCsr, int *pRc);
+
+/* fts3_tokenizer.c */
+SQLITE_PRIVATE const char *sqlite3Fts3NextToken(const char *, int *);
+SQLITE_PRIVATE int sqlite3Fts3InitHashTable(sqlite3 *, Fts3Hash *, const char *);
+SQLITE_PRIVATE int sqlite3Fts3InitTokenizer(Fts3Hash *pHash, const char *, 
+    sqlite3_tokenizer **, char **
+);
+SQLITE_PRIVATE int sqlite3Fts3IsIdChar(char);
+
+/* fts3_snippet.c */
+SQLITE_PRIVATE void sqlite3Fts3Offsets(sqlite3_context*, Fts3Cursor*);
+SQLITE_PRIVATE void sqlite3Fts3Snippet(sqlite3_context *, Fts3Cursor *, const char *,
+  const char *, const char *, int, int
+);
+SQLITE_PRIVATE void sqlite3Fts3Matchinfo(sqlite3_context *, Fts3Cursor *, const char *);
+SQLITE_PRIVATE void sqlite3Fts3MIBufferFree(MatchinfoBuffer *p);
+
+/* fts3_expr.c */
+SQLITE_PRIVATE int sqlite3Fts3ExprParse(sqlite3_tokenizer *, int,
+  char **, int, int, int, const char *, int, Fts3Expr **, char **
+);
+SQLITE_PRIVATE void sqlite3Fts3ExprFree(Fts3Expr *);
+#ifdef SQLITE_TEST
+SQLITE_PRIVATE int sqlite3Fts3ExprInitTestInterface(sqlite3 *db);
+SQLITE_PRIVATE int sqlite3Fts3InitTerm(sqlite3 *db);
+#endif
+
+SQLITE_PRIVATE int sqlite3Fts3OpenTokenizer(sqlite3_tokenizer *, int, const char *, int,
+  sqlite3_tokenizer_cursor **
+);
+
+/* fts3_aux.c */
+SQLITE_PRIVATE int sqlite3Fts3InitAux(sqlite3 *db);
+
+SQLITE_PRIVATE void sqlite3Fts3EvalPhraseCleanup(Fts3Phrase *);
+
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrStart(
+    Fts3Table*, Fts3MultiSegReader*, int, const char*, int);
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrNext(
+    Fts3Table *, Fts3MultiSegReader *, sqlite3_int64 *, char **, int *);
+SQLITE_PRIVATE int sqlite3Fts3EvalPhrasePoslist(Fts3Cursor *, Fts3Expr *, int iCol, char **); 
+SQLITE_PRIVATE int sqlite3Fts3MsrOvfl(Fts3Cursor *, Fts3MultiSegReader *, int *);
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrRestart(Fts3MultiSegReader *pCsr);
+
+/* fts3_tokenize_vtab.c */
+SQLITE_PRIVATE int sqlite3Fts3InitTok(sqlite3*, Fts3Hash *);
+
+/* fts3_unicode2.c (functions generated by parsing unicode text files) */
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+SQLITE_PRIVATE int sqlite3FtsUnicodeFold(int, int);
+SQLITE_PRIVATE int sqlite3FtsUnicodeIsalnum(int);
+SQLITE_PRIVATE int sqlite3FtsUnicodeIsdiacritic(int);
+#endif
+
+#endif /* !SQLITE_CORE || SQLITE_ENABLE_FTS3 */
+#endif /* _FTSINT_H */
+
+/************** End of fts3Int.h *********************************************/
+/************** Continuing where we left off in fts3.c ***********************/
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+#if defined(SQLITE_ENABLE_FTS3) && !defined(SQLITE_CORE)
+# define SQLITE_CORE 1
+#endif
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <stddef.h> */
+/* #include <stdio.h> */
+/* #include <string.h> */
+/* #include <stdarg.h> */
+
+/* #include "fts3.h" */
+#ifndef SQLITE_CORE 
+/* # include "sqlite3ext.h" */
+  SQLITE_EXTENSION_INIT1
+#endif
+
+static int fts3EvalNext(Fts3Cursor *pCsr);
+static int fts3EvalStart(Fts3Cursor *pCsr);
+static int fts3TermSegReaderCursor(
+    Fts3Cursor *, const char *, int, int, Fts3MultiSegReader **);
+
+#ifndef SQLITE_AMALGAMATION
+# if defined(SQLITE_DEBUG)
+SQLITE_PRIVATE int sqlite3Fts3Always(int b) { assert( b ); return b; }
+SQLITE_PRIVATE int sqlite3Fts3Never(int b)  { assert( !b ); return b; }
+# endif
+#endif
+
+/* 
+** Write a 64-bit variable-length integer to memory starting at p[0].
+** The length of data written will be between 1 and FTS3_VARINT_MAX bytes.
+** The number of bytes written is returned.
+*/
+SQLITE_PRIVATE int sqlite3Fts3PutVarint(char *p, sqlite_int64 v){
+  unsigned char *q = (unsigned char *) p;
+  sqlite_uint64 vu = v;
+  do{
+    *q++ = (unsigned char) ((vu & 0x7f) | 0x80);
+    vu >>= 7;
+  }while( vu!=0 );
+  q[-1] &= 0x7f;  /* turn off high bit in final byte */
+  assert( q - (unsigned char *)p <= FTS3_VARINT_MAX );
+  return (int) (q - (unsigned char *)p);
+}
+
+#define GETVARINT_STEP(v, ptr, shift, mask1, mask2, var, ret) \
+  v = (v & mask1) | ( (*ptr++) << shift );                    \
+  if( (v & mask2)==0 ){ var = v; return ret; }
+#define GETVARINT_INIT(v, ptr, shift, mask1, mask2, var, ret) \
+  v = (*ptr++);                                               \
+  if( (v & mask2)==0 ){ var = v; return ret; }
+
+/* 
+** Read a 64-bit variable-length integer from memory starting at p[0].
+** Return the number of bytes read, or 0 on error.
+** The value is stored in *v.
+*/
+SQLITE_PRIVATE int sqlite3Fts3GetVarint(const char *p, sqlite_int64 *v){
+  const char *pStart = p;
+  u32 a;
+  u64 b;
+  int shift;
+
+  GETVARINT_INIT(a, p, 0,  0x00,     0x80, *v, 1);
+  GETVARINT_STEP(a, p, 7,  0x7F,     0x4000, *v, 2);
+  GETVARINT_STEP(a, p, 14, 0x3FFF,   0x200000, *v, 3);
+  GETVARINT_STEP(a, p, 21, 0x1FFFFF, 0x10000000, *v, 4);
+  b = (a & 0x0FFFFFFF );
+
+  for(shift=28; shift<=63; shift+=7){
+    u64 c = *p++;
+    b += (c&0x7F) << shift;
+    if( (c & 0x80)==0 ) break;
+  }
+  *v = b;
+  return (int)(p - pStart);
+}
+
+/*
+** Similar to sqlite3Fts3GetVarint(), except that the output is truncated to a
+** 32-bit integer before it is returned.
+*/
+SQLITE_PRIVATE int sqlite3Fts3GetVarint32(const char *p, int *pi){
+  u32 a;
+
+#ifndef fts3GetVarint32
+  GETVARINT_INIT(a, p, 0,  0x00,     0x80, *pi, 1);
+#else
+  a = (*p++);
+  assert( a & 0x80 );
+#endif
+
+  GETVARINT_STEP(a, p, 7,  0x7F,     0x4000, *pi, 2);
+  GETVARINT_STEP(a, p, 14, 0x3FFF,   0x200000, *pi, 3);
+  GETVARINT_STEP(a, p, 21, 0x1FFFFF, 0x10000000, *pi, 4);
+  a = (a & 0x0FFFFFFF );
+  *pi = (int)(a | ((u32)(*p & 0x0F) << 28));
+  return 5;
+}
+
+/*
+** Return the number of bytes required to encode v as a varint
+*/
+SQLITE_PRIVATE int sqlite3Fts3VarintLen(sqlite3_uint64 v){
+  int i = 0;
+  do{
+    i++;
+    v >>= 7;
+  }while( v!=0 );
+  return i;
+}
+
+/*
+** Convert an SQL-style quoted string into a normal string by removing
+** the quote characters.  The conversion is done in-place.  If the
+** input does not begin with a quote character, then this routine
+** is a no-op.
+**
+** Examples:
+**
+**     "abc"   becomes   abc
+**     'xyz'   becomes   xyz
+**     [pqr]   becomes   pqr
+**     `mno`   becomes   mno
+**
+*/
+SQLITE_PRIVATE void sqlite3Fts3Dequote(char *z){
+  char quote;                     /* Quote character (if any ) */
+
+  quote = z[0];
+  if( quote=='[' || quote=='\'' || quote=='"' || quote=='`' ){
+    int iIn = 1;                  /* Index of next byte to read from input */
+    int iOut = 0;                 /* Index of next byte to write to output */
+
+    /* If the first byte was a '[', then the close-quote character is a ']' */
+    if( quote=='[' ) quote = ']';  
+
+    while( z[iIn] ){
+      if( z[iIn]==quote ){
+        if( z[iIn+1]!=quote ) break;
+        z[iOut++] = quote;
+        iIn += 2;
+      }else{
+        z[iOut++] = z[iIn++];
+      }
+    }
+    z[iOut] = '\0';
+  }
+}
+
+/*
+** Read a single varint from the doclist at *pp and advance *pp to point
+** to the first byte past the end of the varint.  Add the value of the varint
+** to *pVal.
+*/
+static void fts3GetDeltaVarint(char **pp, sqlite3_int64 *pVal){
+  sqlite3_int64 iVal;
+  *pp += sqlite3Fts3GetVarint(*pp, &iVal);
+  *pVal += iVal;
+}
+
+/*
+** When this function is called, *pp points to the first byte following a
+** varint that is part of a doclist (or position-list, or any other list
+** of varints). This function moves *pp to point to the start of that varint,
+** and sets *pVal by the varint value.
+**
+** Argument pStart points to the first byte of the doclist that the
+** varint is part of.
+*/
+static void fts3GetReverseVarint(
+  char **pp, 
+  char *pStart, 
+  sqlite3_int64 *pVal
+){
+  sqlite3_int64 iVal;
+  char *p;
+
+  /* Pointer p now points at the first byte past the varint we are 
+  ** interested in. So, unless the doclist is corrupt, the 0x80 bit is
+  ** clear on character p[-1]. */
+  for(p = (*pp)-2; p>=pStart && *p&0x80; p--);
+  p++;
+  *pp = p;
+
+  sqlite3Fts3GetVarint(p, &iVal);
+  *pVal = iVal;
+}
+
+/*
+** The xDisconnect() virtual table method.
+*/
+static int fts3DisconnectMethod(sqlite3_vtab *pVtab){
+  Fts3Table *p = (Fts3Table *)pVtab;
+  int i;
+
+  assert( p->nPendingData==0 );
+  assert( p->pSegments==0 );
+
+  /* Free any prepared statements held */
+  sqlite3_finalize(p->pSeekStmt);
+  for(i=0; i<SizeofArray(p->aStmt); i++){
+    sqlite3_finalize(p->aStmt[i]);
+  }
+  sqlite3_free(p->zSegmentsTbl);
+  sqlite3_free(p->zReadExprlist);
+  sqlite3_free(p->zWriteExprlist);
+  sqlite3_free(p->zContentTbl);
+  sqlite3_free(p->zLanguageid);
+
+  /* Invoke the tokenizer destructor to free the tokenizer. */
+  p->pTokenizer->pModule->xDestroy(p->pTokenizer);
+
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Write an error message into *pzErr
+*/
+SQLITE_PRIVATE void sqlite3Fts3ErrMsg(char **pzErr, const char *zFormat, ...){
+  va_list ap;
+  sqlite3_free(*pzErr);
+  va_start(ap, zFormat);
+  *pzErr = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+}
+
+/*
+** Construct one or more SQL statements from the format string given
+** and then evaluate those statements. The success code is written
+** into *pRc.
+**
+** If *pRc is initially non-zero then this routine is a no-op.
+*/
+static void fts3DbExec(
+  int *pRc,              /* Success code */
+  sqlite3 *db,           /* Database in which to run SQL */
+  const char *zFormat,   /* Format string for SQL */
+  ...                    /* Arguments to the format string */
+){
+  va_list ap;
+  char *zSql;
+  if( *pRc ) return;
+  va_start(ap, zFormat);
+  zSql = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  if( zSql==0 ){
+    *pRc = SQLITE_NOMEM;
+  }else{
+    *pRc = sqlite3_exec(db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+}
+
+/*
+** The xDestroy() virtual table method.
+*/
+static int fts3DestroyMethod(sqlite3_vtab *pVtab){
+  Fts3Table *p = (Fts3Table *)pVtab;
+  int rc = SQLITE_OK;              /* Return code */
+  const char *zDb = p->zDb;        /* Name of database (e.g. "main", "temp") */
+  sqlite3 *db = p->db;             /* Database handle */
+
+  /* Drop the shadow tables */
+  if( p->zContentTbl==0 ){
+    fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_content'", zDb, p->zName);
+  }
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_segments'", zDb,p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_segdir'", zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_docsize'", zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_stat'", zDb, p->zName);
+
+  /* If everything has worked, invoke fts3DisconnectMethod() to free the
+  ** memory associated with the Fts3Table structure and return SQLITE_OK.
+  ** Otherwise, return an SQLite error code.
+  */
+  return (rc==SQLITE_OK ? fts3DisconnectMethod(pVtab) : rc);
+}
+
+
+/*
+** Invoke sqlite3_declare_vtab() to declare the schema for the FTS3 table
+** passed as the first argument. This is done as part of the xConnect()
+** and xCreate() methods.
+**
+** If *pRc is non-zero when this function is called, it is a no-op. 
+** Otherwise, if an error occurs, an SQLite error code is stored in *pRc
+** before returning.
+*/
+static void fts3DeclareVtab(int *pRc, Fts3Table *p){
+  if( *pRc==SQLITE_OK ){
+    int i;                        /* Iterator variable */
+    int rc;                       /* Return code */
+    char *zSql;                   /* SQL statement passed to declare_vtab() */
+    char *zCols;                  /* List of user defined columns */
+    const char *zLanguageid;
+
+    zLanguageid = (p->zLanguageid ? p->zLanguageid : "__langid");
+    sqlite3_vtab_config(p->db, SQLITE_VTAB_CONSTRAINT_SUPPORT, 1);
+
+    /* Create a list of user columns for the virtual table */
+    zCols = sqlite3_mprintf("%Q, ", p->azColumn[0]);
+    for(i=1; zCols && i<p->nColumn; i++){
+      zCols = sqlite3_mprintf("%z%Q, ", zCols, p->azColumn[i]);
+    }
+
+    /* Create the whole "CREATE TABLE" statement to pass to SQLite */
+    zSql = sqlite3_mprintf(
+        "CREATE TABLE x(%s %Q HIDDEN, docid HIDDEN, %Q HIDDEN)", 
+        zCols, p->zName, zLanguageid
+    );
+    if( !zCols || !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_declare_vtab(p->db, zSql);
+    }
+
+    sqlite3_free(zSql);
+    sqlite3_free(zCols);
+    *pRc = rc;
+  }
+}
+
+/*
+** Create the %_stat table if it does not already exist.
+*/
+SQLITE_PRIVATE void sqlite3Fts3CreateStatTable(int *pRc, Fts3Table *p){
+  fts3DbExec(pRc, p->db, 
+      "CREATE TABLE IF NOT EXISTS %Q.'%q_stat'"
+          "(id INTEGER PRIMARY KEY, value BLOB);",
+      p->zDb, p->zName
+  );
+  if( (*pRc)==SQLITE_OK ) p->bHasStat = 1;
+}
+
+/*
+** Create the backing store tables (%_content, %_segments and %_segdir)
+** required by the FTS3 table passed as the only argument. This is done
+** as part of the vtab xCreate() method.
+**
+** If the p->bHasDocsize boolean is true (indicating that this is an
+** FTS4 table, not an FTS3 table) then also create the %_docsize and
+** %_stat tables required by FTS4.
+*/
+static int fts3CreateTables(Fts3Table *p){
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* Iterator variable */
+  sqlite3 *db = p->db;            /* The database connection */
+
+  if( p->zContentTbl==0 ){
+    const char *zLanguageid = p->zLanguageid;
+    char *zContentCols;           /* Columns of %_content table */
+
+    /* Create a list of user columns for the content table */
+    zContentCols = sqlite3_mprintf("docid INTEGER PRIMARY KEY");
+    for(i=0; zContentCols && i<p->nColumn; i++){
+      char *z = p->azColumn[i];
+      zContentCols = sqlite3_mprintf("%z, 'c%d%q'", zContentCols, i, z);
+    }
+    if( zLanguageid && zContentCols ){
+      zContentCols = sqlite3_mprintf("%z, langid", zContentCols, zLanguageid);
+    }
+    if( zContentCols==0 ) rc = SQLITE_NOMEM;
+  
+    /* Create the content table */
+    fts3DbExec(&rc, db, 
+       "CREATE TABLE %Q.'%q_content'(%s)",
+       p->zDb, p->zName, zContentCols
+    );
+    sqlite3_free(zContentCols);
+  }
+
+  /* Create other tables */
+  fts3DbExec(&rc, db, 
+      "CREATE TABLE %Q.'%q_segments'(blockid INTEGER PRIMARY KEY, block BLOB);",
+      p->zDb, p->zName
+  );
+  fts3DbExec(&rc, db, 
+      "CREATE TABLE %Q.'%q_segdir'("
+        "level INTEGER,"
+        "idx INTEGER,"
+        "start_block INTEGER,"
+        "leaves_end_block INTEGER,"
+        "end_block INTEGER,"
+        "root BLOB,"
+        "PRIMARY KEY(level, idx)"
+      ");",
+      p->zDb, p->zName
+  );
+  if( p->bHasDocsize ){
+    fts3DbExec(&rc, db, 
+        "CREATE TABLE %Q.'%q_docsize'(docid INTEGER PRIMARY KEY, size BLOB);",
+        p->zDb, p->zName
+    );
+  }
+  assert( p->bHasStat==p->bFts4 );
+  if( p->bHasStat ){
+    sqlite3Fts3CreateStatTable(&rc, p);
+  }
+  return rc;
+}
+
+/*
+** Store the current database page-size in bytes in p->nPgsz.
+**
+** If *pRc is non-zero when this function is called, it is a no-op. 
+** Otherwise, if an error occurs, an SQLite error code is stored in *pRc
+** before returning.
+*/
+static void fts3DatabasePageSize(int *pRc, Fts3Table *p){
+  if( *pRc==SQLITE_OK ){
+    int rc;                       /* Return code */
+    char *zSql;                   /* SQL text "PRAGMA %Q.page_size" */
+    sqlite3_stmt *pStmt;          /* Compiled "PRAGMA %Q.page_size" statement */
+  
+    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", p->zDb);
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare(p->db, zSql, -1, &pStmt, 0);
+      if( rc==SQLITE_OK ){
+        sqlite3_step(pStmt);
+        p->nPgsz = sqlite3_column_int(pStmt, 0);
+        rc = sqlite3_finalize(pStmt);
+      }else if( rc==SQLITE_AUTH ){
+        p->nPgsz = 1024;
+        rc = SQLITE_OK;
+      }
+    }
+    assert( p->nPgsz>0 || rc!=SQLITE_OK );
+    sqlite3_free(zSql);
+    *pRc = rc;
+  }
+}
+
+/*
+** "Special" FTS4 arguments are column specifications of the following form:
+**
+**   <key> = <value>
+**
+** There may not be whitespace surrounding the "=" character. The <value> 
+** term may be quoted, but the <key> may not.
+*/
+static int fts3IsSpecialColumn(
+  const char *z, 
+  int *pnKey,
+  char **pzValue
+){
+  char *zValue;
+  const char *zCsr = z;
+
+  while( *zCsr!='=' ){
+    if( *zCsr=='\0' ) return 0;
+    zCsr++;
+  }
+
+  *pnKey = (int)(zCsr-z);
+  zValue = sqlite3_mprintf("%s", &zCsr[1]);
+  if( zValue ){
+    sqlite3Fts3Dequote(zValue);
+  }
+  *pzValue = zValue;
+  return 1;
+}
+
+/*
+** Append the output of a printf() style formatting to an existing string.
+*/
+static void fts3Appendf(
+  int *pRc,                       /* IN/OUT: Error code */
+  char **pz,                      /* IN/OUT: Pointer to string buffer */
+  const char *zFormat,            /* Printf format string to append */
+  ...                             /* Arguments for printf format string */
+){
+  if( *pRc==SQLITE_OK ){
+    va_list ap;
+    char *z;
+    va_start(ap, zFormat);
+    z = sqlite3_vmprintf(zFormat, ap);
+    va_end(ap);
+    if( z && *pz ){
+      char *z2 = sqlite3_mprintf("%s%s", *pz, z);
+      sqlite3_free(z);
+      z = z2;
+    }
+    if( z==0 ) *pRc = SQLITE_NOMEM;
+    sqlite3_free(*pz);
+    *pz = z;
+  }
+}
+
+/*
+** Return a copy of input string zInput enclosed in double-quotes (") and
+** with all double quote characters escaped. For example:
+**
+**     fts3QuoteId("un \"zip\"")   ->    "un \"\"zip\"\""
+**
+** The pointer returned points to memory obtained from sqlite3_malloc(). It
+** is the callers responsibility to call sqlite3_free() to release this
+** memory.
+*/
+static char *fts3QuoteId(char const *zInput){
+  int nRet;
+  char *zRet;
+  nRet = 2 + (int)strlen(zInput)*2 + 1;
+  zRet = sqlite3_malloc(nRet);
+  if( zRet ){
+    int i;
+    char *z = zRet;
+    *(z++) = '"';
+    for(i=0; zInput[i]; i++){
+      if( zInput[i]=='"' ) *(z++) = '"';
+      *(z++) = zInput[i];
+    }
+    *(z++) = '"';
+    *(z++) = '\0';
+  }
+  return zRet;
+}
+
+/*
+** Return a list of comma separated SQL expressions and a FROM clause that 
+** could be used in a SELECT statement such as the following:
+**
+**     SELECT <list of expressions> FROM %_content AS x ...
+**
+** to return the docid, followed by each column of text data in order
+** from left to write. If parameter zFunc is not NULL, then instead of
+** being returned directly each column of text data is passed to an SQL
+** function named zFunc first. For example, if zFunc is "unzip" and the
+** table has the three user-defined columns "a", "b", and "c", the following
+** string is returned:
+**
+**     "docid, unzip(x.'a'), unzip(x.'b'), unzip(x.'c') FROM %_content AS x"
+**
+** The pointer returned points to a buffer allocated by sqlite3_malloc(). It
+** is the responsibility of the caller to eventually free it.
+**
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op (and
+** a NULL pointer is returned). Otherwise, if an OOM error is encountered
+** by this function, NULL is returned and *pRc is set to SQLITE_NOMEM. If
+** no error occurs, *pRc is left unmodified.
+*/
+static char *fts3ReadExprList(Fts3Table *p, const char *zFunc, int *pRc){
+  char *zRet = 0;
+  char *zFree = 0;
+  char *zFunction;
+  int i;
+
+  if( p->zContentTbl==0 ){
+    if( !zFunc ){
+      zFunction = "";
+    }else{
+      zFree = zFunction = fts3QuoteId(zFunc);
+    }
+    fts3Appendf(pRc, &zRet, "docid");
+    for(i=0; i<p->nColumn; i++){
+      fts3Appendf(pRc, &zRet, ",%s(x.'c%d%q')", zFunction, i, p->azColumn[i]);
+    }
+    if( p->zLanguageid ){
+      fts3Appendf(pRc, &zRet, ", x.%Q", "langid");
+    }
+    sqlite3_free(zFree);
+  }else{
+    fts3Appendf(pRc, &zRet, "rowid");
+    for(i=0; i<p->nColumn; i++){
+      fts3Appendf(pRc, &zRet, ", x.'%q'", p->azColumn[i]);
+    }
+    if( p->zLanguageid ){
+      fts3Appendf(pRc, &zRet, ", x.%Q", p->zLanguageid);
+    }
+  }
+  fts3Appendf(pRc, &zRet, " FROM '%q'.'%q%s' AS x", 
+      p->zDb,
+      (p->zContentTbl ? p->zContentTbl : p->zName),
+      (p->zContentTbl ? "" : "_content")
+  );
+  return zRet;
+}
+
+/*
+** Return a list of N comma separated question marks, where N is the number
+** of columns in the %_content table (one for the docid plus one for each
+** user-defined text column).
+**
+** If argument zFunc is not NULL, then all but the first question mark
+** is preceded by zFunc and an open bracket, and followed by a closed
+** bracket. For example, if zFunc is "zip" and the FTS3 table has three 
+** user-defined text columns, the following string is returned:
+**
+**     "?, zip(?), zip(?), zip(?)"
+**
+** The pointer returned points to a buffer allocated by sqlite3_malloc(). It
+** is the responsibility of the caller to eventually free it.
+**
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op (and
+** a NULL pointer is returned). Otherwise, if an OOM error is encountered
+** by this function, NULL is returned and *pRc is set to SQLITE_NOMEM. If
+** no error occurs, *pRc is left unmodified.
+*/
+static char *fts3WriteExprList(Fts3Table *p, const char *zFunc, int *pRc){
+  char *zRet = 0;
+  char *zFree = 0;
+  char *zFunction;
+  int i;
+
+  if( !zFunc ){
+    zFunction = "";
+  }else{
+    zFree = zFunction = fts3QuoteId(zFunc);
+  }
+  fts3Appendf(pRc, &zRet, "?");
+  for(i=0; i<p->nColumn; i++){
+    fts3Appendf(pRc, &zRet, ",%s(?)", zFunction);
+  }
+  if( p->zLanguageid ){
+    fts3Appendf(pRc, &zRet, ", ?");
+  }
+  sqlite3_free(zFree);
+  return zRet;
+}
+
+/*
+** This function interprets the string at (*pp) as a non-negative integer
+** value. It reads the integer and sets *pnOut to the value read, then 
+** sets *pp to point to the byte immediately following the last byte of
+** the integer value.
+**
+** Only decimal digits ('0'..'9') may be part of an integer value. 
+**
+** If *pp does not being with a decimal digit SQLITE_ERROR is returned and
+** the output value undefined. Otherwise SQLITE_OK is returned.
+**
+** This function is used when parsing the "prefix=" FTS4 parameter.
+*/
+static int fts3GobbleInt(const char **pp, int *pnOut){
+  const int MAX_NPREFIX = 10000000;
+  const char *p;                  /* Iterator pointer */
+  int nInt = 0;                   /* Output value */
+
+  for(p=*pp; p[0]>='0' && p[0]<='9'; p++){
+    nInt = nInt * 10 + (p[0] - '0');
+    if( nInt>MAX_NPREFIX ){
+      nInt = 0;
+      break;
+    }
+  }
+  if( p==*pp ) return SQLITE_ERROR;
+  *pnOut = nInt;
+  *pp = p;
+  return SQLITE_OK;
+}
+
+/*
+** This function is called to allocate an array of Fts3Index structures
+** representing the indexes maintained by the current FTS table. FTS tables
+** always maintain the main "terms" index, but may also maintain one or
+** more "prefix" indexes, depending on the value of the "prefix=" parameter
+** (if any) specified as part of the CREATE VIRTUAL TABLE statement.
+**
+** Argument zParam is passed the value of the "prefix=" option if one was
+** specified, or NULL otherwise.
+**
+** If no error occurs, SQLITE_OK is returned and *apIndex set to point to
+** the allocated array. *pnIndex is set to the number of elements in the
+** array. If an error does occur, an SQLite error code is returned.
+**
+** Regardless of whether or not an error is returned, it is the responsibility
+** of the caller to call sqlite3_free() on the output array to free it.
+*/
+static int fts3PrefixParameter(
+  const char *zParam,             /* ABC in prefix=ABC parameter to parse */
+  int *pnIndex,                   /* OUT: size of *apIndex[] array */
+  struct Fts3Index **apIndex      /* OUT: Array of indexes for this table */
+){
+  struct Fts3Index *aIndex;       /* Allocated array */
+  int nIndex = 1;                 /* Number of entries in array */
+
+  if( zParam && zParam[0] ){
+    const char *p;
+    nIndex++;
+    for(p=zParam; *p; p++){
+      if( *p==',' ) nIndex++;
+    }
+  }
+
+  aIndex = sqlite3_malloc(sizeof(struct Fts3Index) * nIndex);
+  *apIndex = aIndex;
+  if( !aIndex ){
+    return SQLITE_NOMEM;
+  }
+
+  memset(aIndex, 0, sizeof(struct Fts3Index) * nIndex);
+  if( zParam ){
+    const char *p = zParam;
+    int i;
+    for(i=1; i<nIndex; i++){
+      int nPrefix = 0;
+      if( fts3GobbleInt(&p, &nPrefix) ) return SQLITE_ERROR;
+      assert( nPrefix>=0 );
+      if( nPrefix==0 ){
+        nIndex--;
+        i--;
+      }else{
+        aIndex[i].nPrefix = nPrefix;
+      }
+      p++;
+    }
+  }
+
+  *pnIndex = nIndex;
+  return SQLITE_OK;
+}
+
+/*
+** This function is called when initializing an FTS4 table that uses the
+** content=xxx option. It determines the number of and names of the columns
+** of the new FTS4 table.
+**
+** The third argument passed to this function is the value passed to the
+** config=xxx option (i.e. "xxx"). This function queries the database for
+** a table of that name. If found, the output variables are populated
+** as follows:
+**
+**   *pnCol:   Set to the number of columns table xxx has,
+**
+**   *pnStr:   Set to the total amount of space required to store a copy
+**             of each columns name, including the nul-terminator.
+**
+**   *pazCol:  Set to point to an array of *pnCol strings. Each string is
+**             the name of the corresponding column in table xxx. The array
+**             and its contents are allocated using a single allocation. It
+**             is the responsibility of the caller to free this allocation
+**             by eventually passing the *pazCol value to sqlite3_free().
+**
+** If the table cannot be found, an error code is returned and the output
+** variables are undefined. Or, if an OOM is encountered, SQLITE_NOMEM is
+** returned (and the output variables are undefined).
+*/
+static int fts3ContentColumns(
+  sqlite3 *db,                    /* Database handle */
+  const char *zDb,                /* Name of db (i.e. "main", "temp" etc.) */
+  const char *zTbl,               /* Name of content table */
+  const char ***pazCol,           /* OUT: Malloc'd array of column names */
+  int *pnCol,                     /* OUT: Size of array *pazCol */
+  int *pnStr,                     /* OUT: Bytes of string content */
+  char **pzErr                    /* OUT: error message */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  char *zSql;                     /* "SELECT *" statement on zTbl */  
+  sqlite3_stmt *pStmt = 0;        /* Compiled version of zSql */
+
+  zSql = sqlite3_mprintf("SELECT * FROM %Q.%Q", zDb, zTbl);
+  if( !zSql ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+    if( rc!=SQLITE_OK ){
+      sqlite3Fts3ErrMsg(pzErr, "%s", sqlite3_errmsg(db));
+    }
+  }
+  sqlite3_free(zSql);
+
+  if( rc==SQLITE_OK ){
+    const char **azCol;           /* Output array */
+    int nStr = 0;                 /* Size of all column names (incl. 0x00) */
+    int nCol;                     /* Number of table columns */
+    int i;                        /* Used to iterate through columns */
+
+    /* Loop through the returned columns. Set nStr to the number of bytes of
+    ** space required to store a copy of each column name, including the
+    ** nul-terminator byte.  */
+    nCol = sqlite3_column_count(pStmt);
+    for(i=0; i<nCol; i++){
+      const char *zCol = sqlite3_column_name(pStmt, i);
+      nStr += (int)strlen(zCol) + 1;
+    }
+
+    /* Allocate and populate the array to return. */
+    azCol = (const char **)sqlite3_malloc(sizeof(char *) * nCol + nStr);
+    if( azCol==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      char *p = (char *)&azCol[nCol];
+      for(i=0; i<nCol; i++){
+        const char *zCol = sqlite3_column_name(pStmt, i);
+        int n = (int)strlen(zCol)+1;
+        memcpy(p, zCol, n);
+        azCol[i] = p;
+        p += n;
+      }
+    }
+    sqlite3_finalize(pStmt);
+
+    /* Set the output variables. */
+    *pnCol = nCol;
+    *pnStr = nStr;
+    *pazCol = azCol;
+  }
+
+  return rc;
+}
+
+/*
+** This function is the implementation of both the xConnect and xCreate
+** methods of the FTS3 virtual table.
+**
+** The argv[] array contains the following:
+**
+**   argv[0]   -> module name  ("fts3" or "fts4")
+**   argv[1]   -> database name
+**   argv[2]   -> table name
+**   argv[...] -> "column name" and other module argument fields.
+*/
+static int fts3InitVtab(
+  int isCreate,                   /* True for xCreate, false for xConnect */
+  sqlite3 *db,                    /* The SQLite database connection */
+  void *pAux,                     /* Hash table containing tokenizers */
+  int argc,                       /* Number of elements in argv array */
+  const char * const *argv,       /* xCreate/xConnect argument array */
+  sqlite3_vtab **ppVTab,          /* Write the resulting vtab structure here */
+  char **pzErr                    /* Write any error message here */
+){
+  Fts3Hash *pHash = (Fts3Hash *)pAux;
+  Fts3Table *p = 0;               /* Pointer to allocated vtab */
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* Iterator variable */
+  int nByte;                      /* Size of allocation used for *p */
+  int iCol;                       /* Column index */
+  int nString = 0;                /* Bytes required to hold all column names */
+  int nCol = 0;                   /* Number of columns in the FTS table */
+  char *zCsr;                     /* Space for holding column names */
+  int nDb;                        /* Bytes required to hold database name */
+  int nName;                      /* Bytes required to hold table name */
+  int isFts4 = (argv[0][3]=='4'); /* True for FTS4, false for FTS3 */
+  const char **aCol;              /* Array of column names */
+  sqlite3_tokenizer *pTokenizer = 0;        /* Tokenizer for this table */
+
+  int nIndex = 0;                 /* Size of aIndex[] array */
+  struct Fts3Index *aIndex = 0;   /* Array of indexes for this table */
+
+  /* The results of parsing supported FTS4 key=value options: */
+  int bNoDocsize = 0;             /* True to omit %_docsize table */
+  int bDescIdx = 0;               /* True to store descending indexes */
+  char *zPrefix = 0;              /* Prefix parameter value (or NULL) */
+  char *zCompress = 0;            /* compress=? parameter (or NULL) */
+  char *zUncompress = 0;          /* uncompress=? parameter (or NULL) */
+  char *zContent = 0;             /* content=? parameter (or NULL) */
+  char *zLanguageid = 0;          /* languageid=? parameter (or NULL) */
+  char **azNotindexed = 0;        /* The set of notindexed= columns */
+  int nNotindexed = 0;            /* Size of azNotindexed[] array */
+
+  assert( strlen(argv[0])==4 );
+  assert( (sqlite3_strnicmp(argv[0], "fts4", 4)==0 && isFts4)
+       || (sqlite3_strnicmp(argv[0], "fts3", 4)==0 && !isFts4)
+  );
+
+  nDb = (int)strlen(argv[1]) + 1;
+  nName = (int)strlen(argv[2]) + 1;
+
+  nByte = sizeof(const char *) * (argc-2);
+  aCol = (const char **)sqlite3_malloc(nByte);
+  if( aCol ){
+    memset((void*)aCol, 0, nByte);
+    azNotindexed = (char **)sqlite3_malloc(nByte);
+  }
+  if( azNotindexed ){
+    memset(azNotindexed, 0, nByte);
+  }
+  if( !aCol || !azNotindexed ){
+    rc = SQLITE_NOMEM;
+    goto fts3_init_out;
+  }
+
+  /* Loop through all of the arguments passed by the user to the FTS3/4
+  ** module (i.e. all the column names and special arguments). This loop
+  ** does the following:
+  **
+  **   + Figures out the number of columns the FTSX table will have, and
+  **     the number of bytes of space that must be allocated to store copies
+  **     of the column names.
+  **
+  **   + If there is a tokenizer specification included in the arguments,
+  **     initializes the tokenizer pTokenizer.
+  */
+  for(i=3; rc==SQLITE_OK && i<argc; i++){
+    char const *z = argv[i];
+    int nKey;
+    char *zVal;
+
+    /* Check if this is a tokenizer specification */
+    if( !pTokenizer 
+     && strlen(z)>8
+     && 0==sqlite3_strnicmp(z, "tokenize", 8) 
+     && 0==sqlite3Fts3IsIdChar(z[8])
+    ){
+      rc = sqlite3Fts3InitTokenizer(pHash, &z[9], &pTokenizer, pzErr);
+    }
+
+    /* Check if it is an FTS4 special argument. */
+    else if( isFts4 && fts3IsSpecialColumn(z, &nKey, &zVal) ){
+      struct Fts4Option {
+        const char *zOpt;
+        int nOpt;
+      } aFts4Opt[] = {
+        { "matchinfo",   9 },     /* 0 -> MATCHINFO */
+        { "prefix",      6 },     /* 1 -> PREFIX */
+        { "compress",    8 },     /* 2 -> COMPRESS */
+        { "uncompress", 10 },     /* 3 -> UNCOMPRESS */
+        { "order",       5 },     /* 4 -> ORDER */
+        { "content",     7 },     /* 5 -> CONTENT */
+        { "languageid", 10 },     /* 6 -> LANGUAGEID */
+        { "notindexed", 10 }      /* 7 -> NOTINDEXED */
+      };
+
+      int iOpt;
+      if( !zVal ){
+        rc = SQLITE_NOMEM;
+      }else{
+        for(iOpt=0; iOpt<SizeofArray(aFts4Opt); iOpt++){
+          struct Fts4Option *pOp = &aFts4Opt[iOpt];
+          if( nKey==pOp->nOpt && !sqlite3_strnicmp(z, pOp->zOpt, pOp->nOpt) ){
+            break;
+          }
+        }
+        if( iOpt==SizeofArray(aFts4Opt) ){
+          sqlite3Fts3ErrMsg(pzErr, "unrecognized parameter: %s", z);
+          rc = SQLITE_ERROR;
+        }else{
+          switch( iOpt ){
+            case 0:               /* MATCHINFO */
+              if( strlen(zVal)!=4 || sqlite3_strnicmp(zVal, "fts3", 4) ){
+                sqlite3Fts3ErrMsg(pzErr, "unrecognized matchinfo: %s", zVal);
+                rc = SQLITE_ERROR;
+              }
+              bNoDocsize = 1;
+              break;
+
+            case 1:               /* PREFIX */
+              sqlite3_free(zPrefix);
+              zPrefix = zVal;
+              zVal = 0;
+              break;
+
+            case 2:               /* COMPRESS */
+              sqlite3_free(zCompress);
+              zCompress = zVal;
+              zVal = 0;
+              break;
+
+            case 3:               /* UNCOMPRESS */
+              sqlite3_free(zUncompress);
+              zUncompress = zVal;
+              zVal = 0;
+              break;
+
+            case 4:               /* ORDER */
+              if( (strlen(zVal)!=3 || sqlite3_strnicmp(zVal, "asc", 3)) 
+               && (strlen(zVal)!=4 || sqlite3_strnicmp(zVal, "desc", 4)) 
+              ){
+                sqlite3Fts3ErrMsg(pzErr, "unrecognized order: %s", zVal);
+                rc = SQLITE_ERROR;
+              }
+              bDescIdx = (zVal[0]=='d' || zVal[0]=='D');
+              break;
+
+            case 5:              /* CONTENT */
+              sqlite3_free(zContent);
+              zContent = zVal;
+              zVal = 0;
+              break;
+
+            case 6:              /* LANGUAGEID */
+              assert( iOpt==6 );
+              sqlite3_free(zLanguageid);
+              zLanguageid = zVal;
+              zVal = 0;
+              break;
+
+            case 7:              /* NOTINDEXED */
+              azNotindexed[nNotindexed++] = zVal;
+              zVal = 0;
+              break;
+          }
+        }
+        sqlite3_free(zVal);
+      }
+    }
+
+    /* Otherwise, the argument is a column name. */
+    else {
+      nString += (int)(strlen(z) + 1);
+      aCol[nCol++] = z;
+    }
+  }
+
+  /* If a content=xxx option was specified, the following:
+  **
+  **   1. Ignore any compress= and uncompress= options.
+  **
+  **   2. If no column names were specified as part of the CREATE VIRTUAL
+  **      TABLE statement, use all columns from the content table.
+  */
+  if( rc==SQLITE_OK && zContent ){
+    sqlite3_free(zCompress); 
+    sqlite3_free(zUncompress); 
+    zCompress = 0;
+    zUncompress = 0;
+    if( nCol==0 ){
+      sqlite3_free((void*)aCol); 
+      aCol = 0;
+      rc = fts3ContentColumns(db, argv[1], zContent,&aCol,&nCol,&nString,pzErr);
+
+      /* If a languageid= option was specified, remove the language id
+      ** column from the aCol[] array. */ 
+      if( rc==SQLITE_OK && zLanguageid ){
+        int j;
+        for(j=0; j<nCol; j++){
+          if( sqlite3_stricmp(zLanguageid, aCol[j])==0 ){
+            int k;
+            for(k=j; k<nCol; k++) aCol[k] = aCol[k+1];
+            nCol--;
+            break;
+          }
+        }
+      }
+    }
+  }
+  if( rc!=SQLITE_OK ) goto fts3_init_out;
+
+  if( nCol==0 ){
+    assert( nString==0 );
+    aCol[0] = "content";
+    nString = 8;
+    nCol = 1;
+  }
+
+  if( pTokenizer==0 ){
+    rc = sqlite3Fts3InitTokenizer(pHash, "simple", &pTokenizer, pzErr);
+    if( rc!=SQLITE_OK ) goto fts3_init_out;
+  }
+  assert( pTokenizer );
+
+  rc = fts3PrefixParameter(zPrefix, &nIndex, &aIndex);
+  if( rc==SQLITE_ERROR ){
+    assert( zPrefix );
+    sqlite3Fts3ErrMsg(pzErr, "error parsing prefix parameter: %s", zPrefix);
+  }
+  if( rc!=SQLITE_OK ) goto fts3_init_out;
+
+  /* Allocate and populate the Fts3Table structure. */
+  nByte = sizeof(Fts3Table) +                  /* Fts3Table */
+          nCol * sizeof(char *) +              /* azColumn */
+          nIndex * sizeof(struct Fts3Index) +  /* aIndex */
+          nCol * sizeof(u8) +                  /* abNotindexed */
+          nName +                              /* zName */
+          nDb +                                /* zDb */
+          nString;                             /* Space for azColumn strings */
+  p = (Fts3Table*)sqlite3_malloc(nByte);
+  if( p==0 ){
+    rc = SQLITE_NOMEM;
+    goto fts3_init_out;
+  }
+  memset(p, 0, nByte);
+  p->db = db;
+  p->nColumn = nCol;
+  p->nPendingData = 0;
+  p->azColumn = (char **)&p[1];
+  p->pTokenizer = pTokenizer;
+  p->nMaxPendingData = FTS3_MAX_PENDING_DATA;
+  p->bHasDocsize = (isFts4 && bNoDocsize==0);
+  p->bHasStat = (u8)isFts4;
+  p->bFts4 = (u8)isFts4;
+  p->bDescIdx = (u8)bDescIdx;
+  p->nAutoincrmerge = 0xff;   /* 0xff means setting unknown */
+  p->zContentTbl = zContent;
+  p->zLanguageid = zLanguageid;
+  zContent = 0;
+  zLanguageid = 0;
+  TESTONLY( p->inTransaction = -1 );
+  TESTONLY( p->mxSavepoint = -1 );
+
+  p->aIndex = (struct Fts3Index *)&p->azColumn[nCol];
+  memcpy(p->aIndex, aIndex, sizeof(struct Fts3Index) * nIndex);
+  p->nIndex = nIndex;
+  for(i=0; i<nIndex; i++){
+    fts3HashInit(&p->aIndex[i].hPending, FTS3_HASH_STRING, 1);
+  }
+  p->abNotindexed = (u8 *)&p->aIndex[nIndex];
+
+  /* Fill in the zName and zDb fields of the vtab structure. */
+  zCsr = (char *)&p->abNotindexed[nCol];
+  p->zName = zCsr;
+  memcpy(zCsr, argv[2], nName);
+  zCsr += nName;
+  p->zDb = zCsr;
+  memcpy(zCsr, argv[1], nDb);
+  zCsr += nDb;
+
+  /* Fill in the azColumn array */
+  for(iCol=0; iCol<nCol; iCol++){
+    char *z; 
+    int n = 0;
+    z = (char *)sqlite3Fts3NextToken(aCol[iCol], &n);
+    memcpy(zCsr, z, n);
+    zCsr[n] = '\0';
+    sqlite3Fts3Dequote(zCsr);
+    p->azColumn[iCol] = zCsr;
+    zCsr += n+1;
+    assert( zCsr <= &((char *)p)[nByte] );
+  }
+
+  /* Fill in the abNotindexed array */
+  for(iCol=0; iCol<nCol; iCol++){
+    int n = (int)strlen(p->azColumn[iCol]);
+    for(i=0; i<nNotindexed; i++){
+      char *zNot = azNotindexed[i];
+      if( zNot && n==(int)strlen(zNot)
+       && 0==sqlite3_strnicmp(p->azColumn[iCol], zNot, n) 
+      ){
+        p->abNotindexed[iCol] = 1;
+        sqlite3_free(zNot);
+        azNotindexed[i] = 0;
+      }
+    }
+  }
+  for(i=0; i<nNotindexed; i++){
+    if( azNotindexed[i] ){
+      sqlite3Fts3ErrMsg(pzErr, "no such column: %s", azNotindexed[i]);
+      rc = SQLITE_ERROR;
+    }
+  }
+
+  if( rc==SQLITE_OK && (zCompress==0)!=(zUncompress==0) ){
+    char const *zMiss = (zCompress==0 ? "compress" : "uncompress");
+    rc = SQLITE_ERROR;
+    sqlite3Fts3ErrMsg(pzErr, "missing %s parameter in fts4 constructor", zMiss);
+  }
+  p->zReadExprlist = fts3ReadExprList(p, zUncompress, &rc);
+  p->zWriteExprlist = fts3WriteExprList(p, zCompress, &rc);
+  if( rc!=SQLITE_OK ) goto fts3_init_out;
+
+  /* If this is an xCreate call, create the underlying tables in the 
+  ** database. TODO: For xConnect(), it could verify that said tables exist.
+  */
+  if( isCreate ){
+    rc = fts3CreateTables(p);
+  }
+
+  /* Check to see if a legacy fts3 table has been "upgraded" by the
+  ** addition of a %_stat table so that it can use incremental merge.
+  */
+  if( !isFts4 && !isCreate ){
+    p->bHasStat = 2;
+  }
+
+  /* Figure out the page-size for the database. This is required in order to
+  ** estimate the cost of loading large doclists from the database.  */
+  fts3DatabasePageSize(&rc, p);
+  p->nNodeSize = p->nPgsz-35;
+
+  /* Declare the table schema to SQLite. */
+  fts3DeclareVtab(&rc, p);
+
+fts3_init_out:
+  sqlite3_free(zPrefix);
+  sqlite3_free(aIndex);
+  sqlite3_free(zCompress);
+  sqlite3_free(zUncompress);
+  sqlite3_free(zContent);
+  sqlite3_free(zLanguageid);
+  for(i=0; i<nNotindexed; i++) sqlite3_free(azNotindexed[i]);
+  sqlite3_free((void *)aCol);
+  sqlite3_free((void *)azNotindexed);
+  if( rc!=SQLITE_OK ){
+    if( p ){
+      fts3DisconnectMethod((sqlite3_vtab *)p);
+    }else if( pTokenizer ){
+      pTokenizer->pModule->xDestroy(pTokenizer);
+    }
+  }else{
+    assert( p->pSegments==0 );
+    *ppVTab = &p->base;
+  }
+  return rc;
+}
+
+/*
+** The xConnect() and xCreate() methods for the virtual table. All the
+** work is done in function fts3InitVtab().
+*/
+static int fts3ConnectMethod(
+  sqlite3 *db,                    /* Database connection */
+  void *pAux,                     /* Pointer to tokenizer hash table */
+  int argc,                       /* Number of elements in argv array */
+  const char * const *argv,       /* xCreate/xConnect argument array */
+  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
+  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
+){
+  return fts3InitVtab(0, db, pAux, argc, argv, ppVtab, pzErr);
+}
+static int fts3CreateMethod(
+  sqlite3 *db,                    /* Database connection */
+  void *pAux,                     /* Pointer to tokenizer hash table */
+  int argc,                       /* Number of elements in argv array */
+  const char * const *argv,       /* xCreate/xConnect argument array */
+  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
+  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
+){
+  return fts3InitVtab(1, db, pAux, argc, argv, ppVtab, pzErr);
+}
+
+/*
+** Set the pIdxInfo->estimatedRows variable to nRow. Unless this
+** extension is currently being used by a version of SQLite too old to
+** support estimatedRows. In that case this function is a no-op.
+*/
+static void fts3SetEstimatedRows(sqlite3_index_info *pIdxInfo, i64 nRow){
+#if SQLITE_VERSION_NUMBER>=3008002
+  if( sqlite3_libversion_number()>=3008002 ){
+    pIdxInfo->estimatedRows = nRow;
+  }
+#endif
+}
+
+/*
+** Set the SQLITE_INDEX_SCAN_UNIQUE flag in pIdxInfo->flags. Unless this
+** extension is currently being used by a version of SQLite too old to
+** support index-info flags. In that case this function is a no-op.
+*/
+static void fts3SetUniqueFlag(sqlite3_index_info *pIdxInfo){
+#if SQLITE_VERSION_NUMBER>=3008012
+  if( sqlite3_libversion_number()>=3008012 ){
+    pIdxInfo->idxFlags |= SQLITE_INDEX_SCAN_UNIQUE;
+  }
+#endif
+}
+
+/* 
+** Implementation of the xBestIndex method for FTS3 tables. There
+** are three possible strategies, in order of preference:
+**
+**   1. Direct lookup by rowid or docid. 
+**   2. Full-text search using a MATCH operator on a non-docid column.
+**   3. Linear scan of %_content table.
+*/
+static int fts3BestIndexMethod(sqlite3_vtab *pVTab, sqlite3_index_info *pInfo){
+  Fts3Table *p = (Fts3Table *)pVTab;
+  int i;                          /* Iterator variable */
+  int iCons = -1;                 /* Index of constraint to use */
+
+  int iLangidCons = -1;           /* Index of langid=x constraint, if present */
+  int iDocidGe = -1;              /* Index of docid>=x constraint, if present */
+  int iDocidLe = -1;              /* Index of docid<=x constraint, if present */
+  int iIdx;
+
+  /* By default use a full table scan. This is an expensive option,
+  ** so search through the constraints to see if a more efficient 
+  ** strategy is possible.
+  */
+  pInfo->idxNum = FTS3_FULLSCAN_SEARCH;
+  pInfo->estimatedCost = 5000000;
+  for(i=0; i<pInfo->nConstraint; i++){
+    int bDocid;                 /* True if this constraint is on docid */
+    struct sqlite3_index_constraint *pCons = &pInfo->aConstraint[i];
+    if( pCons->usable==0 ){
+      if( pCons->op==SQLITE_INDEX_CONSTRAINT_MATCH ){
+        /* There exists an unusable MATCH constraint. This means that if
+        ** the planner does elect to use the results of this call as part
+        ** of the overall query plan the user will see an "unable to use
+        ** function MATCH in the requested context" error. To discourage
+        ** this, return a very high cost here.  */
+        pInfo->idxNum = FTS3_FULLSCAN_SEARCH;
+        pInfo->estimatedCost = 1e50;
+        fts3SetEstimatedRows(pInfo, ((sqlite3_int64)1) << 50);
+        return SQLITE_OK;
+      }
+      continue;
+    }
+
+    bDocid = (pCons->iColumn<0 || pCons->iColumn==p->nColumn+1);
+
+    /* A direct lookup on the rowid or docid column. Assign a cost of 1.0. */
+    if( iCons<0 && pCons->op==SQLITE_INDEX_CONSTRAINT_EQ && bDocid ){
+      pInfo->idxNum = FTS3_DOCID_SEARCH;
+      pInfo->estimatedCost = 1.0;
+      iCons = i;
+    }
+
+    /* A MATCH constraint. Use a full-text search.
+    **
+    ** If there is more than one MATCH constraint available, use the first
+    ** one encountered. If there is both a MATCH constraint and a direct
+    ** rowid/docid lookup, prefer the MATCH strategy. This is done even 
+    ** though the rowid/docid lookup is faster than a MATCH query, selecting
+    ** it would lead to an "unable to use function MATCH in the requested 
+    ** context" error.
+    */
+    if( pCons->op==SQLITE_INDEX_CONSTRAINT_MATCH 
+     && pCons->iColumn>=0 && pCons->iColumn<=p->nColumn
+    ){
+      pInfo->idxNum = FTS3_FULLTEXT_SEARCH + pCons->iColumn;
+      pInfo->estimatedCost = 2.0;
+      iCons = i;
+    }
+
+    /* Equality constraint on the langid column */
+    if( pCons->op==SQLITE_INDEX_CONSTRAINT_EQ 
+     && pCons->iColumn==p->nColumn + 2
+    ){
+      iLangidCons = i;
+    }
+
+    if( bDocid ){
+      switch( pCons->op ){
+        case SQLITE_INDEX_CONSTRAINT_GE:
+        case SQLITE_INDEX_CONSTRAINT_GT:
+          iDocidGe = i;
+          break;
+
+        case SQLITE_INDEX_CONSTRAINT_LE:
+        case SQLITE_INDEX_CONSTRAINT_LT:
+          iDocidLe = i;
+          break;
+      }
+    }
+  }
+
+  /* If using a docid=? or rowid=? strategy, set the UNIQUE flag. */
+  if( pInfo->idxNum==FTS3_DOCID_SEARCH ) fts3SetUniqueFlag(pInfo);
+
+  iIdx = 1;
+  if( iCons>=0 ){
+    pInfo->aConstraintUsage[iCons].argvIndex = iIdx++;
+    pInfo->aConstraintUsage[iCons].omit = 1;
+  } 
+  if( iLangidCons>=0 ){
+    pInfo->idxNum |= FTS3_HAVE_LANGID;
+    pInfo->aConstraintUsage[iLangidCons].argvIndex = iIdx++;
+  } 
+  if( iDocidGe>=0 ){
+    pInfo->idxNum |= FTS3_HAVE_DOCID_GE;
+    pInfo->aConstraintUsage[iDocidGe].argvIndex = iIdx++;
+  } 
+  if( iDocidLe>=0 ){
+    pInfo->idxNum |= FTS3_HAVE_DOCID_LE;
+    pInfo->aConstraintUsage[iDocidLe].argvIndex = iIdx++;
+  } 
+
+  /* Regardless of the strategy selected, FTS can deliver rows in rowid (or
+  ** docid) order. Both ascending and descending are possible. 
+  */
+  if( pInfo->nOrderBy==1 ){
+    struct sqlite3_index_orderby *pOrder = &pInfo->aOrderBy[0];
+    if( pOrder->iColumn<0 || pOrder->iColumn==p->nColumn+1 ){
+      if( pOrder->desc ){
+        pInfo->idxStr = "DESC";
+      }else{
+        pInfo->idxStr = "ASC";
+      }
+      pInfo->orderByConsumed = 1;
+    }
+  }
+
+  assert( p->pSegments==0 );
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of xOpen method.
+*/
+static int fts3OpenMethod(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCsr){
+  sqlite3_vtab_cursor *pCsr;               /* Allocated cursor */
+
+  UNUSED_PARAMETER(pVTab);
+
+  /* Allocate a buffer large enough for an Fts3Cursor structure. If the
+  ** allocation succeeds, zero it and return SQLITE_OK. Otherwise, 
+  ** if the allocation fails, return SQLITE_NOMEM.
+  */
+  *ppCsr = pCsr = (sqlite3_vtab_cursor *)sqlite3_malloc(sizeof(Fts3Cursor));
+  if( !pCsr ){
+    return SQLITE_NOMEM;
+  }
+  memset(pCsr, 0, sizeof(Fts3Cursor));
+  return SQLITE_OK;
+}
+
+/*
+** Finalize the statement handle at pCsr->pStmt.
+**
+** Or, if that statement handle is one created by fts3CursorSeekStmt(),
+** and the Fts3Table.pSeekStmt slot is currently NULL, save the statement
+** pointer there instead of finalizing it.
+*/
+static void fts3CursorFinalizeStmt(Fts3Cursor *pCsr){
+  if( pCsr->bSeekStmt ){
+    Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
+    if( p->pSeekStmt==0 ){
+      p->pSeekStmt = pCsr->pStmt;
+      sqlite3_reset(pCsr->pStmt);
+      pCsr->pStmt = 0;
+    }
+    pCsr->bSeekStmt = 0;
+  }
+  sqlite3_finalize(pCsr->pStmt);
+}
+
+/*
+** Close the cursor.  For additional information see the documentation
+** on the xClose method of the virtual table interface.
+*/
+static int fts3CloseMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3Cursor *pCsr = (Fts3Cursor *)pCursor;
+  assert( ((Fts3Table *)pCsr->base.pVtab)->pSegments==0 );
+  fts3CursorFinalizeStmt(pCsr);
+  sqlite3Fts3ExprFree(pCsr->pExpr);
+  sqlite3Fts3FreeDeferredTokens(pCsr);
+  sqlite3_free(pCsr->aDoclist);
+  sqlite3Fts3MIBufferFree(pCsr->pMIBuffer);
+  assert( ((Fts3Table *)pCsr->base.pVtab)->pSegments==0 );
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/*
+** If pCsr->pStmt has not been prepared (i.e. if pCsr->pStmt==0), then
+** compose and prepare an SQL statement of the form:
+**
+**    "SELECT <columns> FROM %_content WHERE rowid = ?"
+**
+** (or the equivalent for a content=xxx table) and set pCsr->pStmt to
+** it. If an error occurs, return an SQLite error code.
+*/
+static int fts3CursorSeekStmt(Fts3Cursor *pCsr){
+  int rc = SQLITE_OK;
+  if( pCsr->pStmt==0 ){
+    Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
+    char *zSql;
+    if( p->pSeekStmt ){
+      pCsr->pStmt = p->pSeekStmt;
+      p->pSeekStmt = 0;
+    }else{
+      zSql = sqlite3_mprintf("SELECT %s WHERE rowid = ?", p->zReadExprlist);
+      if( !zSql ) return SQLITE_NOMEM;
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pCsr->pStmt, 0);
+      sqlite3_free(zSql);
+    }
+    if( rc==SQLITE_OK ) pCsr->bSeekStmt = 1;
+  }
+  return rc;
+}
+
+/*
+** Position the pCsr->pStmt statement so that it is on the row
+** of the %_content table that contains the last match.  Return
+** SQLITE_OK on success.  
+*/
+static int fts3CursorSeek(sqlite3_context *pContext, Fts3Cursor *pCsr){
+  int rc = SQLITE_OK;
+  if( pCsr->isRequireSeek ){
+    rc = fts3CursorSeekStmt(pCsr);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pCsr->pStmt, 1, pCsr->iPrevId);
+      pCsr->isRequireSeek = 0;
+      if( SQLITE_ROW==sqlite3_step(pCsr->pStmt) ){
+        return SQLITE_OK;
+      }else{
+        rc = sqlite3_reset(pCsr->pStmt);
+        if( rc==SQLITE_OK && ((Fts3Table *)pCsr->base.pVtab)->zContentTbl==0 ){
+          /* If no row was found and no error has occurred, then the %_content
+          ** table is missing a row that is present in the full-text index.
+          ** The data structures are corrupt.  */
+          rc = FTS_CORRUPT_VTAB;
+          pCsr->isEof = 1;
+        }
+      }
+    }
+  }
+
+  if( rc!=SQLITE_OK && pContext ){
+    sqlite3_result_error_code(pContext, rc);
+  }
+  return rc;
+}
+
+/*
+** This function is used to process a single interior node when searching
+** a b-tree for a term or term prefix. The node data is passed to this 
+** function via the zNode/nNode parameters. The term to search for is
+** passed in zTerm/nTerm.
+**
+** If piFirst is not NULL, then this function sets *piFirst to the blockid
+** of the child node that heads the sub-tree that may contain the term.
+**
+** If piLast is not NULL, then *piLast is set to the right-most child node
+** that heads a sub-tree that may contain a term for which zTerm/nTerm is
+** a prefix.
+**
+** If an OOM error occurs, SQLITE_NOMEM is returned. Otherwise, SQLITE_OK.
+*/
+static int fts3ScanInteriorNode(
+  const char *zTerm,              /* Term to select leaves for */
+  int nTerm,                      /* Size of term zTerm in bytes */
+  const char *zNode,              /* Buffer containing segment interior node */
+  int nNode,                      /* Size of buffer at zNode */
+  sqlite3_int64 *piFirst,         /* OUT: Selected child node */
+  sqlite3_int64 *piLast           /* OUT: Selected child node */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  const char *zCsr = zNode;       /* Cursor to iterate through node */
+  const char *zEnd = &zCsr[nNode];/* End of interior node buffer */
+  char *zBuffer = 0;              /* Buffer to load terms into */
+  int nAlloc = 0;                 /* Size of allocated buffer */
+  int isFirstTerm = 1;            /* True when processing first term on page */
+  sqlite3_int64 iChild;           /* Block id of child node to descend to */
+
+  /* Skip over the 'height' varint that occurs at the start of every 
+  ** interior node. Then load the blockid of the left-child of the b-tree
+  ** node into variable iChild.  
+  **
+  ** Even if the data structure on disk is corrupted, this (reading two
+  ** varints from the buffer) does not risk an overread. If zNode is a
+  ** root node, then the buffer comes from a SELECT statement. SQLite does
+  ** not make this guarantee explicitly, but in practice there are always
+  ** either more than 20 bytes of allocated space following the nNode bytes of
+  ** contents, or two zero bytes. Or, if the node is read from the %_segments
+  ** table, then there are always 20 bytes of zeroed padding following the
+  ** nNode bytes of content (see sqlite3Fts3ReadBlock() for details).
+  */
+  zCsr += sqlite3Fts3GetVarint(zCsr, &iChild);
+  zCsr += sqlite3Fts3GetVarint(zCsr, &iChild);
+  if( zCsr>zEnd ){
+    return FTS_CORRUPT_VTAB;
+  }
+  
+  while( zCsr<zEnd && (piFirst || piLast) ){
+    int cmp;                      /* memcmp() result */
+    int nSuffix;                  /* Size of term suffix */
+    int nPrefix = 0;              /* Size of term prefix */
+    int nBuffer;                  /* Total term size */
+  
+    /* Load the next term on the node into zBuffer. Use realloc() to expand
+    ** the size of zBuffer if required.  */
+    if( !isFirstTerm ){
+      zCsr += fts3GetVarint32(zCsr, &nPrefix);
+    }
+    isFirstTerm = 0;
+    zCsr += fts3GetVarint32(zCsr, &nSuffix);
+    
+    /* NOTE(shess): Previous code checked for negative nPrefix and
+    ** nSuffix and suffix overrunning zEnd.  Additionally corrupt if
+    ** the prefix is longer than the previous term, or if the suffix
+    ** causes overflow.
+    */
+    if( nPrefix<0 || nSuffix<0 /* || nPrefix>nBuffer */
+     || &zCsr[nSuffix]<zCsr || &zCsr[nSuffix]>zEnd ){
+      rc = FTS_CORRUPT_VTAB;
+      goto finish_scan;
+    }
+    if( nPrefix+nSuffix>nAlloc ){
+      char *zNew;
+      nAlloc = (nPrefix+nSuffix) * 2;
+      zNew = (char *)sqlite3_realloc(zBuffer, nAlloc);
+      if( !zNew ){
+        rc = SQLITE_NOMEM;
+        goto finish_scan;
+      }
+      zBuffer = zNew;
+    }
+    assert( zBuffer );
+    memcpy(&zBuffer[nPrefix], zCsr, nSuffix);
+    nBuffer = nPrefix + nSuffix;
+    zCsr += nSuffix;
+
+    /* Compare the term we are searching for with the term just loaded from
+    ** the interior node. If the specified term is greater than or equal
+    ** to the term from the interior node, then all terms on the sub-tree 
+    ** headed by node iChild are smaller than zTerm. No need to search 
+    ** iChild.
+    **
+    ** If the interior node term is larger than the specified term, then
+    ** the tree headed by iChild may contain the specified term.
+    */
+    cmp = memcmp(zTerm, zBuffer, (nBuffer>nTerm ? nTerm : nBuffer));
+    if( piFirst && (cmp<0 || (cmp==0 && nBuffer>nTerm)) ){
+      *piFirst = iChild;
+      piFirst = 0;
+    }
+
+    if( piLast && cmp<0 ){
+      *piLast = iChild;
+      piLast = 0;
+    }
+
+    iChild++;
+  };
+
+  if( piFirst ) *piFirst = iChild;
+  if( piLast ) *piLast = iChild;
+
+ finish_scan:
+  sqlite3_free(zBuffer);
+  return rc;
+}
+
+
+/*
+** The buffer pointed to by argument zNode (size nNode bytes) contains an
+** interior node of a b-tree segment. The zTerm buffer (size nTerm bytes)
+** contains a term. This function searches the sub-tree headed by the zNode
+** node for the range of leaf nodes that may contain the specified term
+** or terms for which the specified term is a prefix.
+**
+** If piLeaf is not NULL, then *piLeaf is set to the blockid of the 
+** left-most leaf node in the tree that may contain the specified term.
+** If piLeaf2 is not NULL, then *piLeaf2 is set to the blockid of the
+** right-most leaf node that may contain a term for which the specified
+** term is a prefix.
+**
+** It is possible that the range of returned leaf nodes does not contain 
+** the specified term or any terms for which it is a prefix. However, if the 
+** segment does contain any such terms, they are stored within the identified
+** range. Because this function only inspects interior segment nodes (and
+** never loads leaf nodes into memory), it is not possible to be sure.
+**
+** If an error occurs, an error code other than SQLITE_OK is returned.
+*/ 
+static int fts3SelectLeaf(
+  Fts3Table *p,                   /* Virtual table handle */
+  const char *zTerm,              /* Term to select leaves for */
+  int nTerm,                      /* Size of term zTerm in bytes */
+  const char *zNode,              /* Buffer containing segment interior node */
+  int nNode,                      /* Size of buffer at zNode */
+  sqlite3_int64 *piLeaf,          /* Selected leaf node */
+  sqlite3_int64 *piLeaf2          /* Selected leaf node */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  int iHeight;                    /* Height of this node in tree */
+
+  assert( piLeaf || piLeaf2 );
+
+  fts3GetVarint32(zNode, &iHeight);
+  rc = fts3ScanInteriorNode(zTerm, nTerm, zNode, nNode, piLeaf, piLeaf2);
+  assert( !piLeaf2 || !piLeaf || rc!=SQLITE_OK || (*piLeaf<=*piLeaf2) );
+
+  if( rc==SQLITE_OK && iHeight>1 ){
+    char *zBlob = 0;              /* Blob read from %_segments table */
+    int nBlob = 0;                /* Size of zBlob in bytes */
+
+    if( piLeaf && piLeaf2 && (*piLeaf!=*piLeaf2) ){
+      rc = sqlite3Fts3ReadBlock(p, *piLeaf, &zBlob, &nBlob, 0);
+      if( rc==SQLITE_OK ){
+        rc = fts3SelectLeaf(p, zTerm, nTerm, zBlob, nBlob, piLeaf, 0);
+      }
+      sqlite3_free(zBlob);
+      piLeaf = 0;
+      zBlob = 0;
+    }
+
+    if( rc==SQLITE_OK ){
+      rc = sqlite3Fts3ReadBlock(p, piLeaf?*piLeaf:*piLeaf2, &zBlob, &nBlob, 0);
+    }
+    if( rc==SQLITE_OK ){
+      rc = fts3SelectLeaf(p, zTerm, nTerm, zBlob, nBlob, piLeaf, piLeaf2);
+    }
+    sqlite3_free(zBlob);
+  }
+
+  return rc;
+}
+
+/*
+** This function is used to create delta-encoded serialized lists of FTS3 
+** varints. Each call to this function appends a single varint to a list.
+*/
+static void fts3PutDeltaVarint(
+  char **pp,                      /* IN/OUT: Output pointer */
+  sqlite3_int64 *piPrev,          /* IN/OUT: Previous value written to list */
+  sqlite3_int64 iVal              /* Write this value to the list */
+){
+  assert( iVal-*piPrev > 0 || (*piPrev==0 && iVal==0) );
+  *pp += sqlite3Fts3PutVarint(*pp, iVal-*piPrev);
+  *piPrev = iVal;
+}
+
+/*
+** When this function is called, *ppPoslist is assumed to point to the 
+** start of a position-list. After it returns, *ppPoslist points to the
+** first byte after the position-list.
+**
+** A position list is list of positions (delta encoded) and columns for 
+** a single document record of a doclist.  So, in other words, this
+** routine advances *ppPoslist so that it points to the next docid in
+** the doclist, or to the first byte past the end of the doclist.
+**
+** If pp is not NULL, then the contents of the position list are copied
+** to *pp. *pp is set to point to the first byte past the last byte copied
+** before this function returns.
+*/
+static void fts3PoslistCopy(char **pp, char **ppPoslist){
+  char *pEnd = *ppPoslist;
+  char c = 0;
+
+  /* The end of a position list is marked by a zero encoded as an FTS3 
+  ** varint. A single POS_END (0) byte. Except, if the 0 byte is preceded by
+  ** a byte with the 0x80 bit set, then it is not a varint 0, but the tail
+  ** of some other, multi-byte, value.
+  **
+  ** The following while-loop moves pEnd to point to the first byte that is not 
+  ** immediately preceded by a byte with the 0x80 bit set. Then increments
+  ** pEnd once more so that it points to the byte immediately following the
+  ** last byte in the position-list.
+  */
+  while( *pEnd | c ){
+    c = *pEnd++ & 0x80;
+    testcase( c!=0 && (*pEnd)==0 );
+  }
+  pEnd++;  /* Advance past the POS_END terminator byte */
+
+  if( pp ){
+    int n = (int)(pEnd - *ppPoslist);
+    char *p = *pp;
+    memcpy(p, *ppPoslist, n);
+    p += n;
+    *pp = p;
+  }
+  *ppPoslist = pEnd;
+}
+
+/*
+** When this function is called, *ppPoslist is assumed to point to the 
+** start of a column-list. After it returns, *ppPoslist points to the
+** to the terminator (POS_COLUMN or POS_END) byte of the column-list.
+**
+** A column-list is list of delta-encoded positions for a single column
+** within a single document within a doclist.
+**
+** The column-list is terminated either by a POS_COLUMN varint (1) or
+** a POS_END varint (0).  This routine leaves *ppPoslist pointing to
+** the POS_COLUMN or POS_END that terminates the column-list.
+**
+** If pp is not NULL, then the contents of the column-list are copied
+** to *pp. *pp is set to point to the first byte past the last byte copied
+** before this function returns.  The POS_COLUMN or POS_END terminator
+** is not copied into *pp.
+*/
+static void fts3ColumnlistCopy(char **pp, char **ppPoslist){
+  char *pEnd = *ppPoslist;
+  char c = 0;
+
+  /* A column-list is terminated by either a 0x01 or 0x00 byte that is
+  ** not part of a multi-byte varint.
+  */
+  while( 0xFE & (*pEnd | c) ){
+    c = *pEnd++ & 0x80;
+    testcase( c!=0 && ((*pEnd)&0xfe)==0 );
+  }
+  if( pp ){
+    int n = (int)(pEnd - *ppPoslist);
+    char *p = *pp;
+    memcpy(p, *ppPoslist, n);
+    p += n;
+    *pp = p;
+  }
+  *ppPoslist = pEnd;
+}
+
+/*
+** Value used to signify the end of an position-list. This is safe because
+** it is not possible to have a document with 2^31 terms.
+*/
+#define POSITION_LIST_END 0x7fffffff
+
+/*
+** This function is used to help parse position-lists. When this function is
+** called, *pp may point to the start of the next varint in the position-list
+** being parsed, or it may point to 1 byte past the end of the position-list
+** (in which case **pp will be a terminator bytes POS_END (0) or
+** (1)).
+**
+** If *pp points past the end of the current position-list, set *pi to 
+** POSITION_LIST_END and return. Otherwise, read the next varint from *pp,
+** increment the current value of *pi by the value read, and set *pp to
+** point to the next value before returning.
+**
+** Before calling this routine *pi must be initialized to the value of
+** the previous position, or zero if we are reading the first position
+** in the position-list.  Because positions are delta-encoded, the value
+** of the previous position is needed in order to compute the value of
+** the next position.
+*/
+static void fts3ReadNextPos(
+  char **pp,                    /* IN/OUT: Pointer into position-list buffer */
+  sqlite3_int64 *pi             /* IN/OUT: Value read from position-list */
+){
+  if( (**pp)&0xFE ){
+    fts3GetDeltaVarint(pp, pi);
+    *pi -= 2;
+  }else{
+    *pi = POSITION_LIST_END;
+  }
+}
+
+/*
+** If parameter iCol is not 0, write an POS_COLUMN (1) byte followed by
+** the value of iCol encoded as a varint to *pp.   This will start a new
+** column list.
+**
+** Set *pp to point to the byte just after the last byte written before 
+** returning (do not modify it if iCol==0). Return the total number of bytes
+** written (0 if iCol==0).
+*/
+static int fts3PutColNumber(char **pp, int iCol){
+  int n = 0;                      /* Number of bytes written */
+  if( iCol ){
+    char *p = *pp;                /* Output pointer */
+    n = 1 + sqlite3Fts3PutVarint(&p[1], iCol);
+    *p = 0x01;
+    *pp = &p[n];
+  }
+  return n;
+}
+
+/*
+** Compute the union of two position lists.  The output written
+** into *pp contains all positions of both *pp1 and *pp2 in sorted
+** order and with any duplicates removed.  All pointers are
+** updated appropriately.   The caller is responsible for insuring
+** that there is enough space in *pp to hold the complete output.
+*/
+static void fts3PoslistMerge(
+  char **pp,                      /* Output buffer */
+  char **pp1,                     /* Left input list */
+  char **pp2                      /* Right input list */
+){
+  char *p = *pp;
+  char *p1 = *pp1;
+  char *p2 = *pp2;
+
+  while( *p1 || *p2 ){
+    int iCol1;         /* The current column index in pp1 */
+    int iCol2;         /* The current column index in pp2 */
+
+    if( *p1==POS_COLUMN ) fts3GetVarint32(&p1[1], &iCol1);
+    else if( *p1==POS_END ) iCol1 = POSITION_LIST_END;
+    else iCol1 = 0;
+
+    if( *p2==POS_COLUMN ) fts3GetVarint32(&p2[1], &iCol2);
+    else if( *p2==POS_END ) iCol2 = POSITION_LIST_END;
+    else iCol2 = 0;
+
+    if( iCol1==iCol2 ){
+      sqlite3_int64 i1 = 0;       /* Last position from pp1 */
+      sqlite3_int64 i2 = 0;       /* Last position from pp2 */
+      sqlite3_int64 iPrev = 0;
+      int n = fts3PutColNumber(&p, iCol1);
+      p1 += n;
+      p2 += n;
+
+      /* At this point, both p1 and p2 point to the start of column-lists
+      ** for the same column (the column with index iCol1 and iCol2).
+      ** A column-list is a list of non-negative delta-encoded varints, each 
+      ** incremented by 2 before being stored. Each list is terminated by a
+      ** POS_END (0) or POS_COLUMN (1). The following block merges the two lists
+      ** and writes the results to buffer p. p is left pointing to the byte
+      ** after the list written. No terminator (POS_END or POS_COLUMN) is
+      ** written to the output.
+      */
+      fts3GetDeltaVarint(&p1, &i1);
+      fts3GetDeltaVarint(&p2, &i2);
+      do {
+        fts3PutDeltaVarint(&p, &iPrev, (i1<i2) ? i1 : i2); 
+        iPrev -= 2;
+        if( i1==i2 ){
+          fts3ReadNextPos(&p1, &i1);
+          fts3ReadNextPos(&p2, &i2);
+        }else if( i1<i2 ){
+          fts3ReadNextPos(&p1, &i1);
+        }else{
+          fts3ReadNextPos(&p2, &i2);
+        }
+      }while( i1!=POSITION_LIST_END || i2!=POSITION_LIST_END );
+    }else if( iCol1<iCol2 ){
+      p1 += fts3PutColNumber(&p, iCol1);
+      fts3ColumnlistCopy(&p, &p1);
+    }else{
+      p2 += fts3PutColNumber(&p, iCol2);
+      fts3ColumnlistCopy(&p, &p2);
+    }
+  }
+
+  *p++ = POS_END;
+  *pp = p;
+  *pp1 = p1 + 1;
+  *pp2 = p2 + 1;
+}
+
+/*
+** This function is used to merge two position lists into one. When it is
+** called, *pp1 and *pp2 must both point to position lists. A position-list is
+** the part of a doclist that follows each document id. For example, if a row
+** contains:
+**
+**     'a b c'|'x y z'|'a b b a'
+**
+** Then the position list for this row for token 'b' would consist of:
+**
+**     0x02 0x01 0x02 0x03 0x03 0x00
+**
+** When this function returns, both *pp1 and *pp2 are left pointing to the
+** byte following the 0x00 terminator of their respective position lists.
+**
+** If isSaveLeft is 0, an entry is added to the output position list for 
+** each position in *pp2 for which there exists one or more positions in
+** *pp1 so that (pos(*pp2)>pos(*pp1) && pos(*pp2)-pos(*pp1)<=nToken). i.e.
+** when the *pp1 token appears before the *pp2 token, but not more than nToken
+** slots before it.
+**
+** e.g. nToken==1 searches for adjacent positions.
+*/
+static int fts3PoslistPhraseMerge(
+  char **pp,                      /* IN/OUT: Preallocated output buffer */
+  int nToken,                     /* Maximum difference in token positions */
+  int isSaveLeft,                 /* Save the left position */
+  int isExact,                    /* If *pp1 is exactly nTokens before *pp2 */
+  char **pp1,                     /* IN/OUT: Left input list */
+  char **pp2                      /* IN/OUT: Right input list */
+){
+  char *p = *pp;
+  char *p1 = *pp1;
+  char *p2 = *pp2;
+  int iCol1 = 0;
+  int iCol2 = 0;
+
+  /* Never set both isSaveLeft and isExact for the same invocation. */
+  assert( isSaveLeft==0 || isExact==0 );
+
+  assert( p!=0 && *p1!=0 && *p2!=0 );
+  if( *p1==POS_COLUMN ){ 
+    p1++;
+    p1 += fts3GetVarint32(p1, &iCol1);
+  }
+  if( *p2==POS_COLUMN ){ 
+    p2++;
+    p2 += fts3GetVarint32(p2, &iCol2);
+  }
+
+  while( 1 ){
+    if( iCol1==iCol2 ){
+      char *pSave = p;
+      sqlite3_int64 iPrev = 0;
+      sqlite3_int64 iPos1 = 0;
+      sqlite3_int64 iPos2 = 0;
+
+      if( iCol1 ){
+        *p++ = POS_COLUMN;
+        p += sqlite3Fts3PutVarint(p, iCol1);
+      }
+
+      assert( *p1!=POS_END && *p1!=POS_COLUMN );
+      assert( *p2!=POS_END && *p2!=POS_COLUMN );
+      fts3GetDeltaVarint(&p1, &iPos1); iPos1 -= 2;
+      fts3GetDeltaVarint(&p2, &iPos2); iPos2 -= 2;
+
+      while( 1 ){
+        if( iPos2==iPos1+nToken 
+         || (isExact==0 && iPos2>iPos1 && iPos2<=iPos1+nToken) 
+        ){
+          sqlite3_int64 iSave;
+          iSave = isSaveLeft ? iPos1 : iPos2;
+          fts3PutDeltaVarint(&p, &iPrev, iSave+2); iPrev -= 2;
+          pSave = 0;
+          assert( p );
+        }
+        if( (!isSaveLeft && iPos2<=(iPos1+nToken)) || iPos2<=iPos1 ){
+          if( (*p2&0xFE)==0 ) break;
+          fts3GetDeltaVarint(&p2, &iPos2); iPos2 -= 2;
+        }else{
+          if( (*p1&0xFE)==0 ) break;
+          fts3GetDeltaVarint(&p1, &iPos1); iPos1 -= 2;
+        }
+      }
+
+      if( pSave ){
+        assert( pp && p );
+        p = pSave;
+      }
+
+      fts3ColumnlistCopy(0, &p1);
+      fts3ColumnlistCopy(0, &p2);
+      assert( (*p1&0xFE)==0 && (*p2&0xFE)==0 );
+      if( 0==*p1 || 0==*p2 ) break;
+
+      p1++;
+      p1 += fts3GetVarint32(p1, &iCol1);
+      p2++;
+      p2 += fts3GetVarint32(p2, &iCol2);
+    }
+
+    /* Advance pointer p1 or p2 (whichever corresponds to the smaller of
+    ** iCol1 and iCol2) so that it points to either the 0x00 that marks the
+    ** end of the position list, or the 0x01 that precedes the next 
+    ** column-number in the position list. 
+    */
+    else if( iCol1<iCol2 ){
+      fts3ColumnlistCopy(0, &p1);
+      if( 0==*p1 ) break;
+      p1++;
+      p1 += fts3GetVarint32(p1, &iCol1);
+    }else{
+      fts3ColumnlistCopy(0, &p2);
+      if( 0==*p2 ) break;
+      p2++;
+      p2 += fts3GetVarint32(p2, &iCol2);
+    }
+  }
+
+  fts3PoslistCopy(0, &p2);
+  fts3PoslistCopy(0, &p1);
+  *pp1 = p1;
+  *pp2 = p2;
+  if( *pp==p ){
+    return 0;
+  }
+  *p++ = 0x00;
+  *pp = p;
+  return 1;
+}
+
+/*
+** Merge two position-lists as required by the NEAR operator. The argument
+** position lists correspond to the left and right phrases of an expression 
+** like:
+**
+**     "phrase 1" NEAR "phrase number 2"
+**
+** Position list *pp1 corresponds to the left-hand side of the NEAR 
+** expression and *pp2 to the right. As usual, the indexes in the position 
+** lists are the offsets of the last token in each phrase (tokens "1" and "2" 
+** in the example above).
+**
+** The output position list - written to *pp - is a copy of *pp2 with those
+** entries that are not sufficiently NEAR entries in *pp1 removed.
+*/
+static int fts3PoslistNearMerge(
+  char **pp,                      /* Output buffer */
+  char *aTmp,                     /* Temporary buffer space */
+  int nRight,                     /* Maximum difference in token positions */
+  int nLeft,                      /* Maximum difference in token positions */
+  char **pp1,                     /* IN/OUT: Left input list */
+  char **pp2                      /* IN/OUT: Right input list */
+){
+  char *p1 = *pp1;
+  char *p2 = *pp2;
+
+  char *pTmp1 = aTmp;
+  char *pTmp2;
+  char *aTmp2;
+  int res = 1;
+
+  fts3PoslistPhraseMerge(&pTmp1, nRight, 0, 0, pp1, pp2);
+  aTmp2 = pTmp2 = pTmp1;
+  *pp1 = p1;
+  *pp2 = p2;
+  fts3PoslistPhraseMerge(&pTmp2, nLeft, 1, 0, pp2, pp1);
+  if( pTmp1!=aTmp && pTmp2!=aTmp2 ){
+    fts3PoslistMerge(pp, &aTmp, &aTmp2);
+  }else if( pTmp1!=aTmp ){
+    fts3PoslistCopy(pp, &aTmp);
+  }else if( pTmp2!=aTmp2 ){
+    fts3PoslistCopy(pp, &aTmp2);
+  }else{
+    res = 0;
+  }
+
+  return res;
+}
+
+/* 
+** An instance of this function is used to merge together the (potentially
+** large number of) doclists for each term that matches a prefix query.
+** See function fts3TermSelectMerge() for details.
+*/
+typedef struct TermSelect TermSelect;
+struct TermSelect {
+  char *aaOutput[16];             /* Malloc'd output buffers */
+  int anOutput[16];               /* Size each output buffer in bytes */
+};
+
+/*
+** This function is used to read a single varint from a buffer. Parameter
+** pEnd points 1 byte past the end of the buffer. When this function is
+** called, if *pp points to pEnd or greater, then the end of the buffer
+** has been reached. In this case *pp is set to 0 and the function returns.
+**
+** If *pp does not point to or past pEnd, then a single varint is read
+** from *pp. *pp is then set to point 1 byte past the end of the read varint.
+**
+** If bDescIdx is false, the value read is added to *pVal before returning.
+** If it is true, the value read is subtracted from *pVal before this 
+** function returns.
+*/
+static void fts3GetDeltaVarint3(
+  char **pp,                      /* IN/OUT: Point to read varint from */
+  char *pEnd,                     /* End of buffer */
+  int bDescIdx,                   /* True if docids are descending */
+  sqlite3_int64 *pVal             /* IN/OUT: Integer value */
+){
+  if( *pp>=pEnd ){
+    *pp = 0;
+  }else{
+    sqlite3_int64 iVal;
+    *pp += sqlite3Fts3GetVarint(*pp, &iVal);
+    if( bDescIdx ){
+      *pVal -= iVal;
+    }else{
+      *pVal += iVal;
+    }
+  }
+}
+
+/*
+** This function is used to write a single varint to a buffer. The varint
+** is written to *pp. Before returning, *pp is set to point 1 byte past the
+** end of the value written.
+**
+** If *pbFirst is zero when this function is called, the value written to
+** the buffer is that of parameter iVal. 
+**
+** If *pbFirst is non-zero when this function is called, then the value 
+** written is either (iVal-*piPrev) (if bDescIdx is zero) or (*piPrev-iVal)
+** (if bDescIdx is non-zero).
+**
+** Before returning, this function always sets *pbFirst to 1 and *piPrev
+** to the value of parameter iVal.
+*/
+static void fts3PutDeltaVarint3(
+  char **pp,                      /* IN/OUT: Output pointer */
+  int bDescIdx,                   /* True for descending docids */
+  sqlite3_int64 *piPrev,          /* IN/OUT: Previous value written to list */
+  int *pbFirst,                   /* IN/OUT: True after first int written */
+  sqlite3_int64 iVal              /* Write this value to the list */
+){
+  sqlite3_int64 iWrite;
+  if( bDescIdx==0 || *pbFirst==0 ){
+    iWrite = iVal - *piPrev;
+  }else{
+    iWrite = *piPrev - iVal;
+  }
+  assert( *pbFirst || *piPrev==0 );
+  assert( *pbFirst==0 || iWrite>0 );
+  *pp += sqlite3Fts3PutVarint(*pp, iWrite);
+  *piPrev = iVal;
+  *pbFirst = 1;
+}
+
+
+/*
+** This macro is used by various functions that merge doclists. The two
+** arguments are 64-bit docid values. If the value of the stack variable
+** bDescDoclist is 0 when this macro is invoked, then it returns (i1-i2). 
+** Otherwise, (i2-i1).
+**
+** Using this makes it easier to write code that can merge doclists that are
+** sorted in either ascending or descending order.
+*/
+#define DOCID_CMP(i1, i2) ((bDescDoclist?-1:1) * (i1-i2))
+
+/*
+** This function does an "OR" merge of two doclists (output contains all
+** positions contained in either argument doclist). If the docids in the 
+** input doclists are sorted in ascending order, parameter bDescDoclist
+** should be false. If they are sorted in ascending order, it should be
+** passed a non-zero value.
+**
+** If no error occurs, *paOut is set to point at an sqlite3_malloc'd buffer
+** containing the output doclist and SQLITE_OK is returned. In this case
+** *pnOut is set to the number of bytes in the output doclist.
+**
+** If an error occurs, an SQLite error code is returned. The output values
+** are undefined in this case.
+*/
+static int fts3DoclistOrMerge(
+  int bDescDoclist,               /* True if arguments are desc */
+  char *a1, int n1,               /* First doclist */
+  char *a2, int n2,               /* Second doclist */
+  char **paOut, int *pnOut        /* OUT: Malloc'd doclist */
+){
+  sqlite3_int64 i1 = 0;
+  sqlite3_int64 i2 = 0;
+  sqlite3_int64 iPrev = 0;
+  char *pEnd1 = &a1[n1];
+  char *pEnd2 = &a2[n2];
+  char *p1 = a1;
+  char *p2 = a2;
+  char *p;
+  char *aOut;
+  int bFirstOut = 0;
+
+  *paOut = 0;
+  *pnOut = 0;
+
+  /* Allocate space for the output. Both the input and output doclists
+  ** are delta encoded. If they are in ascending order (bDescDoclist==0),
+  ** then the first docid in each list is simply encoded as a varint. For
+  ** each subsequent docid, the varint stored is the difference between the
+  ** current and previous docid (a positive number - since the list is in
+  ** ascending order).
+  **
+  ** The first docid written to the output is therefore encoded using the 
+  ** same number of bytes as it is in whichever of the input lists it is
+  ** read from. And each subsequent docid read from the same input list 
+  ** consumes either the same or less bytes as it did in the input (since
+  ** the difference between it and the previous value in the output must
+  ** be a positive value less than or equal to the delta value read from 
+  ** the input list). The same argument applies to all but the first docid
+  ** read from the 'other' list. And to the contents of all position lists
+  ** that will be copied and merged from the input to the output.
+  **
+  ** However, if the first docid copied to the output is a negative number,
+  ** then the encoding of the first docid from the 'other' input list may
+  ** be larger in the output than it was in the input (since the delta value
+  ** may be a larger positive integer than the actual docid).
+  **
+  ** The space required to store the output is therefore the sum of the
+  ** sizes of the two inputs, plus enough space for exactly one of the input
+  ** docids to grow. 
+  **
+  ** A symetric argument may be made if the doclists are in descending 
+  ** order.
+  */
+  aOut = sqlite3_malloc(n1+n2+FTS3_VARINT_MAX-1);
+  if( !aOut ) return SQLITE_NOMEM;
+
+  p = aOut;
+  fts3GetDeltaVarint3(&p1, pEnd1, 0, &i1);
+  fts3GetDeltaVarint3(&p2, pEnd2, 0, &i2);
+  while( p1 || p2 ){
+    sqlite3_int64 iDiff = DOCID_CMP(i1, i2);
+
+    if( p2 && p1 && iDiff==0 ){
+      fts3PutDeltaVarint3(&p, bDescDoclist, &iPrev, &bFirstOut, i1);
+      fts3PoslistMerge(&p, &p1, &p2);
+      fts3GetDeltaVarint3(&p1, pEnd1, bDescDoclist, &i1);
+      fts3GetDeltaVarint3(&p2, pEnd2, bDescDoclist, &i2);
+    }else if( !p2 || (p1 && iDiff<0) ){
+      fts3PutDeltaVarint3(&p, bDescDoclist, &iPrev, &bFirstOut, i1);
+      fts3PoslistCopy(&p, &p1);
+      fts3GetDeltaVarint3(&p1, pEnd1, bDescDoclist, &i1);
+    }else{
+      fts3PutDeltaVarint3(&p, bDescDoclist, &iPrev, &bFirstOut, i2);
+      fts3PoslistCopy(&p, &p2);
+      fts3GetDeltaVarint3(&p2, pEnd2, bDescDoclist, &i2);
+    }
+  }
+
+  *paOut = aOut;
+  *pnOut = (int)(p-aOut);
+  assert( *pnOut<=n1+n2+FTS3_VARINT_MAX-1 );
+  return SQLITE_OK;
+}
+
+/*
+** This function does a "phrase" merge of two doclists. In a phrase merge,
+** the output contains a copy of each position from the right-hand input
+** doclist for which there is a position in the left-hand input doclist
+** exactly nDist tokens before it.
+**
+** If the docids in the input doclists are sorted in ascending order,
+** parameter bDescDoclist should be false. If they are sorted in ascending 
+** order, it should be passed a non-zero value.
+**
+** The right-hand input doclist is overwritten by this function.
+*/
+static int fts3DoclistPhraseMerge(
+  int bDescDoclist,               /* True if arguments are desc */
+  int nDist,                      /* Distance from left to right (1=adjacent) */
+  char *aLeft, int nLeft,         /* Left doclist */
+  char **paRight, int *pnRight    /* IN/OUT: Right/output doclist */
+){
+  sqlite3_int64 i1 = 0;
+  sqlite3_int64 i2 = 0;
+  sqlite3_int64 iPrev = 0;
+  char *aRight = *paRight;
+  char *pEnd1 = &aLeft[nLeft];
+  char *pEnd2 = &aRight[*pnRight];
+  char *p1 = aLeft;
+  char *p2 = aRight;
+  char *p;
+  int bFirstOut = 0;
+  char *aOut;
+
+  assert( nDist>0 );
+  if( bDescDoclist ){
+    aOut = sqlite3_malloc(*pnRight + FTS3_VARINT_MAX);
+    if( aOut==0 ) return SQLITE_NOMEM;
+  }else{
+    aOut = aRight;
+  }
+  p = aOut;
+
+  fts3GetDeltaVarint3(&p1, pEnd1, 0, &i1);
+  fts3GetDeltaVarint3(&p2, pEnd2, 0, &i2);
+
+  while( p1 && p2 ){
+    sqlite3_int64 iDiff = DOCID_CMP(i1, i2);
+    if( iDiff==0 ){
+      char *pSave = p;
+      sqlite3_int64 iPrevSave = iPrev;
+      int bFirstOutSave = bFirstOut;
+
+      fts3PutDeltaVarint3(&p, bDescDoclist, &iPrev, &bFirstOut, i1);
+      if( 0==fts3PoslistPhraseMerge(&p, nDist, 0, 1, &p1, &p2) ){
+        p = pSave;
+        iPrev = iPrevSave;
+        bFirstOut = bFirstOutSave;
+      }
+      fts3GetDeltaVarint3(&p1, pEnd1, bDescDoclist, &i1);
+      fts3GetDeltaVarint3(&p2, pEnd2, bDescDoclist, &i2);
+    }else if( iDiff<0 ){
+      fts3PoslistCopy(0, &p1);
+      fts3GetDeltaVarint3(&p1, pEnd1, bDescDoclist, &i1);
+    }else{
+      fts3PoslistCopy(0, &p2);
+      fts3GetDeltaVarint3(&p2, pEnd2, bDescDoclist, &i2);
+    }
+  }
+
+  *pnRight = (int)(p - aOut);
+  if( bDescDoclist ){
+    sqlite3_free(aRight);
+    *paRight = aOut;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Argument pList points to a position list nList bytes in size. This
+** function checks to see if the position list contains any entries for
+** a token in position 0 (of any column). If so, it writes argument iDelta
+** to the output buffer pOut, followed by a position list consisting only
+** of the entries from pList at position 0, and terminated by an 0x00 byte.
+** The value returned is the number of bytes written to pOut (if any).
+*/
+SQLITE_PRIVATE int sqlite3Fts3FirstFilter(
+  sqlite3_int64 iDelta,           /* Varint that may be written to pOut */
+  char *pList,                    /* Position list (no 0x00 term) */
+  int nList,                      /* Size of pList in bytes */
+  char *pOut                      /* Write output here */
+){
+  int nOut = 0;
+  int bWritten = 0;               /* True once iDelta has been written */
+  char *p = pList;
+  char *pEnd = &pList[nList];
+
+  if( *p!=0x01 ){
+    if( *p==0x02 ){
+      nOut += sqlite3Fts3PutVarint(&pOut[nOut], iDelta);
+      pOut[nOut++] = 0x02;
+      bWritten = 1;
+    }
+    fts3ColumnlistCopy(0, &p);
+  }
+
+  while( p<pEnd && *p==0x01 ){
+    sqlite3_int64 iCol;
+    p++;
+    p += sqlite3Fts3GetVarint(p, &iCol);
+    if( *p==0x02 ){
+      if( bWritten==0 ){
+        nOut += sqlite3Fts3PutVarint(&pOut[nOut], iDelta);
+        bWritten = 1;
+      }
+      pOut[nOut++] = 0x01;
+      nOut += sqlite3Fts3PutVarint(&pOut[nOut], iCol);
+      pOut[nOut++] = 0x02;
+    }
+    fts3ColumnlistCopy(0, &p);
+  }
+  if( bWritten ){
+    pOut[nOut++] = 0x00;
+  }
+
+  return nOut;
+}
+
+
+/*
+** Merge all doclists in the TermSelect.aaOutput[] array into a single
+** doclist stored in TermSelect.aaOutput[0]. If successful, delete all
+** other doclists (except the aaOutput[0] one) and return SQLITE_OK.
+**
+** If an OOM error occurs, return SQLITE_NOMEM. In this case it is
+** the responsibility of the caller to free any doclists left in the
+** TermSelect.aaOutput[] array.
+*/
+static int fts3TermSelectFinishMerge(Fts3Table *p, TermSelect *pTS){
+  char *aOut = 0;
+  int nOut = 0;
+  int i;
+
+  /* Loop through the doclists in the aaOutput[] array. Merge them all
+  ** into a single doclist.
+  */
+  for(i=0; i<SizeofArray(pTS->aaOutput); i++){
+    if( pTS->aaOutput[i] ){
+      if( !aOut ){
+        aOut = pTS->aaOutput[i];
+        nOut = pTS->anOutput[i];
+        pTS->aaOutput[i] = 0;
+      }else{
+        int nNew;
+        char *aNew;
+
+        int rc = fts3DoclistOrMerge(p->bDescIdx, 
+            pTS->aaOutput[i], pTS->anOutput[i], aOut, nOut, &aNew, &nNew
+        );
+        if( rc!=SQLITE_OK ){
+          sqlite3_free(aOut);
+          return rc;
+        }
+
+        sqlite3_free(pTS->aaOutput[i]);
+        sqlite3_free(aOut);
+        pTS->aaOutput[i] = 0;
+        aOut = aNew;
+        nOut = nNew;
+      }
+    }
+  }
+
+  pTS->aaOutput[0] = aOut;
+  pTS->anOutput[0] = nOut;
+  return SQLITE_OK;
+}
+
+/*
+** Merge the doclist aDoclist/nDoclist into the TermSelect object passed
+** as the first argument. The merge is an "OR" merge (see function
+** fts3DoclistOrMerge() for details).
+**
+** This function is called with the doclist for each term that matches
+** a queried prefix. It merges all these doclists into one, the doclist
+** for the specified prefix. Since there can be a very large number of
+** doclists to merge, the merging is done pair-wise using the TermSelect
+** object.
+**
+** This function returns SQLITE_OK if the merge is successful, or an
+** SQLite error code (SQLITE_NOMEM) if an error occurs.
+*/
+static int fts3TermSelectMerge(
+  Fts3Table *p,                   /* FTS table handle */
+  TermSelect *pTS,                /* TermSelect object to merge into */
+  char *aDoclist,                 /* Pointer to doclist */
+  int nDoclist                    /* Size of aDoclist in bytes */
+){
+  if( pTS->aaOutput[0]==0 ){
+    /* If this is the first term selected, copy the doclist to the output
+    ** buffer using memcpy(). 
+    **
+    ** Add FTS3_VARINT_MAX bytes of unused space to the end of the 
+    ** allocation. This is so as to ensure that the buffer is big enough
+    ** to hold the current doclist AND'd with any other doclist. If the
+    ** doclists are stored in order=ASC order, this padding would not be
+    ** required (since the size of [doclistA AND doclistB] is always less
+    ** than or equal to the size of [doclistA] in that case). But this is
+    ** not true for order=DESC. For example, a doclist containing (1, -1) 
+    ** may be smaller than (-1), as in the first example the -1 may be stored
+    ** as a single-byte delta, whereas in the second it must be stored as a
+    ** FTS3_VARINT_MAX byte varint.
+    **
+    ** Similar padding is added in the fts3DoclistOrMerge() function.
+    */
+    pTS->aaOutput[0] = sqlite3_malloc(nDoclist + FTS3_VARINT_MAX + 1);
+    pTS->anOutput[0] = nDoclist;
+    if( pTS->aaOutput[0] ){
+      memcpy(pTS->aaOutput[0], aDoclist, nDoclist);
+    }else{
+      return SQLITE_NOMEM;
+    }
+  }else{
+    char *aMerge = aDoclist;
+    int nMerge = nDoclist;
+    int iOut;
+
+    for(iOut=0; iOut<SizeofArray(pTS->aaOutput); iOut++){
+      if( pTS->aaOutput[iOut]==0 ){
+        assert( iOut>0 );
+        pTS->aaOutput[iOut] = aMerge;
+        pTS->anOutput[iOut] = nMerge;
+        break;
+      }else{
+        char *aNew;
+        int nNew;
+
+        int rc = fts3DoclistOrMerge(p->bDescIdx, aMerge, nMerge, 
+            pTS->aaOutput[iOut], pTS->anOutput[iOut], &aNew, &nNew
+        );
+        if( rc!=SQLITE_OK ){
+          if( aMerge!=aDoclist ) sqlite3_free(aMerge);
+          return rc;
+        }
+
+        if( aMerge!=aDoclist ) sqlite3_free(aMerge);
+        sqlite3_free(pTS->aaOutput[iOut]);
+        pTS->aaOutput[iOut] = 0;
+  
+        aMerge = aNew;
+        nMerge = nNew;
+        if( (iOut+1)==SizeofArray(pTS->aaOutput) ){
+          pTS->aaOutput[iOut] = aMerge;
+          pTS->anOutput[iOut] = nMerge;
+        }
+      }
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Append SegReader object pNew to the end of the pCsr->apSegment[] array.
+*/
+static int fts3SegReaderCursorAppend(
+  Fts3MultiSegReader *pCsr, 
+  Fts3SegReader *pNew
+){
+  if( (pCsr->nSegment%16)==0 ){
+    Fts3SegReader **apNew;
+    int nByte = (pCsr->nSegment + 16)*sizeof(Fts3SegReader*);
+    apNew = (Fts3SegReader **)sqlite3_realloc(pCsr->apSegment, nByte);
+    if( !apNew ){
+      sqlite3Fts3SegReaderFree(pNew);
+      return SQLITE_NOMEM;
+    }
+    pCsr->apSegment = apNew;
+  }
+  pCsr->apSegment[pCsr->nSegment++] = pNew;
+  return SQLITE_OK;
+}
+
+/*
+** Add seg-reader objects to the Fts3MultiSegReader object passed as the
+** 8th argument.
+**
+** This function returns SQLITE_OK if successful, or an SQLite error code
+** otherwise.
+*/
+static int fts3SegReaderCursor(
+  Fts3Table *p,                   /* FTS3 table handle */
+  int iLangid,                    /* Language id */
+  int iIndex,                     /* Index to search (from 0 to p->nIndex-1) */
+  int iLevel,                     /* Level of segments to scan */
+  const char *zTerm,              /* Term to query for */
+  int nTerm,                      /* Size of zTerm in bytes */
+  int isPrefix,                   /* True for a prefix search */
+  int isScan,                     /* True to scan from zTerm to EOF */
+  Fts3MultiSegReader *pCsr        /* Cursor object to populate */
+){
+  int rc = SQLITE_OK;             /* Error code */
+  sqlite3_stmt *pStmt = 0;        /* Statement to iterate through segments */
+  int rc2;                        /* Result of sqlite3_reset() */
+
+  /* If iLevel is less than 0 and this is not a scan, include a seg-reader 
+  ** for the pending-terms. If this is a scan, then this call must be being
+  ** made by an fts4aux module, not an FTS table. In this case calling
+  ** Fts3SegReaderPending might segfault, as the data structures used by 
+  ** fts4aux are not completely populated. So it's easiest to filter these
+  ** calls out here.  */
+  if( iLevel<0 && p->aIndex ){
+    Fts3SegReader *pSeg = 0;
+    rc = sqlite3Fts3SegReaderPending(p, iIndex, zTerm, nTerm, isPrefix||isScan, &pSeg);
+    if( rc==SQLITE_OK && pSeg ){
+      rc = fts3SegReaderCursorAppend(pCsr, pSeg);
+    }
+  }
+
+  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
+    if( rc==SQLITE_OK ){
+      rc = sqlite3Fts3AllSegdirs(p, iLangid, iIndex, iLevel, &pStmt);
+    }
+
+    while( rc==SQLITE_OK && SQLITE_ROW==(rc = sqlite3_step(pStmt)) ){
+      Fts3SegReader *pSeg = 0;
+
+      /* Read the values returned by the SELECT into local variables. */
+      sqlite3_int64 iStartBlock = sqlite3_column_int64(pStmt, 1);
+      sqlite3_int64 iLeavesEndBlock = sqlite3_column_int64(pStmt, 2);
+      sqlite3_int64 iEndBlock = sqlite3_column_int64(pStmt, 3);
+      int nRoot = sqlite3_column_bytes(pStmt, 4);
+      char const *zRoot = sqlite3_column_blob(pStmt, 4);
+
+      /* If zTerm is not NULL, and this segment is not stored entirely on its
+      ** root node, the range of leaves scanned can be reduced. Do this. */
+      if( iStartBlock && zTerm ){
+        sqlite3_int64 *pi = (isPrefix ? &iLeavesEndBlock : 0);
+        rc = fts3SelectLeaf(p, zTerm, nTerm, zRoot, nRoot, &iStartBlock, pi);
+        if( rc!=SQLITE_OK ) goto finished;
+        if( isPrefix==0 && isScan==0 ) iLeavesEndBlock = iStartBlock;
+      }
+ 
+      rc = sqlite3Fts3SegReaderNew(pCsr->nSegment+1, 
+          (isPrefix==0 && isScan==0),
+          iStartBlock, iLeavesEndBlock, 
+          iEndBlock, zRoot, nRoot, &pSeg
+      );
+      if( rc!=SQLITE_OK ) goto finished;
+      rc = fts3SegReaderCursorAppend(pCsr, pSeg);
+    }
+  }
+
+ finished:
+  rc2 = sqlite3_reset(pStmt);
+  if( rc==SQLITE_DONE ) rc = rc2;
+
+  return rc;
+}
+
+/*
+** Set up a cursor object for iterating through a full-text index or a 
+** single level therein.
+*/
+SQLITE_PRIVATE int sqlite3Fts3SegReaderCursor(
+  Fts3Table *p,                   /* FTS3 table handle */
+  int iLangid,                    /* Language-id to search */
+  int iIndex,                     /* Index to search (from 0 to p->nIndex-1) */
+  int iLevel,                     /* Level of segments to scan */
+  const char *zTerm,              /* Term to query for */
+  int nTerm,                      /* Size of zTerm in bytes */
+  int isPrefix,                   /* True for a prefix search */
+  int isScan,                     /* True to scan from zTerm to EOF */
+  Fts3MultiSegReader *pCsr       /* Cursor object to populate */
+){
+  assert( iIndex>=0 && iIndex<p->nIndex );
+  assert( iLevel==FTS3_SEGCURSOR_ALL
+      ||  iLevel==FTS3_SEGCURSOR_PENDING 
+      ||  iLevel>=0
+  );
+  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
+  assert( FTS3_SEGCURSOR_ALL<0 && FTS3_SEGCURSOR_PENDING<0 );
+  assert( isPrefix==0 || isScan==0 );
+
+  memset(pCsr, 0, sizeof(Fts3MultiSegReader));
+  return fts3SegReaderCursor(
+      p, iLangid, iIndex, iLevel, zTerm, nTerm, isPrefix, isScan, pCsr
+  );
+}
+
+/*
+** In addition to its current configuration, have the Fts3MultiSegReader
+** passed as the 4th argument also scan the doclist for term zTerm/nTerm.
+**
+** SQLITE_OK is returned if no error occurs, otherwise an SQLite error code.
+*/
+static int fts3SegReaderCursorAddZero(
+  Fts3Table *p,                   /* FTS virtual table handle */
+  int iLangid,
+  const char *zTerm,              /* Term to scan doclist of */
+  int nTerm,                      /* Number of bytes in zTerm */
+  Fts3MultiSegReader *pCsr        /* Fts3MultiSegReader to modify */
+){
+  return fts3SegReaderCursor(p, 
+      iLangid, 0, FTS3_SEGCURSOR_ALL, zTerm, nTerm, 0, 0,pCsr
+  );
+}
+
+/*
+** Open an Fts3MultiSegReader to scan the doclist for term zTerm/nTerm. Or,
+** if isPrefix is true, to scan the doclist for all terms for which 
+** zTerm/nTerm is a prefix. If successful, return SQLITE_OK and write
+** a pointer to the new Fts3MultiSegReader to *ppSegcsr. Otherwise, return
+** an SQLite error code.
+**
+** It is the responsibility of the caller to free this object by eventually
+** passing it to fts3SegReaderCursorFree() 
+**
+** SQLITE_OK is returned if no error occurs, otherwise an SQLite error code.
+** Output parameter *ppSegcsr is set to 0 if an error occurs.
+*/
+static int fts3TermSegReaderCursor(
+  Fts3Cursor *pCsr,               /* Virtual table cursor handle */
+  const char *zTerm,              /* Term to query for */
+  int nTerm,                      /* Size of zTerm in bytes */
+  int isPrefix,                   /* True for a prefix search */
+  Fts3MultiSegReader **ppSegcsr   /* OUT: Allocated seg-reader cursor */
+){
+  Fts3MultiSegReader *pSegcsr;    /* Object to allocate and return */
+  int rc = SQLITE_NOMEM;          /* Return code */
+
+  pSegcsr = sqlite3_malloc(sizeof(Fts3MultiSegReader));
+  if( pSegcsr ){
+    int i;
+    int bFound = 0;               /* True once an index has been found */
+    Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
+
+    if( isPrefix ){
+      for(i=1; bFound==0 && i<p->nIndex; i++){
+        if( p->aIndex[i].nPrefix==nTerm ){
+          bFound = 1;
+          rc = sqlite3Fts3SegReaderCursor(p, pCsr->iLangid, 
+              i, FTS3_SEGCURSOR_ALL, zTerm, nTerm, 0, 0, pSegcsr
+          );
+          pSegcsr->bLookup = 1;
+        }
+      }
+
+      for(i=1; bFound==0 && i<p->nIndex; i++){
+        if( p->aIndex[i].nPrefix==nTerm+1 ){
+          bFound = 1;
+          rc = sqlite3Fts3SegReaderCursor(p, pCsr->iLangid, 
+              i, FTS3_SEGCURSOR_ALL, zTerm, nTerm, 1, 0, pSegcsr
+          );
+          if( rc==SQLITE_OK ){
+            rc = fts3SegReaderCursorAddZero(
+                p, pCsr->iLangid, zTerm, nTerm, pSegcsr
+            );
+          }
+        }
+      }
+    }
+
+    if( bFound==0 ){
+      rc = sqlite3Fts3SegReaderCursor(p, pCsr->iLangid, 
+          0, FTS3_SEGCURSOR_ALL, zTerm, nTerm, isPrefix, 0, pSegcsr
+      );
+      pSegcsr->bLookup = !isPrefix;
+    }
+  }
+
+  *ppSegcsr = pSegcsr;
+  return rc;
+}
+
+/*
+** Free an Fts3MultiSegReader allocated by fts3TermSegReaderCursor().
+*/
+static void fts3SegReaderCursorFree(Fts3MultiSegReader *pSegcsr){
+  sqlite3Fts3SegReaderFinish(pSegcsr);
+  sqlite3_free(pSegcsr);
+}
+
+/*
+** This function retrieves the doclist for the specified term (or term
+** prefix) from the database.
+*/
+static int fts3TermSelect(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3PhraseToken *pTok,          /* Token to query for */
+  int iColumn,                    /* Column to query (or -ve for all columns) */
+  int *pnOut,                     /* OUT: Size of buffer at *ppOut */
+  char **ppOut                    /* OUT: Malloced result buffer */
+){
+  int rc;                         /* Return code */
+  Fts3MultiSegReader *pSegcsr;    /* Seg-reader cursor for this term */
+  TermSelect tsc;                 /* Object for pair-wise doclist merging */
+  Fts3SegFilter filter;           /* Segment term filter configuration */
+
+  pSegcsr = pTok->pSegcsr;
+  memset(&tsc, 0, sizeof(TermSelect));
+
+  filter.flags = FTS3_SEGMENT_IGNORE_EMPTY | FTS3_SEGMENT_REQUIRE_POS
+        | (pTok->isPrefix ? FTS3_SEGMENT_PREFIX : 0)
+        | (pTok->bFirst ? FTS3_SEGMENT_FIRST : 0)
+        | (iColumn<p->nColumn ? FTS3_SEGMENT_COLUMN_FILTER : 0);
+  filter.iCol = iColumn;
+  filter.zTerm = pTok->z;
+  filter.nTerm = pTok->n;
+
+  rc = sqlite3Fts3SegReaderStart(p, pSegcsr, &filter);
+  while( SQLITE_OK==rc
+      && SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, pSegcsr)) 
+  ){
+    rc = fts3TermSelectMerge(p, &tsc, pSegcsr->aDoclist, pSegcsr->nDoclist);
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = fts3TermSelectFinishMerge(p, &tsc);
+  }
+  if( rc==SQLITE_OK ){
+    *ppOut = tsc.aaOutput[0];
+    *pnOut = tsc.anOutput[0];
+  }else{
+    int i;
+    for(i=0; i<SizeofArray(tsc.aaOutput); i++){
+      sqlite3_free(tsc.aaOutput[i]);
+    }
+  }
+
+  fts3SegReaderCursorFree(pSegcsr);
+  pTok->pSegcsr = 0;
+  return rc;
+}
+
+/*
+** This function counts the total number of docids in the doclist stored
+** in buffer aList[], size nList bytes.
+**
+** If the isPoslist argument is true, then it is assumed that the doclist
+** contains a position-list following each docid. Otherwise, it is assumed
+** that the doclist is simply a list of docids stored as delta encoded 
+** varints.
+*/
+static int fts3DoclistCountDocids(char *aList, int nList){
+  int nDoc = 0;                   /* Return value */
+  if( aList ){
+    char *aEnd = &aList[nList];   /* Pointer to one byte after EOF */
+    char *p = aList;              /* Cursor */
+    while( p<aEnd ){
+      nDoc++;
+      while( (*p++)&0x80 );     /* Skip docid varint */
+      fts3PoslistCopy(0, &p);   /* Skip over position list */
+    }
+  }
+
+  return nDoc;
+}
+
+/*
+** Advance the cursor to the next row in the %_content table that
+** matches the search criteria.  For a MATCH search, this will be
+** the next row that matches. For a full-table scan, this will be
+** simply the next row in the %_content table.  For a docid lookup,
+** this routine simply sets the EOF flag.
+**
+** Return SQLITE_OK if nothing goes wrong.  SQLITE_OK is returned
+** even if we reach end-of-file.  The fts3EofMethod() will be called
+** subsequently to determine whether or not an EOF was hit.
+*/
+static int fts3NextMethod(sqlite3_vtab_cursor *pCursor){
+  int rc;
+  Fts3Cursor *pCsr = (Fts3Cursor *)pCursor;
+  if( pCsr->eSearch==FTS3_DOCID_SEARCH || pCsr->eSearch==FTS3_FULLSCAN_SEARCH ){
+    if( SQLITE_ROW!=sqlite3_step(pCsr->pStmt) ){
+      pCsr->isEof = 1;
+      rc = sqlite3_reset(pCsr->pStmt);
+    }else{
+      pCsr->iPrevId = sqlite3_column_int64(pCsr->pStmt, 0);
+      rc = SQLITE_OK;
+    }
+  }else{
+    rc = fts3EvalNext((Fts3Cursor *)pCursor);
+  }
+  assert( ((Fts3Table *)pCsr->base.pVtab)->pSegments==0 );
+  return rc;
+}
+
+/*
+** The following are copied from sqliteInt.h.
+**
+** Constants for the largest and smallest possible 64-bit signed integers.
+** These macros are designed to work correctly on both 32-bit and 64-bit
+** compilers.
+*/
+#ifndef SQLITE_AMALGAMATION
+# define LARGEST_INT64  (0xffffffff|(((sqlite3_int64)0x7fffffff)<<32))
+# define SMALLEST_INT64 (((sqlite3_int64)-1) - LARGEST_INT64)
+#endif
+
+/*
+** If the numeric type of argument pVal is "integer", then return it
+** converted to a 64-bit signed integer. Otherwise, return a copy of
+** the second parameter, iDefault.
+*/
+static sqlite3_int64 fts3DocidRange(sqlite3_value *pVal, i64 iDefault){
+  if( pVal ){
+    int eType = sqlite3_value_numeric_type(pVal);
+    if( eType==SQLITE_INTEGER ){
+      return sqlite3_value_int64(pVal);
+    }
+  }
+  return iDefault;
+}
+
+/*
+** This is the xFilter interface for the virtual table.  See
+** the virtual table xFilter method documentation for additional
+** information.
+**
+** If idxNum==FTS3_FULLSCAN_SEARCH then do a full table scan against
+** the %_content table.
+**
+** If idxNum==FTS3_DOCID_SEARCH then do a docid lookup for a single entry
+** in the %_content table.
+**
+** If idxNum>=FTS3_FULLTEXT_SEARCH then use the full text index.  The
+** column on the left-hand side of the MATCH operator is column
+** number idxNum-FTS3_FULLTEXT_SEARCH, 0 indexed.  argv[0] is the right-hand
+** side of the MATCH operator.
+*/
+static int fts3FilterMethod(
+  sqlite3_vtab_cursor *pCursor,   /* The cursor used for this query */
+  int idxNum,                     /* Strategy index */
+  const char *idxStr,             /* Unused */
+  int nVal,                       /* Number of elements in apVal */
+  sqlite3_value **apVal           /* Arguments for the indexing scheme */
+){
+  int rc = SQLITE_OK;
+  char *zSql;                     /* SQL statement used to access %_content */
+  int eSearch;
+  Fts3Table *p = (Fts3Table *)pCursor->pVtab;
+  Fts3Cursor *pCsr = (Fts3Cursor *)pCursor;
+
+  sqlite3_value *pCons = 0;       /* The MATCH or rowid constraint, if any */
+  sqlite3_value *pLangid = 0;     /* The "langid = ?" constraint, if any */
+  sqlite3_value *pDocidGe = 0;    /* The "docid >= ?" constraint, if any */
+  sqlite3_value *pDocidLe = 0;    /* The "docid <= ?" constraint, if any */
+  int iIdx;
+
+  UNUSED_PARAMETER(idxStr);
+  UNUSED_PARAMETER(nVal);
+
+  eSearch = (idxNum & 0x0000FFFF);
+  assert( eSearch>=0 && eSearch<=(FTS3_FULLTEXT_SEARCH+p->nColumn) );
+  assert( p->pSegments==0 );
+
+  /* Collect arguments into local variables */
+  iIdx = 0;
+  if( eSearch!=FTS3_FULLSCAN_SEARCH ) pCons = apVal[iIdx++];
+  if( idxNum & FTS3_HAVE_LANGID ) pLangid = apVal[iIdx++];
+  if( idxNum & FTS3_HAVE_DOCID_GE ) pDocidGe = apVal[iIdx++];
+  if( idxNum & FTS3_HAVE_DOCID_LE ) pDocidLe = apVal[iIdx++];
+  assert( iIdx==nVal );
+
+  /* In case the cursor has been used before, clear it now. */
+  fts3CursorFinalizeStmt(pCsr);
+  sqlite3_free(pCsr->aDoclist);
+  sqlite3Fts3MIBufferFree(pCsr->pMIBuffer);
+  sqlite3Fts3ExprFree(pCsr->pExpr);
+  memset(&pCursor[1], 0, sizeof(Fts3Cursor)-sizeof(sqlite3_vtab_cursor));
+
+  /* Set the lower and upper bounds on docids to return */
+  pCsr->iMinDocid = fts3DocidRange(pDocidGe, SMALLEST_INT64);
+  pCsr->iMaxDocid = fts3DocidRange(pDocidLe, LARGEST_INT64);
+
+  if( idxStr ){
+    pCsr->bDesc = (idxStr[0]=='D');
+  }else{
+    pCsr->bDesc = p->bDescIdx;
+  }
+  pCsr->eSearch = (i16)eSearch;
+
+  if( eSearch!=FTS3_DOCID_SEARCH && eSearch!=FTS3_FULLSCAN_SEARCH ){
+    int iCol = eSearch-FTS3_FULLTEXT_SEARCH;
+    const char *zQuery = (const char *)sqlite3_value_text(pCons);
+
+    if( zQuery==0 && sqlite3_value_type(pCons)!=SQLITE_NULL ){
+      return SQLITE_NOMEM;
+    }
+
+    pCsr->iLangid = 0;
+    if( pLangid ) pCsr->iLangid = sqlite3_value_int(pLangid);
+
+    assert( p->base.zErrMsg==0 );
+    rc = sqlite3Fts3ExprParse(p->pTokenizer, pCsr->iLangid,
+        p->azColumn, p->bFts4, p->nColumn, iCol, zQuery, -1, &pCsr->pExpr, 
+        &p->base.zErrMsg
+    );
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+
+    rc = fts3EvalStart(pCsr);
+    sqlite3Fts3SegmentsClose(p);
+    if( rc!=SQLITE_OK ) return rc;
+    pCsr->pNextId = pCsr->aDoclist;
+    pCsr->iPrevId = 0;
+  }
+
+  /* Compile a SELECT statement for this cursor. For a full-table-scan, the
+  ** statement loops through all rows of the %_content table. For a
+  ** full-text query or docid lookup, the statement retrieves a single
+  ** row by docid.
+  */
+  if( eSearch==FTS3_FULLSCAN_SEARCH ){
+    if( pDocidGe || pDocidLe ){
+      zSql = sqlite3_mprintf(
+          "SELECT %s WHERE rowid BETWEEN %lld AND %lld ORDER BY rowid %s",
+          p->zReadExprlist, pCsr->iMinDocid, pCsr->iMaxDocid,
+          (pCsr->bDesc ? "DESC" : "ASC")
+      );
+    }else{
+      zSql = sqlite3_mprintf("SELECT %s ORDER BY rowid %s", 
+          p->zReadExprlist, (pCsr->bDesc ? "DESC" : "ASC")
+      );
+    }
+    if( zSql ){
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pCsr->pStmt, 0);
+      sqlite3_free(zSql);
+    }else{
+      rc = SQLITE_NOMEM;
+    }
+  }else if( eSearch==FTS3_DOCID_SEARCH ){
+    rc = fts3CursorSeekStmt(pCsr);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3_bind_value(pCsr->pStmt, 1, pCons);
+    }
+  }
+  if( rc!=SQLITE_OK ) return rc;
+
+  return fts3NextMethod(pCursor);
+}
+
+/* 
+** This is the xEof method of the virtual table. SQLite calls this 
+** routine to find out if it has reached the end of a result set.
+*/
+static int fts3EofMethod(sqlite3_vtab_cursor *pCursor){
+  return ((Fts3Cursor *)pCursor)->isEof;
+}
+
+/* 
+** This is the xRowid method. The SQLite core calls this routine to
+** retrieve the rowid for the current row of the result set. fts3
+** exposes %_content.docid as the rowid for the virtual table. The
+** rowid should be written to *pRowid.
+*/
+static int fts3RowidMethod(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
+  Fts3Cursor *pCsr = (Fts3Cursor *) pCursor;
+  *pRowid = pCsr->iPrevId;
+  return SQLITE_OK;
+}
+
+/* 
+** This is the xColumn method, called by SQLite to request a value from
+** the row that the supplied cursor currently points to.
+**
+** If:
+**
+**   (iCol <  p->nColumn)   -> The value of the iCol'th user column.
+**   (iCol == p->nColumn)   -> Magic column with the same name as the table.
+**   (iCol == p->nColumn+1) -> Docid column
+**   (iCol == p->nColumn+2) -> Langid column
+*/
+static int fts3ColumnMethod(
+  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
+  sqlite3_context *pCtx,          /* Context for sqlite3_result_xxx() calls */
+  int iCol                        /* Index of column to read value from */
+){
+  int rc = SQLITE_OK;             /* Return Code */
+  Fts3Cursor *pCsr = (Fts3Cursor *) pCursor;
+  Fts3Table *p = (Fts3Table *)pCursor->pVtab;
+
+  /* The column value supplied by SQLite must be in range. */
+  assert( iCol>=0 && iCol<=p->nColumn+2 );
+
+  if( iCol==p->nColumn+1 ){
+    /* This call is a request for the "docid" column. Since "docid" is an 
+    ** alias for "rowid", use the xRowid() method to obtain the value.
+    */
+    sqlite3_result_int64(pCtx, pCsr->iPrevId);
+  }else if( iCol==p->nColumn ){
+    /* The extra column whose name is the same as the table.
+    ** Return a blob which is a pointer to the cursor.  */
+    sqlite3_result_blob(pCtx, &pCsr, sizeof(pCsr), SQLITE_TRANSIENT);
+  }else if( iCol==p->nColumn+2 && pCsr->pExpr ){
+    sqlite3_result_int64(pCtx, pCsr->iLangid);
+  }else{
+    /* The requested column is either a user column (one that contains 
+    ** indexed data), or the language-id column.  */
+    rc = fts3CursorSeek(0, pCsr);
+
+    if( rc==SQLITE_OK ){
+      if( iCol==p->nColumn+2 ){
+        int iLangid = 0;
+        if( p->zLanguageid ){
+          iLangid = sqlite3_column_int(pCsr->pStmt, p->nColumn+1);
+        }
+        sqlite3_result_int(pCtx, iLangid);
+      }else if( sqlite3_data_count(pCsr->pStmt)>(iCol+1) ){
+        sqlite3_result_value(pCtx, sqlite3_column_value(pCsr->pStmt, iCol+1));
+      }
+    }
+  }
+
+  assert( ((Fts3Table *)pCsr->base.pVtab)->pSegments==0 );
+  return rc;
+}
+
+/* 
+** This function is the implementation of the xUpdate callback used by 
+** FTS3 virtual tables. It is invoked by SQLite each time a row is to be
+** inserted, updated or deleted.
+*/
+static int fts3UpdateMethod(
+  sqlite3_vtab *pVtab,            /* Virtual table handle */
+  int nArg,                       /* Size of argument array */
+  sqlite3_value **apVal,          /* Array of arguments */
+  sqlite_int64 *pRowid            /* OUT: The affected (or effected) rowid */
+){
+  return sqlite3Fts3UpdateMethod(pVtab, nArg, apVal, pRowid);
+}
+
+/*
+** Implementation of xSync() method. Flush the contents of the pending-terms
+** hash-table to the database.
+*/
+static int fts3SyncMethod(sqlite3_vtab *pVtab){
+
+  /* Following an incremental-merge operation, assuming that the input
+  ** segments are not completely consumed (the usual case), they are updated
+  ** in place to remove the entries that have already been merged. This
+  ** involves updating the leaf block that contains the smallest unmerged
+  ** entry and each block (if any) between the leaf and the root node. So
+  ** if the height of the input segment b-trees is N, and input segments
+  ** are merged eight at a time, updating the input segments at the end
+  ** of an incremental-merge requires writing (8*(1+N)) blocks. N is usually
+  ** small - often between 0 and 2. So the overhead of the incremental
+  ** merge is somewhere between 8 and 24 blocks. To avoid this overhead
+  ** dwarfing the actual productive work accomplished, the incremental merge
+  ** is only attempted if it will write at least 64 leaf blocks. Hence
+  ** nMinMerge.
+  **
+  ** Of course, updating the input segments also involves deleting a bunch
+  ** of blocks from the segments table. But this is not considered overhead
+  ** as it would also be required by a crisis-merge that used the same input 
+  ** segments.
+  */
+  const u32 nMinMerge = 64;       /* Minimum amount of incr-merge work to do */
+
+  Fts3Table *p = (Fts3Table*)pVtab;
+  int rc = sqlite3Fts3PendingTermsFlush(p);
+
+  if( rc==SQLITE_OK 
+   && p->nLeafAdd>(nMinMerge/16) 
+   && p->nAutoincrmerge && p->nAutoincrmerge!=0xff
+  ){
+    int mxLevel = 0;              /* Maximum relative level value in db */
+    int A;                        /* Incr-merge parameter A */
+
+    rc = sqlite3Fts3MaxLevel(p, &mxLevel);
+    assert( rc==SQLITE_OK || mxLevel==0 );
+    A = p->nLeafAdd * mxLevel;
+    A += (A/2);
+    if( A>(int)nMinMerge ) rc = sqlite3Fts3Incrmerge(p, A, p->nAutoincrmerge);
+  }
+  sqlite3Fts3SegmentsClose(p);
+  return rc;
+}
+
+/*
+** If it is currently unknown whether or not the FTS table has an %_stat
+** table (if p->bHasStat==2), attempt to determine this (set p->bHasStat
+** to 0 or 1). Return SQLITE_OK if successful, or an SQLite error code
+** if an error occurs.
+*/
+static int fts3SetHasStat(Fts3Table *p){
+  int rc = SQLITE_OK;
+  if( p->bHasStat==2 ){
+    const char *zFmt ="SELECT 1 FROM %Q.sqlite_master WHERE tbl_name='%q_stat'";
+    char *zSql = sqlite3_mprintf(zFmt, p->zDb, p->zName);
+    if( zSql ){
+      sqlite3_stmt *pStmt = 0;
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+      if( rc==SQLITE_OK ){
+        int bHasStat = (sqlite3_step(pStmt)==SQLITE_ROW);
+        rc = sqlite3_finalize(pStmt);
+        if( rc==SQLITE_OK ) p->bHasStat = (u8)bHasStat;
+      }
+      sqlite3_free(zSql);
+    }else{
+      rc = SQLITE_NOMEM;
+    }
+  }
+  return rc;
+}
+
+/*
+** Implementation of xBegin() method. 
+*/
+static int fts3BeginMethod(sqlite3_vtab *pVtab){
+  Fts3Table *p = (Fts3Table*)pVtab;
+  UNUSED_PARAMETER(pVtab);
+  assert( p->pSegments==0 );
+  assert( p->nPendingData==0 );
+  assert( p->inTransaction!=1 );
+  TESTONLY( p->inTransaction = 1 );
+  TESTONLY( p->mxSavepoint = -1; );
+  p->nLeafAdd = 0;
+  return fts3SetHasStat(p);
+}
+
+/*
+** Implementation of xCommit() method. This is a no-op. The contents of
+** the pending-terms hash-table have already been flushed into the database
+** by fts3SyncMethod().
+*/
+static int fts3CommitMethod(sqlite3_vtab *pVtab){
+  TESTONLY( Fts3Table *p = (Fts3Table*)pVtab );
+  UNUSED_PARAMETER(pVtab);
+  assert( p->nPendingData==0 );
+  assert( p->inTransaction!=0 );
+  assert( p->pSegments==0 );
+  TESTONLY( p->inTransaction = 0 );
+  TESTONLY( p->mxSavepoint = -1; );
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of xRollback(). Discard the contents of the pending-terms
+** hash-table. Any changes made to the database are reverted by SQLite.
+*/
+static int fts3RollbackMethod(sqlite3_vtab *pVtab){
+  Fts3Table *p = (Fts3Table*)pVtab;
+  sqlite3Fts3PendingTermsClear(p);
+  assert( p->inTransaction!=0 );
+  TESTONLY( p->inTransaction = 0 );
+  TESTONLY( p->mxSavepoint = -1; );
+  return SQLITE_OK;
+}
+
+/*
+** When called, *ppPoslist must point to the byte immediately following the
+** end of a position-list. i.e. ( (*ppPoslist)[-1]==POS_END ). This function
+** moves *ppPoslist so that it instead points to the first byte of the
+** same position list.
+*/
+static void fts3ReversePoslist(char *pStart, char **ppPoslist){
+  char *p = &(*ppPoslist)[-2];
+  char c = 0;
+
+  /* Skip backwards passed any trailing 0x00 bytes added by NearTrim() */
+  while( p>pStart && (c=*p--)==0 );
+
+  /* Search backwards for a varint with value zero (the end of the previous 
+  ** poslist). This is an 0x00 byte preceded by some byte that does not
+  ** have the 0x80 bit set.  */
+  while( p>pStart && (*p & 0x80) | c ){ 
+    c = *p--; 
+  }
+  assert( p==pStart || c==0 );
+
+  /* At this point p points to that preceding byte without the 0x80 bit
+  ** set. So to find the start of the poslist, skip forward 2 bytes then
+  ** over a varint. 
+  **
+  ** Normally. The other case is that p==pStart and the poslist to return
+  ** is the first in the doclist. In this case do not skip forward 2 bytes.
+  ** The second part of the if condition (c==0 && *ppPoslist>&p[2])
+  ** is required for cases where the first byte of a doclist and the
+  ** doclist is empty. For example, if the first docid is 10, a doclist
+  ** that begins with:
+  **
+  **   0x0A 0x00 <next docid delta varint>
+  */
+  if( p>pStart || (c==0 && *ppPoslist>&p[2]) ){ p = &p[2]; }
+  while( *p++&0x80 );
+  *ppPoslist = p;
+}
+
+/*
+** Helper function used by the implementation of the overloaded snippet(),
+** offsets() and optimize() SQL functions.
+**
+** If the value passed as the third argument is a blob of size
+** sizeof(Fts3Cursor*), then the blob contents are copied to the 
+** output variable *ppCsr and SQLITE_OK is returned. Otherwise, an error
+** message is written to context pContext and SQLITE_ERROR returned. The
+** string passed via zFunc is used as part of the error message.
+*/
+static int fts3FunctionArg(
+  sqlite3_context *pContext,      /* SQL function call context */
+  const char *zFunc,              /* Function name */
+  sqlite3_value *pVal,            /* argv[0] passed to function */
+  Fts3Cursor **ppCsr              /* OUT: Store cursor handle here */
+){
+  Fts3Cursor *pRet;
+  if( sqlite3_value_type(pVal)!=SQLITE_BLOB 
+   || sqlite3_value_bytes(pVal)!=sizeof(Fts3Cursor *)
+  ){
+    char *zErr = sqlite3_mprintf("illegal first argument to %s", zFunc);
+    sqlite3_result_error(pContext, zErr, -1);
+    sqlite3_free(zErr);
+    return SQLITE_ERROR;
+  }
+  memcpy(&pRet, sqlite3_value_blob(pVal), sizeof(Fts3Cursor *));
+  *ppCsr = pRet;
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of the snippet() function for FTS3
+*/
+static void fts3SnippetFunc(
+  sqlite3_context *pContext,      /* SQLite function call context */
+  int nVal,                       /* Size of apVal[] array */
+  sqlite3_value **apVal           /* Array of arguments */
+){
+  Fts3Cursor *pCsr;               /* Cursor handle passed through apVal[0] */
+  const char *zStart = "<b>";
+  const char *zEnd = "</b>";
+  const char *zEllipsis = "<b>...</b>";
+  int iCol = -1;
+  int nToken = 15;                /* Default number of tokens in snippet */
+
+  /* There must be at least one argument passed to this function (otherwise
+  ** the non-overloaded version would have been called instead of this one).
+  */
+  assert( nVal>=1 );
+
+  if( nVal>6 ){
+    sqlite3_result_error(pContext, 
+        "wrong number of arguments to function snippet()", -1);
+    return;
+  }
+  if( fts3FunctionArg(pContext, "snippet", apVal[0], &pCsr) ) return;
+
+  switch( nVal ){
+    case 6: nToken = sqlite3_value_int(apVal[5]);
+    case 5: iCol = sqlite3_value_int(apVal[4]);
+    case 4: zEllipsis = (const char*)sqlite3_value_text(apVal[3]);
+    case 3: zEnd = (const char*)sqlite3_value_text(apVal[2]);
+    case 2: zStart = (const char*)sqlite3_value_text(apVal[1]);
+  }
+  if( !zEllipsis || !zEnd || !zStart ){
+    sqlite3_result_error_nomem(pContext);
+  }else if( nToken==0 ){
+    sqlite3_result_text(pContext, "", -1, SQLITE_STATIC);
+  }else if( SQLITE_OK==fts3CursorSeek(pContext, pCsr) ){
+    sqlite3Fts3Snippet(pContext, pCsr, zStart, zEnd, zEllipsis, iCol, nToken);
+  }
+}
+
+/*
+** Implementation of the offsets() function for FTS3
+*/
+static void fts3OffsetsFunc(
+  sqlite3_context *pContext,      /* SQLite function call context */
+  int nVal,                       /* Size of argument array */
+  sqlite3_value **apVal           /* Array of arguments */
+){
+  Fts3Cursor *pCsr;               /* Cursor handle passed through apVal[0] */
+
+  UNUSED_PARAMETER(nVal);
+
+  assert( nVal==1 );
+  if( fts3FunctionArg(pContext, "offsets", apVal[0], &pCsr) ) return;
+  assert( pCsr );
+  if( SQLITE_OK==fts3CursorSeek(pContext, pCsr) ){
+    sqlite3Fts3Offsets(pContext, pCsr);
+  }
+}
+
+/* 
+** Implementation of the special optimize() function for FTS3. This 
+** function merges all segments in the database to a single segment.
+** Example usage is:
+**
+**   SELECT optimize(t) FROM t LIMIT 1;
+**
+** where 't' is the name of an FTS3 table.
+*/
+static void fts3OptimizeFunc(
+  sqlite3_context *pContext,      /* SQLite function call context */
+  int nVal,                       /* Size of argument array */
+  sqlite3_value **apVal           /* Array of arguments */
+){
+  int rc;                         /* Return code */
+  Fts3Table *p;                   /* Virtual table handle */
+  Fts3Cursor *pCursor;            /* Cursor handle passed through apVal[0] */
+
+  UNUSED_PARAMETER(nVal);
+
+  assert( nVal==1 );
+  if( fts3FunctionArg(pContext, "optimize", apVal[0], &pCursor) ) return;
+  p = (Fts3Table *)pCursor->base.pVtab;
+  assert( p );
+
+  rc = sqlite3Fts3Optimize(p);
+
+  switch( rc ){
+    case SQLITE_OK:
+      sqlite3_result_text(pContext, "Index optimized", -1, SQLITE_STATIC);
+      break;
+    case SQLITE_DONE:
+      sqlite3_result_text(pContext, "Index already optimal", -1, SQLITE_STATIC);
+      break;
+    default:
+      sqlite3_result_error_code(pContext, rc);
+      break;
+  }
+}
+
+/*
+** Implementation of the matchinfo() function for FTS3
+*/
+static void fts3MatchinfoFunc(
+  sqlite3_context *pContext,      /* SQLite function call context */
+  int nVal,                       /* Size of argument array */
+  sqlite3_value **apVal           /* Array of arguments */
+){
+  Fts3Cursor *pCsr;               /* Cursor handle passed through apVal[0] */
+  assert( nVal==1 || nVal==2 );
+  if( SQLITE_OK==fts3FunctionArg(pContext, "matchinfo", apVal[0], &pCsr) ){
+    const char *zArg = 0;
+    if( nVal>1 ){
+      zArg = (const char *)sqlite3_value_text(apVal[1]);
+    }
+    sqlite3Fts3Matchinfo(pContext, pCsr, zArg);
+  }
+}
+
+/*
+** This routine implements the xFindFunction method for the FTS3
+** virtual table.
+*/
+static int fts3FindFunctionMethod(
+  sqlite3_vtab *pVtab,            /* Virtual table handle */
+  int nArg,                       /* Number of SQL function arguments */
+  const char *zName,              /* Name of SQL function */
+  void (**pxFunc)(sqlite3_context*,int,sqlite3_value**), /* OUT: Result */
+  void **ppArg                    /* Unused */
+){
+  struct Overloaded {
+    const char *zName;
+    void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
+  } aOverload[] = {
+    { "snippet", fts3SnippetFunc },
+    { "offsets", fts3OffsetsFunc },
+    { "optimize", fts3OptimizeFunc },
+    { "matchinfo", fts3MatchinfoFunc },
+  };
+  int i;                          /* Iterator variable */
+
+  UNUSED_PARAMETER(pVtab);
+  UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(ppArg);
+
+  for(i=0; i<SizeofArray(aOverload); i++){
+    if( strcmp(zName, aOverload[i].zName)==0 ){
+      *pxFunc = aOverload[i].xFunc;
+      return 1;
+    }
+  }
+
+  /* No function of the specified name was found. Return 0. */
+  return 0;
+}
+
+/*
+** Implementation of FTS3 xRename method. Rename an fts3 table.
+*/
+static int fts3RenameMethod(
+  sqlite3_vtab *pVtab,            /* Virtual table handle */
+  const char *zName               /* New name of table */
+){
+  Fts3Table *p = (Fts3Table *)pVtab;
+  sqlite3 *db = p->db;            /* Database connection */
+  int rc;                         /* Return Code */
+
+  /* At this point it must be known if the %_stat table exists or not.
+  ** So bHasStat may not be 2.  */
+  rc = fts3SetHasStat(p);
+  
+  /* As it happens, the pending terms table is always empty here. This is
+  ** because an "ALTER TABLE RENAME TABLE" statement inside a transaction 
+  ** always opens a savepoint transaction. And the xSavepoint() method 
+  ** flushes the pending terms table. But leave the (no-op) call to
+  ** PendingTermsFlush() in in case that changes.
+  */
+  assert( p->nPendingData==0 );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3Fts3PendingTermsFlush(p);
+  }
+
+  if( p->zContentTbl==0 ){
+    fts3DbExec(&rc, db,
+      "ALTER TABLE %Q.'%q_content'  RENAME TO '%q_content';",
+      p->zDb, p->zName, zName
+    );
+  }
+
+  if( p->bHasDocsize ){
+    fts3DbExec(&rc, db,
+      "ALTER TABLE %Q.'%q_docsize'  RENAME TO '%q_docsize';",
+      p->zDb, p->zName, zName
+    );
+  }
+  if( p->bHasStat ){
+    fts3DbExec(&rc, db,
+      "ALTER TABLE %Q.'%q_stat'  RENAME TO '%q_stat';",
+      p->zDb, p->zName, zName
+    );
+  }
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_segments' RENAME TO '%q_segments';",
+    p->zDb, p->zName, zName
+  );
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_segdir'   RENAME TO '%q_segdir';",
+    p->zDb, p->zName, zName
+  );
+  return rc;
+}
+
+/*
+** The xSavepoint() method.
+**
+** Flush the contents of the pending-terms table to disk.
+*/
+static int fts3SavepointMethod(sqlite3_vtab *pVtab, int iSavepoint){
+  int rc = SQLITE_OK;
+  UNUSED_PARAMETER(iSavepoint);
+  assert( ((Fts3Table *)pVtab)->inTransaction );
+  assert( ((Fts3Table *)pVtab)->mxSavepoint < iSavepoint );
+  TESTONLY( ((Fts3Table *)pVtab)->mxSavepoint = iSavepoint );
+  if( ((Fts3Table *)pVtab)->bIgnoreSavepoint==0 ){
+    rc = fts3SyncMethod(pVtab);
+  }
+  return rc;
+}
+
+/*
+** The xRelease() method.
+**
+** This is a no-op.
+*/
+static int fts3ReleaseMethod(sqlite3_vtab *pVtab, int iSavepoint){
+  TESTONLY( Fts3Table *p = (Fts3Table*)pVtab );
+  UNUSED_PARAMETER(iSavepoint);
+  UNUSED_PARAMETER(pVtab);
+  assert( p->inTransaction );
+  assert( p->mxSavepoint >= iSavepoint );
+  TESTONLY( p->mxSavepoint = iSavepoint-1 );
+  return SQLITE_OK;
+}
+
+/*
+** The xRollbackTo() method.
+**
+** Discard the contents of the pending terms table.
+*/
+static int fts3RollbackToMethod(sqlite3_vtab *pVtab, int iSavepoint){
+  Fts3Table *p = (Fts3Table*)pVtab;
+  UNUSED_PARAMETER(iSavepoint);
+  assert( p->inTransaction );
+  assert( p->mxSavepoint >= iSavepoint );
+  TESTONLY( p->mxSavepoint = iSavepoint );
+  sqlite3Fts3PendingTermsClear(p);
+  return SQLITE_OK;
+}
+
+static const sqlite3_module fts3Module = {
+  /* iVersion      */ 2,
+  /* xCreate       */ fts3CreateMethod,
+  /* xConnect      */ fts3ConnectMethod,
+  /* xBestIndex    */ fts3BestIndexMethod,
+  /* xDisconnect   */ fts3DisconnectMethod,
+  /* xDestroy      */ fts3DestroyMethod,
+  /* xOpen         */ fts3OpenMethod,
+  /* xClose        */ fts3CloseMethod,
+  /* xFilter       */ fts3FilterMethod,
+  /* xNext         */ fts3NextMethod,
+  /* xEof          */ fts3EofMethod,
+  /* xColumn       */ fts3ColumnMethod,
+  /* xRowid        */ fts3RowidMethod,
+  /* xUpdate       */ fts3UpdateMethod,
+  /* xBegin        */ fts3BeginMethod,
+  /* xSync         */ fts3SyncMethod,
+  /* xCommit       */ fts3CommitMethod,
+  /* xRollback     */ fts3RollbackMethod,
+  /* xFindFunction */ fts3FindFunctionMethod,
+  /* xRename */       fts3RenameMethod,
+  /* xSavepoint    */ fts3SavepointMethod,
+  /* xRelease      */ fts3ReleaseMethod,
+  /* xRollbackTo   */ fts3RollbackToMethod,
+};
+
+/*
+** This function is registered as the module destructor (called when an
+** FTS3 enabled database connection is closed). It frees the memory
+** allocated for the tokenizer hash table.
+*/
+static void hashDestroy(void *p){
+  Fts3Hash *pHash = (Fts3Hash *)p;
+  sqlite3Fts3HashClear(pHash);
+  sqlite3_free(pHash);
+}
+
+/*
+** The fts3 built-in tokenizers - "simple", "porter" and "icu"- are 
+** implemented in files fts3_tokenizer1.c, fts3_porter.c and fts3_icu.c
+** respectively. The following three forward declarations are for functions
+** declared in these files used to retrieve the respective implementations.
+**
+** Calling sqlite3Fts3SimpleTokenizerModule() sets the value pointed
+** to by the argument to point to the "simple" tokenizer implementation.
+** And so on.
+*/
+SQLITE_PRIVATE void sqlite3Fts3SimpleTokenizerModule(sqlite3_tokenizer_module const**ppModule);
+SQLITE_PRIVATE void sqlite3Fts3PorterTokenizerModule(sqlite3_tokenizer_module const**ppModule);
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+SQLITE_PRIVATE void sqlite3Fts3UnicodeTokenizer(sqlite3_tokenizer_module const**ppModule);
+#endif
+#ifdef SQLITE_ENABLE_ICU
+SQLITE_PRIVATE void sqlite3Fts3IcuTokenizerModule(sqlite3_tokenizer_module const**ppModule);
+#endif
+
+/*
+** Initialize the fts3 extension. If this extension is built as part
+** of the sqlite library, then this function is called directly by
+** SQLite. If fts3 is built as a dynamically loadable extension, this
+** function is called by the sqlite3_extension_init() entry point.
+*/
+SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db){
+  int rc = SQLITE_OK;
+  Fts3Hash *pHash = 0;
+  const sqlite3_tokenizer_module *pSimple = 0;
+  const sqlite3_tokenizer_module *pPorter = 0;
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+  const sqlite3_tokenizer_module *pUnicode = 0;
+#endif
+
+#ifdef SQLITE_ENABLE_ICU
+  const sqlite3_tokenizer_module *pIcu = 0;
+  sqlite3Fts3IcuTokenizerModule(&pIcu);
+#endif
+
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+  sqlite3Fts3UnicodeTokenizer(&pUnicode);
+#endif
+
+#ifdef SQLITE_TEST
+  rc = sqlite3Fts3InitTerm(db);
+  if( rc!=SQLITE_OK ) return rc;
+#endif
+
+  rc = sqlite3Fts3InitAux(db);
+  if( rc!=SQLITE_OK ) return rc;
+
+  sqlite3Fts3SimpleTokenizerModule(&pSimple);
+  sqlite3Fts3PorterTokenizerModule(&pPorter);
+
+  /* Allocate and initialize the hash-table used to store tokenizers. */
+  pHash = sqlite3_malloc(sizeof(Fts3Hash));
+  if( !pHash ){
+    rc = SQLITE_NOMEM;
+  }else{
+    sqlite3Fts3HashInit(pHash, FTS3_HASH_STRING, 1);
+  }
+
+  /* Load the built-in tokenizers into the hash table */
+  if( rc==SQLITE_OK ){
+    if( sqlite3Fts3HashInsert(pHash, "simple", 7, (void *)pSimple)
+     || sqlite3Fts3HashInsert(pHash, "porter", 7, (void *)pPorter) 
+
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+     || sqlite3Fts3HashInsert(pHash, "unicode61", 10, (void *)pUnicode) 
+#endif
+#ifdef SQLITE_ENABLE_ICU
+     || (pIcu && sqlite3Fts3HashInsert(pHash, "icu", 4, (void *)pIcu))
+#endif
+    ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+
+#ifdef SQLITE_TEST
+  if( rc==SQLITE_OK ){
+    rc = sqlite3Fts3ExprInitTestInterface(db);
+  }
+#endif
+
+  /* Create the virtual table wrapper around the hash-table and overload 
+  ** the two scalar functions. If this is successful, register the
+  ** module with sqlite.
+  */
+  if( SQLITE_OK==rc 
+#if CHROMIUM_FTS3_CHANGES && !SQLITE_TEST
+      /* fts3_tokenizer() disabled for security reasons. */
+#else
+   && SQLITE_OK==(rc = sqlite3Fts3InitHashTable(db, pHash, "fts3_tokenizer"))
+#endif
+   && SQLITE_OK==(rc = sqlite3_overload_function(db, "snippet", -1))
+   && SQLITE_OK==(rc = sqlite3_overload_function(db, "offsets", 1))
+   && SQLITE_OK==(rc = sqlite3_overload_function(db, "matchinfo", 1))
+   && SQLITE_OK==(rc = sqlite3_overload_function(db, "matchinfo", 2))
+   && SQLITE_OK==(rc = sqlite3_overload_function(db, "optimize", 1))
+  ){
+    rc = sqlite3_create_module_v2(
+        db, "fts3", &fts3Module, (void *)pHash, hashDestroy
+    );
+#if CHROMIUM_FTS3_CHANGES && !SQLITE_TEST
+    /* Disable fts4 and tokenizer vtab pending review. */
+#else
+    if( rc==SQLITE_OK ){
+      rc = sqlite3_create_module_v2(
+          db, "fts4", &fts3Module, (void *)pHash, 0
+      );
+    }
+    if( rc==SQLITE_OK ){
+      rc = sqlite3Fts3InitTok(db, (void *)pHash);
+    }
+#endif
+    return rc;
+  }
+
+
+  /* An error has occurred. Delete the hash table and return the error code. */
+  assert( rc!=SQLITE_OK );
+  if( pHash ){
+    sqlite3Fts3HashClear(pHash);
+    sqlite3_free(pHash);
+  }
+  return rc;
+}
+
+/*
+** Allocate an Fts3MultiSegReader for each token in the expression headed
+** by pExpr. 
+**
+** An Fts3SegReader object is a cursor that can seek or scan a range of
+** entries within a single segment b-tree. An Fts3MultiSegReader uses multiple
+** Fts3SegReader objects internally to provide an interface to seek or scan
+** within the union of all segments of a b-tree. Hence the name.
+**
+** If the allocated Fts3MultiSegReader just seeks to a single entry in a
+** segment b-tree (if the term is not a prefix or it is a prefix for which
+** there exists prefix b-tree of the right length) then it may be traversed
+** and merged incrementally. Otherwise, it has to be merged into an in-memory 
+** doclist and then traversed.
+*/
+static void fts3EvalAllocateReaders(
+  Fts3Cursor *pCsr,               /* FTS cursor handle */
+  Fts3Expr *pExpr,                /* Allocate readers for this expression */
+  int *pnToken,                   /* OUT: Total number of tokens in phrase. */
+  int *pnOr,                      /* OUT: Total number of OR nodes in expr. */
+  int *pRc                        /* IN/OUT: Error code */
+){
+  if( pExpr && SQLITE_OK==*pRc ){
+    if( pExpr->eType==FTSQUERY_PHRASE ){
+      int i;
+      int nToken = pExpr->pPhrase->nToken;
+      *pnToken += nToken;
+      for(i=0; i<nToken; i++){
+        Fts3PhraseToken *pToken = &pExpr->pPhrase->aToken[i];
+        int rc = fts3TermSegReaderCursor(pCsr, 
+            pToken->z, pToken->n, pToken->isPrefix, &pToken->pSegcsr
+        );
+        if( rc!=SQLITE_OK ){
+          *pRc = rc;
+          return;
+        }
+      }
+      assert( pExpr->pPhrase->iDoclistToken==0 );
+      pExpr->pPhrase->iDoclistToken = -1;
+    }else{
+      *pnOr += (pExpr->eType==FTSQUERY_OR);
+      fts3EvalAllocateReaders(pCsr, pExpr->pLeft, pnToken, pnOr, pRc);
+      fts3EvalAllocateReaders(pCsr, pExpr->pRight, pnToken, pnOr, pRc);
+    }
+  }
+}
+
+/*
+** Arguments pList/nList contain the doclist for token iToken of phrase p.
+** It is merged into the main doclist stored in p->doclist.aAll/nAll.
+**
+** This function assumes that pList points to a buffer allocated using
+** sqlite3_malloc(). This function takes responsibility for eventually
+** freeing the buffer.
+**
+** SQLITE_OK is returned if successful, or SQLITE_NOMEM if an error occurs.
+*/
+static int fts3EvalPhraseMergeToken(
+  Fts3Table *pTab,                /* FTS Table pointer */
+  Fts3Phrase *p,                  /* Phrase to merge pList/nList into */
+  int iToken,                     /* Token pList/nList corresponds to */
+  char *pList,                    /* Pointer to doclist */
+  int nList                       /* Number of bytes in pList */
+){
+  int rc = SQLITE_OK;
+  assert( iToken!=p->iDoclistToken );
+
+  if( pList==0 ){
+    sqlite3_free(p->doclist.aAll);
+    p->doclist.aAll = 0;
+    p->doclist.nAll = 0;
+  }
+
+  else if( p->iDoclistToken<0 ){
+    p->doclist.aAll = pList;
+    p->doclist.nAll = nList;
+  }
+
+  else if( p->doclist.aAll==0 ){
+    sqlite3_free(pList);
+  }
+
+  else {
+    char *pLeft;
+    char *pRight;
+    int nLeft;
+    int nRight;
+    int nDiff;
+
+    if( p->iDoclistToken<iToken ){
+      pLeft = p->doclist.aAll;
+      nLeft = p->doclist.nAll;
+      pRight = pList;
+      nRight = nList;
+      nDiff = iToken - p->iDoclistToken;
+    }else{
+      pRight = p->doclist.aAll;
+      nRight = p->doclist.nAll;
+      pLeft = pList;
+      nLeft = nList;
+      nDiff = p->iDoclistToken - iToken;
+    }
+
+    rc = fts3DoclistPhraseMerge(
+        pTab->bDescIdx, nDiff, pLeft, nLeft, &pRight, &nRight
+    );
+    sqlite3_free(pLeft);
+    p->doclist.aAll = pRight;
+    p->doclist.nAll = nRight;
+  }
+
+  if( iToken>p->iDoclistToken ) p->iDoclistToken = iToken;
+  return rc;
+}
+
+/*
+** Load the doclist for phrase p into p->doclist.aAll/nAll. The loaded doclist
+** does not take deferred tokens into account.
+**
+** SQLITE_OK is returned if no error occurs, otherwise an SQLite error code.
+*/
+static int fts3EvalPhraseLoad(
+  Fts3Cursor *pCsr,               /* FTS Cursor handle */
+  Fts3Phrase *p                   /* Phrase object */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int iToken;
+  int rc = SQLITE_OK;
+
+  for(iToken=0; rc==SQLITE_OK && iToken<p->nToken; iToken++){
+    Fts3PhraseToken *pToken = &p->aToken[iToken];
+    assert( pToken->pDeferred==0 || pToken->pSegcsr==0 );
+
+    if( pToken->pSegcsr ){
+      int nThis = 0;
+      char *pThis = 0;
+      rc = fts3TermSelect(pTab, pToken, p->iColumn, &nThis, &pThis);
+      if( rc==SQLITE_OK ){
+        rc = fts3EvalPhraseMergeToken(pTab, p, iToken, pThis, nThis);
+      }
+    }
+    assert( pToken->pSegcsr==0 );
+  }
+
+  return rc;
+}
+
+/*
+** This function is called on each phrase after the position lists for
+** any deferred tokens have been loaded into memory. It updates the phrases
+** current position list to include only those positions that are really
+** instances of the phrase (after considering deferred tokens). If this
+** means that the phrase does not appear in the current row, doclist.pList
+** and doclist.nList are both zeroed.
+**
+** SQLITE_OK is returned if no error occurs, otherwise an SQLite error code.
+*/
+static int fts3EvalDeferredPhrase(Fts3Cursor *pCsr, Fts3Phrase *pPhrase){
+  int iToken;                     /* Used to iterate through phrase tokens */
+  char *aPoslist = 0;             /* Position list for deferred tokens */
+  int nPoslist = 0;               /* Number of bytes in aPoslist */
+  int iPrev = -1;                 /* Token number of previous deferred token */
+
+  assert( pPhrase->doclist.bFreeList==0 );
+
+  for(iToken=0; iToken<pPhrase->nToken; iToken++){
+    Fts3PhraseToken *pToken = &pPhrase->aToken[iToken];
+    Fts3DeferredToken *pDeferred = pToken->pDeferred;
+
+    if( pDeferred ){
+      char *pList = 0;
+      int nList = 0;
+      int rc = sqlite3Fts3DeferredTokenList(pDeferred, &pList, &nList);
+      if( rc!=SQLITE_OK ) return rc;
+
+      if( pList==0 ){
+        sqlite3_free(aPoslist);
+        pPhrase->doclist.pList = 0;
+        pPhrase->doclist.nList = 0;
+        return SQLITE_OK;
+
+      }else if( aPoslist==0 ){
+        aPoslist = pList;
+        nPoslist = nList;
+
+      }else{
+        char *aOut = pList;
+        char *p1 = aPoslist;
+        char *p2 = aOut;
+
+        assert( iPrev>=0 );
+        fts3PoslistPhraseMerge(&aOut, iToken-iPrev, 0, 1, &p1, &p2);
+        sqlite3_free(aPoslist);
+        aPoslist = pList;
+        nPoslist = (int)(aOut - aPoslist);
+        if( nPoslist==0 ){
+          sqlite3_free(aPoslist);
+          pPhrase->doclist.pList = 0;
+          pPhrase->doclist.nList = 0;
+          return SQLITE_OK;
+        }
+      }
+      iPrev = iToken;
+    }
+  }
+
+  if( iPrev>=0 ){
+    int nMaxUndeferred = pPhrase->iDoclistToken;
+    if( nMaxUndeferred<0 ){
+      pPhrase->doclist.pList = aPoslist;
+      pPhrase->doclist.nList = nPoslist;
+      pPhrase->doclist.iDocid = pCsr->iPrevId;
+      pPhrase->doclist.bFreeList = 1;
+    }else{
+      int nDistance;
+      char *p1;
+      char *p2;
+      char *aOut;
+
+      if( nMaxUndeferred>iPrev ){
+        p1 = aPoslist;
+        p2 = pPhrase->doclist.pList;
+        nDistance = nMaxUndeferred - iPrev;
+      }else{
+        p1 = pPhrase->doclist.pList;
+        p2 = aPoslist;
+        nDistance = iPrev - nMaxUndeferred;
+      }
+
+      aOut = (char *)sqlite3_malloc(nPoslist+8);
+      if( !aOut ){
+        sqlite3_free(aPoslist);
+        return SQLITE_NOMEM;
+      }
+      
+      pPhrase->doclist.pList = aOut;
+      if( fts3PoslistPhraseMerge(&aOut, nDistance, 0, 1, &p1, &p2) ){
+        pPhrase->doclist.bFreeList = 1;
+        pPhrase->doclist.nList = (int)(aOut - pPhrase->doclist.pList);
+      }else{
+        sqlite3_free(aOut);
+        pPhrase->doclist.pList = 0;
+        pPhrase->doclist.nList = 0;
+      }
+      sqlite3_free(aPoslist);
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Maximum number of tokens a phrase may have to be considered for the
+** incremental doclists strategy.
+*/
+#define MAX_INCR_PHRASE_TOKENS 4
+
+/*
+** This function is called for each Fts3Phrase in a full-text query 
+** expression to initialize the mechanism for returning rows. Once this
+** function has been called successfully on an Fts3Phrase, it may be
+** used with fts3EvalPhraseNext() to iterate through the matching docids.
+**
+** If parameter bOptOk is true, then the phrase may (or may not) use the
+** incremental loading strategy. Otherwise, the entire doclist is loaded into
+** memory within this call.
+**
+** SQLITE_OK is returned if no error occurs, otherwise an SQLite error code.
+*/
+static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;             /* Error code */
+  int i;
+
+  /* Determine if doclists may be loaded from disk incrementally. This is
+  ** possible if the bOptOk argument is true, the FTS doclists will be
+  ** scanned in forward order, and the phrase consists of 
+  ** MAX_INCR_PHRASE_TOKENS or fewer tokens, none of which are are "^first"
+  ** tokens or prefix tokens that cannot use a prefix-index.  */
+  int bHaveIncr = 0;
+  int bIncrOk = (bOptOk 
+   && pCsr->bDesc==pTab->bDescIdx 
+   && p->nToken<=MAX_INCR_PHRASE_TOKENS && p->nToken>0
+#ifdef SQLITE_TEST
+   && pTab->bNoIncrDoclist==0
+#endif
+  );
+  for(i=0; bIncrOk==1 && i<p->nToken; i++){
+    Fts3PhraseToken *pToken = &p->aToken[i];
+    if( pToken->bFirst || (pToken->pSegcsr!=0 && !pToken->pSegcsr->bLookup) ){
+      bIncrOk = 0;
+    }
+    if( pToken->pSegcsr ) bHaveIncr = 1;
+  }
+
+  if( bIncrOk && bHaveIncr ){
+    /* Use the incremental approach. */
+    int iCol = (p->iColumn >= pTab->nColumn ? -1 : p->iColumn);
+    for(i=0; rc==SQLITE_OK && i<p->nToken; i++){
+      Fts3PhraseToken *pToken = &p->aToken[i];
+      Fts3MultiSegReader *pSegcsr = pToken->pSegcsr;
+      if( pSegcsr ){
+        rc = sqlite3Fts3MsrIncrStart(pTab, pSegcsr, iCol, pToken->z, pToken->n);
+      }
+    }
+    p->bIncr = 1;
+  }else{
+    /* Load the full doclist for the phrase into memory. */
+    rc = fts3EvalPhraseLoad(pCsr, p);
+    p->bIncr = 0;
+  }
+
+  assert( rc!=SQLITE_OK || p->nToken<1 || p->aToken[0].pSegcsr==0 || p->bIncr );
+  return rc;
+}
+
+/*
+** This function is used to iterate backwards (from the end to start) 
+** through doclists. It is used by this module to iterate through phrase
+** doclists in reverse and by the fts3_write.c module to iterate through
+** pending-terms lists when writing to databases with "order=desc".
+**
+** The doclist may be sorted in ascending (parameter bDescIdx==0) or 
+** descending (parameter bDescIdx==1) order of docid. Regardless, this
+** function iterates from the end of the doclist to the beginning.
+*/
+SQLITE_PRIVATE void sqlite3Fts3DoclistPrev(
+  int bDescIdx,                   /* True if the doclist is desc */
+  char *aDoclist,                 /* Pointer to entire doclist */
+  int nDoclist,                   /* Length of aDoclist in bytes */
+  char **ppIter,                  /* IN/OUT: Iterator pointer */
+  sqlite3_int64 *piDocid,         /* IN/OUT: Docid pointer */
+  int *pnList,                    /* OUT: List length pointer */
+  u8 *pbEof                       /* OUT: End-of-file flag */
+){
+  char *p = *ppIter;
+
+  assert( nDoclist>0 );
+  assert( *pbEof==0 );
+  assert( p || *piDocid==0 );
+  assert( !p || (p>aDoclist && p<&aDoclist[nDoclist]) );
+
+  if( p==0 ){
+    sqlite3_int64 iDocid = 0;
+    char *pNext = 0;
+    char *pDocid = aDoclist;
+    char *pEnd = &aDoclist[nDoclist];
+    int iMul = 1;
+
+    while( pDocid<pEnd ){
+      sqlite3_int64 iDelta;
+      pDocid += sqlite3Fts3GetVarint(pDocid, &iDelta);
+      iDocid += (iMul * iDelta);
+      pNext = pDocid;
+      fts3PoslistCopy(0, &pDocid);
+      while( pDocid<pEnd && *pDocid==0 ) pDocid++;
+      iMul = (bDescIdx ? -1 : 1);
+    }
+
+    *pnList = (int)(pEnd - pNext);
+    *ppIter = pNext;
+    *piDocid = iDocid;
+  }else{
+    int iMul = (bDescIdx ? -1 : 1);
+    sqlite3_int64 iDelta;
+    fts3GetReverseVarint(&p, aDoclist, &iDelta);
+    *piDocid -= (iMul * iDelta);
+
+    if( p==aDoclist ){
+      *pbEof = 1;
+    }else{
+      char *pSave = p;
+      fts3ReversePoslist(aDoclist, &p);
+      *pnList = (int)(pSave - p);
+    }
+    *ppIter = p;
+  }
+}
+
+/*
+** Iterate forwards through a doclist.
+*/
+SQLITE_PRIVATE void sqlite3Fts3DoclistNext(
+  int bDescIdx,                   /* True if the doclist is desc */
+  char *aDoclist,                 /* Pointer to entire doclist */
+  int nDoclist,                   /* Length of aDoclist in bytes */
+  char **ppIter,                  /* IN/OUT: Iterator pointer */
+  sqlite3_int64 *piDocid,         /* IN/OUT: Docid pointer */
+  u8 *pbEof                       /* OUT: End-of-file flag */
+){
+  char *p = *ppIter;
+
+  assert( nDoclist>0 );
+  assert( *pbEof==0 );
+  assert( p || *piDocid==0 );
+  assert( !p || (p>=aDoclist && p<=&aDoclist[nDoclist]) );
+
+  if( p==0 ){
+    p = aDoclist;
+    p += sqlite3Fts3GetVarint(p, piDocid);
+  }else{
+    fts3PoslistCopy(0, &p);
+    while( p<&aDoclist[nDoclist] && *p==0 ) p++; 
+    if( p>=&aDoclist[nDoclist] ){
+      *pbEof = 1;
+    }else{
+      sqlite3_int64 iVar;
+      p += sqlite3Fts3GetVarint(p, &iVar);
+      *piDocid += ((bDescIdx ? -1 : 1) * iVar);
+    }
+  }
+
+  *ppIter = p;
+}
+
+/*
+** Advance the iterator pDL to the next entry in pDL->aAll/nAll. Set *pbEof
+** to true if EOF is reached.
+*/
+static void fts3EvalDlPhraseNext(
+  Fts3Table *pTab,
+  Fts3Doclist *pDL,
+  u8 *pbEof
+){
+  char *pIter;                            /* Used to iterate through aAll */
+  char *pEnd = &pDL->aAll[pDL->nAll];     /* 1 byte past end of aAll */
+ 
+  if( pDL->pNextDocid ){
+    pIter = pDL->pNextDocid;
+  }else{
+    pIter = pDL->aAll;
+  }
+
+  if( pIter>=pEnd ){
+    /* We have already reached the end of this doclist. EOF. */
+    *pbEof = 1;
+  }else{
+    sqlite3_int64 iDelta;
+    pIter += sqlite3Fts3GetVarint(pIter, &iDelta);
+    if( pTab->bDescIdx==0 || pDL->pNextDocid==0 ){
+      pDL->iDocid += iDelta;
+    }else{
+      pDL->iDocid -= iDelta;
+    }
+    pDL->pList = pIter;
+    fts3PoslistCopy(0, &pIter);
+    pDL->nList = (int)(pIter - pDL->pList);
+
+    /* pIter now points just past the 0x00 that terminates the position-
+    ** list for document pDL->iDocid. However, if this position-list was
+    ** edited in place by fts3EvalNearTrim(), then pIter may not actually
+    ** point to the start of the next docid value. The following line deals
+    ** with this case by advancing pIter past the zero-padding added by
+    ** fts3EvalNearTrim().  */
+    while( pIter<pEnd && *pIter==0 ) pIter++;
+
+    pDL->pNextDocid = pIter;
+    assert( pIter>=&pDL->aAll[pDL->nAll] || *pIter );
+    *pbEof = 0;
+  }
+}
+
+/*
+** Helper type used by fts3EvalIncrPhraseNext() and incrPhraseTokenNext().
+*/
+typedef struct TokenDoclist TokenDoclist;
+struct TokenDoclist {
+  int bIgnore;
+  sqlite3_int64 iDocid;
+  char *pList;
+  int nList;
+};
+
+/*
+** Token pToken is an incrementally loaded token that is part of a 
+** multi-token phrase. Advance it to the next matching document in the
+** database and populate output variable *p with the details of the new
+** entry. Or, if the iterator has reached EOF, set *pbEof to true.
+**
+** If an error occurs, return an SQLite error code. Otherwise, return 
+** SQLITE_OK.
+*/
+static int incrPhraseTokenNext(
+  Fts3Table *pTab,                /* Virtual table handle */
+  Fts3Phrase *pPhrase,            /* Phrase to advance token of */
+  int iToken,                     /* Specific token to advance */
+  TokenDoclist *p,                /* OUT: Docid and doclist for new entry */
+  u8 *pbEof                       /* OUT: True if iterator is at EOF */
+){
+  int rc = SQLITE_OK;
+
+  if( pPhrase->iDoclistToken==iToken ){
+    assert( p->bIgnore==0 );
+    assert( pPhrase->aToken[iToken].pSegcsr==0 );
+    fts3EvalDlPhraseNext(pTab, &pPhrase->doclist, pbEof);
+    p->pList = pPhrase->doclist.pList;
+    p->nList = pPhrase->doclist.nList;
+    p->iDocid = pPhrase->doclist.iDocid;
+  }else{
+    Fts3PhraseToken *pToken = &pPhrase->aToken[iToken];
+    assert( pToken->pDeferred==0 );
+    assert( pToken->pSegcsr || pPhrase->iDoclistToken>=0 );
+    if( pToken->pSegcsr ){
+      assert( p->bIgnore==0 );
+      rc = sqlite3Fts3MsrIncrNext(
+          pTab, pToken->pSegcsr, &p->iDocid, &p->pList, &p->nList
+      );
+      if( p->pList==0 ) *pbEof = 1;
+    }else{
+      p->bIgnore = 1;
+    }
+  }
+
+  return rc;
+}
+
+
+/*
+** The phrase iterator passed as the second argument:
+**
+**   * features at least one token that uses an incremental doclist, and 
+**
+**   * does not contain any deferred tokens.
+**
+** Advance it to the next matching documnent in the database and populate
+** the Fts3Doclist.pList and nList fields. 
+**
+** If there is no "next" entry and no error occurs, then *pbEof is set to
+** 1 before returning. Otherwise, if no error occurs and the iterator is
+** successfully advanced, *pbEof is set to 0.
+**
+** If an error occurs, return an SQLite error code. Otherwise, return 
+** SQLITE_OK.
+*/
+static int fts3EvalIncrPhraseNext(
+  Fts3Cursor *pCsr,               /* FTS Cursor handle */
+  Fts3Phrase *p,                  /* Phrase object to advance to next docid */
+  u8 *pbEof                       /* OUT: Set to 1 if EOF */
+){
+  int rc = SQLITE_OK;
+  Fts3Doclist *pDL = &p->doclist;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  u8 bEof = 0;
+
+  /* This is only called if it is guaranteed that the phrase has at least
+  ** one incremental token. In which case the bIncr flag is set. */
+  assert( p->bIncr==1 );
+
+  if( p->nToken==1 && p->bIncr ){
+    rc = sqlite3Fts3MsrIncrNext(pTab, p->aToken[0].pSegcsr, 
+        &pDL->iDocid, &pDL->pList, &pDL->nList
+    );
+    if( pDL->pList==0 ) bEof = 1;
+  }else{
+    int bDescDoclist = pCsr->bDesc;
+    struct TokenDoclist a[MAX_INCR_PHRASE_TOKENS];
+
+    memset(a, 0, sizeof(a));
+    assert( p->nToken<=MAX_INCR_PHRASE_TOKENS );
+    assert( p->iDoclistToken<MAX_INCR_PHRASE_TOKENS );
+
+    while( bEof==0 ){
+      int bMaxSet = 0;
+      sqlite3_int64 iMax = 0;     /* Largest docid for all iterators */
+      int i;                      /* Used to iterate through tokens */
+
+      /* Advance the iterator for each token in the phrase once. */
+      for(i=0; rc==SQLITE_OK && i<p->nToken && bEof==0; i++){
+        rc = incrPhraseTokenNext(pTab, p, i, &a[i], &bEof);
+        if( a[i].bIgnore==0 && (bMaxSet==0 || DOCID_CMP(iMax, a[i].iDocid)<0) ){
+          iMax = a[i].iDocid;
+          bMaxSet = 1;
+        }
+      }
+      assert( rc!=SQLITE_OK || (p->nToken>=1 && a[p->nToken-1].bIgnore==0) );
+      assert( rc!=SQLITE_OK || bMaxSet );
+
+      /* Keep advancing iterators until they all point to the same document */
+      for(i=0; i<p->nToken; i++){
+        while( rc==SQLITE_OK && bEof==0 
+            && a[i].bIgnore==0 && DOCID_CMP(a[i].iDocid, iMax)<0 
+        ){
+          rc = incrPhraseTokenNext(pTab, p, i, &a[i], &bEof);
+          if( DOCID_CMP(a[i].iDocid, iMax)>0 ){
+            iMax = a[i].iDocid;
+            i = 0;
+          }
+        }
+      }
+
+      /* Check if the current entries really are a phrase match */
+      if( bEof==0 ){
+        int nList = 0;
+        int nByte = a[p->nToken-1].nList;
+        char *aDoclist = sqlite3_malloc(nByte+1);
+        if( !aDoclist ) return SQLITE_NOMEM;
+        memcpy(aDoclist, a[p->nToken-1].pList, nByte+1);
+
+        for(i=0; i<(p->nToken-1); i++){
+          if( a[i].bIgnore==0 ){
+            char *pL = a[i].pList;
+            char *pR = aDoclist;
+            char *pOut = aDoclist;
+            int nDist = p->nToken-1-i;
+            int res = fts3PoslistPhraseMerge(&pOut, nDist, 0, 1, &pL, &pR);
+            if( res==0 ) break;
+            nList = (int)(pOut - aDoclist);
+          }
+        }
+        if( i==(p->nToken-1) ){
+          pDL->iDocid = iMax;
+          pDL->pList = aDoclist;
+          pDL->nList = nList;
+          pDL->bFreeList = 1;
+          break;
+        }
+        sqlite3_free(aDoclist);
+      }
+    }
+  }
+
+  *pbEof = bEof;
+  return rc;
+}
+
+/*
+** Attempt to move the phrase iterator to point to the next matching docid. 
+** If an error occurs, return an SQLite error code. Otherwise, return 
+** SQLITE_OK.
+**
+** If there is no "next" entry and no error occurs, then *pbEof is set to
+** 1 before returning. Otherwise, if no error occurs and the iterator is
+** successfully advanced, *pbEof is set to 0.
+*/
+static int fts3EvalPhraseNext(
+  Fts3Cursor *pCsr,               /* FTS Cursor handle */
+  Fts3Phrase *p,                  /* Phrase object to advance to next docid */
+  u8 *pbEof                       /* OUT: Set to 1 if EOF */
+){
+  int rc = SQLITE_OK;
+  Fts3Doclist *pDL = &p->doclist;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+
+  if( p->bIncr ){
+    rc = fts3EvalIncrPhraseNext(pCsr, p, pbEof);
+  }else if( pCsr->bDesc!=pTab->bDescIdx && pDL->nAll ){
+    sqlite3Fts3DoclistPrev(pTab->bDescIdx, pDL->aAll, pDL->nAll, 
+        &pDL->pNextDocid, &pDL->iDocid, &pDL->nList, pbEof
+    );
+    pDL->pList = pDL->pNextDocid;
+  }else{
+    fts3EvalDlPhraseNext(pTab, pDL, pbEof);
+  }
+
+  return rc;
+}
+
+/*
+**
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
+** Otherwise, fts3EvalPhraseStart() is called on all phrases within the
+** expression. Also the Fts3Expr.bDeferred variable is set to true for any
+** expressions for which all descendent tokens are deferred.
+**
+** If parameter bOptOk is zero, then it is guaranteed that the
+** Fts3Phrase.doclist.aAll/nAll variables contain the entire doclist for
+** each phrase in the expression (subject to deferred token processing).
+** Or, if bOptOk is non-zero, then one or more tokens within the expression
+** may be loaded incrementally, meaning doclist.aAll/nAll is not available.
+**
+** If an error occurs within this function, *pRc is set to an SQLite error
+** code before returning.
+*/
+static void fts3EvalStartReaders(
+  Fts3Cursor *pCsr,               /* FTS Cursor handle */
+  Fts3Expr *pExpr,                /* Expression to initialize phrases in */
+  int *pRc                        /* IN/OUT: Error code */
+){
+  if( pExpr && SQLITE_OK==*pRc ){
+    if( pExpr->eType==FTSQUERY_PHRASE ){
+      int nToken = pExpr->pPhrase->nToken;
+      if( nToken ){
+        int i;
+        for(i=0; i<nToken; i++){
+          if( pExpr->pPhrase->aToken[i].pDeferred==0 ) break;
+        }
+        pExpr->bDeferred = (i==nToken);
+      }
+      *pRc = fts3EvalPhraseStart(pCsr, 1, pExpr->pPhrase);
+    }else{
+      fts3EvalStartReaders(pCsr, pExpr->pLeft, pRc);
+      fts3EvalStartReaders(pCsr, pExpr->pRight, pRc);
+      pExpr->bDeferred = (pExpr->pLeft->bDeferred && pExpr->pRight->bDeferred);
+    }
+  }
+}
+
+/*
+** An array of the following structures is assembled as part of the process
+** of selecting tokens to defer before the query starts executing (as part
+** of the xFilter() method). There is one element in the array for each
+** token in the FTS expression.
+**
+** Tokens are divided into AND/NEAR clusters. All tokens in a cluster belong
+** to phrases that are connected only by AND and NEAR operators (not OR or
+** NOT). When determining tokens to defer, each AND/NEAR cluster is considered
+** separately. The root of a tokens AND/NEAR cluster is stored in 
+** Fts3TokenAndCost.pRoot.
+*/
+typedef struct Fts3TokenAndCost Fts3TokenAndCost;
+struct Fts3TokenAndCost {
+  Fts3Phrase *pPhrase;            /* The phrase the token belongs to */
+  int iToken;                     /* Position of token in phrase */
+  Fts3PhraseToken *pToken;        /* The token itself */
+  Fts3Expr *pRoot;                /* Root of NEAR/AND cluster */
+  int nOvfl;                      /* Number of overflow pages to load doclist */
+  int iCol;                       /* The column the token must match */
+};
+
+/*
+** This function is used to populate an allocated Fts3TokenAndCost array.
+**
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
+** Otherwise, if an error occurs during execution, *pRc is set to an
+** SQLite error code.
+*/
+static void fts3EvalTokenCosts(
+  Fts3Cursor *pCsr,               /* FTS Cursor handle */
+  Fts3Expr *pRoot,                /* Root of current AND/NEAR cluster */
+  Fts3Expr *pExpr,                /* Expression to consider */
+  Fts3TokenAndCost **ppTC,        /* Write new entries to *(*ppTC)++ */
+  Fts3Expr ***ppOr,               /* Write new OR root to *(*ppOr)++ */
+  int *pRc                        /* IN/OUT: Error code */
+){
+  if( *pRc==SQLITE_OK ){
+    if( pExpr->eType==FTSQUERY_PHRASE ){
+      Fts3Phrase *pPhrase = pExpr->pPhrase;
+      int i;
+      for(i=0; *pRc==SQLITE_OK && i<pPhrase->nToken; i++){
+        Fts3TokenAndCost *pTC = (*ppTC)++;
+        pTC->pPhrase = pPhrase;
+        pTC->iToken = i;
+        pTC->pRoot = pRoot;
+        pTC->pToken = &pPhrase->aToken[i];
+        pTC->iCol = pPhrase->iColumn;
+        *pRc = sqlite3Fts3MsrOvfl(pCsr, pTC->pToken->pSegcsr, &pTC->nOvfl);
+      }
+    }else if( pExpr->eType!=FTSQUERY_NOT ){
+      assert( pExpr->eType==FTSQUERY_OR
+           || pExpr->eType==FTSQUERY_AND
+           || pExpr->eType==FTSQUERY_NEAR
+      );
+      assert( pExpr->pLeft && pExpr->pRight );
+      if( pExpr->eType==FTSQUERY_OR ){
+        pRoot = pExpr->pLeft;
+        **ppOr = pRoot;
+        (*ppOr)++;
+      }
+      fts3EvalTokenCosts(pCsr, pRoot, pExpr->pLeft, ppTC, ppOr, pRc);
+      if( pExpr->eType==FTSQUERY_OR ){
+        pRoot = pExpr->pRight;
+        **ppOr = pRoot;
+        (*ppOr)++;
+      }
+      fts3EvalTokenCosts(pCsr, pRoot, pExpr->pRight, ppTC, ppOr, pRc);
+    }
+  }
+}
+
+/*
+** Determine the average document (row) size in pages. If successful,
+** write this value to *pnPage and return SQLITE_OK. Otherwise, return
+** an SQLite error code.
+**
+** The average document size in pages is calculated by first calculating 
+** determining the average size in bytes, B. If B is less than the amount
+** of data that will fit on a single leaf page of an intkey table in
+** this database, then the average docsize is 1. Otherwise, it is 1 plus
+** the number of overflow pages consumed by a record B bytes in size.
+*/
+static int fts3EvalAverageDocsize(Fts3Cursor *pCsr, int *pnPage){
+  if( pCsr->nRowAvg==0 ){
+    /* The average document size, which is required to calculate the cost
+    ** of each doclist, has not yet been determined. Read the required 
+    ** data from the %_stat table to calculate it.
+    **
+    ** Entry 0 of the %_stat table is a blob containing (nCol+1) FTS3 
+    ** varints, where nCol is the number of columns in the FTS3 table.
+    ** The first varint is the number of documents currently stored in
+    ** the table. The following nCol varints contain the total amount of
+    ** data stored in all rows of each column of the table, from left
+    ** to right.
+    */
+    int rc;
+    Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
+    sqlite3_stmt *pStmt;
+    sqlite3_int64 nDoc = 0;
+    sqlite3_int64 nByte = 0;
+    const char *pEnd;
+    const char *a;
+
+    rc = sqlite3Fts3SelectDoctotal(p, &pStmt);
+    if( rc!=SQLITE_OK ) return rc;
+    a = sqlite3_column_blob(pStmt, 0);
+    assert( a );
+
+    pEnd = &a[sqlite3_column_bytes(pStmt, 0)];
+    a += sqlite3Fts3GetVarint(a, &nDoc);
+    while( a<pEnd ){
+      a += sqlite3Fts3GetVarint(a, &nByte);
+    }
+    if( nDoc==0 || nByte==0 ){
+      sqlite3_reset(pStmt);
+      return FTS_CORRUPT_VTAB;
+    }
+
+    pCsr->nDoc = nDoc;
+    pCsr->nRowAvg = (int)(((nByte / nDoc) + p->nPgsz) / p->nPgsz);
+    assert( pCsr->nRowAvg>0 ); 
+    rc = sqlite3_reset(pStmt);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+
+  *pnPage = pCsr->nRowAvg;
+  return SQLITE_OK;
+}
+
+/*
+** This function is called to select the tokens (if any) that will be 
+** deferred. The array aTC[] has already been populated when this is
+** called.
+**
+** This function is called once for each AND/NEAR cluster in the 
+** expression. Each invocation determines which tokens to defer within
+** the cluster with root node pRoot. See comments above the definition
+** of struct Fts3TokenAndCost for more details.
+**
+** If no error occurs, SQLITE_OK is returned and sqlite3Fts3DeferToken()
+** called on each token to defer. Otherwise, an SQLite error code is
+** returned.
+*/
+static int fts3EvalSelectDeferred(
+  Fts3Cursor *pCsr,               /* FTS Cursor handle */
+  Fts3Expr *pRoot,                /* Consider tokens with this root node */
+  Fts3TokenAndCost *aTC,          /* Array of expression tokens and costs */
+  int nTC                         /* Number of entries in aTC[] */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int nDocSize = 0;               /* Number of pages per doc loaded */
+  int rc = SQLITE_OK;             /* Return code */
+  int ii;                         /* Iterator variable for various purposes */
+  int nOvfl = 0;                  /* Total overflow pages used by doclists */
+  int nToken = 0;                 /* Total number of tokens in cluster */
+
+  int nMinEst = 0;                /* The minimum count for any phrase so far. */
+  int nLoad4 = 1;                 /* (Phrases that will be loaded)^4. */
+
+  /* Tokens are never deferred for FTS tables created using the content=xxx
+  ** option. The reason being that it is not guaranteed that the content
+  ** table actually contains the same data as the index. To prevent this from
+  ** causing any problems, the deferred token optimization is completely
+  ** disabled for content=xxx tables. */
+  if( pTab->zContentTbl ){
+    return SQLITE_OK;
+  }
+
+  /* Count the tokens in this AND/NEAR cluster. If none of the doclists
+  ** associated with the tokens spill onto overflow pages, or if there is
+  ** only 1 token, exit early. No tokens to defer in this case. */
+  for(ii=0; ii<nTC; ii++){
+    if( aTC[ii].pRoot==pRoot ){
+      nOvfl += aTC[ii].nOvfl;
+      nToken++;
+    }
+  }
+  if( nOvfl==0 || nToken<2 ) return SQLITE_OK;
+
+  /* Obtain the average docsize (in pages). */
+  rc = fts3EvalAverageDocsize(pCsr, &nDocSize);
+  assert( rc!=SQLITE_OK || nDocSize>0 );
+
+
+  /* Iterate through all tokens in this AND/NEAR cluster, in ascending order 
+  ** of the number of overflow pages that will be loaded by the pager layer 
+  ** to retrieve the entire doclist for the token from the full-text index.
+  ** Load the doclists for tokens that are either:
+  **
+  **   a. The cheapest token in the entire query (i.e. the one visited by the
+  **      first iteration of this loop), or
+  **
+  **   b. Part of a multi-token phrase.
+  **
+  ** After each token doclist is loaded, merge it with the others from the
+  ** same phrase and count the number of documents that the merged doclist
+  ** contains. Set variable "nMinEst" to the smallest number of documents in 
+  ** any phrase doclist for which 1 or more token doclists have been loaded.
+  ** Let nOther be the number of other phrases for which it is certain that
+  ** one or more tokens will not be deferred.
+  **
+  ** Then, for each token, defer it if loading the doclist would result in
+  ** loading N or more overflow pages into memory, where N is computed as:
+  **
+  **    (nMinEst + 4^nOther - 1) / (4^nOther)
+  */
+  for(ii=0; ii<nToken && rc==SQLITE_OK; ii++){
+    int iTC;                      /* Used to iterate through aTC[] array. */
+    Fts3TokenAndCost *pTC = 0;    /* Set to cheapest remaining token. */
+
+    /* Set pTC to point to the cheapest remaining token. */
+    for(iTC=0; iTC<nTC; iTC++){
+      if( aTC[iTC].pToken && aTC[iTC].pRoot==pRoot 
+       && (!pTC || aTC[iTC].nOvfl<pTC->nOvfl) 
+      ){
+        pTC = &aTC[iTC];
+      }
+    }
+    assert( pTC );
+
+    if( ii && pTC->nOvfl>=((nMinEst+(nLoad4/4)-1)/(nLoad4/4))*nDocSize ){
+      /* The number of overflow pages to load for this (and therefore all
+      ** subsequent) tokens is greater than the estimated number of pages 
+      ** that will be loaded if all subsequent tokens are deferred.
+      */
+      Fts3PhraseToken *pToken = pTC->pToken;
+      rc = sqlite3Fts3DeferToken(pCsr, pToken, pTC->iCol);
+      fts3SegReaderCursorFree(pToken->pSegcsr);
+      pToken->pSegcsr = 0;
+    }else{
+      /* Set nLoad4 to the value of (4^nOther) for the next iteration of the
+      ** for-loop. Except, limit the value to 2^24 to prevent it from 
+      ** overflowing the 32-bit integer it is stored in. */
+      if( ii<12 ) nLoad4 = nLoad4*4;
+
+      if( ii==0 || (pTC->pPhrase->nToken>1 && ii!=nToken-1) ){
+        /* Either this is the cheapest token in the entire query, or it is
+        ** part of a multi-token phrase. Either way, the entire doclist will
+        ** (eventually) be loaded into memory. It may as well be now. */
+        Fts3PhraseToken *pToken = pTC->pToken;
+        int nList = 0;
+        char *pList = 0;
+        rc = fts3TermSelect(pTab, pToken, pTC->iCol, &nList, &pList);
+        assert( rc==SQLITE_OK || pList==0 );
+        if( rc==SQLITE_OK ){
+          rc = fts3EvalPhraseMergeToken(
+              pTab, pTC->pPhrase, pTC->iToken,pList,nList
+          );
+        }
+        if( rc==SQLITE_OK ){
+          int nCount;
+          nCount = fts3DoclistCountDocids(
+              pTC->pPhrase->doclist.aAll, pTC->pPhrase->doclist.nAll
+          );
+          if( ii==0 || nCount<nMinEst ) nMinEst = nCount;
+        }
+      }
+    }
+    pTC->pToken = 0;
+  }
+
+  return rc;
+}
+
+/*
+** This function is called from within the xFilter method. It initializes
+** the full-text query currently stored in pCsr->pExpr. To iterate through
+** the results of a query, the caller does:
+**
+**    fts3EvalStart(pCsr);
+**    while( 1 ){
+**      fts3EvalNext(pCsr);
+**      if( pCsr->bEof ) break;
+**      ... return row pCsr->iPrevId to the caller ...
+**    }
+*/
+static int fts3EvalStart(Fts3Cursor *pCsr){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+  int nToken = 0;
+  int nOr = 0;
+
+  /* Allocate a MultiSegReader for each token in the expression. */
+  fts3EvalAllocateReaders(pCsr, pCsr->pExpr, &nToken, &nOr, &rc);
+
+  /* Determine which, if any, tokens in the expression should be deferred. */
+#ifndef SQLITE_DISABLE_FTS4_DEFERRED
+  if( rc==SQLITE_OK && nToken>1 && pTab->bFts4 ){
+    Fts3TokenAndCost *aTC;
+    Fts3Expr **apOr;
+    aTC = (Fts3TokenAndCost *)sqlite3_malloc(
+        sizeof(Fts3TokenAndCost) * nToken
+      + sizeof(Fts3Expr *) * nOr * 2
+    );
+    apOr = (Fts3Expr **)&aTC[nToken];
+
+    if( !aTC ){
+      rc = SQLITE_NOMEM;
+    }else{
+      int ii;
+      Fts3TokenAndCost *pTC = aTC;
+      Fts3Expr **ppOr = apOr;
+
+      fts3EvalTokenCosts(pCsr, 0, pCsr->pExpr, &pTC, &ppOr, &rc);
+      nToken = (int)(pTC-aTC);
+      nOr = (int)(ppOr-apOr);
+
+      if( rc==SQLITE_OK ){
+        rc = fts3EvalSelectDeferred(pCsr, 0, aTC, nToken);
+        for(ii=0; rc==SQLITE_OK && ii<nOr; ii++){
+          rc = fts3EvalSelectDeferred(pCsr, apOr[ii], aTC, nToken);
+        }
+      }
+
+      sqlite3_free(aTC);
+    }
+  }
+#endif
+
+  fts3EvalStartReaders(pCsr, pCsr->pExpr, &rc);
+  return rc;
+}
+
+/*
+** Invalidate the current position list for phrase pPhrase.
+*/
+static void fts3EvalInvalidatePoslist(Fts3Phrase *pPhrase){
+  if( pPhrase->doclist.bFreeList ){
+    sqlite3_free(pPhrase->doclist.pList);
+  }
+  pPhrase->doclist.pList = 0;
+  pPhrase->doclist.nList = 0;
+  pPhrase->doclist.bFreeList = 0;
+}
+
+/*
+** This function is called to edit the position list associated with
+** the phrase object passed as the fifth argument according to a NEAR
+** condition. For example:
+**
+**     abc NEAR/5 "def ghi"
+**
+** Parameter nNear is passed the NEAR distance of the expression (5 in
+** the example above). When this function is called, *paPoslist points to
+** the position list, and *pnToken is the number of phrase tokens in, the
+** phrase on the other side of the NEAR operator to pPhrase. For example,
+** if pPhrase refers to the "def ghi" phrase, then *paPoslist points to
+** the position list associated with phrase "abc".
+**
+** All positions in the pPhrase position list that are not sufficiently
+** close to a position in the *paPoslist position list are removed. If this
+** leaves 0 positions, zero is returned. Otherwise, non-zero.
+**
+** Before returning, *paPoslist is set to point to the position lsit 
+** associated with pPhrase. And *pnToken is set to the number of tokens in
+** pPhrase.
+*/
+static int fts3EvalNearTrim(
+  int nNear,                      /* NEAR distance. As in "NEAR/nNear". */
+  char *aTmp,                     /* Temporary space to use */
+  char **paPoslist,               /* IN/OUT: Position list */
+  int *pnToken,                   /* IN/OUT: Tokens in phrase of *paPoslist */
+  Fts3Phrase *pPhrase             /* The phrase object to trim the doclist of */
+){
+  int nParam1 = nNear + pPhrase->nToken;
+  int nParam2 = nNear + *pnToken;
+  int nNew;
+  char *p2; 
+  char *pOut; 
+  int res;
+
+  assert( pPhrase->doclist.pList );
+
+  p2 = pOut = pPhrase->doclist.pList;
+  res = fts3PoslistNearMerge(
+    &pOut, aTmp, nParam1, nParam2, paPoslist, &p2
+  );
+  if( res ){
+    nNew = (int)(pOut - pPhrase->doclist.pList) - 1;
+    assert( pPhrase->doclist.pList[nNew]=='\0' );
+    assert( nNew<=pPhrase->doclist.nList && nNew>0 );
+    memset(&pPhrase->doclist.pList[nNew], 0, pPhrase->doclist.nList - nNew);
+    pPhrase->doclist.nList = nNew;
+    *paPoslist = pPhrase->doclist.pList;
+    *pnToken = pPhrase->nToken;
+  }
+
+  return res;
+}
+
+/*
+** This function is a no-op if *pRc is other than SQLITE_OK when it is called.
+** Otherwise, it advances the expression passed as the second argument to
+** point to the next matching row in the database. Expressions iterate through
+** matching rows in docid order. Ascending order if Fts3Cursor.bDesc is zero,
+** or descending if it is non-zero.
+**
+** If an error occurs, *pRc is set to an SQLite error code. Otherwise, if
+** successful, the following variables in pExpr are set:
+**
+**   Fts3Expr.bEof                (non-zero if EOF - there is no next row)
+**   Fts3Expr.iDocid              (valid if bEof==0. The docid of the next row)
+**
+** If the expression is of type FTSQUERY_PHRASE, and the expression is not
+** at EOF, then the following variables are populated with the position list
+** for the phrase for the visited row:
+**
+**   FTs3Expr.pPhrase->doclist.nList        (length of pList in bytes)
+**   FTs3Expr.pPhrase->doclist.pList        (pointer to position list)
+**
+** It says above that this function advances the expression to the next
+** matching row. This is usually true, but there are the following exceptions:
+**
+**   1. Deferred tokens are not taken into account. If a phrase consists
+**      entirely of deferred tokens, it is assumed to match every row in
+**      the db. In this case the position-list is not populated at all. 
+**
+**      Or, if a phrase contains one or more deferred tokens and one or
+**      more non-deferred tokens, then the expression is advanced to the 
+**      next possible match, considering only non-deferred tokens. In other
+**      words, if the phrase is "A B C", and "B" is deferred, the expression
+**      is advanced to the next row that contains an instance of "A * C", 
+**      where "*" may match any single token. The position list in this case
+**      is populated as for "A * C" before returning.
+**
+**   2. NEAR is treated as AND. If the expression is "x NEAR y", it is 
+**      advanced to point to the next row that matches "x AND y".
+** 
+** See sqlite3Fts3EvalTestDeferred() for details on testing if a row is
+** really a match, taking into account deferred tokens and NEAR operators.
+*/
+static void fts3EvalNextRow(
+  Fts3Cursor *pCsr,               /* FTS Cursor handle */
+  Fts3Expr *pExpr,                /* Expr. to advance to next matching row */
+  int *pRc                        /* IN/OUT: Error code */
+){
+  if( *pRc==SQLITE_OK ){
+    int bDescDoclist = pCsr->bDesc;         /* Used by DOCID_CMP() macro */
+    assert( pExpr->bEof==0 );
+    pExpr->bStart = 1;
+
+    switch( pExpr->eType ){
+      case FTSQUERY_NEAR:
+      case FTSQUERY_AND: {
+        Fts3Expr *pLeft = pExpr->pLeft;
+        Fts3Expr *pRight = pExpr->pRight;
+        assert( !pLeft->bDeferred || !pRight->bDeferred );
+
+        if( pLeft->bDeferred ){
+          /* LHS is entirely deferred. So we assume it matches every row.
+          ** Advance the RHS iterator to find the next row visited. */
+          fts3EvalNextRow(pCsr, pRight, pRc);
+          pExpr->iDocid = pRight->iDocid;
+          pExpr->bEof = pRight->bEof;
+        }else if( pRight->bDeferred ){
+          /* RHS is entirely deferred. So we assume it matches every row.
+          ** Advance the LHS iterator to find the next row visited. */
+          fts3EvalNextRow(pCsr, pLeft, pRc);
+          pExpr->iDocid = pLeft->iDocid;
+          pExpr->bEof = pLeft->bEof;
+        }else{
+          /* Neither the RHS or LHS are deferred. */
+          fts3EvalNextRow(pCsr, pLeft, pRc);
+          fts3EvalNextRow(pCsr, pRight, pRc);
+          while( !pLeft->bEof && !pRight->bEof && *pRc==SQLITE_OK ){
+            sqlite3_int64 iDiff = DOCID_CMP(pLeft->iDocid, pRight->iDocid);
+            if( iDiff==0 ) break;
+            if( iDiff<0 ){
+              fts3EvalNextRow(pCsr, pLeft, pRc);
+            }else{
+              fts3EvalNextRow(pCsr, pRight, pRc);
+            }
+          }
+          pExpr->iDocid = pLeft->iDocid;
+          pExpr->bEof = (pLeft->bEof || pRight->bEof);
+          if( pExpr->eType==FTSQUERY_NEAR && pExpr->bEof ){
+            if( pRight->pPhrase && pRight->pPhrase->doclist.aAll ){
+              Fts3Doclist *pDl = &pRight->pPhrase->doclist;
+              while( *pRc==SQLITE_OK && pRight->bEof==0 ){
+                memset(pDl->pList, 0, pDl->nList);
+                fts3EvalNextRow(pCsr, pRight, pRc);
+              }
+            }
+            if( pLeft->pPhrase && pLeft->pPhrase->doclist.aAll ){
+              Fts3Doclist *pDl = &pLeft->pPhrase->doclist;
+              while( *pRc==SQLITE_OK && pLeft->bEof==0 ){
+                memset(pDl->pList, 0, pDl->nList);
+                fts3EvalNextRow(pCsr, pLeft, pRc);
+              }
+            }
+          }
+        }
+        break;
+      }
+  
+      case FTSQUERY_OR: {
+        Fts3Expr *pLeft = pExpr->pLeft;
+        Fts3Expr *pRight = pExpr->pRight;
+        sqlite3_int64 iCmp = DOCID_CMP(pLeft->iDocid, pRight->iDocid);
+
+        assert( pLeft->bStart || pLeft->iDocid==pRight->iDocid );
+        assert( pRight->bStart || pLeft->iDocid==pRight->iDocid );
+
+        if( pRight->bEof || (pLeft->bEof==0 && iCmp<0) ){
+          fts3EvalNextRow(pCsr, pLeft, pRc);
+        }else if( pLeft->bEof || (pRight->bEof==0 && iCmp>0) ){
+          fts3EvalNextRow(pCsr, pRight, pRc);
+        }else{
+          fts3EvalNextRow(pCsr, pLeft, pRc);
+          fts3EvalNextRow(pCsr, pRight, pRc);
+        }
+
+        pExpr->bEof = (pLeft->bEof && pRight->bEof);
+        iCmp = DOCID_CMP(pLeft->iDocid, pRight->iDocid);
+        if( pRight->bEof || (pLeft->bEof==0 &&  iCmp<0) ){
+          pExpr->iDocid = pLeft->iDocid;
+        }else{
+          pExpr->iDocid = pRight->iDocid;
+        }
+
+        break;
+      }
+
+      case FTSQUERY_NOT: {
+        Fts3Expr *pLeft = pExpr->pLeft;
+        Fts3Expr *pRight = pExpr->pRight;
+
+        if( pRight->bStart==0 ){
+          fts3EvalNextRow(pCsr, pRight, pRc);
+          assert( *pRc!=SQLITE_OK || pRight->bStart );
+        }
+
+        fts3EvalNextRow(pCsr, pLeft, pRc);
+        if( pLeft->bEof==0 ){
+          while( !*pRc 
+              && !pRight->bEof 
+              && DOCID_CMP(pLeft->iDocid, pRight->iDocid)>0 
+          ){
+            fts3EvalNextRow(pCsr, pRight, pRc);
+          }
+        }
+        pExpr->iDocid = pLeft->iDocid;
+        pExpr->bEof = pLeft->bEof;
+        break;
+      }
+
+      default: {
+        Fts3Phrase *pPhrase = pExpr->pPhrase;
+        fts3EvalInvalidatePoslist(pPhrase);
+        *pRc = fts3EvalPhraseNext(pCsr, pPhrase, &pExpr->bEof);
+        pExpr->iDocid = pPhrase->doclist.iDocid;
+        break;
+      }
+    }
+  }
+}
+
+/*
+** If *pRc is not SQLITE_OK, or if pExpr is not the root node of a NEAR
+** cluster, then this function returns 1 immediately.
+**
+** Otherwise, it checks if the current row really does match the NEAR 
+** expression, using the data currently stored in the position lists 
+** (Fts3Expr->pPhrase.doclist.pList/nList) for each phrase in the expression. 
+**
+** If the current row is a match, the position list associated with each
+** phrase in the NEAR expression is edited in place to contain only those
+** phrase instances sufficiently close to their peers to satisfy all NEAR
+** constraints. In this case it returns 1. If the NEAR expression does not 
+** match the current row, 0 is returned. The position lists may or may not
+** be edited if 0 is returned.
+*/
+static int fts3EvalNearTest(Fts3Expr *pExpr, int *pRc){
+  int res = 1;
+
+  /* The following block runs if pExpr is the root of a NEAR query.
+  ** For example, the query:
+  **
+  **         "w" NEAR "x" NEAR "y" NEAR "z"
+  **
+  ** which is represented in tree form as:
+  **
+  **                               |
+  **                          +--NEAR--+      <-- root of NEAR query
+  **                          |        |
+  **                     +--NEAR--+   "z"
+  **                     |        |
+  **                +--NEAR--+   "y"
+  **                |        |
+  **               "w"      "x"
+  **
+  ** The right-hand child of a NEAR node is always a phrase. The 
+  ** left-hand child may be either a phrase or a NEAR node. There are
+  ** no exceptions to this - it's the way the parser in fts3_expr.c works.
+  */
+  if( *pRc==SQLITE_OK 
+   && pExpr->eType==FTSQUERY_NEAR 
+   && pExpr->bEof==0
+   && (pExpr->pParent==0 || pExpr->pParent->eType!=FTSQUERY_NEAR)
+  ){
+    Fts3Expr *p; 
+    int nTmp = 0;                 /* Bytes of temp space */
+    char *aTmp;                   /* Temp space for PoslistNearMerge() */
+
+    /* Allocate temporary working space. */
+    for(p=pExpr; p->pLeft; p=p->pLeft){
+      nTmp += p->pRight->pPhrase->doclist.nList;
+    }
+    nTmp += p->pPhrase->doclist.nList;
+    if( nTmp==0 ){
+      res = 0;
+    }else{
+      aTmp = sqlite3_malloc(nTmp*2);
+      if( !aTmp ){
+        *pRc = SQLITE_NOMEM;
+        res = 0;
+      }else{
+        char *aPoslist = p->pPhrase->doclist.pList;
+        int nToken = p->pPhrase->nToken;
+
+        for(p=p->pParent;res && p && p->eType==FTSQUERY_NEAR; p=p->pParent){
+          Fts3Phrase *pPhrase = p->pRight->pPhrase;
+          int nNear = p->nNear;
+          res = fts3EvalNearTrim(nNear, aTmp, &aPoslist, &nToken, pPhrase);
+        }
+
+        aPoslist = pExpr->pRight->pPhrase->doclist.pList;
+        nToken = pExpr->pRight->pPhrase->nToken;
+        for(p=pExpr->pLeft; p && res; p=p->pLeft){
+          int nNear;
+          Fts3Phrase *pPhrase;
+          assert( p->pParent && p->pParent->pLeft==p );
+          nNear = p->pParent->nNear;
+          pPhrase = (
+              p->eType==FTSQUERY_NEAR ? p->pRight->pPhrase : p->pPhrase
+              );
+          res = fts3EvalNearTrim(nNear, aTmp, &aPoslist, &nToken, pPhrase);
+        }
+      }
+
+      sqlite3_free(aTmp);
+    }
+  }
+
+  return res;
+}
+
+/*
+** This function is a helper function for sqlite3Fts3EvalTestDeferred().
+** Assuming no error occurs or has occurred, It returns non-zero if the
+** expression passed as the second argument matches the row that pCsr 
+** currently points to, or zero if it does not.
+**
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
+** If an error occurs during execution of this function, *pRc is set to 
+** the appropriate SQLite error code. In this case the returned value is 
+** undefined.
+*/
+static int fts3EvalTestExpr(
+  Fts3Cursor *pCsr,               /* FTS cursor handle */
+  Fts3Expr *pExpr,                /* Expr to test. May or may not be root. */
+  int *pRc                        /* IN/OUT: Error code */
+){
+  int bHit = 1;                   /* Return value */
+  if( *pRc==SQLITE_OK ){
+    switch( pExpr->eType ){
+      case FTSQUERY_NEAR:
+      case FTSQUERY_AND:
+        bHit = (
+            fts3EvalTestExpr(pCsr, pExpr->pLeft, pRc)
+         && fts3EvalTestExpr(pCsr, pExpr->pRight, pRc)
+         && fts3EvalNearTest(pExpr, pRc)
+        );
+
+        /* If the NEAR expression does not match any rows, zero the doclist for 
+        ** all phrases involved in the NEAR. This is because the snippet(),
+        ** offsets() and matchinfo() functions are not supposed to recognize 
+        ** any instances of phrases that are part of unmatched NEAR queries. 
+        ** For example if this expression:
+        **
+        **    ... MATCH 'a OR (b NEAR c)'
+        **
+        ** is matched against a row containing:
+        **
+        **        'a b d e'
+        **
+        ** then any snippet() should ony highlight the "a" term, not the "b"
+        ** (as "b" is part of a non-matching NEAR clause).
+        */
+        if( bHit==0 
+         && pExpr->eType==FTSQUERY_NEAR 
+         && (pExpr->pParent==0 || pExpr->pParent->eType!=FTSQUERY_NEAR)
+        ){
+          Fts3Expr *p;
+          for(p=pExpr; p->pPhrase==0; p=p->pLeft){
+            if( p->pRight->iDocid==pCsr->iPrevId ){
+              fts3EvalInvalidatePoslist(p->pRight->pPhrase);
+            }
+          }
+          if( p->iDocid==pCsr->iPrevId ){
+            fts3EvalInvalidatePoslist(p->pPhrase);
+          }
+        }
+
+        break;
+
+      case FTSQUERY_OR: {
+        int bHit1 = fts3EvalTestExpr(pCsr, pExpr->pLeft, pRc);
+        int bHit2 = fts3EvalTestExpr(pCsr, pExpr->pRight, pRc);
+        bHit = bHit1 || bHit2;
+        break;
+      }
+
+      case FTSQUERY_NOT:
+        bHit = (
+            fts3EvalTestExpr(pCsr, pExpr->pLeft, pRc)
+         && !fts3EvalTestExpr(pCsr, pExpr->pRight, pRc)
+        );
+        break;
+
+      default: {
+#ifndef SQLITE_DISABLE_FTS4_DEFERRED
+        if( pCsr->pDeferred 
+         && (pExpr->iDocid==pCsr->iPrevId || pExpr->bDeferred)
+        ){
+          Fts3Phrase *pPhrase = pExpr->pPhrase;
+          assert( pExpr->bDeferred || pPhrase->doclist.bFreeList==0 );
+          if( pExpr->bDeferred ){
+            fts3EvalInvalidatePoslist(pPhrase);
+          }
+          *pRc = fts3EvalDeferredPhrase(pCsr, pPhrase);
+          bHit = (pPhrase->doclist.pList!=0);
+          pExpr->iDocid = pCsr->iPrevId;
+        }else
+#endif
+        {
+          bHit = (pExpr->bEof==0 && pExpr->iDocid==pCsr->iPrevId);
+        }
+        break;
+      }
+    }
+  }
+  return bHit;
+}
+
+/*
+** This function is called as the second part of each xNext operation when
+** iterating through the results of a full-text query. At this point the
+** cursor points to a row that matches the query expression, with the
+** following caveats:
+**
+**   * Up until this point, "NEAR" operators in the expression have been
+**     treated as "AND".
+**
+**   * Deferred tokens have not yet been considered.
+**
+** If *pRc is not SQLITE_OK when this function is called, it immediately
+** returns 0. Otherwise, it tests whether or not after considering NEAR
+** operators and deferred tokens the current row is still a match for the
+** expression. It returns 1 if both of the following are true:
+**
+**   1. *pRc is SQLITE_OK when this function returns, and
+**
+**   2. After scanning the current FTS table row for the deferred tokens,
+**      it is determined that the row does *not* match the query.
+**
+** Or, if no error occurs and it seems the current row does match the FTS
+** query, return 0.
+*/
+SQLITE_PRIVATE int sqlite3Fts3EvalTestDeferred(Fts3Cursor *pCsr, int *pRc){
+  int rc = *pRc;
+  int bMiss = 0;
+  if( rc==SQLITE_OK ){
+
+    /* If there are one or more deferred tokens, load the current row into
+    ** memory and scan it to determine the position list for each deferred
+    ** token. Then, see if this row is really a match, considering deferred
+    ** tokens and NEAR operators (neither of which were taken into account
+    ** earlier, by fts3EvalNextRow()). 
+    */
+    if( pCsr->pDeferred ){
+      rc = fts3CursorSeek(0, pCsr);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3Fts3CacheDeferredDoclists(pCsr);
+      }
+    }
+    bMiss = (0==fts3EvalTestExpr(pCsr, pCsr->pExpr, &rc));
+
+    /* Free the position-lists accumulated for each deferred token above. */
+    sqlite3Fts3FreeDeferredDoclists(pCsr);
+    *pRc = rc;
+  }
+  return (rc==SQLITE_OK && bMiss);
+}
+
+/*
+** Advance to the next document that matches the FTS expression in
+** Fts3Cursor.pExpr.
+*/
+static int fts3EvalNext(Fts3Cursor *pCsr){
+  int rc = SQLITE_OK;             /* Return Code */
+  Fts3Expr *pExpr = pCsr->pExpr;
+  assert( pCsr->isEof==0 );
+  if( pExpr==0 ){
+    pCsr->isEof = 1;
+  }else{
+    do {
+      if( pCsr->isRequireSeek==0 ){
+        sqlite3_reset(pCsr->pStmt);
+      }
+      assert( sqlite3_data_count(pCsr->pStmt)==0 );
+      fts3EvalNextRow(pCsr, pExpr, &rc);
+      pCsr->isEof = pExpr->bEof;
+      pCsr->isRequireSeek = 1;
+      pCsr->isMatchinfoNeeded = 1;
+      pCsr->iPrevId = pExpr->iDocid;
+    }while( pCsr->isEof==0 && sqlite3Fts3EvalTestDeferred(pCsr, &rc) );
+  }
+
+  /* Check if the cursor is past the end of the docid range specified
+  ** by Fts3Cursor.iMinDocid/iMaxDocid. If so, set the EOF flag.  */
+  if( rc==SQLITE_OK && (
+        (pCsr->bDesc==0 && pCsr->iPrevId>pCsr->iMaxDocid)
+     || (pCsr->bDesc!=0 && pCsr->iPrevId<pCsr->iMinDocid)
+  )){
+    pCsr->isEof = 1;
+  }
+
+  return rc;
+}
+
+/*
+** Restart interation for expression pExpr so that the next call to
+** fts3EvalNext() visits the first row. Do not allow incremental 
+** loading or merging of phrase doclists for this iteration.
+**
+** If *pRc is other than SQLITE_OK when this function is called, it is
+** a no-op. If an error occurs within this function, *pRc is set to an
+** SQLite error code before returning.
+*/
+static void fts3EvalRestart(
+  Fts3Cursor *pCsr,
+  Fts3Expr *pExpr,
+  int *pRc
+){
+  if( pExpr && *pRc==SQLITE_OK ){
+    Fts3Phrase *pPhrase = pExpr->pPhrase;
+
+    if( pPhrase ){
+      fts3EvalInvalidatePoslist(pPhrase);
+      if( pPhrase->bIncr ){
+        int i;
+        for(i=0; i<pPhrase->nToken; i++){
+          Fts3PhraseToken *pToken = &pPhrase->aToken[i];
+          assert( pToken->pDeferred==0 );
+          if( pToken->pSegcsr ){
+            sqlite3Fts3MsrIncrRestart(pToken->pSegcsr);
+          }
+        }
+        *pRc = fts3EvalPhraseStart(pCsr, 0, pPhrase);
+      }
+      pPhrase->doclist.pNextDocid = 0;
+      pPhrase->doclist.iDocid = 0;
+      pPhrase->pOrPoslist = 0;
+    }
+
+    pExpr->iDocid = 0;
+    pExpr->bEof = 0;
+    pExpr->bStart = 0;
+
+    fts3EvalRestart(pCsr, pExpr->pLeft, pRc);
+    fts3EvalRestart(pCsr, pExpr->pRight, pRc);
+  }
+}
+
+/*
+** After allocating the Fts3Expr.aMI[] array for each phrase in the 
+** expression rooted at pExpr, the cursor iterates through all rows matched
+** by pExpr, calling this function for each row. This function increments
+** the values in Fts3Expr.aMI[] according to the position-list currently
+** found in Fts3Expr.pPhrase->doclist.pList for each of the phrase 
+** expression nodes.
+*/
+static void fts3EvalUpdateCounts(Fts3Expr *pExpr){
+  if( pExpr ){
+    Fts3Phrase *pPhrase = pExpr->pPhrase;
+    if( pPhrase && pPhrase->doclist.pList ){
+      int iCol = 0;
+      char *p = pPhrase->doclist.pList;
+
+      assert( *p );
+      while( 1 ){
+        u8 c = 0;
+        int iCnt = 0;
+        while( 0xFE & (*p | c) ){
+          if( (c&0x80)==0 ) iCnt++;
+          c = *p++ & 0x80;
+        }
+
+        /* aMI[iCol*3 + 1] = Number of occurrences
+        ** aMI[iCol*3 + 2] = Number of rows containing at least one instance
+        */
+        pExpr->aMI[iCol*3 + 1] += iCnt;
+        pExpr->aMI[iCol*3 + 2] += (iCnt>0);
+        if( *p==0x00 ) break;
+        p++;
+        p += fts3GetVarint32(p, &iCol);
+      }
+    }
+
+    fts3EvalUpdateCounts(pExpr->pLeft);
+    fts3EvalUpdateCounts(pExpr->pRight);
+  }
+}
+
+/*
+** Expression pExpr must be of type FTSQUERY_PHRASE.
+**
+** If it is not already allocated and populated, this function allocates and
+** populates the Fts3Expr.aMI[] array for expression pExpr. If pExpr is part
+** of a NEAR expression, then it also allocates and populates the same array
+** for all other phrases that are part of the NEAR expression.
+**
+** SQLITE_OK is returned if the aMI[] array is successfully allocated and
+** populated. Otherwise, if an error occurs, an SQLite error code is returned.
+*/
+static int fts3EvalGatherStats(
+  Fts3Cursor *pCsr,               /* Cursor object */
+  Fts3Expr *pExpr                 /* FTSQUERY_PHRASE expression */
+){
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( pExpr->eType==FTSQUERY_PHRASE );
+  if( pExpr->aMI==0 ){
+    Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+    Fts3Expr *pRoot;                /* Root of NEAR expression */
+    Fts3Expr *p;                    /* Iterator used for several purposes */
+
+    sqlite3_int64 iPrevId = pCsr->iPrevId;
+    sqlite3_int64 iDocid;
+    u8 bEof;
+
+    /* Find the root of the NEAR expression */
+    pRoot = pExpr;
+    while( pRoot->pParent && pRoot->pParent->eType==FTSQUERY_NEAR ){
+      pRoot = pRoot->pParent;
+    }
+    iDocid = pRoot->iDocid;
+    bEof = pRoot->bEof;
+    assert( pRoot->bStart );
+
+    /* Allocate space for the aMSI[] array of each FTSQUERY_PHRASE node */
+    for(p=pRoot; p; p=p->pLeft){
+      Fts3Expr *pE = (p->eType==FTSQUERY_PHRASE?p:p->pRight);
+      assert( pE->aMI==0 );
+      pE->aMI = (u32 *)sqlite3_malloc(pTab->nColumn * 3 * sizeof(u32));
+      if( !pE->aMI ) return SQLITE_NOMEM;
+      memset(pE->aMI, 0, pTab->nColumn * 3 * sizeof(u32));
+    }
+
+    fts3EvalRestart(pCsr, pRoot, &rc);
+
+    while( pCsr->isEof==0 && rc==SQLITE_OK ){
+
+      do {
+        /* Ensure the %_content statement is reset. */
+        if( pCsr->isRequireSeek==0 ) sqlite3_reset(pCsr->pStmt);
+        assert( sqlite3_data_count(pCsr->pStmt)==0 );
+
+        /* Advance to the next document */
+        fts3EvalNextRow(pCsr, pRoot, &rc);
+        pCsr->isEof = pRoot->bEof;
+        pCsr->isRequireSeek = 1;
+        pCsr->isMatchinfoNeeded = 1;
+        pCsr->iPrevId = pRoot->iDocid;
+      }while( pCsr->isEof==0 
+           && pRoot->eType==FTSQUERY_NEAR 
+           && sqlite3Fts3EvalTestDeferred(pCsr, &rc) 
+      );
+
+      if( rc==SQLITE_OK && pCsr->isEof==0 ){
+        fts3EvalUpdateCounts(pRoot);
+      }
+    }
+
+    pCsr->isEof = 0;
+    pCsr->iPrevId = iPrevId;
+
+    if( bEof ){
+      pRoot->bEof = bEof;
+    }else{
+      /* Caution: pRoot may iterate through docids in ascending or descending
+      ** order. For this reason, even though it seems more defensive, the 
+      ** do loop can not be written:
+      **
+      **   do {...} while( pRoot->iDocid<iDocid && rc==SQLITE_OK );
+      */
+      fts3EvalRestart(pCsr, pRoot, &rc);
+      do {
+        fts3EvalNextRow(pCsr, pRoot, &rc);
+        assert( pRoot->bEof==0 );
+      }while( pRoot->iDocid!=iDocid && rc==SQLITE_OK );
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is used by the matchinfo() module to query a phrase 
+** expression node for the following information:
+**
+**   1. The total number of occurrences of the phrase in each column of 
+**      the FTS table (considering all rows), and
+**
+**   2. For each column, the number of rows in the table for which the
+**      column contains at least one instance of the phrase.
+**
+** If no error occurs, SQLITE_OK is returned and the values for each column
+** written into the array aiOut as follows:
+**
+**   aiOut[iCol*3 + 1] = Number of occurrences
+**   aiOut[iCol*3 + 2] = Number of rows containing at least one instance
+**
+** Caveats:
+**
+**   * If a phrase consists entirely of deferred tokens, then all output 
+**     values are set to the number of documents in the table. In other
+**     words we assume that very common tokens occur exactly once in each 
+**     column of each row of the table.
+**
+**   * If a phrase contains some deferred tokens (and some non-deferred 
+**     tokens), count the potential occurrence identified by considering
+**     the non-deferred tokens instead of actual phrase occurrences.
+**
+**   * If the phrase is part of a NEAR expression, then only phrase instances
+**     that meet the NEAR constraint are included in the counts.
+*/
+SQLITE_PRIVATE int sqlite3Fts3EvalPhraseStats(
+  Fts3Cursor *pCsr,               /* FTS cursor handle */
+  Fts3Expr *pExpr,                /* Phrase expression */
+  u32 *aiOut                      /* Array to write results into (see above) */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+  int iCol;
+
+  if( pExpr->bDeferred && pExpr->pParent->eType!=FTSQUERY_NEAR ){
+    assert( pCsr->nDoc>0 );
+    for(iCol=0; iCol<pTab->nColumn; iCol++){
+      aiOut[iCol*3 + 1] = (u32)pCsr->nDoc;
+      aiOut[iCol*3 + 2] = (u32)pCsr->nDoc;
+    }
+  }else{
+    rc = fts3EvalGatherStats(pCsr, pExpr);
+    if( rc==SQLITE_OK ){
+      assert( pExpr->aMI );
+      for(iCol=0; iCol<pTab->nColumn; iCol++){
+        aiOut[iCol*3 + 1] = pExpr->aMI[iCol*3 + 1];
+        aiOut[iCol*3 + 2] = pExpr->aMI[iCol*3 + 2];
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** The expression pExpr passed as the second argument to this function
+** must be of type FTSQUERY_PHRASE. 
+**
+** The returned value is either NULL or a pointer to a buffer containing
+** a position-list indicating the occurrences of the phrase in column iCol
+** of the current row. 
+**
+** More specifically, the returned buffer contains 1 varint for each 
+** occurrence of the phrase in the column, stored using the normal (delta+2) 
+** compression and is terminated by either an 0x01 or 0x00 byte. For example,
+** if the requested column contains "a b X c d X X" and the position-list
+** for 'X' is requested, the buffer returned may contain:
+**
+**     0x04 0x05 0x03 0x01   or   0x04 0x05 0x03 0x00
+**
+** This function works regardless of whether or not the phrase is deferred,
+** incremental, or neither.
+*/
+SQLITE_PRIVATE int sqlite3Fts3EvalPhrasePoslist(
+  Fts3Cursor *pCsr,               /* FTS3 cursor object */
+  Fts3Expr *pExpr,                /* Phrase to return doclist for */
+  int iCol,                       /* Column to return position list for */
+  char **ppOut                    /* OUT: Pointer to position list */
+){
+  Fts3Phrase *pPhrase = pExpr->pPhrase;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  char *pIter;
+  int iThis;
+  sqlite3_int64 iDocid;
+
+  /* If this phrase is applies specifically to some column other than 
+  ** column iCol, return a NULL pointer.  */
+  *ppOut = 0;
+  assert( iCol>=0 && iCol<pTab->nColumn );
+  if( (pPhrase->iColumn<pTab->nColumn && pPhrase->iColumn!=iCol) ){
+    return SQLITE_OK;
+  }
+
+  iDocid = pExpr->iDocid;
+  pIter = pPhrase->doclist.pList;
+  if( iDocid!=pCsr->iPrevId || pExpr->bEof ){
+    int rc = SQLITE_OK;
+    int bDescDoclist = pTab->bDescIdx;      /* For DOCID_CMP macro */
+    int bOr = 0;
+    u8 bTreeEof = 0;
+    Fts3Expr *p;                  /* Used to iterate from pExpr to root */
+    Fts3Expr *pNear;              /* Most senior NEAR ancestor (or pExpr) */
+    int bMatch;
+
+    /* Check if this phrase descends from an OR expression node. If not, 
+    ** return NULL. Otherwise, the entry that corresponds to docid 
+    ** pCsr->iPrevId may lie earlier in the doclist buffer. Or, if the
+    ** tree that the node is part of has been marked as EOF, but the node
+    ** itself is not EOF, then it may point to an earlier entry. */
+    pNear = pExpr;
+    for(p=pExpr->pParent; p; p=p->pParent){
+      if( p->eType==FTSQUERY_OR ) bOr = 1;
+      if( p->eType==FTSQUERY_NEAR ) pNear = p;
+      if( p->bEof ) bTreeEof = 1;
+    }
+    if( bOr==0 ) return SQLITE_OK;
+
+    /* This is the descendent of an OR node. In this case we cannot use
+    ** an incremental phrase. Load the entire doclist for the phrase
+    ** into memory in this case.  */
+    if( pPhrase->bIncr ){
+      int bEofSave = pNear->bEof;
+      fts3EvalRestart(pCsr, pNear, &rc);
+      while( rc==SQLITE_OK && !pNear->bEof ){
+        fts3EvalNextRow(pCsr, pNear, &rc);
+        if( bEofSave==0 && pNear->iDocid==iDocid ) break;
+      }
+      assert( rc!=SQLITE_OK || pPhrase->bIncr==0 );
+    }
+    if( bTreeEof ){
+      while( rc==SQLITE_OK && !pNear->bEof ){
+        fts3EvalNextRow(pCsr, pNear, &rc);
+      }
+    }
+    if( rc!=SQLITE_OK ) return rc;
+
+    bMatch = 1;
+    for(p=pNear; p; p=p->pLeft){
+      u8 bEof = 0;
+      Fts3Expr *pTest = p;
+      Fts3Phrase *pPh;
+      assert( pTest->eType==FTSQUERY_NEAR || pTest->eType==FTSQUERY_PHRASE );
+      if( pTest->eType==FTSQUERY_NEAR ) pTest = pTest->pRight;
+      assert( pTest->eType==FTSQUERY_PHRASE );
+      pPh = pTest->pPhrase;
+
+      pIter = pPh->pOrPoslist;
+      iDocid = pPh->iOrDocid;
+      if( pCsr->bDesc==bDescDoclist ){
+        bEof = !pPh->doclist.nAll ||
+          (pIter >= (pPh->doclist.aAll + pPh->doclist.nAll));
+        while( (pIter==0 || DOCID_CMP(iDocid, pCsr->iPrevId)<0 ) && bEof==0 ){
+          sqlite3Fts3DoclistNext(
+              bDescDoclist, pPh->doclist.aAll, pPh->doclist.nAll, 
+              &pIter, &iDocid, &bEof
+          );
+        }
+      }else{
+        bEof = !pPh->doclist.nAll || (pIter && pIter<=pPh->doclist.aAll);
+        while( (pIter==0 || DOCID_CMP(iDocid, pCsr->iPrevId)>0 ) && bEof==0 ){
+          int dummy;
+          sqlite3Fts3DoclistPrev(
+              bDescDoclist, pPh->doclist.aAll, pPh->doclist.nAll, 
+              &pIter, &iDocid, &dummy, &bEof
+              );
+        }
+      }
+      pPh->pOrPoslist = pIter;
+      pPh->iOrDocid = iDocid;
+      if( bEof || iDocid!=pCsr->iPrevId ) bMatch = 0;
+    }
+
+    if( bMatch ){
+      pIter = pPhrase->pOrPoslist;
+    }else{
+      pIter = 0;
+    }
+  }
+  if( pIter==0 ) return SQLITE_OK;
+
+  if( *pIter==0x01 ){
+    pIter++;
+    pIter += fts3GetVarint32(pIter, &iThis);
+  }else{
+    iThis = 0;
+  }
+  while( iThis<iCol ){
+    fts3ColumnlistCopy(0, &pIter);
+    if( *pIter==0x00 ) return SQLITE_OK;
+    pIter++;
+    pIter += fts3GetVarint32(pIter, &iThis);
+  }
+  if( *pIter==0x00 ){
+    pIter = 0;
+  }
+
+  *ppOut = ((iCol==iThis)?pIter:0);
+  return SQLITE_OK;
+}
+
+/*
+** Free all components of the Fts3Phrase structure that were allocated by
+** the eval module. Specifically, this means to free:
+**
+**   * the contents of pPhrase->doclist, and
+**   * any Fts3MultiSegReader objects held by phrase tokens.
+*/
+SQLITE_PRIVATE void sqlite3Fts3EvalPhraseCleanup(Fts3Phrase *pPhrase){
+  if( pPhrase ){
+    int i;
+    sqlite3_free(pPhrase->doclist.aAll);
+    fts3EvalInvalidatePoslist(pPhrase);
+    memset(&pPhrase->doclist, 0, sizeof(Fts3Doclist));
+    for(i=0; i<pPhrase->nToken; i++){
+      fts3SegReaderCursorFree(pPhrase->aToken[i].pSegcsr);
+      pPhrase->aToken[i].pSegcsr = 0;
+    }
+  }
+}
+
+
+/*
+** Return SQLITE_CORRUPT_VTAB.
+*/
+#ifdef SQLITE_DEBUG
+SQLITE_PRIVATE int sqlite3Fts3Corrupt(){
+  return SQLITE_CORRUPT_VTAB;
+}
+#endif
+
+#if !SQLITE_CORE
+/*
+** Initialize API pointer table, if required.
+*/
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+SQLITE_API int sqlite3_fts3_init(
+  sqlite3 *db, 
+  char **pzErrMsg,
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi)
+  return sqlite3Fts3Init(db);
+}
+#endif
+
+#endif
+
+/************** End of fts3.c ************************************************/
+/************** Begin file fts3_aux.c ****************************************/
+/*
+** 2011 Jan 27
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <string.h> */
+/* #include <assert.h> */
+
+typedef struct Fts3auxTable Fts3auxTable;
+typedef struct Fts3auxCursor Fts3auxCursor;
+
+struct Fts3auxTable {
+  sqlite3_vtab base;              /* Base class used by SQLite core */
+  Fts3Table *pFts3Tab;
+};
+
+struct Fts3auxCursor {
+  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
+  Fts3MultiSegReader csr;        /* Must be right after "base" */
+  Fts3SegFilter filter;
+  char *zStop;
+  int nStop;                      /* Byte-length of string zStop */
+  int iLangid;                    /* Language id to query */
+  int isEof;                      /* True if cursor is at EOF */
+  sqlite3_int64 iRowid;           /* Current rowid */
+
+  int iCol;                       /* Current value of 'col' column */
+  int nStat;                      /* Size of aStat[] array */
+  struct Fts3auxColstats {
+    sqlite3_int64 nDoc;           /* 'documents' values for current csr row */
+    sqlite3_int64 nOcc;           /* 'occurrences' values for current csr row */
+  } *aStat;
+};
+
+/*
+** Schema of the terms table.
+*/
+#define FTS3_AUX_SCHEMA \
+  "CREATE TABLE x(term, col, documents, occurrences, languageid HIDDEN)"
+
+/*
+** This function does all the work for both the xConnect and xCreate methods.
+** These tables have no persistent representation of their own, so xConnect
+** and xCreate are identical operations.
+*/
+static int fts3auxConnectMethod(
+  sqlite3 *db,                    /* Database connection */
+  void *pUnused,                  /* Unused */
+  int argc,                       /* Number of elements in argv array */
+  const char * const *argv,       /* xCreate/xConnect argument array */
+  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
+  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
+){
+  char const *zDb;                /* Name of database (e.g. "main") */
+  char const *zFts3;              /* Name of fts3 table */
+  int nDb;                        /* Result of strlen(zDb) */
+  int nFts3;                      /* Result of strlen(zFts3) */
+  int nByte;                      /* Bytes of space to allocate here */
+  int rc;                         /* value returned by declare_vtab() */
+  Fts3auxTable *p;                /* Virtual table object to return */
+
+  UNUSED_PARAMETER(pUnused);
+
+  /* The user should invoke this in one of two forms:
+  **
+  **     CREATE VIRTUAL TABLE xxx USING fts4aux(fts4-table);
+  **     CREATE VIRTUAL TABLE xxx USING fts4aux(fts4-table-db, fts4-table);
+  */
+  if( argc!=4 && argc!=5 ) goto bad_args;
+
+  zDb = argv[1]; 
+  nDb = (int)strlen(zDb);
+  if( argc==5 ){
+    if( nDb==4 && 0==sqlite3_strnicmp("temp", zDb, 4) ){
+      zDb = argv[3]; 
+      nDb = (int)strlen(zDb);
+      zFts3 = argv[4];
+    }else{
+      goto bad_args;
+    }
+  }else{
+    zFts3 = argv[3];
+  }
+  nFts3 = (int)strlen(zFts3);
+
+  rc = sqlite3_declare_vtab(db, FTS3_AUX_SCHEMA);
+  if( rc!=SQLITE_OK ) return rc;
+
+  nByte = sizeof(Fts3auxTable) + sizeof(Fts3Table) + nDb + nFts3 + 2;
+  p = (Fts3auxTable *)sqlite3_malloc(nByte);
+  if( !p ) return SQLITE_NOMEM;
+  memset(p, 0, nByte);
+
+  p->pFts3Tab = (Fts3Table *)&p[1];
+  p->pFts3Tab->zDb = (char *)&p->pFts3Tab[1];
+  p->pFts3Tab->zName = &p->pFts3Tab->zDb[nDb+1];
+  p->pFts3Tab->db = db;
+  p->pFts3Tab->nIndex = 1;
+
+  memcpy((char *)p->pFts3Tab->zDb, zDb, nDb);
+  memcpy((char *)p->pFts3Tab->zName, zFts3, nFts3);
+  sqlite3Fts3Dequote((char *)p->pFts3Tab->zName);
+
+  *ppVtab = (sqlite3_vtab *)p;
+  return SQLITE_OK;
+
+ bad_args:
+  sqlite3Fts3ErrMsg(pzErr, "invalid arguments to fts4aux constructor");
+  return SQLITE_ERROR;
+}
+
+/*
+** This function does the work for both the xDisconnect and xDestroy methods.
+** These tables have no persistent representation of their own, so xDisconnect
+** and xDestroy are identical operations.
+*/
+static int fts3auxDisconnectMethod(sqlite3_vtab *pVtab){
+  Fts3auxTable *p = (Fts3auxTable *)pVtab;
+  Fts3Table *pFts3 = p->pFts3Tab;
+  int i;
+
+  /* Free any prepared statements held */
+  for(i=0; i<SizeofArray(pFts3->aStmt); i++){
+    sqlite3_finalize(pFts3->aStmt[i]);
+  }
+  sqlite3_free(pFts3->zSegmentsTbl);
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+#define FTS4AUX_EQ_CONSTRAINT 1
+#define FTS4AUX_GE_CONSTRAINT 2
+#define FTS4AUX_LE_CONSTRAINT 4
+
+/*
+** xBestIndex - Analyze a WHERE and ORDER BY clause.
+*/
+static int fts3auxBestIndexMethod(
+  sqlite3_vtab *pVTab, 
+  sqlite3_index_info *pInfo
+){
+  int i;
+  int iEq = -1;
+  int iGe = -1;
+  int iLe = -1;
+  int iLangid = -1;
+  int iNext = 1;                  /* Next free argvIndex value */
+
+  UNUSED_PARAMETER(pVTab);
+
+  /* This vtab delivers always results in "ORDER BY term ASC" order. */
+  if( pInfo->nOrderBy==1 
+   && pInfo->aOrderBy[0].iColumn==0 
+   && pInfo->aOrderBy[0].desc==0
+  ){
+    pInfo->orderByConsumed = 1;
+  }
+
+  /* Search for equality and range constraints on the "term" column. 
+  ** And equality constraints on the hidden "languageid" column. */
+  for(i=0; i<pInfo->nConstraint; i++){
+    if( pInfo->aConstraint[i].usable ){
+      int op = pInfo->aConstraint[i].op;
+      int iCol = pInfo->aConstraint[i].iColumn;
+
+      if( iCol==0 ){
+        if( op==SQLITE_INDEX_CONSTRAINT_EQ ) iEq = i;
+        if( op==SQLITE_INDEX_CONSTRAINT_LT ) iLe = i;
+        if( op==SQLITE_INDEX_CONSTRAINT_LE ) iLe = i;
+        if( op==SQLITE_INDEX_CONSTRAINT_GT ) iGe = i;
+        if( op==SQLITE_INDEX_CONSTRAINT_GE ) iGe = i;
+      }
+      if( iCol==4 ){
+        if( op==SQLITE_INDEX_CONSTRAINT_EQ ) iLangid = i;
+      }
+    }
+  }
+
+  if( iEq>=0 ){
+    pInfo->idxNum = FTS4AUX_EQ_CONSTRAINT;
+    pInfo->aConstraintUsage[iEq].argvIndex = iNext++;
+    pInfo->estimatedCost = 5;
+  }else{
+    pInfo->idxNum = 0;
+    pInfo->estimatedCost = 20000;
+    if( iGe>=0 ){
+      pInfo->idxNum += FTS4AUX_GE_CONSTRAINT;
+      pInfo->aConstraintUsage[iGe].argvIndex = iNext++;
+      pInfo->estimatedCost /= 2;
+    }
+    if( iLe>=0 ){
+      pInfo->idxNum += FTS4AUX_LE_CONSTRAINT;
+      pInfo->aConstraintUsage[iLe].argvIndex = iNext++;
+      pInfo->estimatedCost /= 2;
+    }
+  }
+  if( iLangid>=0 ){
+    pInfo->aConstraintUsage[iLangid].argvIndex = iNext++;
+    pInfo->estimatedCost--;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** xOpen - Open a cursor.
+*/
+static int fts3auxOpenMethod(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCsr){
+  Fts3auxCursor *pCsr;            /* Pointer to cursor object to return */
+
+  UNUSED_PARAMETER(pVTab);
+
+  pCsr = (Fts3auxCursor *)sqlite3_malloc(sizeof(Fts3auxCursor));
+  if( !pCsr ) return SQLITE_NOMEM;
+  memset(pCsr, 0, sizeof(Fts3auxCursor));
+
+  *ppCsr = (sqlite3_vtab_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+/*
+** xClose - Close a cursor.
+*/
+static int fts3auxCloseMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3Table *pFts3 = ((Fts3auxTable *)pCursor->pVtab)->pFts3Tab;
+  Fts3auxCursor *pCsr = (Fts3auxCursor *)pCursor;
+
+  sqlite3Fts3SegmentsClose(pFts3);
+  sqlite3Fts3SegReaderFinish(&pCsr->csr);
+  sqlite3_free((void *)pCsr->filter.zTerm);
+  sqlite3_free(pCsr->zStop);
+  sqlite3_free(pCsr->aStat);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+static int fts3auxGrowStatArray(Fts3auxCursor *pCsr, int nSize){
+  if( nSize>pCsr->nStat ){
+    struct Fts3auxColstats *aNew;
+    aNew = (struct Fts3auxColstats *)sqlite3_realloc(pCsr->aStat, 
+        sizeof(struct Fts3auxColstats) * nSize
+    );
+    if( aNew==0 ) return SQLITE_NOMEM;
+    memset(&aNew[pCsr->nStat], 0, 
+        sizeof(struct Fts3auxColstats) * (nSize - pCsr->nStat)
+    );
+    pCsr->aStat = aNew;
+    pCsr->nStat = nSize;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** xNext - Advance the cursor to the next row, if any.
+*/
+static int fts3auxNextMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3auxCursor *pCsr = (Fts3auxCursor *)pCursor;
+  Fts3Table *pFts3 = ((Fts3auxTable *)pCursor->pVtab)->pFts3Tab;
+  int rc;
+
+  /* Increment our pretend rowid value. */
+  pCsr->iRowid++;
+
+  for(pCsr->iCol++; pCsr->iCol<pCsr->nStat; pCsr->iCol++){
+    if( pCsr->aStat[pCsr->iCol].nDoc>0 ) return SQLITE_OK;
+  }
+
+  rc = sqlite3Fts3SegReaderStep(pFts3, &pCsr->csr);
+  if( rc==SQLITE_ROW ){
+    int i = 0;
+    int nDoclist = pCsr->csr.nDoclist;
+    char *aDoclist = pCsr->csr.aDoclist;
+    int iCol;
+
+    int eState = 0;
+
+    if( pCsr->zStop ){
+      int n = (pCsr->nStop<pCsr->csr.nTerm) ? pCsr->nStop : pCsr->csr.nTerm;
+      int mc = memcmp(pCsr->zStop, pCsr->csr.zTerm, n);
+      if( mc<0 || (mc==0 && pCsr->csr.nTerm>pCsr->nStop) ){
+        pCsr->isEof = 1;
+        return SQLITE_OK;
+      }
+    }
+
+    if( fts3auxGrowStatArray(pCsr, 2) ) return SQLITE_NOMEM;
+    memset(pCsr->aStat, 0, sizeof(struct Fts3auxColstats) * pCsr->nStat);
+    iCol = 0;
+
+    while( i<nDoclist ){
+      sqlite3_int64 v = 0;
+
+      i += sqlite3Fts3GetVarint(&aDoclist[i], &v);
+      switch( eState ){
+        /* State 0. In this state the integer just read was a docid. */
+        case 0:
+          pCsr->aStat[0].nDoc++;
+          eState = 1;
+          iCol = 0;
+          break;
+
+        /* State 1. In this state we are expecting either a 1, indicating
+        ** that the following integer will be a column number, or the
+        ** start of a position list for column 0.  
+        ** 
+        ** The only difference between state 1 and state 2 is that if the
+        ** integer encountered in state 1 is not 0 or 1, then we need to
+        ** increment the column 0 "nDoc" count for this term.
+        */
+        case 1:
+          assert( iCol==0 );
+          if( v>1 ){
+            pCsr->aStat[1].nDoc++;
+          }
+          eState = 2;
+          /* fall through */
+
+        case 2:
+          if( v==0 ){       /* 0x00. Next integer will be a docid. */
+            eState = 0;
+          }else if( v==1 ){ /* 0x01. Next integer will be a column number. */
+            eState = 3;
+          }else{            /* 2 or greater. A position. */
+            pCsr->aStat[iCol+1].nOcc++;
+            pCsr->aStat[0].nOcc++;
+          }
+          break;
+
+        /* State 3. The integer just read is a column number. */
+        default: assert( eState==3 );
+          iCol = (int)v;
+          if( fts3auxGrowStatArray(pCsr, iCol+2) ) return SQLITE_NOMEM;
+          pCsr->aStat[iCol+1].nDoc++;
+          eState = 2;
+          break;
+      }
+    }
+
+    pCsr->iCol = 0;
+    rc = SQLITE_OK;
+  }else{
+    pCsr->isEof = 1;
+  }
+  return rc;
+}
+
+/*
+** xFilter - Initialize a cursor to point at the start of its data.
+*/
+static int fts3auxFilterMethod(
+  sqlite3_vtab_cursor *pCursor,   /* The cursor used for this query */
+  int idxNum,                     /* Strategy index */
+  const char *idxStr,             /* Unused */
+  int nVal,                       /* Number of elements in apVal */
+  sqlite3_value **apVal           /* Arguments for the indexing scheme */
+){
+  Fts3auxCursor *pCsr = (Fts3auxCursor *)pCursor;
+  Fts3Table *pFts3 = ((Fts3auxTable *)pCursor->pVtab)->pFts3Tab;
+  int rc;
+  int isScan = 0;
+  int iLangVal = 0;               /* Language id to query */
+
+  int iEq = -1;                   /* Index of term=? value in apVal */
+  int iGe = -1;                   /* Index of term>=? value in apVal */
+  int iLe = -1;                   /* Index of term<=? value in apVal */
+  int iLangid = -1;               /* Index of languageid=? value in apVal */
+  int iNext = 0;
+
+  UNUSED_PARAMETER(nVal);
+  UNUSED_PARAMETER(idxStr);
+
+  assert( idxStr==0 );
+  assert( idxNum==FTS4AUX_EQ_CONSTRAINT || idxNum==0
+       || idxNum==FTS4AUX_LE_CONSTRAINT || idxNum==FTS4AUX_GE_CONSTRAINT
+       || idxNum==(FTS4AUX_LE_CONSTRAINT|FTS4AUX_GE_CONSTRAINT)
+  );
+
+  if( idxNum==FTS4AUX_EQ_CONSTRAINT ){
+    iEq = iNext++;
+  }else{
+    isScan = 1;
+    if( idxNum & FTS4AUX_GE_CONSTRAINT ){
+      iGe = iNext++;
+    }
+    if( idxNum & FTS4AUX_LE_CONSTRAINT ){
+      iLe = iNext++;
+    }
+  }
+  if( iNext<nVal ){
+    iLangid = iNext++;
+  }
+
+  /* In case this cursor is being reused, close and zero it. */
+  testcase(pCsr->filter.zTerm);
+  sqlite3Fts3SegReaderFinish(&pCsr->csr);
+  sqlite3_free((void *)pCsr->filter.zTerm);
+  sqlite3_free(pCsr->aStat);
+  memset(&pCsr->csr, 0, ((u8*)&pCsr[1]) - (u8*)&pCsr->csr);
+
+  pCsr->filter.flags = FTS3_SEGMENT_REQUIRE_POS|FTS3_SEGMENT_IGNORE_EMPTY;
+  if( isScan ) pCsr->filter.flags |= FTS3_SEGMENT_SCAN;
+
+  if( iEq>=0 || iGe>=0 ){
+    const unsigned char *zStr = sqlite3_value_text(apVal[0]);
+    assert( (iEq==0 && iGe==-1) || (iEq==-1 && iGe==0) );
+    if( zStr ){
+      pCsr->filter.zTerm = sqlite3_mprintf("%s", zStr);
+      pCsr->filter.nTerm = sqlite3_value_bytes(apVal[0]);
+      if( pCsr->filter.zTerm==0 ) return SQLITE_NOMEM;
+    }
+  }
+
+  if( iLe>=0 ){
+    pCsr->zStop = sqlite3_mprintf("%s", sqlite3_value_text(apVal[iLe]));
+    pCsr->nStop = sqlite3_value_bytes(apVal[iLe]);
+    if( pCsr->zStop==0 ) return SQLITE_NOMEM;
+  }
+  
+  if( iLangid>=0 ){
+    iLangVal = sqlite3_value_int(apVal[iLangid]);
+
+    /* If the user specified a negative value for the languageid, use zero
+    ** instead. This works, as the "languageid=?" constraint will also
+    ** be tested by the VDBE layer. The test will always be false (since
+    ** this module will not return a row with a negative languageid), and
+    ** so the overall query will return zero rows.  */
+    if( iLangVal<0 ) iLangVal = 0;
+  }
+  pCsr->iLangid = iLangVal;
+
+  rc = sqlite3Fts3SegReaderCursor(pFts3, iLangVal, 0, FTS3_SEGCURSOR_ALL,
+      pCsr->filter.zTerm, pCsr->filter.nTerm, 0, isScan, &pCsr->csr
+  );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3Fts3SegReaderStart(pFts3, &pCsr->csr, &pCsr->filter);
+  }
+
+  if( rc==SQLITE_OK ) rc = fts3auxNextMethod(pCursor);
+  return rc;
+}
+
+/*
+** xEof - Return true if the cursor is at EOF, or false otherwise.
+*/
+static int fts3auxEofMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3auxCursor *pCsr = (Fts3auxCursor *)pCursor;
+  return pCsr->isEof;
+}
+
+/*
+** xColumn - Return a column value.
+*/
+static int fts3auxColumnMethod(
+  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
+  sqlite3_context *pCtx,          /* Context for sqlite3_result_xxx() calls */
+  int iCol                        /* Index of column to read value from */
+){
+  Fts3auxCursor *p = (Fts3auxCursor *)pCursor;
+
+  assert( p->isEof==0 );
+  switch( iCol ){
+    case 0: /* term */
+      sqlite3_result_text(pCtx, p->csr.zTerm, p->csr.nTerm, SQLITE_TRANSIENT);
+      break;
+
+    case 1: /* col */
+      if( p->iCol ){
+        sqlite3_result_int(pCtx, p->iCol-1);
+      }else{
+        sqlite3_result_text(pCtx, "*", -1, SQLITE_STATIC);
+      }
+      break;
+
+    case 2: /* documents */
+      sqlite3_result_int64(pCtx, p->aStat[p->iCol].nDoc);
+      break;
+
+    case 3: /* occurrences */
+      sqlite3_result_int64(pCtx, p->aStat[p->iCol].nOcc);
+      break;
+
+    default: /* languageid */
+      assert( iCol==4 );
+      sqlite3_result_int(pCtx, p->iLangid);
+      break;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** xRowid - Return the current rowid for the cursor.
+*/
+static int fts3auxRowidMethod(
+  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
+  sqlite_int64 *pRowid            /* OUT: Rowid value */
+){
+  Fts3auxCursor *pCsr = (Fts3auxCursor *)pCursor;
+  *pRowid = pCsr->iRowid;
+  return SQLITE_OK;
+}
+
+/*
+** Register the fts3aux module with database connection db. Return SQLITE_OK
+** if successful or an error code if sqlite3_create_module() fails.
+*/
+SQLITE_PRIVATE int sqlite3Fts3InitAux(sqlite3 *db){
+  static const sqlite3_module fts3aux_module = {
+     0,                           /* iVersion      */
+     fts3auxConnectMethod,        /* xCreate       */
+     fts3auxConnectMethod,        /* xConnect      */
+     fts3auxBestIndexMethod,      /* xBestIndex    */
+     fts3auxDisconnectMethod,     /* xDisconnect   */
+     fts3auxDisconnectMethod,     /* xDestroy      */
+     fts3auxOpenMethod,           /* xOpen         */
+     fts3auxCloseMethod,          /* xClose        */
+     fts3auxFilterMethod,         /* xFilter       */
+     fts3auxNextMethod,           /* xNext         */
+     fts3auxEofMethod,            /* xEof          */
+     fts3auxColumnMethod,         /* xColumn       */
+     fts3auxRowidMethod,          /* xRowid        */
+     0,                           /* xUpdate       */
+     0,                           /* xBegin        */
+     0,                           /* xSync         */
+     0,                           /* xCommit       */
+     0,                           /* xRollback     */
+     0,                           /* xFindFunction */
+     0,                           /* xRename       */
+     0,                           /* xSavepoint    */
+     0,                           /* xRelease      */
+     0                            /* xRollbackTo   */
+  };
+  int rc;                         /* Return code */
+
+  rc = sqlite3_create_module(db, "fts4aux", &fts3aux_module, 0);
+  return rc;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_aux.c ********************************************/
+/************** Begin file fts3_expr.c ***************************************/
+/*
+** 2008 Nov 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This module contains code that implements a parser for fts3 query strings
+** (the right-hand argument to the MATCH operator). Because the supported 
+** syntax is relatively simple, the whole tokenizer/parser system is
+** hand-coded. 
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/*
+** By default, this module parses the legacy syntax that has been 
+** traditionally used by fts3. Or, if SQLITE_ENABLE_FTS3_PARENTHESIS
+** is defined, then it uses the new syntax. The differences between
+** the new and the old syntaxes are:
+**
+**  a) The new syntax supports parenthesis. The old does not.
+**
+**  b) The new syntax supports the AND and NOT operators. The old does not.
+**
+**  c) The old syntax supports the "-" token qualifier. This is not 
+**     supported by the new syntax (it is replaced by the NOT operator).
+**
+**  d) When using the old syntax, the OR operator has a greater precedence
+**     than an implicit AND. When using the new, both implicity and explicit
+**     AND operators have a higher precedence than OR.
+**
+** If compiled with SQLITE_TEST defined, then this module exports the
+** symbol "int sqlite3_fts3_enable_parentheses". Setting this variable
+** to zero causes the module to use the old syntax. If it is set to 
+** non-zero the new syntax is activated. This is so both syntaxes can
+** be tested using a single build of testfixture.
+**
+** The following describes the syntax supported by the fts3 MATCH
+** operator in a similar format to that used by the lemon parser
+** generator. This module does not use actually lemon, it uses a
+** custom parser.
+**
+**   query ::= andexpr (OR andexpr)*.
+**
+**   andexpr ::= notexpr (AND? notexpr)*.
+**
+**   notexpr ::= nearexpr (NOT nearexpr|-TOKEN)*.
+**   notexpr ::= LP query RP.
+**
+**   nearexpr ::= phrase (NEAR distance_opt nearexpr)*.
+**
+**   distance_opt ::= .
+**   distance_opt ::= / INTEGER.
+**
+**   phrase ::= TOKEN.
+**   phrase ::= COLUMN:TOKEN.
+**   phrase ::= "TOKEN TOKEN TOKEN...".
+*/
+
+#ifdef SQLITE_TEST
+SQLITE_API int sqlite3_fts3_enable_parentheses = 0;
+#else
+# ifdef SQLITE_ENABLE_FTS3_PARENTHESIS 
+#  define sqlite3_fts3_enable_parentheses 1
+# else
+#  define sqlite3_fts3_enable_parentheses 0
+# endif
+#endif
+
+/*
+** Default span for NEAR operators.
+*/
+#define SQLITE_FTS3_DEFAULT_NEAR_PARAM 10
+
+/* #include <string.h> */
+/* #include <assert.h> */
+
+/*
+** isNot:
+**   This variable is used by function getNextNode(). When getNextNode() is
+**   called, it sets ParseContext.isNot to true if the 'next node' is a 
+**   FTSQUERY_PHRASE with a unary "-" attached to it. i.e. "mysql" in the
+**   FTS3 query "sqlite -mysql". Otherwise, ParseContext.isNot is set to
+**   zero.
+*/
+typedef struct ParseContext ParseContext;
+struct ParseContext {
+  sqlite3_tokenizer *pTokenizer;      /* Tokenizer module */
+  int iLangid;                        /* Language id used with tokenizer */
+  const char **azCol;                 /* Array of column names for fts3 table */
+  int bFts4;                          /* True to allow FTS4-only syntax */
+  int nCol;                           /* Number of entries in azCol[] */
+  int iDefaultCol;                    /* Default column to query */
+  int isNot;                          /* True if getNextNode() sees a unary - */
+  sqlite3_context *pCtx;              /* Write error message here */
+  int nNest;                          /* Number of nested brackets */
+};
+
+/*
+** This function is equivalent to the standard isspace() function. 
+**
+** The standard isspace() can be awkward to use safely, because although it
+** is defined to accept an argument of type int, its behavior when passed
+** an integer that falls outside of the range of the unsigned char type
+** is undefined (and sometimes, "undefined" means segfault). This wrapper
+** is defined to accept an argument of type char, and always returns 0 for
+** any values that fall outside of the range of the unsigned char type (i.e.
+** negative values).
+*/
+static int fts3isspace(char c){
+  return c==' ' || c=='\t' || c=='\n' || c=='\r' || c=='\v' || c=='\f';
+}
+
+/*
+** Allocate nByte bytes of memory using sqlite3_malloc(). If successful,
+** zero the memory before returning a pointer to it. If unsuccessful, 
+** return NULL.
+*/
+static void *fts3MallocZero(int nByte){
+  void *pRet = sqlite3_malloc(nByte);
+  if( pRet ) memset(pRet, 0, nByte);
+  return pRet;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3OpenTokenizer(
+  sqlite3_tokenizer *pTokenizer,
+  int iLangid,
+  const char *z,
+  int n,
+  sqlite3_tokenizer_cursor **ppCsr
+){
+  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
+  sqlite3_tokenizer_cursor *pCsr = 0;
+  int rc;
+
+  rc = pModule->xOpen(pTokenizer, z, n, &pCsr);
+  assert( rc==SQLITE_OK || pCsr==0 );
+  if( rc==SQLITE_OK ){
+    pCsr->pTokenizer = pTokenizer;
+    if( pModule->iVersion>=1 ){
+      rc = pModule->xLanguageid(pCsr, iLangid);
+      if( rc!=SQLITE_OK ){
+        pModule->xClose(pCsr);
+        pCsr = 0;
+      }
+    }
+  }
+  *ppCsr = pCsr;
+  return rc;
+}
+
+/*
+** Function getNextNode(), which is called by fts3ExprParse(), may itself
+** call fts3ExprParse(). So this forward declaration is required.
+*/
+static int fts3ExprParse(ParseContext *, const char *, int, Fts3Expr **, int *);
+
+/*
+** Extract the next token from buffer z (length n) using the tokenizer
+** and other information (column names etc.) in pParse. Create an Fts3Expr
+** structure of type FTSQUERY_PHRASE containing a phrase consisting of this
+** single token and set *ppExpr to point to it. If the end of the buffer is
+** reached before a token is found, set *ppExpr to zero. It is the
+** responsibility of the caller to eventually deallocate the allocated 
+** Fts3Expr structure (if any) by passing it to sqlite3_free().
+**
+** Return SQLITE_OK if successful, or SQLITE_NOMEM if a memory allocation
+** fails.
+*/
+static int getNextToken(
+  ParseContext *pParse,                   /* fts3 query parse context */
+  int iCol,                               /* Value for Fts3Phrase.iColumn */
+  const char *z, int n,                   /* Input string */
+  Fts3Expr **ppExpr,                      /* OUT: expression */
+  int *pnConsumed                         /* OUT: Number of bytes consumed */
+){
+  sqlite3_tokenizer *pTokenizer = pParse->pTokenizer;
+  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
+  int rc;
+  sqlite3_tokenizer_cursor *pCursor;
+  Fts3Expr *pRet = 0;
+  int i = 0;
+
+  /* Set variable i to the maximum number of bytes of input to tokenize. */
+  for(i=0; i<n; i++){
+    if( sqlite3_fts3_enable_parentheses && (z[i]=='(' || z[i]==')') ) break;
+    if( z[i]=='"' ) break;
+  }
+
+  *pnConsumed = i;
+  rc = sqlite3Fts3OpenTokenizer(pTokenizer, pParse->iLangid, z, i, &pCursor);
+  if( rc==SQLITE_OK ){
+    const char *zToken;
+    int nToken = 0, iStart = 0, iEnd = 0, iPosition = 0;
+    int nByte;                               /* total space to allocate */
+
+    rc = pModule->xNext(pCursor, &zToken, &nToken, &iStart, &iEnd, &iPosition);
+    if( rc==SQLITE_OK ){
+      nByte = sizeof(Fts3Expr) + sizeof(Fts3Phrase) + nToken;
+      pRet = (Fts3Expr *)fts3MallocZero(nByte);
+      if( !pRet ){
+        rc = SQLITE_NOMEM;
+      }else{
+        pRet->eType = FTSQUERY_PHRASE;
+        pRet->pPhrase = (Fts3Phrase *)&pRet[1];
+        pRet->pPhrase->nToken = 1;
+        pRet->pPhrase->iColumn = iCol;
+        pRet->pPhrase->aToken[0].n = nToken;
+        pRet->pPhrase->aToken[0].z = (char *)&pRet->pPhrase[1];
+        memcpy(pRet->pPhrase->aToken[0].z, zToken, nToken);
+
+        if( iEnd<n && z[iEnd]=='*' ){
+          pRet->pPhrase->aToken[0].isPrefix = 1;
+          iEnd++;
+        }
+
+        while( 1 ){
+          if( !sqlite3_fts3_enable_parentheses 
+           && iStart>0 && z[iStart-1]=='-' 
+          ){
+            pParse->isNot = 1;
+            iStart--;
+          }else if( pParse->bFts4 && iStart>0 && z[iStart-1]=='^' ){
+            pRet->pPhrase->aToken[0].bFirst = 1;
+            iStart--;
+          }else{
+            break;
+          }
+        }
+
+      }
+      *pnConsumed = iEnd;
+    }else if( i && rc==SQLITE_DONE ){
+      rc = SQLITE_OK;
+    }
+
+    pModule->xClose(pCursor);
+  }
+  
+  *ppExpr = pRet;
+  return rc;
+}
+
+
+/*
+** Enlarge a memory allocation.  If an out-of-memory allocation occurs,
+** then free the old allocation.
+*/
+static void *fts3ReallocOrFree(void *pOrig, int nNew){
+  void *pRet = sqlite3_realloc(pOrig, nNew);
+  if( !pRet ){
+    sqlite3_free(pOrig);
+  }
+  return pRet;
+}
+
+/*
+** Buffer zInput, length nInput, contains the contents of a quoted string
+** that appeared as part of an fts3 query expression. Neither quote character
+** is included in the buffer. This function attempts to tokenize the entire
+** input buffer and create an Fts3Expr structure of type FTSQUERY_PHRASE 
+** containing the results.
+**
+** If successful, SQLITE_OK is returned and *ppExpr set to point at the
+** allocated Fts3Expr structure. Otherwise, either SQLITE_NOMEM (out of memory
+** error) or SQLITE_ERROR (tokenization error) is returned and *ppExpr set
+** to 0.
+*/
+static int getNextString(
+  ParseContext *pParse,                   /* fts3 query parse context */
+  const char *zInput, int nInput,         /* Input string */
+  Fts3Expr **ppExpr                       /* OUT: expression */
+){
+  sqlite3_tokenizer *pTokenizer = pParse->pTokenizer;
+  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
+  int rc;
+  Fts3Expr *p = 0;
+  sqlite3_tokenizer_cursor *pCursor = 0;
+  char *zTemp = 0;
+  int nTemp = 0;
+
+  const int nSpace = sizeof(Fts3Expr) + sizeof(Fts3Phrase);
+  int nToken = 0;
+
+  /* The final Fts3Expr data structure, including the Fts3Phrase,
+  ** Fts3PhraseToken structures token buffers are all stored as a single 
+  ** allocation so that the expression can be freed with a single call to
+  ** sqlite3_free(). Setting this up requires a two pass approach.
+  **
+  ** The first pass, in the block below, uses a tokenizer cursor to iterate
+  ** through the tokens in the expression. This pass uses fts3ReallocOrFree()
+  ** to assemble data in two dynamic buffers:
+  **
+  **   Buffer p: Points to the Fts3Expr structure, followed by the Fts3Phrase
+  **             structure, followed by the array of Fts3PhraseToken 
+  **             structures. This pass only populates the Fts3PhraseToken array.
+  **
+  **   Buffer zTemp: Contains copies of all tokens.
+  **
+  ** The second pass, in the block that begins "if( rc==SQLITE_DONE )" below,
+  ** appends buffer zTemp to buffer p, and fills in the Fts3Expr and Fts3Phrase
+  ** structures.
+  */
+  rc = sqlite3Fts3OpenTokenizer(
+      pTokenizer, pParse->iLangid, zInput, nInput, &pCursor);
+  if( rc==SQLITE_OK ){
+    int ii;
+    for(ii=0; rc==SQLITE_OK; ii++){
+      const char *zByte;
+      int nByte = 0, iBegin = 0, iEnd = 0, iPos = 0;
+      rc = pModule->xNext(pCursor, &zByte, &nByte, &iBegin, &iEnd, &iPos);
+      if( rc==SQLITE_OK ){
+        Fts3PhraseToken *pToken;
+
+        p = fts3ReallocOrFree(p, nSpace + ii*sizeof(Fts3PhraseToken));
+        if( !p ) goto no_mem;
+
+        zTemp = fts3ReallocOrFree(zTemp, nTemp + nByte);
+        if( !zTemp ) goto no_mem;
+
+        assert( nToken==ii );
+        pToken = &((Fts3Phrase *)(&p[1]))->aToken[ii];
+        memset(pToken, 0, sizeof(Fts3PhraseToken));
+
+        memcpy(&zTemp[nTemp], zByte, nByte);
+        nTemp += nByte;
+
+        pToken->n = nByte;
+        pToken->isPrefix = (iEnd<nInput && zInput[iEnd]=='*');
+        pToken->bFirst = (iBegin>0 && zInput[iBegin-1]=='^');
+        nToken = ii+1;
+      }
+    }
+
+    pModule->xClose(pCursor);
+    pCursor = 0;
+  }
+
+  if( rc==SQLITE_DONE ){
+    int jj;
+    char *zBuf = 0;
+
+    p = fts3ReallocOrFree(p, nSpace + nToken*sizeof(Fts3PhraseToken) + nTemp);
+    if( !p ) goto no_mem;
+    memset(p, 0, (char *)&(((Fts3Phrase *)&p[1])->aToken[0])-(char *)p);
+    p->eType = FTSQUERY_PHRASE;
+    p->pPhrase = (Fts3Phrase *)&p[1];
+    p->pPhrase->iColumn = pParse->iDefaultCol;
+    p->pPhrase->nToken = nToken;
+
+    zBuf = (char *)&p->pPhrase->aToken[nToken];
+    if( zTemp ){
+      memcpy(zBuf, zTemp, nTemp);
+      sqlite3_free(zTemp);
+    }else{
+      assert( nTemp==0 );
+    }
+
+    for(jj=0; jj<p->pPhrase->nToken; jj++){
+      p->pPhrase->aToken[jj].z = zBuf;
+      zBuf += p->pPhrase->aToken[jj].n;
+    }
+    rc = SQLITE_OK;
+  }
+
+  *ppExpr = p;
+  return rc;
+no_mem:
+
+  if( pCursor ){
+    pModule->xClose(pCursor);
+  }
+  sqlite3_free(zTemp);
+  sqlite3_free(p);
+  *ppExpr = 0;
+  return SQLITE_NOMEM;
+}
+
+/*
+** The output variable *ppExpr is populated with an allocated Fts3Expr 
+** structure, or set to 0 if the end of the input buffer is reached.
+**
+** Returns an SQLite error code. SQLITE_OK if everything works, SQLITE_NOMEM
+** if a malloc failure occurs, or SQLITE_ERROR if a parse error is encountered.
+** If SQLITE_ERROR is returned, pContext is populated with an error message.
+*/
+static int getNextNode(
+  ParseContext *pParse,                   /* fts3 query parse context */
+  const char *z, int n,                   /* Input string */
+  Fts3Expr **ppExpr,                      /* OUT: expression */
+  int *pnConsumed                         /* OUT: Number of bytes consumed */
+){
+  static const struct Fts3Keyword {
+    char *z;                              /* Keyword text */
+    unsigned char n;                      /* Length of the keyword */
+    unsigned char parenOnly;              /* Only valid in paren mode */
+    unsigned char eType;                  /* Keyword code */
+  } aKeyword[] = {
+    { "OR" ,  2, 0, FTSQUERY_OR   },
+    { "AND",  3, 1, FTSQUERY_AND  },
+    { "NOT",  3, 1, FTSQUERY_NOT  },
+    { "NEAR", 4, 0, FTSQUERY_NEAR }
+  };
+  int ii;
+  int iCol;
+  int iColLen;
+  int rc;
+  Fts3Expr *pRet = 0;
+
+  const char *zInput = z;
+  int nInput = n;
+
+  pParse->isNot = 0;
+
+  /* Skip over any whitespace before checking for a keyword, an open or
+  ** close bracket, or a quoted string. 
+  */
+  while( nInput>0 && fts3isspace(*zInput) ){
+    nInput--;
+    zInput++;
+  }
+  if( nInput==0 ){
+    return SQLITE_DONE;
+  }
+
+  /* See if we are dealing with a keyword. */
+  for(ii=0; ii<(int)(sizeof(aKeyword)/sizeof(struct Fts3Keyword)); ii++){
+    const struct Fts3Keyword *pKey = &aKeyword[ii];
+
+    if( (pKey->parenOnly & ~sqlite3_fts3_enable_parentheses)!=0 ){
+      continue;
+    }
+
+    if( nInput>=pKey->n && 0==memcmp(zInput, pKey->z, pKey->n) ){
+      int nNear = SQLITE_FTS3_DEFAULT_NEAR_PARAM;
+      int nKey = pKey->n;
+      char cNext;
+
+      /* If this is a "NEAR" keyword, check for an explicit nearness. */
+      if( pKey->eType==FTSQUERY_NEAR ){
+        assert( nKey==4 );
+        if( zInput[4]=='/' && zInput[5]>='0' && zInput[5]<='9' ){
+          nNear = 0;
+          for(nKey=5; zInput[nKey]>='0' && zInput[nKey]<='9'; nKey++){
+            nNear = nNear * 10 + (zInput[nKey] - '0');
+          }
+        }
+      }
+
+      /* At this point this is probably a keyword. But for that to be true,
+      ** the next byte must contain either whitespace, an open or close
+      ** parenthesis, a quote character, or EOF. 
+      */
+      cNext = zInput[nKey];
+      if( fts3isspace(cNext) 
+       || cNext=='"' || cNext=='(' || cNext==')' || cNext==0
+      ){
+        pRet = (Fts3Expr *)fts3MallocZero(sizeof(Fts3Expr));
+        if( !pRet ){
+          return SQLITE_NOMEM;
+        }
+        pRet->eType = pKey->eType;
+        pRet->nNear = nNear;
+        *ppExpr = pRet;
+        *pnConsumed = (int)((zInput - z) + nKey);
+        return SQLITE_OK;
+      }
+
+      /* Turns out that wasn't a keyword after all. This happens if the
+      ** user has supplied a token such as "ORacle". Continue.
+      */
+    }
+  }
+
+  /* See if we are dealing with a quoted phrase. If this is the case, then
+  ** search for the closing quote and pass the whole string to getNextString()
+  ** for processing. This is easy to do, as fts3 has no syntax for escaping
+  ** a quote character embedded in a string.
+  */
+  if( *zInput=='"' ){
+    for(ii=1; ii<nInput && zInput[ii]!='"'; ii++);
+    *pnConsumed = (int)((zInput - z) + ii + 1);
+    if( ii==nInput ){
+      return SQLITE_ERROR;
+    }
+    return getNextString(pParse, &zInput[1], ii-1, ppExpr);
+  }
+
+  if( sqlite3_fts3_enable_parentheses ){
+    if( *zInput=='(' ){
+      int nConsumed = 0;
+      pParse->nNest++;
+      rc = fts3ExprParse(pParse, zInput+1, nInput-1, ppExpr, &nConsumed);
+      if( rc==SQLITE_OK && !*ppExpr ){ rc = SQLITE_DONE; }
+      *pnConsumed = (int)(zInput - z) + 1 + nConsumed;
+      return rc;
+    }else if( *zInput==')' ){
+      pParse->nNest--;
+      *pnConsumed = (int)((zInput - z) + 1);
+      *ppExpr = 0;
+      return SQLITE_DONE;
+    }
+  }
+
+  /* If control flows to this point, this must be a regular token, or 
+  ** the end of the input. Read a regular token using the sqlite3_tokenizer
+  ** interface. Before doing so, figure out if there is an explicit
+  ** column specifier for the token. 
+  **
+  ** TODO: Strangely, it is not possible to associate a column specifier
+  ** with a quoted phrase, only with a single token. Not sure if this was
+  ** an implementation artifact or an intentional decision when fts3 was
+  ** first implemented. Whichever it was, this module duplicates the 
+  ** limitation.
+  */
+  iCol = pParse->iDefaultCol;
+  iColLen = 0;
+  for(ii=0; ii<pParse->nCol; ii++){
+    const char *zStr = pParse->azCol[ii];
+    int nStr = (int)strlen(zStr);
+    if( nInput>nStr && zInput[nStr]==':' 
+     && sqlite3_strnicmp(zStr, zInput, nStr)==0 
+    ){
+      iCol = ii;
+      iColLen = (int)((zInput - z) + nStr + 1);
+      break;
+    }
+  }
+  rc = getNextToken(pParse, iCol, &z[iColLen], n-iColLen, ppExpr, pnConsumed);
+  *pnConsumed += iColLen;
+  return rc;
+}
+
+/*
+** The argument is an Fts3Expr structure for a binary operator (any type
+** except an FTSQUERY_PHRASE). Return an integer value representing the
+** precedence of the operator. Lower values have a higher precedence (i.e.
+** group more tightly). For example, in the C language, the == operator
+** groups more tightly than ||, and would therefore have a higher precedence.
+**
+** When using the new fts3 query syntax (when SQLITE_ENABLE_FTS3_PARENTHESIS
+** is defined), the order of the operators in precedence from highest to
+** lowest is:
+**
+**   NEAR
+**   NOT
+**   AND (including implicit ANDs)
+**   OR
+**
+** Note that when using the old query syntax, the OR operator has a higher
+** precedence than the AND operator.
+*/
+static int opPrecedence(Fts3Expr *p){
+  assert( p->eType!=FTSQUERY_PHRASE );
+  if( sqlite3_fts3_enable_parentheses ){
+    return p->eType;
+  }else if( p->eType==FTSQUERY_NEAR ){
+    return 1;
+  }else if( p->eType==FTSQUERY_OR ){
+    return 2;
+  }
+  assert( p->eType==FTSQUERY_AND );
+  return 3;
+}
+
+/*
+** Argument ppHead contains a pointer to the current head of a query 
+** expression tree being parsed. pPrev is the expression node most recently
+** inserted into the tree. This function adds pNew, which is always a binary
+** operator node, into the expression tree based on the relative precedence
+** of pNew and the existing nodes of the tree. This may result in the head
+** of the tree changing, in which case *ppHead is set to the new root node.
+*/
+static void insertBinaryOperator(
+  Fts3Expr **ppHead,       /* Pointer to the root node of a tree */
+  Fts3Expr *pPrev,         /* Node most recently inserted into the tree */
+  Fts3Expr *pNew           /* New binary node to insert into expression tree */
+){
+  Fts3Expr *pSplit = pPrev;
+  while( pSplit->pParent && opPrecedence(pSplit->pParent)<=opPrecedence(pNew) ){
+    pSplit = pSplit->pParent;
+  }
+
+  if( pSplit->pParent ){
+    assert( pSplit->pParent->pRight==pSplit );
+    pSplit->pParent->pRight = pNew;
+    pNew->pParent = pSplit->pParent;
+  }else{
+    *ppHead = pNew;
+  }
+  pNew->pLeft = pSplit;
+  pSplit->pParent = pNew;
+}
+
+/*
+** Parse the fts3 query expression found in buffer z, length n. This function
+** returns either when the end of the buffer is reached or an unmatched 
+** closing bracket - ')' - is encountered.
+**
+** If successful, SQLITE_OK is returned, *ppExpr is set to point to the
+** parsed form of the expression and *pnConsumed is set to the number of
+** bytes read from buffer z. Otherwise, *ppExpr is set to 0 and SQLITE_NOMEM
+** (out of memory error) or SQLITE_ERROR (parse error) is returned.
+*/
+static int fts3ExprParse(
+  ParseContext *pParse,                   /* fts3 query parse context */
+  const char *z, int n,                   /* Text of MATCH query */
+  Fts3Expr **ppExpr,                      /* OUT: Parsed query structure */
+  int *pnConsumed                         /* OUT: Number of bytes consumed */
+){
+  Fts3Expr *pRet = 0;
+  Fts3Expr *pPrev = 0;
+  Fts3Expr *pNotBranch = 0;               /* Only used in legacy parse mode */
+  int nIn = n;
+  const char *zIn = z;
+  int rc = SQLITE_OK;
+  int isRequirePhrase = 1;
+
+  while( rc==SQLITE_OK ){
+    Fts3Expr *p = 0;
+    int nByte = 0;
+
+    rc = getNextNode(pParse, zIn, nIn, &p, &nByte);
+    assert( nByte>0 || (rc!=SQLITE_OK && p==0) );
+    if( rc==SQLITE_OK ){
+      if( p ){
+        int isPhrase;
+
+        if( !sqlite3_fts3_enable_parentheses 
+            && p->eType==FTSQUERY_PHRASE && pParse->isNot 
+        ){
+          /* Create an implicit NOT operator. */
+          Fts3Expr *pNot = fts3MallocZero(sizeof(Fts3Expr));
+          if( !pNot ){
+            sqlite3Fts3ExprFree(p);
+            rc = SQLITE_NOMEM;
+            goto exprparse_out;
+          }
+          pNot->eType = FTSQUERY_NOT;
+          pNot->pRight = p;
+          p->pParent = pNot;
+          if( pNotBranch ){
+            pNot->pLeft = pNotBranch;
+            pNotBranch->pParent = pNot;
+          }
+          pNotBranch = pNot;
+          p = pPrev;
+        }else{
+          int eType = p->eType;
+          isPhrase = (eType==FTSQUERY_PHRASE || p->pLeft);
+
+          /* The isRequirePhrase variable is set to true if a phrase or
+          ** an expression contained in parenthesis is required. If a
+          ** binary operator (AND, OR, NOT or NEAR) is encounted when
+          ** isRequirePhrase is set, this is a syntax error.
+          */
+          if( !isPhrase && isRequirePhrase ){
+            sqlite3Fts3ExprFree(p);
+            rc = SQLITE_ERROR;
+            goto exprparse_out;
+          }
+
+          if( isPhrase && !isRequirePhrase ){
+            /* Insert an implicit AND operator. */
+            Fts3Expr *pAnd;
+            assert( pRet && pPrev );
+            pAnd = fts3MallocZero(sizeof(Fts3Expr));
+            if( !pAnd ){
+              sqlite3Fts3ExprFree(p);
+              rc = SQLITE_NOMEM;
+              goto exprparse_out;
+            }
+            pAnd->eType = FTSQUERY_AND;
+            insertBinaryOperator(&pRet, pPrev, pAnd);
+            pPrev = pAnd;
+          }
+
+          /* This test catches attempts to make either operand of a NEAR
+           ** operator something other than a phrase. For example, either of
+           ** the following:
+           **
+           **    (bracketed expression) NEAR phrase
+           **    phrase NEAR (bracketed expression)
+           **
+           ** Return an error in either case.
+           */
+          if( pPrev && (
+            (eType==FTSQUERY_NEAR && !isPhrase && pPrev->eType!=FTSQUERY_PHRASE)
+         || (eType!=FTSQUERY_PHRASE && isPhrase && pPrev->eType==FTSQUERY_NEAR)
+          )){
+            sqlite3Fts3ExprFree(p);
+            rc = SQLITE_ERROR;
+            goto exprparse_out;
+          }
+
+          if( isPhrase ){
+            if( pRet ){
+              assert( pPrev && pPrev->pLeft && pPrev->pRight==0 );
+              pPrev->pRight = p;
+              p->pParent = pPrev;
+            }else{
+              pRet = p;
+            }
+          }else{
+            insertBinaryOperator(&pRet, pPrev, p);
+          }
+          isRequirePhrase = !isPhrase;
+        }
+        pPrev = p;
+      }
+      assert( nByte>0 );
+    }
+    assert( rc!=SQLITE_OK || (nByte>0 && nByte<=nIn) );
+    nIn -= nByte;
+    zIn += nByte;
+  }
+
+  if( rc==SQLITE_DONE && pRet && isRequirePhrase ){
+    rc = SQLITE_ERROR;
+  }
+
+  if( rc==SQLITE_DONE ){
+    rc = SQLITE_OK;
+    if( !sqlite3_fts3_enable_parentheses && pNotBranch ){
+      if( !pRet ){
+        rc = SQLITE_ERROR;
+      }else{
+        Fts3Expr *pIter = pNotBranch;
+        while( pIter->pLeft ){
+          pIter = pIter->pLeft;
+        }
+        pIter->pLeft = pRet;
+        pRet->pParent = pIter;
+        pRet = pNotBranch;
+      }
+    }
+  }
+  *pnConsumed = n - nIn;
+
+exprparse_out:
+  if( rc!=SQLITE_OK ){
+    sqlite3Fts3ExprFree(pRet);
+    sqlite3Fts3ExprFree(pNotBranch);
+    pRet = 0;
+  }
+  *ppExpr = pRet;
+  return rc;
+}
+
+/*
+** Return SQLITE_ERROR if the maximum depth of the expression tree passed 
+** as the only argument is more than nMaxDepth.
+*/
+static int fts3ExprCheckDepth(Fts3Expr *p, int nMaxDepth){
+  int rc = SQLITE_OK;
+  if( p ){
+    if( nMaxDepth<0 ){ 
+      rc = SQLITE_TOOBIG;
+    }else{
+      rc = fts3ExprCheckDepth(p->pLeft, nMaxDepth-1);
+      if( rc==SQLITE_OK ){
+        rc = fts3ExprCheckDepth(p->pRight, nMaxDepth-1);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** This function attempts to transform the expression tree at (*pp) to
+** an equivalent but more balanced form. The tree is modified in place.
+** If successful, SQLITE_OK is returned and (*pp) set to point to the 
+** new root expression node. 
+**
+** nMaxDepth is the maximum allowable depth of the balanced sub-tree.
+**
+** Otherwise, if an error occurs, an SQLite error code is returned and 
+** expression (*pp) freed.
+*/
+static int fts3ExprBalance(Fts3Expr **pp, int nMaxDepth){
+  int rc = SQLITE_OK;             /* Return code */
+  Fts3Expr *pRoot = *pp;          /* Initial root node */
+  Fts3Expr *pFree = 0;            /* List of free nodes. Linked by pParent. */
+  int eType = pRoot->eType;       /* Type of node in this tree */
+
+  if( nMaxDepth==0 ){
+    rc = SQLITE_ERROR;
+  }
+
+  if( rc==SQLITE_OK ){
+    if( (eType==FTSQUERY_AND || eType==FTSQUERY_OR) ){
+      Fts3Expr **apLeaf;
+      apLeaf = (Fts3Expr **)sqlite3_malloc(sizeof(Fts3Expr *) * nMaxDepth);
+      if( 0==apLeaf ){
+        rc = SQLITE_NOMEM;
+      }else{
+        memset(apLeaf, 0, sizeof(Fts3Expr *) * nMaxDepth);
+      }
+
+      if( rc==SQLITE_OK ){
+        int i;
+        Fts3Expr *p;
+
+        /* Set $p to point to the left-most leaf in the tree of eType nodes. */
+        for(p=pRoot; p->eType==eType; p=p->pLeft){
+          assert( p->pParent==0 || p->pParent->pLeft==p );
+          assert( p->pLeft && p->pRight );
+        }
+
+        /* This loop runs once for each leaf in the tree of eType nodes. */
+        while( 1 ){
+          int iLvl;
+          Fts3Expr *pParent = p->pParent;     /* Current parent of p */
+
+          assert( pParent==0 || pParent->pLeft==p );
+          p->pParent = 0;
+          if( pParent ){
+            pParent->pLeft = 0;
+          }else{
+            pRoot = 0;
+          }
+          rc = fts3ExprBalance(&p, nMaxDepth-1);
+          if( rc!=SQLITE_OK ) break;
+
+          for(iLvl=0; p && iLvl<nMaxDepth; iLvl++){
+            if( apLeaf[iLvl]==0 ){
+              apLeaf[iLvl] = p;
+              p = 0;
+            }else{
+              assert( pFree );
+              pFree->pLeft = apLeaf[iLvl];
+              pFree->pRight = p;
+              pFree->pLeft->pParent = pFree;
+              pFree->pRight->pParent = pFree;
+
+              p = pFree;
+              pFree = pFree->pParent;
+              p->pParent = 0;
+              apLeaf[iLvl] = 0;
+            }
+          }
+          if( p ){
+            sqlite3Fts3ExprFree(p);
+            rc = SQLITE_TOOBIG;
+            break;
+          }
+
+          /* If that was the last leaf node, break out of the loop */
+          if( pParent==0 ) break;
+
+          /* Set $p to point to the next leaf in the tree of eType nodes */
+          for(p=pParent->pRight; p->eType==eType; p=p->pLeft);
+
+          /* Remove pParent from the original tree. */
+          assert( pParent->pParent==0 || pParent->pParent->pLeft==pParent );
+          pParent->pRight->pParent = pParent->pParent;
+          if( pParent->pParent ){
+            pParent->pParent->pLeft = pParent->pRight;
+          }else{
+            assert( pParent==pRoot );
+            pRoot = pParent->pRight;
+          }
+
+          /* Link pParent into the free node list. It will be used as an
+          ** internal node of the new tree.  */
+          pParent->pParent = pFree;
+          pFree = pParent;
+        }
+
+        if( rc==SQLITE_OK ){
+          p = 0;
+          for(i=0; i<nMaxDepth; i++){
+            if( apLeaf[i] ){
+              if( p==0 ){
+                p = apLeaf[i];
+                p->pParent = 0;
+              }else{
+                assert( pFree!=0 );
+                pFree->pRight = p;
+                pFree->pLeft = apLeaf[i];
+                pFree->pLeft->pParent = pFree;
+                pFree->pRight->pParent = pFree;
+
+                p = pFree;
+                pFree = pFree->pParent;
+                p->pParent = 0;
+              }
+            }
+          }
+          pRoot = p;
+        }else{
+          /* An error occurred. Delete the contents of the apLeaf[] array 
+          ** and pFree list. Everything else is cleaned up by the call to
+          ** sqlite3Fts3ExprFree(pRoot) below.  */
+          Fts3Expr *pDel;
+          for(i=0; i<nMaxDepth; i++){
+            sqlite3Fts3ExprFree(apLeaf[i]);
+          }
+          while( (pDel=pFree)!=0 ){
+            pFree = pDel->pParent;
+            sqlite3_free(pDel);
+          }
+        }
+
+        assert( pFree==0 );
+        sqlite3_free( apLeaf );
+      }
+    }else if( eType==FTSQUERY_NOT ){
+      Fts3Expr *pLeft = pRoot->pLeft;
+      Fts3Expr *pRight = pRoot->pRight;
+
+      pRoot->pLeft = 0;
+      pRoot->pRight = 0;
+      pLeft->pParent = 0;
+      pRight->pParent = 0;
+
+      rc = fts3ExprBalance(&pLeft, nMaxDepth-1);
+      if( rc==SQLITE_OK ){
+        rc = fts3ExprBalance(&pRight, nMaxDepth-1);
+      }
+
+      if( rc!=SQLITE_OK ){
+        sqlite3Fts3ExprFree(pRight);
+        sqlite3Fts3ExprFree(pLeft);
+      }else{
+        assert( pLeft && pRight );
+        pRoot->pLeft = pLeft;
+        pLeft->pParent = pRoot;
+        pRoot->pRight = pRight;
+        pRight->pParent = pRoot;
+      }
+    }
+  }
+  
+  if( rc!=SQLITE_OK ){
+    sqlite3Fts3ExprFree(pRoot);
+    pRoot = 0;
+  }
+  *pp = pRoot;
+  return rc;
+}
+
+/*
+** This function is similar to sqlite3Fts3ExprParse(), with the following
+** differences:
+**
+**   1. It does not do expression rebalancing.
+**   2. It does not check that the expression does not exceed the 
+**      maximum allowable depth.
+**   3. Even if it fails, *ppExpr may still be set to point to an 
+**      expression tree. It should be deleted using sqlite3Fts3ExprFree()
+**      in this case.
+*/
+static int fts3ExprParseUnbalanced(
+  sqlite3_tokenizer *pTokenizer,      /* Tokenizer module */
+  int iLangid,                        /* Language id for tokenizer */
+  char **azCol,                       /* Array of column names for fts3 table */
+  int bFts4,                          /* True to allow FTS4-only syntax */
+  int nCol,                           /* Number of entries in azCol[] */
+  int iDefaultCol,                    /* Default column to query */
+  const char *z, int n,               /* Text of MATCH query */
+  Fts3Expr **ppExpr                   /* OUT: Parsed query structure */
+){
+  int nParsed;
+  int rc;
+  ParseContext sParse;
+
+  memset(&sParse, 0, sizeof(ParseContext));
+  sParse.pTokenizer = pTokenizer;
+  sParse.iLangid = iLangid;
+  sParse.azCol = (const char **)azCol;
+  sParse.nCol = nCol;
+  sParse.iDefaultCol = iDefaultCol;
+  sParse.bFts4 = bFts4;
+  if( z==0 ){
+    *ppExpr = 0;
+    return SQLITE_OK;
+  }
+  if( n<0 ){
+    n = (int)strlen(z);
+  }
+  rc = fts3ExprParse(&sParse, z, n, ppExpr, &nParsed);
+  assert( rc==SQLITE_OK || *ppExpr==0 );
+
+  /* Check for mismatched parenthesis */
+  if( rc==SQLITE_OK && sParse.nNest ){
+    rc = SQLITE_ERROR;
+  }
+  
+  return rc;
+}
+
+/*
+** Parameters z and n contain a pointer to and length of a buffer containing
+** an fts3 query expression, respectively. This function attempts to parse the
+** query expression and create a tree of Fts3Expr structures representing the
+** parsed expression. If successful, *ppExpr is set to point to the head
+** of the parsed expression tree and SQLITE_OK is returned. If an error
+** occurs, either SQLITE_NOMEM (out-of-memory error) or SQLITE_ERROR (parse
+** error) is returned and *ppExpr is set to 0.
+**
+** If parameter n is a negative number, then z is assumed to point to a
+** nul-terminated string and the length is determined using strlen().
+**
+** The first parameter, pTokenizer, is passed the fts3 tokenizer module to
+** use to normalize query tokens while parsing the expression. The azCol[]
+** array, which is assumed to contain nCol entries, should contain the names
+** of each column in the target fts3 table, in order from left to right. 
+** Column names must be nul-terminated strings.
+**
+** The iDefaultCol parameter should be passed the index of the table column
+** that appears on the left-hand-side of the MATCH operator (the default
+** column to match against for tokens for which a column name is not explicitly
+** specified as part of the query string), or -1 if tokens may by default
+** match any table column.
+*/
+SQLITE_PRIVATE int sqlite3Fts3ExprParse(
+  sqlite3_tokenizer *pTokenizer,      /* Tokenizer module */
+  int iLangid,                        /* Language id for tokenizer */
+  char **azCol,                       /* Array of column names for fts3 table */
+  int bFts4,                          /* True to allow FTS4-only syntax */
+  int nCol,                           /* Number of entries in azCol[] */
+  int iDefaultCol,                    /* Default column to query */
+  const char *z, int n,               /* Text of MATCH query */
+  Fts3Expr **ppExpr,                  /* OUT: Parsed query structure */
+  char **pzErr                        /* OUT: Error message (sqlite3_malloc) */
+){
+  int rc = fts3ExprParseUnbalanced(
+      pTokenizer, iLangid, azCol, bFts4, nCol, iDefaultCol, z, n, ppExpr
+  );
+  
+  /* Rebalance the expression. And check that its depth does not exceed
+  ** SQLITE_FTS3_MAX_EXPR_DEPTH.  */
+  if( rc==SQLITE_OK && *ppExpr ){
+    rc = fts3ExprBalance(ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
+    if( rc==SQLITE_OK ){
+      rc = fts3ExprCheckDepth(*ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3Fts3ExprFree(*ppExpr);
+    *ppExpr = 0;
+    if( rc==SQLITE_TOOBIG ){
+      sqlite3Fts3ErrMsg(pzErr,
+          "FTS expression tree is too large (maximum depth %d)", 
+          SQLITE_FTS3_MAX_EXPR_DEPTH
+      );
+      rc = SQLITE_ERROR;
+    }else if( rc==SQLITE_ERROR ){
+      sqlite3Fts3ErrMsg(pzErr, "malformed MATCH expression: [%s]", z);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Free a single node of an expression tree.
+*/
+static void fts3FreeExprNode(Fts3Expr *p){
+  assert( p->eType==FTSQUERY_PHRASE || p->pPhrase==0 );
+  sqlite3Fts3EvalPhraseCleanup(p->pPhrase);
+  sqlite3_free(p->aMI);
+  sqlite3_free(p);
+}
+
+/*
+** Free a parsed fts3 query expression allocated by sqlite3Fts3ExprParse().
+**
+** This function would be simpler if it recursively called itself. But
+** that would mean passing a sufficiently large expression to ExprParse()
+** could cause a stack overflow.
+*/
+SQLITE_PRIVATE void sqlite3Fts3ExprFree(Fts3Expr *pDel){
+  Fts3Expr *p;
+  assert( pDel==0 || pDel->pParent==0 );
+  for(p=pDel; p && (p->pLeft||p->pRight); p=(p->pLeft ? p->pLeft : p->pRight)){
+    assert( p->pParent==0 || p==p->pParent->pRight || p==p->pParent->pLeft );
+  }
+  while( p ){
+    Fts3Expr *pParent = p->pParent;
+    fts3FreeExprNode(p);
+    if( pParent && p==pParent->pLeft && pParent->pRight ){
+      p = pParent->pRight;
+      while( p && (p->pLeft || p->pRight) ){
+        assert( p==p->pParent->pRight || p==p->pParent->pLeft );
+        p = (p->pLeft ? p->pLeft : p->pRight);
+      }
+    }else{
+      p = pParent;
+    }
+  }
+}
+
+/****************************************************************************
+*****************************************************************************
+** Everything after this point is just test code.
+*/
+
+#ifdef SQLITE_TEST
+
+/* #include <stdio.h> */
+
+/*
+** Function to query the hash-table of tokenizers (see README.tokenizers).
+*/
+static int queryTestTokenizer(
+  sqlite3 *db, 
+  const char *zName,  
+  const sqlite3_tokenizer_module **pp
+){
+  int rc;
+  sqlite3_stmt *pStmt;
+  const char zSql[] = "SELECT fts3_tokenizer(?)";
+
+  *pp = 0;
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    if( sqlite3_column_type(pStmt, 0)==SQLITE_BLOB ){
+      memcpy((void *)pp, sqlite3_column_blob(pStmt, 0), sizeof(*pp));
+    }
+  }
+
+  return sqlite3_finalize(pStmt);
+}
+
+/*
+** Return a pointer to a buffer containing a text representation of the
+** expression passed as the first argument. The buffer is obtained from
+** sqlite3_malloc(). It is the responsibility of the caller to use 
+** sqlite3_free() to release the memory. If an OOM condition is encountered,
+** NULL is returned.
+**
+** If the second argument is not NULL, then its contents are prepended to 
+** the returned expression text and then freed using sqlite3_free().
+*/
+static char *exprToString(Fts3Expr *pExpr, char *zBuf){
+  if( pExpr==0 ){
+    return sqlite3_mprintf("");
+  }
+  switch( pExpr->eType ){
+    case FTSQUERY_PHRASE: {
+      Fts3Phrase *pPhrase = pExpr->pPhrase;
+      int i;
+      zBuf = sqlite3_mprintf(
+          "%zPHRASE %d 0", zBuf, pPhrase->iColumn);
+      for(i=0; zBuf && i<pPhrase->nToken; i++){
+        zBuf = sqlite3_mprintf("%z %.*s%s", zBuf, 
+            pPhrase->aToken[i].n, pPhrase->aToken[i].z,
+            (pPhrase->aToken[i].isPrefix?"+":"")
+        );
+      }
+      return zBuf;
+    }
+
+    case FTSQUERY_NEAR:
+      zBuf = sqlite3_mprintf("%zNEAR/%d ", zBuf, pExpr->nNear);
+      break;
+    case FTSQUERY_NOT:
+      zBuf = sqlite3_mprintf("%zNOT ", zBuf);
+      break;
+    case FTSQUERY_AND:
+      zBuf = sqlite3_mprintf("%zAND ", zBuf);
+      break;
+    case FTSQUERY_OR:
+      zBuf = sqlite3_mprintf("%zOR ", zBuf);
+      break;
+  }
+
+  if( zBuf ) zBuf = sqlite3_mprintf("%z{", zBuf);
+  if( zBuf ) zBuf = exprToString(pExpr->pLeft, zBuf);
+  if( zBuf ) zBuf = sqlite3_mprintf("%z} {", zBuf);
+
+  if( zBuf ) zBuf = exprToString(pExpr->pRight, zBuf);
+  if( zBuf ) zBuf = sqlite3_mprintf("%z}", zBuf);
+
+  return zBuf;
+}
+
+/*
+** This is the implementation of a scalar SQL function used to test the 
+** expression parser. It should be called as follows:
+**
+**   fts3_exprtest(<tokenizer>, <expr>, <column 1>, ...);
+**
+** The first argument, <tokenizer>, is the name of the fts3 tokenizer used
+** to parse the query expression (see README.tokenizers). The second argument
+** is the query expression to parse. Each subsequent argument is the name
+** of a column of the fts3 table that the query expression may refer to.
+** For example:
+**
+**   SELECT fts3_exprtest('simple', 'Bill col2:Bloggs', 'col1', 'col2');
+*/
+static void fts3ExprTest(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_tokenizer_module const *pModule = 0;
+  sqlite3_tokenizer *pTokenizer = 0;
+  int rc;
+  char **azCol = 0;
+  const char *zExpr;
+  int nExpr;
+  int nCol;
+  int ii;
+  Fts3Expr *pExpr;
+  char *zBuf = 0;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+
+  if( argc<3 ){
+    sqlite3_result_error(context, 
+        "Usage: fts3_exprtest(tokenizer, expr, col1, ...", -1
+    );
+    return;
+  }
+
+  rc = queryTestTokenizer(db,
+                          (const char *)sqlite3_value_text(argv[0]), &pModule);
+  if( rc==SQLITE_NOMEM ){
+    sqlite3_result_error_nomem(context);
+    goto exprtest_out;
+  }else if( !pModule ){
+    sqlite3_result_error(context, "No such tokenizer module", -1);
+    goto exprtest_out;
+  }
+
+  rc = pModule->xCreate(0, 0, &pTokenizer);
+  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
+  if( rc==SQLITE_NOMEM ){
+    sqlite3_result_error_nomem(context);
+    goto exprtest_out;
+  }
+  pTokenizer->pModule = pModule;
+
+  zExpr = (const char *)sqlite3_value_text(argv[1]);
+  nExpr = sqlite3_value_bytes(argv[1]);
+  nCol = argc-2;
+  azCol = (char **)sqlite3_malloc(nCol*sizeof(char *));
+  if( !azCol ){
+    sqlite3_result_error_nomem(context);
+    goto exprtest_out;
+  }
+  for(ii=0; ii<nCol; ii++){
+    azCol[ii] = (char *)sqlite3_value_text(argv[ii+2]);
+  }
+
+  if( sqlite3_user_data(context) ){
+    char *zDummy = 0;
+    rc = sqlite3Fts3ExprParse(
+        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr, &zDummy
+    );
+    assert( rc==SQLITE_OK || pExpr==0 );
+    sqlite3_free(zDummy);
+  }else{
+    rc = fts3ExprParseUnbalanced(
+        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr
+    );
+  }
+
+  if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM ){
+    sqlite3Fts3ExprFree(pExpr);
+    sqlite3_result_error(context, "Error parsing expression", -1);
+  }else if( rc==SQLITE_NOMEM || !(zBuf = exprToString(pExpr, 0)) ){
+    sqlite3_result_error_nomem(context);
+  }else{
+    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+    sqlite3_free(zBuf);
+  }
+
+  sqlite3Fts3ExprFree(pExpr);
+
+exprtest_out:
+  if( pModule && pTokenizer ){
+    rc = pModule->xDestroy(pTokenizer);
+  }
+  sqlite3_free(azCol);
+}
+
+/*
+** Register the query expression parser test function fts3_exprtest() 
+** with database connection db. 
+*/
+SQLITE_PRIVATE int sqlite3Fts3ExprInitTestInterface(sqlite3* db){
+  int rc = sqlite3_create_function(
+      db, "fts3_exprtest", -1, SQLITE_UTF8, 0, fts3ExprTest, 0, 0
+  );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "fts3_exprtest_rebalance", 
+        -1, SQLITE_UTF8, (void *)1, fts3ExprTest, 0, 0
+    );
+  }
+  return rc;
+}
+
+#endif
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_expr.c *******************************************/
+/************** Begin file fts3_hash.c ***************************************/
+/*
+** 2001 September 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the implementation of generic hash-tables used in SQLite.
+** We've modified it slightly to serve as a standalone hash table
+** implementation for the full-text indexing module.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+**     * The FTS3 module is being built as an extension
+**       (in which case SQLITE_CORE is not defined), or
+**
+**     * The FTS3 module is being built into the core of
+**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <string.h> */
+
+/* #include "fts3_hash.h" */
+
+/*
+** Malloc and Free functions
+*/
+static void *fts3HashMalloc(int n){
+  void *p = sqlite3_malloc(n);
+  if( p ){
+    memset(p, 0, n);
+  }
+  return p;
+}
+static void fts3HashFree(void *p){
+  sqlite3_free(p);
+}
+
+/* Turn bulk memory into a hash table object by initializing the
+** fields of the Hash structure.
+**
+** "pNew" is a pointer to the hash table that is to be initialized.
+** keyClass is one of the constants 
+** FTS3_HASH_BINARY or FTS3_HASH_STRING.  The value of keyClass 
+** determines what kind of key the hash table will use.  "copyKey" is
+** true if the hash table should make its own private copy of keys and
+** false if it should just use the supplied pointer.
+*/
+SQLITE_PRIVATE void sqlite3Fts3HashInit(Fts3Hash *pNew, char keyClass, char copyKey){
+  assert( pNew!=0 );
+  assert( keyClass>=FTS3_HASH_STRING && keyClass<=FTS3_HASH_BINARY );
+  pNew->keyClass = keyClass;
+  pNew->copyKey = copyKey;
+  pNew->first = 0;
+  pNew->count = 0;
+  pNew->htsize = 0;
+  pNew->ht = 0;
+}
+
+/* Remove all entries from a hash table.  Reclaim all memory.
+** Call this routine to delete a hash table or to reset a hash table
+** to the empty state.
+*/
+SQLITE_PRIVATE void sqlite3Fts3HashClear(Fts3Hash *pH){
+  Fts3HashElem *elem;         /* For looping over all elements of the table */
+
+  assert( pH!=0 );
+  elem = pH->first;
+  pH->first = 0;
+  fts3HashFree(pH->ht);
+  pH->ht = 0;
+  pH->htsize = 0;
+  while( elem ){
+    Fts3HashElem *next_elem = elem->next;
+    if( pH->copyKey && elem->pKey ){
+      fts3HashFree(elem->pKey);
+    }
+    fts3HashFree(elem);
+    elem = next_elem;
+  }
+  pH->count = 0;
+}
+
+/*
+** Hash and comparison functions when the mode is FTS3_HASH_STRING
+*/
+static int fts3StrHash(const void *pKey, int nKey){
+  const char *z = (const char *)pKey;
+  unsigned h = 0;
+  if( nKey<=0 ) nKey = (int) strlen(z);
+  while( nKey > 0  ){
+    h = (h<<3) ^ h ^ *z++;
+    nKey--;
+  }
+  return (int)(h & 0x7fffffff);
+}
+static int fts3StrCompare(const void *pKey1, int n1, const void *pKey2, int n2){
+  if( n1!=n2 ) return 1;
+  return strncmp((const char*)pKey1,(const char*)pKey2,n1);
+}
+
+/*
+** Hash and comparison functions when the mode is FTS3_HASH_BINARY
+*/
+static int fts3BinHash(const void *pKey, int nKey){
+  int h = 0;
+  const char *z = (const char *)pKey;
+  while( nKey-- > 0 ){
+    h = (h<<3) ^ h ^ *(z++);
+  }
+  return h & 0x7fffffff;
+}
+static int fts3BinCompare(const void *pKey1, int n1, const void *pKey2, int n2){
+  if( n1!=n2 ) return 1;
+  return memcmp(pKey1,pKey2,n1);
+}
+
+/*
+** Return a pointer to the appropriate hash function given the key class.
+**
+** The C syntax in this function definition may be unfamilar to some 
+** programmers, so we provide the following additional explanation:
+**
+** The name of the function is "ftsHashFunction".  The function takes a
+** single parameter "keyClass".  The return value of ftsHashFunction()
+** is a pointer to another function.  Specifically, the return value
+** of ftsHashFunction() is a pointer to a function that takes two parameters
+** with types "const void*" and "int" and returns an "int".
+*/
+static int (*ftsHashFunction(int keyClass))(const void*,int){
+  if( keyClass==FTS3_HASH_STRING ){
+    return &fts3StrHash;
+  }else{
+    assert( keyClass==FTS3_HASH_BINARY );
+    return &fts3BinHash;
+  }
+}
+
+/*
+** Return a pointer to the appropriate hash function given the key class.
+**
+** For help in interpreted the obscure C code in the function definition,
+** see the header comment on the previous function.
+*/
+static int (*ftsCompareFunction(int keyClass))(const void*,int,const void*,int){
+  if( keyClass==FTS3_HASH_STRING ){
+    return &fts3StrCompare;
+  }else{
+    assert( keyClass==FTS3_HASH_BINARY );
+    return &fts3BinCompare;
+  }
+}
+
+/* Link an element into the hash table
+*/
+static void fts3HashInsertElement(
+  Fts3Hash *pH,            /* The complete hash table */
+  struct _fts3ht *pEntry,  /* The entry into which pNew is inserted */
+  Fts3HashElem *pNew       /* The element to be inserted */
+){
+  Fts3HashElem *pHead;     /* First element already in pEntry */
+  pHead = pEntry->chain;
+  if( pHead ){
+    pNew->next = pHead;
+    pNew->prev = pHead->prev;
+    if( pHead->prev ){ pHead->prev->next = pNew; }
+    else             { pH->first = pNew; }
+    pHead->prev = pNew;
+  }else{
+    pNew->next = pH->first;
+    if( pH->first ){ pH->first->prev = pNew; }
+    pNew->prev = 0;
+    pH->first = pNew;
+  }
+  pEntry->count++;
+  pEntry->chain = pNew;
+}
+
+
+/* Resize the hash table so that it cantains "new_size" buckets.
+** "new_size" must be a power of 2.  The hash table might fail 
+** to resize if sqliteMalloc() fails.
+**
+** Return non-zero if a memory allocation error occurs.
+*/
+static int fts3Rehash(Fts3Hash *pH, int new_size){
+  struct _fts3ht *new_ht;          /* The new hash table */
+  Fts3HashElem *elem, *next_elem;  /* For looping over existing elements */
+  int (*xHash)(const void*,int);   /* The hash function */
+
+  assert( (new_size & (new_size-1))==0 );
+  new_ht = (struct _fts3ht *)fts3HashMalloc( new_size*sizeof(struct _fts3ht) );
+  if( new_ht==0 ) return 1;
+  fts3HashFree(pH->ht);
+  pH->ht = new_ht;
+  pH->htsize = new_size;
+  xHash = ftsHashFunction(pH->keyClass);
+  for(elem=pH->first, pH->first=0; elem; elem = next_elem){
+    int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
+    next_elem = elem->next;
+    fts3HashInsertElement(pH, &new_ht[h], elem);
+  }
+  return 0;
+}
+
+/* This function (for internal use only) locates an element in an
+** hash table that matches the given key.  The hash for this key has
+** already been computed and is passed as the 4th parameter.
+*/
+static Fts3HashElem *fts3FindElementByHash(
+  const Fts3Hash *pH, /* The pH to be searched */
+  const void *pKey,   /* The key we are searching for */
+  int nKey,
+  int h               /* The hash for this key. */
+){
+  Fts3HashElem *elem;            /* Used to loop thru the element list */
+  int count;                     /* Number of elements left to test */
+  int (*xCompare)(const void*,int,const void*,int);  /* comparison function */
+
+  if( pH->ht ){
+    struct _fts3ht *pEntry = &pH->ht[h];
+    elem = pEntry->chain;
+    count = pEntry->count;
+    xCompare = ftsCompareFunction(pH->keyClass);
+    while( count-- && elem ){
+      if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){ 
+        return elem;
+      }
+      elem = elem->next;
+    }
+  }
+  return 0;
+}
+
+/* Remove a single entry from the hash table given a pointer to that
+** element and a hash on the element's key.
+*/
+static void fts3RemoveElementByHash(
+  Fts3Hash *pH,         /* The pH containing "elem" */
+  Fts3HashElem* elem,   /* The element to be removed from the pH */
+  int h                 /* Hash value for the element */
+){
+  struct _fts3ht *pEntry;
+  if( elem->prev ){
+    elem->prev->next = elem->next; 
+  }else{
+    pH->first = elem->next;
+  }
+  if( elem->next ){
+    elem->next->prev = elem->prev;
+  }
+  pEntry = &pH->ht[h];
+  if( pEntry->chain==elem ){
+    pEntry->chain = elem->next;
+  }
+  pEntry->count--;
+  if( pEntry->count<=0 ){
+    pEntry->chain = 0;
+  }
+  if( pH->copyKey && elem->pKey ){
+    fts3HashFree(elem->pKey);
+  }
+  fts3HashFree( elem );
+  pH->count--;
+  if( pH->count<=0 ){
+    assert( pH->first==0 );
+    assert( pH->count==0 );
+    fts3HashClear(pH);
+  }
+}
+
+SQLITE_PRIVATE Fts3HashElem *sqlite3Fts3HashFindElem(
+  const Fts3Hash *pH, 
+  const void *pKey, 
+  int nKey
+){
+  int h;                          /* A hash on key */
+  int (*xHash)(const void*,int);  /* The hash function */
+
+  if( pH==0 || pH->ht==0 ) return 0;
+  xHash = ftsHashFunction(pH->keyClass);
+  assert( xHash!=0 );
+  h = (*xHash)(pKey,nKey);
+  assert( (pH->htsize & (pH->htsize-1))==0 );
+  return fts3FindElementByHash(pH,pKey,nKey, h & (pH->htsize-1));
+}
+
+/* 
+** Attempt to locate an element of the hash table pH with a key
+** that matches pKey,nKey.  Return the data for this element if it is
+** found, or NULL if there is no match.
+*/
+SQLITE_PRIVATE void *sqlite3Fts3HashFind(const Fts3Hash *pH, const void *pKey, int nKey){
+  Fts3HashElem *pElem;            /* The element that matches key (if any) */
+
+  pElem = sqlite3Fts3HashFindElem(pH, pKey, nKey);
+  return pElem ? pElem->data : 0;
+}
+
+/* Insert an element into the hash table pH.  The key is pKey,nKey
+** and the data is "data".
+**
+** If no element exists with a matching key, then a new
+** element is created.  A copy of the key is made if the copyKey
+** flag is set.  NULL is returned.
+**
+** If another element already exists with the same key, then the
+** new data replaces the old data and the old data is returned.
+** The key is not copied in this instance.  If a malloc fails, then
+** the new data is returned and the hash table is unchanged.
+**
+** If the "data" parameter to this function is NULL, then the
+** element corresponding to "key" is removed from the hash table.
+*/
+SQLITE_PRIVATE void *sqlite3Fts3HashInsert(
+  Fts3Hash *pH,        /* The hash table to insert into */
+  const void *pKey,    /* The key */
+  int nKey,            /* Number of bytes in the key */
+  void *data           /* The data */
+){
+  int hraw;                 /* Raw hash value of the key */
+  int h;                    /* the hash of the key modulo hash table size */
+  Fts3HashElem *elem;       /* Used to loop thru the element list */
+  Fts3HashElem *new_elem;   /* New element added to the pH */
+  int (*xHash)(const void*,int);  /* The hash function */
+
+  assert( pH!=0 );
+  xHash = ftsHashFunction(pH->keyClass);
+  assert( xHash!=0 );
+  hraw = (*xHash)(pKey, nKey);
+  assert( (pH->htsize & (pH->htsize-1))==0 );
+  h = hraw & (pH->htsize-1);
+  elem = fts3FindElementByHash(pH,pKey,nKey,h);
+  if( elem ){
+    void *old_data = elem->data;
+    if( data==0 ){
+      fts3RemoveElementByHash(pH,elem,h);
+    }else{
+      elem->data = data;
+    }
+    return old_data;
+  }
+  if( data==0 ) return 0;
+  if( (pH->htsize==0 && fts3Rehash(pH,8))
+   || (pH->count>=pH->htsize && fts3Rehash(pH, pH->htsize*2))
+  ){
+    pH->count = 0;
+    return data;
+  }
+  assert( pH->htsize>0 );
+  new_elem = (Fts3HashElem*)fts3HashMalloc( sizeof(Fts3HashElem) );
+  if( new_elem==0 ) return data;
+  if( pH->copyKey && pKey!=0 ){
+    new_elem->pKey = fts3HashMalloc( nKey );
+    if( new_elem->pKey==0 ){
+      fts3HashFree(new_elem);
+      return data;
+    }
+    memcpy((void*)new_elem->pKey, pKey, nKey);
+  }else{
+    new_elem->pKey = (void*)pKey;
+  }
+  new_elem->nKey = nKey;
+  pH->count++;
+  assert( pH->htsize>0 );
+  assert( (pH->htsize & (pH->htsize-1))==0 );
+  h = hraw & (pH->htsize-1);
+  fts3HashInsertElement(pH, &pH->ht[h], new_elem);
+  new_elem->data = data;
+  return 0;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_hash.c *******************************************/
+/************** Begin file fts3_porter.c *************************************/
+/*
+** 2006 September 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Implementation of the full-text-search tokenizer that implements
+** a Porter stemmer.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+**     * The FTS3 module is being built as an extension
+**       (in which case SQLITE_CORE is not defined), or
+**
+**     * The FTS3 module is being built into the core of
+**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <stdio.h> */
+/* #include <string.h> */
+
+/* #include "fts3_tokenizer.h" */
+
+/*
+** Class derived from sqlite3_tokenizer
+*/
+typedef struct porter_tokenizer {
+  sqlite3_tokenizer base;      /* Base class */
+} porter_tokenizer;
+
+/*
+** Class derived from sqlite3_tokenizer_cursor
+*/
+typedef struct porter_tokenizer_cursor {
+  sqlite3_tokenizer_cursor base;
+  const char *zInput;          /* input we are tokenizing */
+  int nInput;                  /* size of the input */
+  int iOffset;                 /* current position in zInput */
+  int iToken;                  /* index of next token to be returned */
+  char *zToken;                /* storage for current token */
+  int nAllocated;              /* space allocated to zToken buffer */
+} porter_tokenizer_cursor;
+
+
+/*
+** Create a new tokenizer instance.
+*/
+static int porterCreate(
+  int argc, const char * const *argv,
+  sqlite3_tokenizer **ppTokenizer
+){
+  porter_tokenizer *t;
+
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+
+  t = (porter_tokenizer *) sqlite3_malloc(sizeof(*t));
+  if( t==NULL ) return SQLITE_NOMEM;
+  memset(t, 0, sizeof(*t));
+  *ppTokenizer = &t->base;
+  return SQLITE_OK;
+}
+
+/*
+** Destroy a tokenizer
+*/
+static int porterDestroy(sqlite3_tokenizer *pTokenizer){
+  sqlite3_free(pTokenizer);
+  return SQLITE_OK;
+}
+
+/*
+** Prepare to begin tokenizing a particular string.  The input
+** string to be tokenized is zInput[0..nInput-1].  A cursor
+** used to incrementally tokenize this string is returned in 
+** *ppCursor.
+*/
+static int porterOpen(
+  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
+  const char *zInput, int nInput,        /* String to be tokenized */
+  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
+){
+  porter_tokenizer_cursor *c;
+
+  UNUSED_PARAMETER(pTokenizer);
+
+  c = (porter_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
+  if( c==NULL ) return SQLITE_NOMEM;
+
+  c->zInput = zInput;
+  if( zInput==0 ){
+    c->nInput = 0;
+  }else if( nInput<0 ){
+    c->nInput = (int)strlen(zInput);
+  }else{
+    c->nInput = nInput;
+  }
+  c->iOffset = 0;                 /* start tokenizing at the beginning */
+  c->iToken = 0;
+  c->zToken = NULL;               /* no space allocated, yet. */
+  c->nAllocated = 0;
+
+  *ppCursor = &c->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a tokenization cursor previously opened by a call to
+** porterOpen() above.
+*/
+static int porterClose(sqlite3_tokenizer_cursor *pCursor){
+  porter_tokenizer_cursor *c = (porter_tokenizer_cursor *) pCursor;
+  sqlite3_free(c->zToken);
+  sqlite3_free(c);
+  return SQLITE_OK;
+}
+/*
+** Vowel or consonant
+*/
+static const char cType[] = {
+   0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0,
+   1, 1, 1, 2, 1
+};
+
+/*
+** isConsonant() and isVowel() determine if their first character in
+** the string they point to is a consonant or a vowel, according
+** to Porter ruls.  
+**
+** A consonate is any letter other than 'a', 'e', 'i', 'o', or 'u'.
+** 'Y' is a consonant unless it follows another consonant,
+** in which case it is a vowel.
+**
+** In these routine, the letters are in reverse order.  So the 'y' rule
+** is that 'y' is a consonant unless it is followed by another
+** consonent.
+*/
+static int isVowel(const char*);
+static int isConsonant(const char *z){
+  int j;
+  char x = *z;
+  if( x==0 ) return 0;
+  assert( x>='a' && x<='z' );
+  j = cType[x-'a'];
+  if( j<2 ) return j;
+  return z[1]==0 || isVowel(z + 1);
+}
+static int isVowel(const char *z){
+  int j;
+  char x = *z;
+  if( x==0 ) return 0;
+  assert( x>='a' && x<='z' );
+  j = cType[x-'a'];
+  if( j<2 ) return 1-j;
+  return isConsonant(z + 1);
+}
+
+/*
+** Let any sequence of one or more vowels be represented by V and let
+** C be sequence of one or more consonants.  Then every word can be
+** represented as:
+**
+**           [C] (VC){m} [V]
+**
+** In prose:  A word is an optional consonant followed by zero or
+** vowel-consonant pairs followed by an optional vowel.  "m" is the
+** number of vowel consonant pairs.  This routine computes the value
+** of m for the first i bytes of a word.
+**
+** Return true if the m-value for z is 1 or more.  In other words,
+** return true if z contains at least one vowel that is followed
+** by a consonant.
+**
+** In this routine z[] is in reverse order.  So we are really looking
+** for an instance of a consonant followed by a vowel.
+*/
+static int m_gt_0(const char *z){
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  return *z!=0;
+}
+
+/* Like mgt0 above except we are looking for a value of m which is
+** exactly 1
+*/
+static int m_eq_1(const char *z){
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 1;
+  while( isConsonant(z) ){ z++; }
+  return *z==0;
+}
+
+/* Like mgt0 above except we are looking for a value of m>1 instead
+** or m>0
+*/
+static int m_gt_1(const char *z){
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  return *z!=0;
+}
+
+/*
+** Return TRUE if there is a vowel anywhere within z[0..n-1]
+*/
+static int hasVowel(const char *z){
+  while( isConsonant(z) ){ z++; }
+  return *z!=0;
+}
+
+/*
+** Return TRUE if the word ends in a double consonant.
+**
+** The text is reversed here. So we are really looking at
+** the first two characters of z[].
+*/
+static int doubleConsonant(const char *z){
+  return isConsonant(z) && z[0]==z[1];
+}
+
+/*
+** Return TRUE if the word ends with three letters which
+** are consonant-vowel-consonent and where the final consonant
+** is not 'w', 'x', or 'y'.
+**
+** The word is reversed here.  So we are really checking the
+** first three letters and the first one cannot be in [wxy].
+*/
+static int star_oh(const char *z){
+  return
+    isConsonant(z) &&
+    z[0]!='w' && z[0]!='x' && z[0]!='y' &&
+    isVowel(z+1) &&
+    isConsonant(z+2);
+}
+
+/*
+** If the word ends with zFrom and xCond() is true for the stem
+** of the word that preceeds the zFrom ending, then change the 
+** ending to zTo.
+**
+** The input word *pz and zFrom are both in reverse order.  zTo
+** is in normal order. 
+**
+** Return TRUE if zFrom matches.  Return FALSE if zFrom does not
+** match.  Not that TRUE is returned even if xCond() fails and
+** no substitution occurs.
+*/
+static int stem(
+  char **pz,             /* The word being stemmed (Reversed) */
+  const char *zFrom,     /* If the ending matches this... (Reversed) */
+  const char *zTo,       /* ... change the ending to this (not reversed) */
+  int (*xCond)(const char*)   /* Condition that must be true */
+){
+  char *z = *pz;
+  while( *zFrom && *zFrom==*z ){ z++; zFrom++; }
+  if( *zFrom!=0 ) return 0;
+  if( xCond && !xCond(z) ) return 1;
+  while( *zTo ){
+    *(--z) = *(zTo++);
+  }
+  *pz = z;
+  return 1;
+}
+
+/*
+** This is the fallback stemmer used when the porter stemmer is
+** inappropriate.  The input word is copied into the output with
+** US-ASCII case folding.  If the input word is too long (more
+** than 20 bytes if it contains no digits or more than 6 bytes if
+** it contains digits) then word is truncated to 20 or 6 bytes
+** by taking 10 or 3 bytes from the beginning and end.
+*/
+static void copy_stemmer(const char *zIn, int nIn, char *zOut, int *pnOut){
+  int i, mx, j;
+  int hasDigit = 0;
+  for(i=0; i<nIn; i++){
+    char c = zIn[i];
+    if( c>='A' && c<='Z' ){
+      zOut[i] = c - 'A' + 'a';
+    }else{
+      if( c>='0' && c<='9' ) hasDigit = 1;
+      zOut[i] = c;
+    }
+  }
+  mx = hasDigit ? 3 : 10;
+  if( nIn>mx*2 ){
+    for(j=mx, i=nIn-mx; i<nIn; i++, j++){
+      zOut[j] = zOut[i];
+    }
+    i = j;
+  }
+  zOut[i] = 0;
+  *pnOut = i;
+}
+
+
+/*
+** Stem the input word zIn[0..nIn-1].  Store the output in zOut.
+** zOut is at least big enough to hold nIn bytes.  Write the actual
+** size of the output word (exclusive of the '\0' terminator) into *pnOut.
+**
+** Any upper-case characters in the US-ASCII character set ([A-Z])
+** are converted to lower case.  Upper-case UTF characters are
+** unchanged.
+**
+** Words that are longer than about 20 bytes are stemmed by retaining
+** a few bytes from the beginning and the end of the word.  If the
+** word contains digits, 3 bytes are taken from the beginning and
+** 3 bytes from the end.  For long words without digits, 10 bytes
+** are taken from each end.  US-ASCII case folding still applies.
+** 
+** If the input word contains not digits but does characters not 
+** in [a-zA-Z] then no stemming is attempted and this routine just 
+** copies the input into the input into the output with US-ASCII
+** case folding.
+**
+** Stemming never increases the length of the word.  So there is
+** no chance of overflowing the zOut buffer.
+*/
+static void porter_stemmer(const char *zIn, int nIn, char *zOut, int *pnOut){
+  int i, j;
+  char zReverse[28];
+  char *z, *z2;
+  if( nIn<3 || nIn>=(int)sizeof(zReverse)-7 ){
+    /* The word is too big or too small for the porter stemmer.
+    ** Fallback to the copy stemmer */
+    copy_stemmer(zIn, nIn, zOut, pnOut);
+    return;
+  }
+  for(i=0, j=sizeof(zReverse)-6; i<nIn; i++, j--){
+    char c = zIn[i];
+    if( c>='A' && c<='Z' ){
+      zReverse[j] = c + 'a' - 'A';
+    }else if( c>='a' && c<='z' ){
+      zReverse[j] = c;
+    }else{
+      /* The use of a character not in [a-zA-Z] means that we fallback
+      ** to the copy stemmer */
+      copy_stemmer(zIn, nIn, zOut, pnOut);
+      return;
+    }
+  }
+  memset(&zReverse[sizeof(zReverse)-5], 0, 5);
+  z = &zReverse[j+1];
+
+
+  /* Step 1a */
+  if( z[0]=='s' ){
+    if(
+     !stem(&z, "sess", "ss", 0) &&
+     !stem(&z, "sei", "i", 0)  &&
+     !stem(&z, "ss", "ss", 0)
+    ){
+      z++;
+    }
+  }
+
+  /* Step 1b */  
+  z2 = z;
+  if( stem(&z, "dee", "ee", m_gt_0) ){
+    /* Do nothing.  The work was all in the test */
+  }else if( 
+     (stem(&z, "gni", "", hasVowel) || stem(&z, "de", "", hasVowel))
+      && z!=z2
+  ){
+     if( stem(&z, "ta", "ate", 0) ||
+         stem(&z, "lb", "ble", 0) ||
+         stem(&z, "zi", "ize", 0) ){
+       /* Do nothing.  The work was all in the test */
+     }else if( doubleConsonant(z) && (*z!='l' && *z!='s' && *z!='z') ){
+       z++;
+     }else if( m_eq_1(z) && star_oh(z) ){
+       *(--z) = 'e';
+     }
+  }
+
+  /* Step 1c */
+  if( z[0]=='y' && hasVowel(z+1) ){
+    z[0] = 'i';
+  }
+
+  /* Step 2 */
+  switch( z[1] ){
+   case 'a':
+     if( !stem(&z, "lanoita", "ate", m_gt_0) ){
+       stem(&z, "lanoit", "tion", m_gt_0);
+     }
+     break;
+   case 'c':
+     if( !stem(&z, "icne", "ence", m_gt_0) ){
+       stem(&z, "icna", "ance", m_gt_0);
+     }
+     break;
+   case 'e':
+     stem(&z, "rezi", "ize", m_gt_0);
+     break;
+   case 'g':
+     stem(&z, "igol", "log", m_gt_0);
+     break;
+   case 'l':
+     if( !stem(&z, "ilb", "ble", m_gt_0) 
+      && !stem(&z, "illa", "al", m_gt_0)
+      && !stem(&z, "iltne", "ent", m_gt_0)
+      && !stem(&z, "ile", "e", m_gt_0)
+     ){
+       stem(&z, "ilsuo", "ous", m_gt_0);
+     }
+     break;
+   case 'o':
+     if( !stem(&z, "noitazi", "ize", m_gt_0)
+      && !stem(&z, "noita", "ate", m_gt_0)
+     ){
+       stem(&z, "rota", "ate", m_gt_0);
+     }
+     break;
+   case 's':
+     if( !stem(&z, "msila", "al", m_gt_0)
+      && !stem(&z, "ssenevi", "ive", m_gt_0)
+      && !stem(&z, "ssenluf", "ful", m_gt_0)
+     ){
+       stem(&z, "ssensuo", "ous", m_gt_0);
+     }
+     break;
+   case 't':
+     if( !stem(&z, "itila", "al", m_gt_0)
+      && !stem(&z, "itivi", "ive", m_gt_0)
+     ){
+       stem(&z, "itilib", "ble", m_gt_0);
+     }
+     break;
+  }
+
+  /* Step 3 */
+  switch( z[0] ){
+   case 'e':
+     if( !stem(&z, "etaci", "ic", m_gt_0)
+      && !stem(&z, "evita", "", m_gt_0)
+     ){
+       stem(&z, "ezila", "al", m_gt_0);
+     }
+     break;
+   case 'i':
+     stem(&z, "itici", "ic", m_gt_0);
+     break;
+   case 'l':
+     if( !stem(&z, "laci", "ic", m_gt_0) ){
+       stem(&z, "luf", "", m_gt_0);
+     }
+     break;
+   case 's':
+     stem(&z, "ssen", "", m_gt_0);
+     break;
+  }
+
+  /* Step 4 */
+  switch( z[1] ){
+   case 'a':
+     if( z[0]=='l' && m_gt_1(z+2) ){
+       z += 2;
+     }
+     break;
+   case 'c':
+     if( z[0]=='e' && z[2]=='n' && (z[3]=='a' || z[3]=='e')  && m_gt_1(z+4)  ){
+       z += 4;
+     }
+     break;
+   case 'e':
+     if( z[0]=='r' && m_gt_1(z+2) ){
+       z += 2;
+     }
+     break;
+   case 'i':
+     if( z[0]=='c' && m_gt_1(z+2) ){
+       z += 2;
+     }
+     break;
+   case 'l':
+     if( z[0]=='e' && z[2]=='b' && (z[3]=='a' || z[3]=='i') && m_gt_1(z+4) ){
+       z += 4;
+     }
+     break;
+   case 'n':
+     if( z[0]=='t' ){
+       if( z[2]=='a' ){
+         if( m_gt_1(z+3) ){
+           z += 3;
+         }
+       }else if( z[2]=='e' ){
+         if( !stem(&z, "tneme", "", m_gt_1)
+          && !stem(&z, "tnem", "", m_gt_1)
+         ){
+           stem(&z, "tne", "", m_gt_1);
+         }
+       }
+     }
+     break;
+   case 'o':
+     if( z[0]=='u' ){
+       if( m_gt_1(z+2) ){
+         z += 2;
+       }
+     }else if( z[3]=='s' || z[3]=='t' ){
+       stem(&z, "noi", "", m_gt_1);
+     }
+     break;
+   case 's':
+     if( z[0]=='m' && z[2]=='i' && m_gt_1(z+3) ){
+       z += 3;
+     }
+     break;
+   case 't':
+     if( !stem(&z, "eta", "", m_gt_1) ){
+       stem(&z, "iti", "", m_gt_1);
+     }
+     break;
+   case 'u':
+     if( z[0]=='s' && z[2]=='o' && m_gt_1(z+3) ){
+       z += 3;
+     }
+     break;
+   case 'v':
+   case 'z':
+     if( z[0]=='e' && z[2]=='i' && m_gt_1(z+3) ){
+       z += 3;
+     }
+     break;
+  }
+
+  /* Step 5a */
+  if( z[0]=='e' ){
+    if( m_gt_1(z+1) ){
+      z++;
+    }else if( m_eq_1(z+1) && !star_oh(z+1) ){
+      z++;
+    }
+  }
+
+  /* Step 5b */
+  if( m_gt_1(z) && z[0]=='l' && z[1]=='l' ){
+    z++;
+  }
+
+  /* z[] is now the stemmed word in reverse order.  Flip it back
+  ** around into forward order and return.
+  */
+  *pnOut = i = (int)strlen(z);
+  zOut[i] = 0;
+  while( *z ){
+    zOut[--i] = *(z++);
+  }
+}
+
+/*
+** Characters that can be part of a token.  We assume any character
+** whose value is greater than 0x80 (any UTF character) can be
+** part of a token.  In other words, delimiters all must have
+** values of 0x7f or lower.
+*/
+static const char porterIdChar[] = {
+/* x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 3x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 4x */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,  /* 5x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 6x */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,  /* 7x */
+};
+#define isDelim(C) (((ch=C)&0x80)==0 && (ch<0x30 || !porterIdChar[ch-0x30]))
+
+/*
+** Extract the next token from a tokenization cursor.  The cursor must
+** have been opened by a prior call to porterOpen().
+*/
+static int porterNext(
+  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by porterOpen */
+  const char **pzToken,               /* OUT: *pzToken is the token text */
+  int *pnBytes,                       /* OUT: Number of bytes in token */
+  int *piStartOffset,                 /* OUT: Starting offset of token */
+  int *piEndOffset,                   /* OUT: Ending offset of token */
+  int *piPosition                     /* OUT: Position integer of token */
+){
+  porter_tokenizer_cursor *c = (porter_tokenizer_cursor *) pCursor;
+  const char *z = c->zInput;
+
+  while( c->iOffset<c->nInput ){
+    int iStartOffset, ch;
+
+    /* Scan past delimiter characters */
+    while( c->iOffset<c->nInput && isDelim(z[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    /* Count non-delimiter characters. */
+    iStartOffset = c->iOffset;
+    while( c->iOffset<c->nInput && !isDelim(z[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    if( c->iOffset>iStartOffset ){
+      int n = c->iOffset-iStartOffset;
+      if( n>c->nAllocated ){
+        char *pNew;
+        c->nAllocated = n+20;
+        pNew = sqlite3_realloc(c->zToken, c->nAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->zToken = pNew;
+      }
+      porter_stemmer(&z[iStartOffset], n, c->zToken, pnBytes);
+      *pzToken = c->zToken;
+      *piStartOffset = iStartOffset;
+      *piEndOffset = c->iOffset;
+      *piPosition = c->iToken++;
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_DONE;
+}
+
+/*
+** The set of routines that implement the porter-stemmer tokenizer
+*/
+static const sqlite3_tokenizer_module porterTokenizerModule = {
+  0,
+  porterCreate,
+  porterDestroy,
+  porterOpen,
+  porterClose,
+  porterNext,
+  0
+};
+
+/*
+** Allocate a new porter tokenizer.  Return a pointer to the new
+** tokenizer in *ppModule
+*/
+SQLITE_PRIVATE void sqlite3Fts3PorterTokenizerModule(
+  sqlite3_tokenizer_module const**ppModule
+){
+  *ppModule = &porterTokenizerModule;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_porter.c *****************************************/
+/************** Begin file fts3_tokenizer.c **********************************/
+/*
+** 2007 June 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This is part of an SQLite module implementing full-text search.
+** This particular file implements the generic tokenizer interface.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+**     * The FTS3 module is being built as an extension
+**       (in which case SQLITE_CORE is not defined), or
+**
+**     * The FTS3 module is being built into the core of
+**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <string.h> */
+
+/*
+** Return true if the two-argument version of fts3_tokenizer()
+** has been activated via a prior call to sqlite3_db_config(db,
+** SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER, 1, 0);
+*/
+static int fts3TokenizerEnabled(sqlite3_context *context){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  int isEnabled = 0;
+  sqlite3_db_config(db,SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER,-1,&isEnabled);
+  return isEnabled;
+}
+
+/*
+** Implementation of the SQL scalar function for accessing the underlying 
+** hash table. This function may be called as follows:
+**
+**   SELECT <function-name>(<key-name>);
+**   SELECT <function-name>(<key-name>, <pointer>);
+**
+** where <function-name> is the name passed as the second argument
+** to the sqlite3Fts3InitHashTable() function (e.g. 'fts3_tokenizer').
+**
+** If the <pointer> argument is specified, it must be a blob value
+** containing a pointer to be stored as the hash data corresponding
+** to the string <key-name>. If <pointer> is not specified, then
+** the string <key-name> must already exist in the has table. Otherwise,
+** an error is returned.
+**
+** Whether or not the <pointer> argument is specified, the value returned
+** is a blob containing the pointer stored as the hash data corresponding
+** to string <key-name> (after the hash-table is updated, if applicable).
+*/
+static void fts3TokenizerFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  Fts3Hash *pHash;
+  void *pPtr = 0;
+  const unsigned char *zName;
+  int nName;
+
+  assert( argc==1 || argc==2 );
+
+  pHash = (Fts3Hash *)sqlite3_user_data(context);
+
+  zName = sqlite3_value_text(argv[0]);
+  nName = sqlite3_value_bytes(argv[0])+1;
+
+  if( argc==2 ){
+    if( fts3TokenizerEnabled(context) ){
+      void *pOld;
+      int n = sqlite3_value_bytes(argv[1]);
+      if( zName==0 || n!=sizeof(pPtr) ){
+        sqlite3_result_error(context, "argument type mismatch", -1);
+        return;
+      }
+      pPtr = *(void **)sqlite3_value_blob(argv[1]);
+      pOld = sqlite3Fts3HashInsert(pHash, (void *)zName, nName, pPtr);
+      if( pOld==pPtr ){
+        sqlite3_result_error(context, "out of memory", -1);
+      }
+    }else{
+      sqlite3_result_error(context, "fts3tokenize disabled", -1);
+      return;
+    }
+  }else{
+    if( zName ){
+      pPtr = sqlite3Fts3HashFind(pHash, zName, nName);
+    }
+    if( !pPtr ){
+      char *zErr = sqlite3_mprintf("unknown tokenizer: %s", zName);
+      sqlite3_result_error(context, zErr, -1);
+      sqlite3_free(zErr);
+      return;
+    }
+  }
+  sqlite3_result_blob(context, (void *)&pPtr, sizeof(pPtr), SQLITE_TRANSIENT);
+}
+
+SQLITE_PRIVATE int sqlite3Fts3IsIdChar(char c){
+  static const char isFtsIdChar[] = {
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 0x */
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 1x */
+      0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 2x */
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 3x */
+      0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 4x */
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,  /* 5x */
+      0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 6x */
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,  /* 7x */
+  };
+  return (c&0x80 || isFtsIdChar[(int)(c)]);
+}
+
+SQLITE_PRIVATE const char *sqlite3Fts3NextToken(const char *zStr, int *pn){
+  const char *z1;
+  const char *z2 = 0;
+
+  /* Find the start of the next token. */
+  z1 = zStr;
+  while( z2==0 ){
+    char c = *z1;
+    switch( c ){
+      case '\0': return 0;        /* No more tokens here */
+      case '\'':
+      case '"':
+      case '`': {
+        z2 = z1;
+        while( *++z2 && (*z2!=c || *++z2==c) );
+        break;
+      }
+      case '[':
+        z2 = &z1[1];
+        while( *z2 && z2[0]!=']' ) z2++;
+        if( *z2 ) z2++;
+        break;
+
+      default:
+        if( sqlite3Fts3IsIdChar(*z1) ){
+          z2 = &z1[1];
+          while( sqlite3Fts3IsIdChar(*z2) ) z2++;
+        }else{
+          z1++;
+        }
+    }
+  }
+
+  *pn = (int)(z2-z1);
+  return z1;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3InitTokenizer(
+  Fts3Hash *pHash,                /* Tokenizer hash table */
+  const char *zArg,               /* Tokenizer name */
+  sqlite3_tokenizer **ppTok,      /* OUT: Tokenizer (if applicable) */
+  char **pzErr                    /* OUT: Set to malloced error message */
+){
+  int rc;
+  char *z = (char *)zArg;
+  int n = 0;
+  char *zCopy;
+  char *zEnd;                     /* Pointer to nul-term of zCopy */
+  sqlite3_tokenizer_module *m;
+
+  zCopy = sqlite3_mprintf("%s", zArg);
+  if( !zCopy ) return SQLITE_NOMEM;
+  zEnd = &zCopy[strlen(zCopy)];
+
+  z = (char *)sqlite3Fts3NextToken(zCopy, &n);
+  if( z==0 ){
+    assert( n==0 );
+    z = zCopy;
+  }
+  z[n] = '\0';
+  sqlite3Fts3Dequote(z);
+
+  m = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash,z,(int)strlen(z)+1);
+  if( !m ){
+    sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer: %s", z);
+    rc = SQLITE_ERROR;
+  }else{
+    char const **aArg = 0;
+    int iArg = 0;
+    z = &z[n+1];
+    while( z<zEnd && (NULL!=(z = (char *)sqlite3Fts3NextToken(z, &n))) ){
+      int nNew = sizeof(char *)*(iArg+1);
+      char const **aNew = (const char **)sqlite3_realloc((void *)aArg, nNew);
+      if( !aNew ){
+        sqlite3_free(zCopy);
+        sqlite3_free((void *)aArg);
+        return SQLITE_NOMEM;
+      }
+      aArg = aNew;
+      aArg[iArg++] = z;
+      z[n] = '\0';
+      sqlite3Fts3Dequote(z);
+      z = &z[n+1];
+    }
+    rc = m->xCreate(iArg, aArg, ppTok);
+    assert( rc!=SQLITE_OK || *ppTok );
+    if( rc!=SQLITE_OK ){
+      sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer");
+    }else{
+      (*ppTok)->pModule = m; 
+    }
+    sqlite3_free((void *)aArg);
+  }
+
+  sqlite3_free(zCopy);
+  return rc;
+}
+
+
+#ifdef SQLITE_TEST
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+/* #include <string.h> */
+
+/*
+** Implementation of a special SQL scalar function for testing tokenizers 
+** designed to be used in concert with the Tcl testing framework. This
+** function must be called with two or more arguments:
+**
+**   SELECT <function-name>(<key-name>, ..., <input-string>);
+**
+** where <function-name> is the name passed as the second argument
+** to the sqlite3Fts3InitHashTable() function (e.g. 'fts3_tokenizer')
+** concatenated with the string '_test' (e.g. 'fts3_tokenizer_test').
+**
+** The return value is a string that may be interpreted as a Tcl
+** list. For each token in the <input-string>, three elements are
+** added to the returned list. The first is the token position, the 
+** second is the token text (folded, stemmed, etc.) and the third is the
+** substring of <input-string> associated with the token. For example, 
+** using the built-in "simple" tokenizer:
+**
+**   SELECT fts_tokenizer_test('simple', 'I don't see how');
+**
+** will return the string:
+**
+**   "{0 i I 1 dont don't 2 see see 3 how how}"
+**   
+*/
+static void testFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  Fts3Hash *pHash;
+  sqlite3_tokenizer_module *p;
+  sqlite3_tokenizer *pTokenizer = 0;
+  sqlite3_tokenizer_cursor *pCsr = 0;
+
+  const char *zErr = 0;
+
+  const char *zName;
+  int nName;
+  const char *zInput;
+  int nInput;
+
+  const char *azArg[64];
+
+  const char *zToken;
+  int nToken = 0;
+  int iStart = 0;
+  int iEnd = 0;
+  int iPos = 0;
+  int i;
+
+  Tcl_Obj *pRet;
+
+  if( argc<2 ){
+    sqlite3_result_error(context, "insufficient arguments", -1);
+    return;
+  }
+
+  nName = sqlite3_value_bytes(argv[0]);
+  zName = (const char *)sqlite3_value_text(argv[0]);
+  nInput = sqlite3_value_bytes(argv[argc-1]);
+  zInput = (const char *)sqlite3_value_text(argv[argc-1]);
+
+  pHash = (Fts3Hash *)sqlite3_user_data(context);
+  p = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash, zName, nName+1);
+
+  if( !p ){
+    char *zErr2 = sqlite3_mprintf("unknown tokenizer: %s", zName);
+    sqlite3_result_error(context, zErr2, -1);
+    sqlite3_free(zErr2);
+    return;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_IncrRefCount(pRet);
+
+  for(i=1; i<argc-1; i++){
+    azArg[i-1] = (const char *)sqlite3_value_text(argv[i]);
+  }
+
+  if( SQLITE_OK!=p->xCreate(argc-2, azArg, &pTokenizer) ){
+    zErr = "error in xCreate()";
+    goto finish;
+  }
+  pTokenizer->pModule = p;
+  if( sqlite3Fts3OpenTokenizer(pTokenizer, 0, zInput, nInput, &pCsr) ){
+    zErr = "error in xOpen()";
+    goto finish;
+  }
+
+  while( SQLITE_OK==p->xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos) ){
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(iPos));
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zToken, nToken));
+    zToken = &zInput[iStart];
+    nToken = iEnd-iStart;
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zToken, nToken));
+  }
+
+  if( SQLITE_OK!=p->xClose(pCsr) ){
+    zErr = "error in xClose()";
+    goto finish;
+  }
+  if( SQLITE_OK!=p->xDestroy(pTokenizer) ){
+    zErr = "error in xDestroy()";
+    goto finish;
+  }
+
+finish:
+  if( zErr ){
+    sqlite3_result_error(context, zErr, -1);
+  }else{
+    sqlite3_result_text(context, Tcl_GetString(pRet), -1, SQLITE_TRANSIENT);
+  }
+  Tcl_DecrRefCount(pRet);
+}
+
+static
+int registerTokenizer(
+  sqlite3 *db, 
+  char *zName, 
+  const sqlite3_tokenizer_module *p
+){
+  int rc;
+  sqlite3_stmt *pStmt;
+  const char zSql[] = "SELECT fts3_tokenizer(?, ?)";
+
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
+  sqlite3_bind_blob(pStmt, 2, &p, sizeof(p), SQLITE_STATIC);
+  sqlite3_step(pStmt);
+
+  return sqlite3_finalize(pStmt);
+}
+
+
+static
+int queryTokenizer(
+  sqlite3 *db, 
+  char *zName,  
+  const sqlite3_tokenizer_module **pp
+){
+  int rc;
+  sqlite3_stmt *pStmt;
+  const char zSql[] = "SELECT fts3_tokenizer(?)";
+
+  *pp = 0;
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    if( sqlite3_column_type(pStmt, 0)==SQLITE_BLOB ){
+      memcpy((void *)pp, sqlite3_column_blob(pStmt, 0), sizeof(*pp));
+    }
+  }
+
+  return sqlite3_finalize(pStmt);
+}
+
+SQLITE_PRIVATE void sqlite3Fts3SimpleTokenizerModule(sqlite3_tokenizer_module const**ppModule);
+
+/*
+** Implementation of the scalar function fts3_tokenizer_internal_test().
+** This function is used for testing only, it is not included in the
+** build unless SQLITE_TEST is defined.
+**
+** The purpose of this is to test that the fts3_tokenizer() function
+** can be used as designed by the C-code in the queryTokenizer and
+** registerTokenizer() functions above. These two functions are repeated
+** in the README.tokenizer file as an example, so it is important to
+** test them.
+**
+** To run the tests, evaluate the fts3_tokenizer_internal_test() scalar
+** function with no arguments. An assert() will fail if a problem is
+** detected. i.e.:
+**
+**     SELECT fts3_tokenizer_internal_test();
+**
+*/
+static void intTestFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int rc;
+  const sqlite3_tokenizer_module *p1;
+  const sqlite3_tokenizer_module *p2;
+  sqlite3 *db = (sqlite3 *)sqlite3_user_data(context);
+
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+
+  /* Test the query function */
+  sqlite3Fts3SimpleTokenizerModule(&p1);
+  rc = queryTokenizer(db, "simple", &p2);
+  assert( rc==SQLITE_OK );
+  assert( p1==p2 );
+  rc = queryTokenizer(db, "nosuchtokenizer", &p2);
+  assert( rc==SQLITE_ERROR );
+  assert( p2==0 );
+  assert( 0==strcmp(sqlite3_errmsg(db), "unknown tokenizer: nosuchtokenizer") );
+
+  /* Test the storage function */
+  if( fts3TokenizerEnabled(context) ){
+    rc = registerTokenizer(db, "nosuchtokenizer", p1);
+    assert( rc==SQLITE_OK );
+    rc = queryTokenizer(db, "nosuchtokenizer", &p2);
+    assert( rc==SQLITE_OK );
+    assert( p2==p1 );
+  }
+
+  sqlite3_result_text(context, "ok", -1, SQLITE_STATIC);
+}
+
+#endif
+
+/*
+** Set up SQL objects in database db used to access the contents of
+** the hash table pointed to by argument pHash. The hash table must
+** been initialized to use string keys, and to take a private copy 
+** of the key when a value is inserted. i.e. by a call similar to:
+**
+**    sqlite3Fts3HashInit(pHash, FTS3_HASH_STRING, 1);
+**
+** This function adds a scalar function (see header comment above
+** fts3TokenizerFunc() in this file for details) and, if ENABLE_TABLE is
+** defined at compilation time, a temporary virtual table (see header 
+** comment above struct HashTableVtab) to the database schema. Both 
+** provide read/write access to the contents of *pHash.
+**
+** The third argument to this function, zName, is used as the name
+** of both the scalar and, if created, the virtual table.
+*/
+SQLITE_PRIVATE int sqlite3Fts3InitHashTable(
+  sqlite3 *db, 
+  Fts3Hash *pHash, 
+  const char *zName
+){
+  int rc = SQLITE_OK;
+  void *p = (void *)pHash;
+  const int any = SQLITE_ANY;
+
+#ifdef SQLITE_TEST
+  char *zTest = 0;
+  char *zTest2 = 0;
+  void *pdb = (void *)db;
+  zTest = sqlite3_mprintf("%s_test", zName);
+  zTest2 = sqlite3_mprintf("%s_internal_test", zName);
+  if( !zTest || !zTest2 ){
+    rc = SQLITE_NOMEM;
+  }
+#endif
+
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zName, 1, any, p, fts3TokenizerFunc, 0, 0);
+  }
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zName, 2, any, p, fts3TokenizerFunc, 0, 0);
+  }
+#ifdef SQLITE_TEST
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zTest, -1, any, p, testFunc, 0, 0);
+  }
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zTest2, 0, any, pdb, intTestFunc, 0, 0);
+  }
+#endif
+
+#ifdef SQLITE_TEST
+  sqlite3_free(zTest);
+  sqlite3_free(zTest2);
+#endif
+
+  return rc;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_tokenizer.c **************************************/
+/************** Begin file fts3_tokenizer1.c *********************************/
+/*
+** 2006 Oct 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** Implementation of the "simple" full-text-search tokenizer.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+**     * The FTS3 module is being built as an extension
+**       (in which case SQLITE_CORE is not defined), or
+**
+**     * The FTS3 module is being built into the core of
+**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <stdio.h> */
+/* #include <string.h> */
+
+/* #include "fts3_tokenizer.h" */
+
+typedef struct simple_tokenizer {
+  sqlite3_tokenizer base;
+  char delim[128];             /* flag ASCII delimiters */
+} simple_tokenizer;
+
+typedef struct simple_tokenizer_cursor {
+  sqlite3_tokenizer_cursor base;
+  const char *pInput;          /* input we are tokenizing */
+  int nBytes;                  /* size of the input */
+  int iOffset;                 /* current position in pInput */
+  int iToken;                  /* index of next token to be returned */
+  char *pToken;                /* storage for current token */
+  int nTokenAllocated;         /* space allocated to zToken buffer */
+} simple_tokenizer_cursor;
+
+
+static int simpleDelim(simple_tokenizer *t, unsigned char c){
+  return c<0x80 && t->delim[c];
+}
+static int fts3_isalnum(int x){
+  return (x>='0' && x<='9') || (x>='A' && x<='Z') || (x>='a' && x<='z');
+}
+
+/*
+** Create a new tokenizer instance.
+*/
+static int simpleCreate(
+  int argc, const char * const *argv,
+  sqlite3_tokenizer **ppTokenizer
+){
+  simple_tokenizer *t;
+
+  t = (simple_tokenizer *) sqlite3_malloc(sizeof(*t));
+  if( t==NULL ) return SQLITE_NOMEM;
+  memset(t, 0, sizeof(*t));
+
+  /* TODO(shess) Delimiters need to remain the same from run to run,
+  ** else we need to reindex.  One solution would be a meta-table to
+  ** track such information in the database, then we'd only want this
+  ** information on the initial create.
+  */
+  if( argc>1 ){
+    int i, n = (int)strlen(argv[1]);
+    for(i=0; i<n; i++){
+      unsigned char ch = argv[1][i];
+      /* We explicitly don't support UTF-8 delimiters for now. */
+      if( ch>=0x80 ){
+        sqlite3_free(t);
+        return SQLITE_ERROR;
+      }
+      t->delim[ch] = 1;
+    }
+  } else {
+    /* Mark non-alphanumeric ASCII characters as delimiters */
+    int i;
+    for(i=1; i<0x80; i++){
+      t->delim[i] = !fts3_isalnum(i) ? -1 : 0;
+    }
+  }
+
+  *ppTokenizer = &t->base;
+  return SQLITE_OK;
+}
+
+/*
+** Destroy a tokenizer
+*/
+static int simpleDestroy(sqlite3_tokenizer *pTokenizer){
+  sqlite3_free(pTokenizer);
+  return SQLITE_OK;
+}
+
+/*
+** Prepare to begin tokenizing a particular string.  The input
+** string to be tokenized is pInput[0..nBytes-1].  A cursor
+** used to incrementally tokenize this string is returned in 
+** *ppCursor.
+*/
+static int simpleOpen(
+  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
+  const char *pInput, int nBytes,        /* String to be tokenized */
+  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
+){
+  simple_tokenizer_cursor *c;
+
+  UNUSED_PARAMETER(pTokenizer);
+
+  c = (simple_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
+  if( c==NULL ) return SQLITE_NOMEM;
+
+  c->pInput = pInput;
+  if( pInput==0 ){
+    c->nBytes = 0;
+  }else if( nBytes<0 ){
+    c->nBytes = (int)strlen(pInput);
+  }else{
+    c->nBytes = nBytes;
+  }
+  c->iOffset = 0;                 /* start tokenizing at the beginning */
+  c->iToken = 0;
+  c->pToken = NULL;               /* no space allocated, yet. */
+  c->nTokenAllocated = 0;
+
+  *ppCursor = &c->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a tokenization cursor previously opened by a call to
+** simpleOpen() above.
+*/
+static int simpleClose(sqlite3_tokenizer_cursor *pCursor){
+  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
+  sqlite3_free(c->pToken);
+  sqlite3_free(c);
+  return SQLITE_OK;
+}
+
+/*
+** Extract the next token from a tokenization cursor.  The cursor must
+** have been opened by a prior call to simpleOpen().
+*/
+static int simpleNext(
+  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
+  const char **ppToken,               /* OUT: *ppToken is the token text */
+  int *pnBytes,                       /* OUT: Number of bytes in token */
+  int *piStartOffset,                 /* OUT: Starting offset of token */
+  int *piEndOffset,                   /* OUT: Ending offset of token */
+  int *piPosition                     /* OUT: Position integer of token */
+){
+  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
+  simple_tokenizer *t = (simple_tokenizer *) pCursor->pTokenizer;
+  unsigned char *p = (unsigned char *)c->pInput;
+
+  while( c->iOffset<c->nBytes ){
+    int iStartOffset;
+
+    /* Scan past delimiter characters */
+    while( c->iOffset<c->nBytes && simpleDelim(t, p[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    /* Count non-delimiter characters. */
+    iStartOffset = c->iOffset;
+    while( c->iOffset<c->nBytes && !simpleDelim(t, p[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    if( c->iOffset>iStartOffset ){
+      int i, n = c->iOffset-iStartOffset;
+      if( n>c->nTokenAllocated ){
+        char *pNew;
+        c->nTokenAllocated = n+20;
+        pNew = sqlite3_realloc(c->pToken, c->nTokenAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->pToken = pNew;
+      }
+      for(i=0; i<n; i++){
+        /* TODO(shess) This needs expansion to handle UTF-8
+        ** case-insensitivity.
+        */
+        unsigned char ch = p[iStartOffset+i];
+        c->pToken[i] = (char)((ch>='A' && ch<='Z') ? ch-'A'+'a' : ch);
+      }
+      *ppToken = c->pToken;
+      *pnBytes = n;
+      *piStartOffset = iStartOffset;
+      *piEndOffset = c->iOffset;
+      *piPosition = c->iToken++;
+
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_DONE;
+}
+
+/*
+** The set of routines that implement the simple tokenizer
+*/
+static const sqlite3_tokenizer_module simpleTokenizerModule = {
+  0,
+  simpleCreate,
+  simpleDestroy,
+  simpleOpen,
+  simpleClose,
+  simpleNext,
+  0,
+};
+
+/*
+** Allocate a new simple tokenizer.  Return a pointer to the new
+** tokenizer in *ppModule
+*/
+SQLITE_PRIVATE void sqlite3Fts3SimpleTokenizerModule(
+  sqlite3_tokenizer_module const**ppModule
+){
+  *ppModule = &simpleTokenizerModule;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_tokenizer1.c *************************************/
+/************** Begin file fts3_tokenize_vtab.c ******************************/
+/*
+** 2013 Apr 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code for the "fts3tokenize" virtual table module.
+** An fts3tokenize virtual table is created as follows:
+**
+**   CREATE VIRTUAL TABLE <tbl> USING fts3tokenize(
+**       <tokenizer-name>, <arg-1>, ...
+**   );
+**
+** The table created has the following schema:
+**
+**   CREATE TABLE <tbl>(input, token, start, end, position)
+**
+** When queried, the query must include a WHERE clause of type:
+**
+**   input = <string>
+**
+** The virtual table module tokenizes this <string>, using the FTS3 
+** tokenizer specified by the arguments to the CREATE VIRTUAL TABLE 
+** statement and returns one row for each token in the result. With
+** fields set as follows:
+**
+**   input:   Always set to a copy of <string>
+**   token:   A token from the input.
+**   start:   Byte offset of the token within the input <string>.
+**   end:     Byte offset of the byte immediately following the end of the
+**            token within the input string.
+**   pos:     Token offset of token within input.
+**
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <string.h> */
+/* #include <assert.h> */
+
+typedef struct Fts3tokTable Fts3tokTable;
+typedef struct Fts3tokCursor Fts3tokCursor;
+
+/*
+** Virtual table structure.
+*/
+struct Fts3tokTable {
+  sqlite3_vtab base;              /* Base class used by SQLite core */
+  const sqlite3_tokenizer_module *pMod;
+  sqlite3_tokenizer *pTok;
+};
+
+/*
+** Virtual table cursor structure.
+*/
+struct Fts3tokCursor {
+  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
+  char *zInput;                   /* Input string */
+  sqlite3_tokenizer_cursor *pCsr; /* Cursor to iterate through zInput */
+  int iRowid;                     /* Current 'rowid' value */
+  const char *zToken;             /* Current 'token' value */
+  int nToken;                     /* Size of zToken in bytes */
+  int iStart;                     /* Current 'start' value */
+  int iEnd;                       /* Current 'end' value */
+  int iPos;                       /* Current 'pos' value */
+};
+
+/*
+** Query FTS for the tokenizer implementation named zName.
+*/
+static int fts3tokQueryTokenizer(
+  Fts3Hash *pHash,
+  const char *zName,
+  const sqlite3_tokenizer_module **pp,
+  char **pzErr
+){
+  sqlite3_tokenizer_module *p;
+  int nName = (int)strlen(zName);
+
+  p = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash, zName, nName+1);
+  if( !p ){
+    sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer: %s", zName);
+    return SQLITE_ERROR;
+  }
+
+  *pp = p;
+  return SQLITE_OK;
+}
+
+/*
+** The second argument, argv[], is an array of pointers to nul-terminated
+** strings. This function makes a copy of the array and strings into a 
+** single block of memory. It then dequotes any of the strings that appear
+** to be quoted.
+**
+** If successful, output parameter *pazDequote is set to point at the
+** array of dequoted strings and SQLITE_OK is returned. The caller is
+** responsible for eventually calling sqlite3_free() to free the array
+** in this case. Or, if an error occurs, an SQLite error code is returned.
+** The final value of *pazDequote is undefined in this case.
+*/
+static int fts3tokDequoteArray(
+  int argc,                       /* Number of elements in argv[] */
+  const char * const *argv,       /* Input array */
+  char ***pazDequote              /* Output array */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  if( argc==0 ){
+    *pazDequote = 0;
+  }else{
+    int i;
+    int nByte = 0;
+    char **azDequote;
+
+    for(i=0; i<argc; i++){
+      nByte += (int)(strlen(argv[i]) + 1);
+    }
+
+    *pazDequote = azDequote = sqlite3_malloc(sizeof(char *)*argc + nByte);
+    if( azDequote==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      char *pSpace = (char *)&azDequote[argc];
+      for(i=0; i<argc; i++){
+        int n = (int)strlen(argv[i]);
+        azDequote[i] = pSpace;
+        memcpy(pSpace, argv[i], n+1);
+        sqlite3Fts3Dequote(pSpace);
+        pSpace += (n+1);
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Schema of the tokenizer table.
+*/
+#define FTS3_TOK_SCHEMA "CREATE TABLE x(input, token, start, end, position)"
+
+/*
+** This function does all the work for both the xConnect and xCreate methods.
+** These tables have no persistent representation of their own, so xConnect
+** and xCreate are identical operations.
+**
+**   argv[0]: module name
+**   argv[1]: database name 
+**   argv[2]: table name
+**   argv[3]: first argument (tokenizer name)
+*/
+static int fts3tokConnectMethod(
+  sqlite3 *db,                    /* Database connection */
+  void *pHash,                    /* Hash table of tokenizers */
+  int argc,                       /* Number of elements in argv array */
+  const char * const *argv,       /* xCreate/xConnect argument array */
+  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
+  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
+){
+  Fts3tokTable *pTab = 0;
+  const sqlite3_tokenizer_module *pMod = 0;
+  sqlite3_tokenizer *pTok = 0;
+  int rc;
+  char **azDequote = 0;
+  int nDequote;
+
+  rc = sqlite3_declare_vtab(db, FTS3_TOK_SCHEMA);
+  if( rc!=SQLITE_OK ) return rc;
+
+  nDequote = argc-3;
+  rc = fts3tokDequoteArray(nDequote, &argv[3], &azDequote);
+
+  if( rc==SQLITE_OK ){
+    const char *zModule;
+    if( nDequote<1 ){
+      zModule = "simple";
+    }else{
+      zModule = azDequote[0];
+    }
+    rc = fts3tokQueryTokenizer((Fts3Hash*)pHash, zModule, &pMod, pzErr);
+  }
+
+  assert( (rc==SQLITE_OK)==(pMod!=0) );
+  if( rc==SQLITE_OK ){
+    const char * const *azArg = (const char * const *)&azDequote[1];
+    rc = pMod->xCreate((nDequote>1 ? nDequote-1 : 0), azArg, &pTok);
+  }
+
+  if( rc==SQLITE_OK ){
+    pTab = (Fts3tokTable *)sqlite3_malloc(sizeof(Fts3tokTable));
+    if( pTab==0 ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    memset(pTab, 0, sizeof(Fts3tokTable));
+    pTab->pMod = pMod;
+    pTab->pTok = pTok;
+    *ppVtab = &pTab->base;
+  }else{
+    if( pTok ){
+      pMod->xDestroy(pTok);
+    }
+  }
+
+  sqlite3_free(azDequote);
+  return rc;
+}
+
+/*
+** This function does the work for both the xDisconnect and xDestroy methods.
+** These tables have no persistent representation of their own, so xDisconnect
+** and xDestroy are identical operations.
+*/
+static int fts3tokDisconnectMethod(sqlite3_vtab *pVtab){
+  Fts3tokTable *pTab = (Fts3tokTable *)pVtab;
+
+  pTab->pMod->xDestroy(pTab->pTok);
+  sqlite3_free(pTab);
+  return SQLITE_OK;
+}
+
+/*
+** xBestIndex - Analyze a WHERE and ORDER BY clause.
+*/
+static int fts3tokBestIndexMethod(
+  sqlite3_vtab *pVTab, 
+  sqlite3_index_info *pInfo
+){
+  int i;
+  UNUSED_PARAMETER(pVTab);
+
+  for(i=0; i<pInfo->nConstraint; i++){
+    if( pInfo->aConstraint[i].usable 
+     && pInfo->aConstraint[i].iColumn==0 
+     && pInfo->aConstraint[i].op==SQLITE_INDEX_CONSTRAINT_EQ 
+    ){
+      pInfo->idxNum = 1;
+      pInfo->aConstraintUsage[i].argvIndex = 1;
+      pInfo->aConstraintUsage[i].omit = 1;
+      pInfo->estimatedCost = 1;
+      return SQLITE_OK;
+    }
+  }
+
+  pInfo->idxNum = 0;
+  assert( pInfo->estimatedCost>1000000.0 );
+
+  return SQLITE_OK;
+}
+
+/*
+** xOpen - Open a cursor.
+*/
+static int fts3tokOpenMethod(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCsr){
+  Fts3tokCursor *pCsr;
+  UNUSED_PARAMETER(pVTab);
+
+  pCsr = (Fts3tokCursor *)sqlite3_malloc(sizeof(Fts3tokCursor));
+  if( pCsr==0 ){
+    return SQLITE_NOMEM;
+  }
+  memset(pCsr, 0, sizeof(Fts3tokCursor));
+
+  *ppCsr = (sqlite3_vtab_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+/*
+** Reset the tokenizer cursor passed as the only argument. As if it had
+** just been returned by fts3tokOpenMethod().
+*/
+static void fts3tokResetCursor(Fts3tokCursor *pCsr){
+  if( pCsr->pCsr ){
+    Fts3tokTable *pTab = (Fts3tokTable *)(pCsr->base.pVtab);
+    pTab->pMod->xClose(pCsr->pCsr);
+    pCsr->pCsr = 0;
+  }
+  sqlite3_free(pCsr->zInput);
+  pCsr->zInput = 0;
+  pCsr->zToken = 0;
+  pCsr->nToken = 0;
+  pCsr->iStart = 0;
+  pCsr->iEnd = 0;
+  pCsr->iPos = 0;
+  pCsr->iRowid = 0;
+}
+
+/*
+** xClose - Close a cursor.
+*/
+static int fts3tokCloseMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+
+  fts3tokResetCursor(pCsr);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/*
+** xNext - Advance the cursor to the next row, if any.
+*/
+static int fts3tokNextMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  Fts3tokTable *pTab = (Fts3tokTable *)(pCursor->pVtab);
+  int rc;                         /* Return code */
+
+  pCsr->iRowid++;
+  rc = pTab->pMod->xNext(pCsr->pCsr,
+      &pCsr->zToken, &pCsr->nToken,
+      &pCsr->iStart, &pCsr->iEnd, &pCsr->iPos
+  );
+
+  if( rc!=SQLITE_OK ){
+    fts3tokResetCursor(pCsr);
+    if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+  }
+
+  return rc;
+}
+
+/*
+** xFilter - Initialize a cursor to point at the start of its data.
+*/
+static int fts3tokFilterMethod(
+  sqlite3_vtab_cursor *pCursor,   /* The cursor used for this query */
+  int idxNum,                     /* Strategy index */
+  const char *idxStr,             /* Unused */
+  int nVal,                       /* Number of elements in apVal */
+  sqlite3_value **apVal           /* Arguments for the indexing scheme */
+){
+  int rc = SQLITE_ERROR;
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  Fts3tokTable *pTab = (Fts3tokTable *)(pCursor->pVtab);
+  UNUSED_PARAMETER(idxStr);
+  UNUSED_PARAMETER(nVal);
+
+  fts3tokResetCursor(pCsr);
+  if( idxNum==1 ){
+    const char *zByte = (const char *)sqlite3_value_text(apVal[0]);
+    int nByte = sqlite3_value_bytes(apVal[0]);
+    pCsr->zInput = sqlite3_malloc(nByte+1);
+    if( pCsr->zInput==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memcpy(pCsr->zInput, zByte, nByte);
+      pCsr->zInput[nByte] = 0;
+      rc = pTab->pMod->xOpen(pTab->pTok, pCsr->zInput, nByte, &pCsr->pCsr);
+      if( rc==SQLITE_OK ){
+        pCsr->pCsr->pTokenizer = pTab->pTok;
+      }
+    }
+  }
+
+  if( rc!=SQLITE_OK ) return rc;
+  return fts3tokNextMethod(pCursor);
+}
+
+/*
+** xEof - Return true if the cursor is at EOF, or false otherwise.
+*/
+static int fts3tokEofMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  return (pCsr->zToken==0);
+}
+
+/*
+** xColumn - Return a column value.
+*/
+static int fts3tokColumnMethod(
+  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
+  sqlite3_context *pCtx,          /* Context for sqlite3_result_xxx() calls */
+  int iCol                        /* Index of column to read value from */
+){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+
+  /* CREATE TABLE x(input, token, start, end, position) */
+  switch( iCol ){
+    case 0:
+      sqlite3_result_text(pCtx, pCsr->zInput, -1, SQLITE_TRANSIENT);
+      break;
+    case 1:
+      sqlite3_result_text(pCtx, pCsr->zToken, pCsr->nToken, SQLITE_TRANSIENT);
+      break;
+    case 2:
+      sqlite3_result_int(pCtx, pCsr->iStart);
+      break;
+    case 3:
+      sqlite3_result_int(pCtx, pCsr->iEnd);
+      break;
+    default:
+      assert( iCol==4 );
+      sqlite3_result_int(pCtx, pCsr->iPos);
+      break;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** xRowid - Return the current rowid for the cursor.
+*/
+static int fts3tokRowidMethod(
+  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
+  sqlite_int64 *pRowid            /* OUT: Rowid value */
+){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  *pRowid = (sqlite3_int64)pCsr->iRowid;
+  return SQLITE_OK;
+}
+
+/*
+** Register the fts3tok module with database connection db. Return SQLITE_OK
+** if successful or an error code if sqlite3_create_module() fails.
+*/
+SQLITE_PRIVATE int sqlite3Fts3InitTok(sqlite3 *db, Fts3Hash *pHash){
+  static const sqlite3_module fts3tok_module = {
+     0,                           /* iVersion      */
+     fts3tokConnectMethod,        /* xCreate       */
+     fts3tokConnectMethod,        /* xConnect      */
+     fts3tokBestIndexMethod,      /* xBestIndex    */
+     fts3tokDisconnectMethod,     /* xDisconnect   */
+     fts3tokDisconnectMethod,     /* xDestroy      */
+     fts3tokOpenMethod,           /* xOpen         */
+     fts3tokCloseMethod,          /* xClose        */
+     fts3tokFilterMethod,         /* xFilter       */
+     fts3tokNextMethod,           /* xNext         */
+     fts3tokEofMethod,            /* xEof          */
+     fts3tokColumnMethod,         /* xColumn       */
+     fts3tokRowidMethod,          /* xRowid        */
+     0,                           /* xUpdate       */
+     0,                           /* xBegin        */
+     0,                           /* xSync         */
+     0,                           /* xCommit       */
+     0,                           /* xRollback     */
+     0,                           /* xFindFunction */
+     0,                           /* xRename       */
+     0,                           /* xSavepoint    */
+     0,                           /* xRelease      */
+     0                            /* xRollbackTo   */
+  };
+  int rc;                         /* Return code */
+
+  rc = sqlite3_create_module(db, "fts3tokenize", &fts3tok_module, (void*)pHash);
+  return rc;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_tokenize_vtab.c **********************************/
+/************** Begin file fts3_write.c **************************************/
+/*
+** 2009 Oct 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file is part of the SQLite FTS3 extension module. Specifically,
+** this file contains code to insert, update and delete rows from FTS3
+** tables. It also contains code to merge FTS3 b-tree segments. Some
+** of the sub-routines used to merge segments are also used by the query 
+** code in fts3.c.
+*/
+
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <string.h> */
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+
+
+#define FTS_MAX_APPENDABLE_HEIGHT 16
+
+/*
+** When full-text index nodes are loaded from disk, the buffer that they
+** are loaded into has the following number of bytes of padding at the end 
+** of it. i.e. if a full-text index node is 900 bytes in size, then a buffer
+** of 920 bytes is allocated for it.
+**
+** This means that if we have a pointer into a buffer containing node data,
+** it is always safe to read up to two varints from it without risking an
+** overread, even if the node data is corrupted.
+*/
+#define FTS3_NODE_PADDING (FTS3_VARINT_MAX*2)
+
+/*
+** Under certain circumstances, b-tree nodes (doclists) can be loaded into
+** memory incrementally instead of all at once. This can be a big performance
+** win (reduced IO and CPU) if SQLite stops calling the virtual table xNext()
+** method before retrieving all query results (as may happen, for example,
+** if a query has a LIMIT clause).
+**
+** Incremental loading is used for b-tree nodes FTS3_NODE_CHUNK_THRESHOLD 
+** bytes and larger. Nodes are loaded in chunks of FTS3_NODE_CHUNKSIZE bytes.
+** The code is written so that the hard lower-limit for each of these values 
+** is 1. Clearly such small values would be inefficient, but can be useful 
+** for testing purposes.
+**
+** If this module is built with SQLITE_TEST defined, these constants may
+** be overridden at runtime for testing purposes. File fts3_test.c contains
+** a Tcl interface to read and write the values.
+*/
+#ifdef SQLITE_TEST
+int test_fts3_node_chunksize = (4*1024);
+int test_fts3_node_chunk_threshold = (4*1024)*4;
+# define FTS3_NODE_CHUNKSIZE       test_fts3_node_chunksize
+# define FTS3_NODE_CHUNK_THRESHOLD test_fts3_node_chunk_threshold
+#else
+# define FTS3_NODE_CHUNKSIZE (4*1024) 
+# define FTS3_NODE_CHUNK_THRESHOLD (FTS3_NODE_CHUNKSIZE*4)
+#endif
+
+/*
+** The two values that may be meaningfully bound to the :1 parameter in
+** statements SQL_REPLACE_STAT and SQL_SELECT_STAT.
+*/
+#define FTS_STAT_DOCTOTAL      0
+#define FTS_STAT_INCRMERGEHINT 1
+#define FTS_STAT_AUTOINCRMERGE 2
+
+/*
+** If FTS_LOG_MERGES is defined, call sqlite3_log() to report each automatic
+** and incremental merge operation that takes place. This is used for 
+** debugging FTS only, it should not usually be turned on in production
+** systems.
+*/
+#ifdef FTS3_LOG_MERGES
+static void fts3LogMerge(int nMerge, sqlite3_int64 iAbsLevel){
+  sqlite3_log(SQLITE_OK, "%d-way merge from level %d", nMerge, (int)iAbsLevel);
+}
+#else
+#define fts3LogMerge(x, y)
+#endif
+
+
+typedef struct PendingList PendingList;
+typedef struct SegmentNode SegmentNode;
+typedef struct SegmentWriter SegmentWriter;
+
+/*
+** An instance of the following data structure is used to build doclists
+** incrementally. See function fts3PendingListAppend() for details.
+*/
+struct PendingList {
+  int nData;
+  char *aData;
+  int nSpace;
+  sqlite3_int64 iLastDocid;
+  sqlite3_int64 iLastCol;
+  sqlite3_int64 iLastPos;
+};
+
+
+/*
+** Each cursor has a (possibly empty) linked list of the following objects.
+*/
+struct Fts3DeferredToken {
+  Fts3PhraseToken *pToken;        /* Pointer to corresponding expr token */
+  int iCol;                       /* Column token must occur in */
+  Fts3DeferredToken *pNext;       /* Next in list of deferred tokens */
+  PendingList *pList;             /* Doclist is assembled here */
+};
+
+/*
+** An instance of this structure is used to iterate through the terms on
+** a contiguous set of segment b-tree leaf nodes. Although the details of
+** this structure are only manipulated by code in this file, opaque handles
+** of type Fts3SegReader* are also used by code in fts3.c to iterate through
+** terms when querying the full-text index. See functions:
+**
+**   sqlite3Fts3SegReaderNew()
+**   sqlite3Fts3SegReaderFree()
+**   sqlite3Fts3SegReaderIterate()
+**
+** Methods used to manipulate Fts3SegReader structures:
+**
+**   fts3SegReaderNext()
+**   fts3SegReaderFirstDocid()
+**   fts3SegReaderNextDocid()
+*/
+struct Fts3SegReader {
+  int iIdx;                       /* Index within level, or 0x7FFFFFFF for PT */
+  u8 bLookup;                     /* True for a lookup only */
+  u8 rootOnly;                    /* True for a root-only reader */
+
+  sqlite3_int64 iStartBlock;      /* Rowid of first leaf block to traverse */
+  sqlite3_int64 iLeafEndBlock;    /* Rowid of final leaf block to traverse */
+  sqlite3_int64 iEndBlock;        /* Rowid of final block in segment (or 0) */
+  sqlite3_int64 iCurrentBlock;    /* Current leaf block (or 0) */
+
+  char *aNode;                    /* Pointer to node data (or NULL) */
+  int nNode;                      /* Size of buffer at aNode (or 0) */
+  int nPopulate;                  /* If >0, bytes of buffer aNode[] loaded */
+  sqlite3_blob *pBlob;            /* If not NULL, blob handle to read node */
+
+  Fts3HashElem **ppNextElem;
+
+  /* Variables set by fts3SegReaderNext(). These may be read directly
+  ** by the caller. They are valid from the time SegmentReaderNew() returns
+  ** until SegmentReaderNext() returns something other than SQLITE_OK
+  ** (i.e. SQLITE_DONE).
+  */
+  int nTerm;                      /* Number of bytes in current term */
+  char *zTerm;                    /* Pointer to current term */
+  int nTermAlloc;                 /* Allocated size of zTerm buffer */
+  char *aDoclist;                 /* Pointer to doclist of current entry */
+  int nDoclist;                   /* Size of doclist in current entry */
+
+  /* The following variables are used by fts3SegReaderNextDocid() to iterate 
+  ** through the current doclist (aDoclist/nDoclist).
+  */
+  char *pOffsetList;
+  int nOffsetList;                /* For descending pending seg-readers only */
+  sqlite3_int64 iDocid;
+};
+
+#define fts3SegReaderIsPending(p) ((p)->ppNextElem!=0)
+#define fts3SegReaderIsRootOnly(p) ((p)->rootOnly!=0)
+
+/*
+** An instance of this structure is used to create a segment b-tree in the
+** database. The internal details of this type are only accessed by the
+** following functions:
+**
+**   fts3SegWriterAdd()
+**   fts3SegWriterFlush()
+**   fts3SegWriterFree()
+*/
+struct SegmentWriter {
+  SegmentNode *pTree;             /* Pointer to interior tree structure */
+  sqlite3_int64 iFirst;           /* First slot in %_segments written */
+  sqlite3_int64 iFree;            /* Next free slot in %_segments */
+  char *zTerm;                    /* Pointer to previous term buffer */
+  int nTerm;                      /* Number of bytes in zTerm */
+  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
+  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
+  int nSize;                      /* Size of allocation at aData */
+  int nData;                      /* Bytes of data in aData */
+  char *aData;                    /* Pointer to block from malloc() */
+  i64 nLeafData;                  /* Number of bytes of leaf data written */
+};
+
+/*
+** Type SegmentNode is used by the following three functions to create
+** the interior part of the segment b+-tree structures (everything except
+** the leaf nodes). These functions and type are only ever used by code
+** within the fts3SegWriterXXX() family of functions described above.
+**
+**   fts3NodeAddTerm()
+**   fts3NodeWrite()
+**   fts3NodeFree()
+**
+** When a b+tree is written to the database (either as a result of a merge
+** or the pending-terms table being flushed), leaves are written into the 
+** database file as soon as they are completely populated. The interior of
+** the tree is assembled in memory and written out only once all leaves have
+** been populated and stored. This is Ok, as the b+-tree fanout is usually
+** very large, meaning that the interior of the tree consumes relatively 
+** little memory.
+*/
+struct SegmentNode {
+  SegmentNode *pParent;           /* Parent node (or NULL for root node) */
+  SegmentNode *pRight;            /* Pointer to right-sibling */
+  SegmentNode *pLeftmost;         /* Pointer to left-most node of this depth */
+  int nEntry;                     /* Number of terms written to node so far */
+  char *zTerm;                    /* Pointer to previous term buffer */
+  int nTerm;                      /* Number of bytes in zTerm */
+  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
+  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
+  int nData;                      /* Bytes of valid data so far */
+  char *aData;                    /* Node data */
+};
+
+/*
+** Valid values for the second argument to fts3SqlStmt().
+*/
+#define SQL_DELETE_CONTENT             0
+#define SQL_IS_EMPTY                   1
+#define SQL_DELETE_ALL_CONTENT         2 
+#define SQL_DELETE_ALL_SEGMENTS        3
+#define SQL_DELETE_ALL_SEGDIR          4
+#define SQL_DELETE_ALL_DOCSIZE         5
+#define SQL_DELETE_ALL_STAT            6
+#define SQL_SELECT_CONTENT_BY_ROWID    7
+#define SQL_NEXT_SEGMENT_INDEX         8
+#define SQL_INSERT_SEGMENTS            9
+#define SQL_NEXT_SEGMENTS_ID          10
+#define SQL_INSERT_SEGDIR             11
+#define SQL_SELECT_LEVEL              12
+#define SQL_SELECT_LEVEL_RANGE        13
+#define SQL_SELECT_LEVEL_COUNT        14
+#define SQL_SELECT_SEGDIR_MAX_LEVEL   15
+#define SQL_DELETE_SEGDIR_LEVEL       16
+#define SQL_DELETE_SEGMENTS_RANGE     17
+#define SQL_CONTENT_INSERT            18
+#define SQL_DELETE_DOCSIZE            19
+#define SQL_REPLACE_DOCSIZE           20
+#define SQL_SELECT_DOCSIZE            21
+#define SQL_SELECT_STAT               22
+#define SQL_REPLACE_STAT              23
+
+#define SQL_SELECT_ALL_PREFIX_LEVEL   24
+#define SQL_DELETE_ALL_TERMS_SEGDIR   25
+#define SQL_DELETE_SEGDIR_RANGE       26
+#define SQL_SELECT_ALL_LANGID         27
+#define SQL_FIND_MERGE_LEVEL          28
+#define SQL_MAX_LEAF_NODE_ESTIMATE    29
+#define SQL_DELETE_SEGDIR_ENTRY       30
+#define SQL_SHIFT_SEGDIR_ENTRY        31
+#define SQL_SELECT_SEGDIR             32
+#define SQL_CHOMP_SEGDIR              33
+#define SQL_SEGMENT_IS_APPENDABLE     34
+#define SQL_SELECT_INDEXES            35
+#define SQL_SELECT_MXLEVEL            36
+
+#define SQL_SELECT_LEVEL_RANGE2       37
+#define SQL_UPDATE_LEVEL_IDX          38
+#define SQL_UPDATE_LEVEL              39
+
+/*
+** This function is used to obtain an SQLite prepared statement handle
+** for the statement identified by the second argument. If successful,
+** *pp is set to the requested statement handle and SQLITE_OK returned.
+** Otherwise, an SQLite error code is returned and *pp is set to 0.
+**
+** If argument apVal is not NULL, then it must point to an array with
+** at least as many entries as the requested statement has bound 
+** parameters. The values are bound to the statements parameters before
+** returning.
+*/
+static int fts3SqlStmt(
+  Fts3Table *p,                   /* Virtual table handle */
+  int eStmt,                      /* One of the SQL_XXX constants above */
+  sqlite3_stmt **pp,              /* OUT: Statement handle */
+  sqlite3_value **apVal           /* Values to bind to statement */
+){
+  const char *azSql[] = {
+/* 0  */  "DELETE FROM %Q.'%q_content' WHERE rowid = ?",
+/* 1  */  "SELECT NOT EXISTS(SELECT docid FROM %Q.'%q_content' WHERE rowid!=?)",
+/* 2  */  "DELETE FROM %Q.'%q_content'",
+/* 3  */  "DELETE FROM %Q.'%q_segments'",
+/* 4  */  "DELETE FROM %Q.'%q_segdir'",
+/* 5  */  "DELETE FROM %Q.'%q_docsize'",
+/* 6  */  "DELETE FROM %Q.'%q_stat'",
+/* 7  */  "SELECT %s WHERE rowid=?",
+/* 8  */  "SELECT (SELECT max(idx) FROM %Q.'%q_segdir' WHERE level = ?) + 1",
+/* 9  */  "REPLACE INTO %Q.'%q_segments'(blockid, block) VALUES(?, ?)",
+/* 10 */  "SELECT coalesce((SELECT max(blockid) FROM %Q.'%q_segments') + 1, 1)",
+/* 11 */  "REPLACE INTO %Q.'%q_segdir' VALUES(?,?,?,?,?,?)",
+
+          /* Return segments in order from oldest to newest.*/ 
+/* 12 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+            "FROM %Q.'%q_segdir' WHERE level = ? ORDER BY idx ASC",
+/* 13 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+            "FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?"
+            "ORDER BY level DESC, idx ASC",
+
+/* 14 */  "SELECT count(*) FROM %Q.'%q_segdir' WHERE level = ?",
+/* 15 */  "SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?",
+
+/* 16 */  "DELETE FROM %Q.'%q_segdir' WHERE level = ?",
+/* 17 */  "DELETE FROM %Q.'%q_segments' WHERE blockid BETWEEN ? AND ?",
+/* 18 */  "INSERT INTO %Q.'%q_content' VALUES(%s)",
+/* 19 */  "DELETE FROM %Q.'%q_docsize' WHERE docid = ?",
+/* 20 */  "REPLACE INTO %Q.'%q_docsize' VALUES(?,?)",
+/* 21 */  "SELECT size FROM %Q.'%q_docsize' WHERE docid=?",
+/* 22 */  "SELECT value FROM %Q.'%q_stat' WHERE id=?",
+/* 23 */  "REPLACE INTO %Q.'%q_stat' VALUES(?,?)",
+/* 24 */  "",
+/* 25 */  "",
+
+/* 26 */ "DELETE FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?",
+/* 27 */ "SELECT ? UNION SELECT level / (1024 * ?) FROM %Q.'%q_segdir'",
+
+/* This statement is used to determine which level to read the input from
+** when performing an incremental merge. It returns the absolute level number
+** of the oldest level in the db that contains at least ? segments. Or,
+** if no level in the FTS index contains more than ? segments, the statement
+** returns zero rows.  */
+/* 28 */ "SELECT level, count(*) AS cnt FROM %Q.'%q_segdir' "
+         "  GROUP BY level HAVING cnt>=?"
+         "  ORDER BY (level %% 1024) ASC LIMIT 1",
+
+/* Estimate the upper limit on the number of leaf nodes in a new segment
+** created by merging the oldest :2 segments from absolute level :1. See 
+** function sqlite3Fts3Incrmerge() for details.  */
+/* 29 */ "SELECT 2 * total(1 + leaves_end_block - start_block) "
+         "  FROM %Q.'%q_segdir' WHERE level = ? AND idx < ?",
+
+/* SQL_DELETE_SEGDIR_ENTRY
+**   Delete the %_segdir entry on absolute level :1 with index :2.  */
+/* 30 */ "DELETE FROM %Q.'%q_segdir' WHERE level = ? AND idx = ?",
+
+/* SQL_SHIFT_SEGDIR_ENTRY
+**   Modify the idx value for the segment with idx=:3 on absolute level :2
+**   to :1.  */
+/* 31 */ "UPDATE %Q.'%q_segdir' SET idx = ? WHERE level=? AND idx=?",
+
+/* SQL_SELECT_SEGDIR
+**   Read a single entry from the %_segdir table. The entry from absolute 
+**   level :1 with index value :2.  */
+/* 32 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+            "FROM %Q.'%q_segdir' WHERE level = ? AND idx = ?",
+
+/* SQL_CHOMP_SEGDIR
+**   Update the start_block (:1) and root (:2) fields of the %_segdir
+**   entry located on absolute level :3 with index :4.  */
+/* 33 */  "UPDATE %Q.'%q_segdir' SET start_block = ?, root = ?"
+            "WHERE level = ? AND idx = ?",
+
+/* SQL_SEGMENT_IS_APPENDABLE
+**   Return a single row if the segment with end_block=? is appendable. Or
+**   no rows otherwise.  */
+/* 34 */  "SELECT 1 FROM %Q.'%q_segments' WHERE blockid=? AND block IS NULL",
+
+/* SQL_SELECT_INDEXES
+**   Return the list of valid segment indexes for absolute level ?  */
+/* 35 */  "SELECT idx FROM %Q.'%q_segdir' WHERE level=? ORDER BY 1 ASC",
+
+/* SQL_SELECT_MXLEVEL
+**   Return the largest relative level in the FTS index or indexes.  */
+/* 36 */  "SELECT max( level %% 1024 ) FROM %Q.'%q_segdir'",
+
+          /* Return segments in order from oldest to newest.*/ 
+/* 37 */  "SELECT level, idx, end_block "
+            "FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ? "
+            "ORDER BY level DESC, idx ASC",
+
+          /* Update statements used while promoting segments */
+/* 38 */  "UPDATE OR FAIL %Q.'%q_segdir' SET level=-1,idx=? "
+            "WHERE level=? AND idx=?",
+/* 39 */  "UPDATE OR FAIL %Q.'%q_segdir' SET level=? WHERE level=-1"
+
+  };
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pStmt;
+
+  assert( SizeofArray(azSql)==SizeofArray(p->aStmt) );
+  assert( eStmt<SizeofArray(azSql) && eStmt>=0 );
+  
+  pStmt = p->aStmt[eStmt];
+  if( !pStmt ){
+    char *zSql;
+    if( eStmt==SQL_CONTENT_INSERT ){
+      zSql = sqlite3_mprintf(azSql[eStmt], p->zDb, p->zName, p->zWriteExprlist);
+    }else if( eStmt==SQL_SELECT_CONTENT_BY_ROWID ){
+      zSql = sqlite3_mprintf(azSql[eStmt], p->zReadExprlist);
+    }else{
+      zSql = sqlite3_mprintf(azSql[eStmt], p->zDb, p->zName);
+    }
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, NULL);
+      sqlite3_free(zSql);
+      assert( rc==SQLITE_OK || pStmt==0 );
+      p->aStmt[eStmt] = pStmt;
+    }
+  }
+  if( apVal ){
+    int i;
+    int nParam = sqlite3_bind_parameter_count(pStmt);
+    for(i=0; rc==SQLITE_OK && i<nParam; i++){
+      rc = sqlite3_bind_value(pStmt, i+1, apVal[i]);
+    }
+  }
+  *pp = pStmt;
+  return rc;
+}
+
+
+static int fts3SelectDocsize(
+  Fts3Table *pTab,                /* FTS3 table handle */
+  sqlite3_int64 iDocid,           /* Docid to bind for SQL_SELECT_DOCSIZE */
+  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
+){
+  sqlite3_stmt *pStmt = 0;        /* Statement requested from fts3SqlStmt() */
+  int rc;                         /* Return code */
+
+  rc = fts3SqlStmt(pTab, SQL_SELECT_DOCSIZE, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pStmt, 1, iDocid);
+    rc = sqlite3_step(pStmt);
+    if( rc!=SQLITE_ROW || sqlite3_column_type(pStmt, 0)!=SQLITE_BLOB ){
+      rc = sqlite3_reset(pStmt);
+      if( rc==SQLITE_OK ) rc = FTS_CORRUPT_VTAB;
+      pStmt = 0;
+    }else{
+      rc = SQLITE_OK;
+    }
+  }
+
+  *ppStmt = pStmt;
+  return rc;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3SelectDoctotal(
+  Fts3Table *pTab,                /* Fts3 table handle */
+  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
+){
+  sqlite3_stmt *pStmt = 0;
+  int rc;
+  rc = fts3SqlStmt(pTab, SQL_SELECT_STAT, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
+    if( sqlite3_step(pStmt)!=SQLITE_ROW
+     || sqlite3_column_type(pStmt, 0)!=SQLITE_BLOB
+    ){
+      rc = sqlite3_reset(pStmt);
+      if( rc==SQLITE_OK ) rc = FTS_CORRUPT_VTAB;
+      pStmt = 0;
+    }
+  }
+  *ppStmt = pStmt;
+  return rc;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3SelectDocsize(
+  Fts3Table *pTab,                /* Fts3 table handle */
+  sqlite3_int64 iDocid,           /* Docid to read size data for */
+  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
+){
+  return fts3SelectDocsize(pTab, iDocid, ppStmt);
+}
+
+/*
+** Similar to fts3SqlStmt(). Except, after binding the parameters in
+** array apVal[] to the SQL statement identified by eStmt, the statement
+** is executed.
+**
+** Returns SQLITE_OK if the statement is successfully executed, or an
+** SQLite error code otherwise.
+*/
+static void fts3SqlExec(
+  int *pRC,                /* Result code */
+  Fts3Table *p,            /* The FTS3 table */
+  int eStmt,               /* Index of statement to evaluate */
+  sqlite3_value **apVal    /* Parameters to bind */
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  if( *pRC ) return;
+  rc = fts3SqlStmt(p, eStmt, &pStmt, apVal); 
+  if( rc==SQLITE_OK ){
+    sqlite3_step(pStmt);
+    rc = sqlite3_reset(pStmt);
+  }
+  *pRC = rc;
+}
+
+
+/*
+** This function ensures that the caller has obtained an exclusive 
+** shared-cache table-lock on the %_segdir table. This is required before 
+** writing data to the fts3 table. If this lock is not acquired first, then
+** the caller may end up attempting to take this lock as part of committing
+** a transaction, causing SQLite to return SQLITE_LOCKED or 
+** LOCKED_SHAREDCACHEto a COMMIT command.
+**
+** It is best to avoid this because if FTS3 returns any error when 
+** committing a transaction, the whole transaction will be rolled back. 
+** And this is not what users expect when they get SQLITE_LOCKED_SHAREDCACHE. 
+** It can still happen if the user locks the underlying tables directly 
+** instead of accessing them via FTS.
+*/
+static int fts3Writelock(Fts3Table *p){
+  int rc = SQLITE_OK;
+  
+  if( p->nPendingData==0 ){
+    sqlite3_stmt *pStmt;
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_LEVEL, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_null(pStmt, 1);
+      sqlite3_step(pStmt);
+      rc = sqlite3_reset(pStmt);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** FTS maintains a separate indexes for each language-id (a 32-bit integer).
+** Within each language id, a separate index is maintained to store the
+** document terms, and each configured prefix size (configured the FTS 
+** "prefix=" option). And each index consists of multiple levels ("relative
+** levels").
+**
+** All three of these values (the language id, the specific index and the
+** level within the index) are encoded in 64-bit integer values stored
+** in the %_segdir table on disk. This function is used to convert three
+** separate component values into the single 64-bit integer value that
+** can be used to query the %_segdir table.
+**
+** Specifically, each language-id/index combination is allocated 1024 
+** 64-bit integer level values ("absolute levels"). The main terms index
+** for language-id 0 is allocate values 0-1023. The first prefix index
+** (if any) for language-id 0 is allocated values 1024-2047. And so on.
+** Language 1 indexes are allocated immediately following language 0.
+**
+** So, for a system with nPrefix prefix indexes configured, the block of
+** absolute levels that corresponds to language-id iLangid and index 
+** iIndex starts at absolute level ((iLangid * (nPrefix+1) + iIndex) * 1024).
+*/
+static sqlite3_int64 getAbsoluteLevel(
+  Fts3Table *p,                   /* FTS3 table handle */
+  int iLangid,                    /* Language id */
+  int iIndex,                     /* Index in p->aIndex[] */
+  int iLevel                      /* Level of segments */
+){
+  sqlite3_int64 iBase;            /* First absolute level for iLangid/iIndex */
+  assert( iLangid>=0 );
+  assert( p->nIndex>0 );
+  assert( iIndex>=0 && iIndex<p->nIndex );
+
+  iBase = ((sqlite3_int64)iLangid * p->nIndex + iIndex) * FTS3_SEGDIR_MAXLEVEL;
+  return iBase + iLevel;
+}
+
+/*
+** Set *ppStmt to a statement handle that may be used to iterate through
+** all rows in the %_segdir table, from oldest to newest. If successful,
+** return SQLITE_OK. If an error occurs while preparing the statement, 
+** return an SQLite error code.
+**
+** There is only ever one instance of this SQL statement compiled for
+** each FTS3 table.
+**
+** The statement returns the following columns from the %_segdir table:
+**
+**   0: idx
+**   1: start_block
+**   2: leaves_end_block
+**   3: end_block
+**   4: root
+*/
+SQLITE_PRIVATE int sqlite3Fts3AllSegdirs(
+  Fts3Table *p,                   /* FTS3 table */
+  int iLangid,                    /* Language being queried */
+  int iIndex,                     /* Index for p->aIndex[] */
+  int iLevel,                     /* Level to select (relative level) */
+  sqlite3_stmt **ppStmt           /* OUT: Compiled statement */
+){
+  int rc;
+  sqlite3_stmt *pStmt = 0;
+
+  assert( iLevel==FTS3_SEGCURSOR_ALL || iLevel>=0 );
+  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
+  assert( iIndex>=0 && iIndex<p->nIndex );
+
+  if( iLevel<0 ){
+    /* "SELECT * FROM %_segdir WHERE level BETWEEN ? AND ? ORDER BY ..." */
+    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL_RANGE, &pStmt, 0);
+    if( rc==SQLITE_OK ){ 
+      sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
+      sqlite3_bind_int64(pStmt, 2, 
+          getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
+      );
+    }
+  }else{
+    /* "SELECT * FROM %_segdir WHERE level = ? ORDER BY ..." */
+    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL, &pStmt, 0);
+    if( rc==SQLITE_OK ){ 
+      sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex,iLevel));
+    }
+  }
+  *ppStmt = pStmt;
+  return rc;
+}
+
+
+/*
+** Append a single varint to a PendingList buffer. SQLITE_OK is returned
+** if successful, or an SQLite error code otherwise.
+**
+** This function also serves to allocate the PendingList structure itself.
+** For example, to create a new PendingList structure containing two
+** varints:
+**
+**   PendingList *p = 0;
+**   fts3PendingListAppendVarint(&p, 1);
+**   fts3PendingListAppendVarint(&p, 2);
+*/
+static int fts3PendingListAppendVarint(
+  PendingList **pp,               /* IN/OUT: Pointer to PendingList struct */
+  sqlite3_int64 i                 /* Value to append to data */
+){
+  PendingList *p = *pp;
+
+  /* Allocate or grow the PendingList as required. */
+  if( !p ){
+    p = sqlite3_malloc(sizeof(*p) + 100);
+    if( !p ){
+      return SQLITE_NOMEM;
+    }
+    p->nSpace = 100;
+    p->aData = (char *)&p[1];
+    p->nData = 0;
+  }
+  else if( p->nData+FTS3_VARINT_MAX+1>p->nSpace ){
+    int nNew = p->nSpace * 2;
+    p = sqlite3_realloc(p, sizeof(*p) + nNew);
+    if( !p ){
+      sqlite3_free(*pp);
+      *pp = 0;
+      return SQLITE_NOMEM;
+    }
+    p->nSpace = nNew;
+    p->aData = (char *)&p[1];
+  }
+
+  /* Append the new serialized varint to the end of the list. */
+  p->nData += sqlite3Fts3PutVarint(&p->aData[p->nData], i);
+  p->aData[p->nData] = '\0';
+  *pp = p;
+  return SQLITE_OK;
+}
+
+/*
+** Add a docid/column/position entry to a PendingList structure. Non-zero
+** is returned if the structure is sqlite3_realloced as part of adding
+** the entry. Otherwise, zero.
+**
+** If an OOM error occurs, *pRc is set to SQLITE_NOMEM before returning.
+** Zero is always returned in this case. Otherwise, if no OOM error occurs,
+** it is set to SQLITE_OK.
+*/
+static int fts3PendingListAppend(
+  PendingList **pp,               /* IN/OUT: PendingList structure */
+  sqlite3_int64 iDocid,           /* Docid for entry to add */
+  sqlite3_int64 iCol,             /* Column for entry to add */
+  sqlite3_int64 iPos,             /* Position of term for entry to add */
+  int *pRc                        /* OUT: Return code */
+){
+  PendingList *p = *pp;
+  int rc = SQLITE_OK;
+
+  assert( !p || p->iLastDocid<=iDocid );
+
+  if( !p || p->iLastDocid!=iDocid ){
+    sqlite3_int64 iDelta = iDocid - (p ? p->iLastDocid : 0);
+    if( p ){
+      assert( p->nData<p->nSpace );
+      assert( p->aData[p->nData]==0 );
+      p->nData++;
+    }
+    if( SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, iDelta)) ){
+      goto pendinglistappend_out;
+    }
+    p->iLastCol = -1;
+    p->iLastPos = 0;
+    p->iLastDocid = iDocid;
+  }
+  if( iCol>0 && p->iLastCol!=iCol ){
+    if( SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, 1))
+     || SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, iCol))
+    ){
+      goto pendinglistappend_out;
+    }
+    p->iLastCol = iCol;
+    p->iLastPos = 0;
+  }
+  if( iCol>=0 ){
+    assert( iPos>p->iLastPos || (iPos==0 && p->iLastPos==0) );
+    rc = fts3PendingListAppendVarint(&p, 2+iPos-p->iLastPos);
+    if( rc==SQLITE_OK ){
+      p->iLastPos = iPos;
+    }
+  }
+
+ pendinglistappend_out:
+  *pRc = rc;
+  if( p!=*pp ){
+    *pp = p;
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Free a PendingList object allocated by fts3PendingListAppend().
+*/
+static void fts3PendingListDelete(PendingList *pList){
+  sqlite3_free(pList);
+}
+
+/*
+** Add an entry to one of the pending-terms hash tables.
+*/
+static int fts3PendingTermsAddOne(
+  Fts3Table *p,
+  int iCol,
+  int iPos,
+  Fts3Hash *pHash,                /* Pending terms hash table to add entry to */
+  const char *zToken,
+  int nToken
+){
+  PendingList *pList;
+  int rc = SQLITE_OK;
+
+  pList = (PendingList *)fts3HashFind(pHash, zToken, nToken);
+  if( pList ){
+    p->nPendingData -= (pList->nData + nToken + sizeof(Fts3HashElem));
+  }
+  if( fts3PendingListAppend(&pList, p->iPrevDocid, iCol, iPos, &rc) ){
+    if( pList==fts3HashInsert(pHash, zToken, nToken, pList) ){
+      /* Malloc failed while inserting the new entry. This can only 
+      ** happen if there was no previous entry for this token.
+      */
+      assert( 0==fts3HashFind(pHash, zToken, nToken) );
+      sqlite3_free(pList);
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    p->nPendingData += (pList->nData + nToken + sizeof(Fts3HashElem));
+  }
+  return rc;
+}
+
+/*
+** Tokenize the nul-terminated string zText and add all tokens to the
+** pending-terms hash-table. The docid used is that currently stored in
+** p->iPrevDocid, and the column is specified by argument iCol.
+**
+** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
+*/
+static int fts3PendingTermsAdd(
+  Fts3Table *p,                   /* Table into which text will be inserted */
+  int iLangid,                    /* Language id to use */
+  const char *zText,              /* Text of document to be inserted */
+  int iCol,                       /* Column into which text is being inserted */
+  u32 *pnWord                     /* IN/OUT: Incr. by number tokens inserted */
+){
+  int rc;
+  int iStart = 0;
+  int iEnd = 0;
+  int iPos = 0;
+  int nWord = 0;
+
+  char const *zToken;
+  int nToken = 0;
+
+  sqlite3_tokenizer *pTokenizer = p->pTokenizer;
+  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
+  sqlite3_tokenizer_cursor *pCsr;
+  int (*xNext)(sqlite3_tokenizer_cursor *pCursor,
+      const char**,int*,int*,int*,int*);
+
+  assert( pTokenizer && pModule );
+
+  /* If the user has inserted a NULL value, this function may be called with
+  ** zText==0. In this case, add zero token entries to the hash table and 
+  ** return early. */
+  if( zText==0 ){
+    *pnWord = 0;
+    return SQLITE_OK;
+  }
+
+  rc = sqlite3Fts3OpenTokenizer(pTokenizer, iLangid, zText, -1, &pCsr);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  xNext = pModule->xNext;
+  while( SQLITE_OK==rc
+      && SQLITE_OK==(rc = xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos))
+  ){
+    int i;
+    if( iPos>=nWord ) nWord = iPos+1;
+
+    /* Positions cannot be negative; we use -1 as a terminator internally.
+    ** Tokens must have a non-zero length.
+    */
+    if( iPos<0 || !zToken || nToken<=0 ){
+      rc = SQLITE_ERROR;
+      break;
+    }
+
+    /* Add the term to the terms index */
+    rc = fts3PendingTermsAddOne(
+        p, iCol, iPos, &p->aIndex[0].hPending, zToken, nToken
+    );
+    
+    /* Add the term to each of the prefix indexes that it is not too 
+    ** short for. */
+    for(i=1; rc==SQLITE_OK && i<p->nIndex; i++){
+      struct Fts3Index *pIndex = &p->aIndex[i];
+      if( nToken<pIndex->nPrefix ) continue;
+      rc = fts3PendingTermsAddOne(
+          p, iCol, iPos, &pIndex->hPending, zToken, pIndex->nPrefix
+      );
+    }
+  }
+
+  pModule->xClose(pCsr);
+  *pnWord += nWord;
+  return (rc==SQLITE_DONE ? SQLITE_OK : rc);
+}
+
+/* 
+** Calling this function indicates that subsequent calls to 
+** fts3PendingTermsAdd() are to add term/position-list pairs for the
+** contents of the document with docid iDocid.
+*/
+static int fts3PendingTermsDocid(
+  Fts3Table *p,                   /* Full-text table handle */
+  int bDelete,                    /* True if this op is a delete */
+  int iLangid,                    /* Language id of row being written */
+  sqlite_int64 iDocid             /* Docid of row being written */
+){
+  assert( iLangid>=0 );
+  assert( bDelete==1 || bDelete==0 );
+
+  /* TODO(shess) Explore whether partially flushing the buffer on
+  ** forced-flush would provide better performance.  I suspect that if
+  ** we ordered the doclists by size and flushed the largest until the
+  ** buffer was half empty, that would let the less frequent terms
+  ** generate longer doclists.
+  */
+  if( iDocid<p->iPrevDocid 
+   || (iDocid==p->iPrevDocid && p->bPrevDelete==0)
+   || p->iPrevLangid!=iLangid
+   || p->nPendingData>p->nMaxPendingData 
+  ){
+    int rc = sqlite3Fts3PendingTermsFlush(p);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  p->iPrevDocid = iDocid;
+  p->iPrevLangid = iLangid;
+  p->bPrevDelete = bDelete;
+  return SQLITE_OK;
+}
+
+/*
+** Discard the contents of the pending-terms hash tables. 
+*/
+SQLITE_PRIVATE void sqlite3Fts3PendingTermsClear(Fts3Table *p){
+  int i;
+  for(i=0; i<p->nIndex; i++){
+    Fts3HashElem *pElem;
+    Fts3Hash *pHash = &p->aIndex[i].hPending;
+    for(pElem=fts3HashFirst(pHash); pElem; pElem=fts3HashNext(pElem)){
+      PendingList *pList = (PendingList *)fts3HashData(pElem);
+      fts3PendingListDelete(pList);
+    }
+    fts3HashClear(pHash);
+  }
+  p->nPendingData = 0;
+}
+
+/*
+** This function is called by the xUpdate() method as part of an INSERT
+** operation. It adds entries for each term in the new record to the
+** pendingTerms hash table.
+**
+** Argument apVal is the same as the similarly named argument passed to
+** fts3InsertData(). Parameter iDocid is the docid of the new row.
+*/
+static int fts3InsertTerms(
+  Fts3Table *p, 
+  int iLangid, 
+  sqlite3_value **apVal, 
+  u32 *aSz
+){
+  int i;                          /* Iterator variable */
+  for(i=2; i<p->nColumn+2; i++){
+    int iCol = i-2;
+    if( p->abNotindexed[iCol]==0 ){
+      const char *zText = (const char *)sqlite3_value_text(apVal[i]);
+      int rc = fts3PendingTermsAdd(p, iLangid, zText, iCol, &aSz[iCol]);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      aSz[p->nColumn] += sqlite3_value_bytes(apVal[i]);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This function is called by the xUpdate() method for an INSERT operation.
+** The apVal parameter is passed a copy of the apVal argument passed by
+** SQLite to the xUpdate() method. i.e:
+**
+**   apVal[0]                Not used for INSERT.
+**   apVal[1]                rowid
+**   apVal[2]                Left-most user-defined column
+**   ...
+**   apVal[p->nColumn+1]     Right-most user-defined column
+**   apVal[p->nColumn+2]     Hidden column with same name as table
+**   apVal[p->nColumn+3]     Hidden "docid" column (alias for rowid)
+**   apVal[p->nColumn+4]     Hidden languageid column
+*/
+static int fts3InsertData(
+  Fts3Table *p,                   /* Full-text table */
+  sqlite3_value **apVal,          /* Array of values to insert */
+  sqlite3_int64 *piDocid          /* OUT: Docid for row just inserted */
+){
+  int rc;                         /* Return code */
+  sqlite3_stmt *pContentInsert;   /* INSERT INTO %_content VALUES(...) */
+
+  if( p->zContentTbl ){
+    sqlite3_value *pRowid = apVal[p->nColumn+3];
+    if( sqlite3_value_type(pRowid)==SQLITE_NULL ){
+      pRowid = apVal[1];
+    }
+    if( sqlite3_value_type(pRowid)!=SQLITE_INTEGER ){
+      return SQLITE_CONSTRAINT;
+    }
+    *piDocid = sqlite3_value_int64(pRowid);
+    return SQLITE_OK;
+  }
+
+  /* Locate the statement handle used to insert data into the %_content
+  ** table. The SQL for this statement is:
+  **
+  **   INSERT INTO %_content VALUES(?, ?, ?, ...)
+  **
+  ** The statement features N '?' variables, where N is the number of user
+  ** defined columns in the FTS3 table, plus one for the docid field.
+  */
+  rc = fts3SqlStmt(p, SQL_CONTENT_INSERT, &pContentInsert, &apVal[1]);
+  if( rc==SQLITE_OK && p->zLanguageid ){
+    rc = sqlite3_bind_int(
+        pContentInsert, p->nColumn+2, 
+        sqlite3_value_int(apVal[p->nColumn+4])
+    );
+  }
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* There is a quirk here. The users INSERT statement may have specified
+  ** a value for the "rowid" field, for the "docid" field, or for both.
+  ** Which is a problem, since "rowid" and "docid" are aliases for the
+  ** same value. For example:
+  **
+  **   INSERT INTO fts3tbl(rowid, docid) VALUES(1, 2);
+  **
+  ** In FTS3, this is an error. It is an error to specify non-NULL values
+  ** for both docid and some other rowid alias.
+  */
+  if( SQLITE_NULL!=sqlite3_value_type(apVal[3+p->nColumn]) ){
+    if( SQLITE_NULL==sqlite3_value_type(apVal[0])
+     && SQLITE_NULL!=sqlite3_value_type(apVal[1])
+    ){
+      /* A rowid/docid conflict. */
+      return SQLITE_ERROR;
+    }
+    rc = sqlite3_bind_value(pContentInsert, 1, apVal[3+p->nColumn]);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+
+  /* Execute the statement to insert the record. Set *piDocid to the 
+  ** new docid value. 
+  */
+  sqlite3_step(pContentInsert);
+  rc = sqlite3_reset(pContentInsert);
+
+  *piDocid = sqlite3_last_insert_rowid(p->db);
+  return rc;
+}
+
+
+
+/*
+** Remove all data from the FTS3 table. Clear the hash table containing
+** pending terms.
+*/
+static int fts3DeleteAll(Fts3Table *p, int bContent){
+  int rc = SQLITE_OK;             /* Return code */
+
+  /* Discard the contents of the pending-terms hash table. */
+  sqlite3Fts3PendingTermsClear(p);
+
+  /* Delete everything from the shadow tables. Except, leave %_content as
+  ** is if bContent is false.  */
+  assert( p->zContentTbl==0 || bContent==0 );
+  if( bContent ) fts3SqlExec(&rc, p, SQL_DELETE_ALL_CONTENT, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGMENTS, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGDIR, 0);
+  if( p->bHasDocsize ){
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_DOCSIZE, 0);
+  }
+  if( p->bHasStat ){
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_STAT, 0);
+  }
+  return rc;
+}
+
+/*
+**
+*/
+static int langidFromSelect(Fts3Table *p, sqlite3_stmt *pSelect){
+  int iLangid = 0;
+  if( p->zLanguageid ) iLangid = sqlite3_column_int(pSelect, p->nColumn+1);
+  return iLangid;
+}
+
+/*
+** The first element in the apVal[] array is assumed to contain the docid
+** (an integer) of a row about to be deleted. Remove all terms from the
+** full-text index.
+*/
+static void fts3DeleteTerms( 
+  int *pRC,               /* Result code */
+  Fts3Table *p,           /* The FTS table to delete from */
+  sqlite3_value *pRowid,  /* The docid to be deleted */
+  u32 *aSz,               /* Sizes of deleted document written here */
+  int *pbFound            /* OUT: Set to true if row really does exist */
+){
+  int rc;
+  sqlite3_stmt *pSelect;
+
+  assert( *pbFound==0 );
+  if( *pRC ) return;
+  rc = fts3SqlStmt(p, SQL_SELECT_CONTENT_BY_ROWID, &pSelect, &pRowid);
+  if( rc==SQLITE_OK ){
+    if( SQLITE_ROW==sqlite3_step(pSelect) ){
+      int i;
+      int iLangid = langidFromSelect(p, pSelect);
+      i64 iDocid = sqlite3_column_int64(pSelect, 0);
+      rc = fts3PendingTermsDocid(p, 1, iLangid, iDocid);
+      for(i=1; rc==SQLITE_OK && i<=p->nColumn; i++){
+        int iCol = i-1;
+        if( p->abNotindexed[iCol]==0 ){
+          const char *zText = (const char *)sqlite3_column_text(pSelect, i);
+          rc = fts3PendingTermsAdd(p, iLangid, zText, -1, &aSz[iCol]);
+          aSz[p->nColumn] += sqlite3_column_bytes(pSelect, i);
+        }
+      }
+      if( rc!=SQLITE_OK ){
+        sqlite3_reset(pSelect);
+        *pRC = rc;
+        return;
+      }
+      *pbFound = 1;
+    }
+    rc = sqlite3_reset(pSelect);
+  }else{
+    sqlite3_reset(pSelect);
+  }
+  *pRC = rc;
+}
+
+/*
+** Forward declaration to account for the circular dependency between
+** functions fts3SegmentMerge() and fts3AllocateSegdirIdx().
+*/
+static int fts3SegmentMerge(Fts3Table *, int, int, int);
+
+/* 
+** This function allocates a new level iLevel index in the segdir table.
+** Usually, indexes are allocated within a level sequentially starting
+** with 0, so the allocated index is one greater than the value returned
+** by:
+**
+**   SELECT max(idx) FROM %_segdir WHERE level = :iLevel
+**
+** However, if there are already FTS3_MERGE_COUNT indexes at the requested
+** level, they are merged into a single level (iLevel+1) segment and the 
+** allocated index is 0.
+**
+** If successful, *piIdx is set to the allocated index slot and SQLITE_OK
+** returned. Otherwise, an SQLite error code is returned.
+*/
+static int fts3AllocateSegdirIdx(
+  Fts3Table *p, 
+  int iLangid,                    /* Language id */
+  int iIndex,                     /* Index for p->aIndex */
+  int iLevel, 
+  int *piIdx
+){
+  int rc;                         /* Return Code */
+  sqlite3_stmt *pNextIdx;         /* Query for next idx at level iLevel */
+  int iNext = 0;                  /* Result of query pNextIdx */
+
+  assert( iLangid>=0 );
+  assert( p->nIndex>=1 );
+
+  /* Set variable iNext to the next available segdir index at level iLevel. */
+  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENT_INDEX, &pNextIdx, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(
+        pNextIdx, 1, getAbsoluteLevel(p, iLangid, iIndex, iLevel)
+    );
+    if( SQLITE_ROW==sqlite3_step(pNextIdx) ){
+      iNext = sqlite3_column_int(pNextIdx, 0);
+    }
+    rc = sqlite3_reset(pNextIdx);
+  }
+
+  if( rc==SQLITE_OK ){
+    /* If iNext is FTS3_MERGE_COUNT, indicating that level iLevel is already
+    ** full, merge all segments in level iLevel into a single iLevel+1
+    ** segment and allocate (newly freed) index 0 at level iLevel. Otherwise,
+    ** if iNext is less than FTS3_MERGE_COUNT, allocate index iNext.
+    */
+    if( iNext>=FTS3_MERGE_COUNT ){
+      fts3LogMerge(16, getAbsoluteLevel(p, iLangid, iIndex, iLevel));
+      rc = fts3SegmentMerge(p, iLangid, iIndex, iLevel);
+      *piIdx = 0;
+    }else{
+      *piIdx = iNext;
+    }
+  }
+
+  return rc;
+}
+
+/*
+** The %_segments table is declared as follows:
+**
+**   CREATE TABLE %_segments(blockid INTEGER PRIMARY KEY, block BLOB)
+**
+** This function reads data from a single row of the %_segments table. The
+** specific row is identified by the iBlockid parameter. If paBlob is not
+** NULL, then a buffer is allocated using sqlite3_malloc() and populated
+** with the contents of the blob stored in the "block" column of the 
+** identified table row is. Whether or not paBlob is NULL, *pnBlob is set
+** to the size of the blob in bytes before returning.
+**
+** If an error occurs, or the table does not contain the specified row,
+** an SQLite error code is returned. Otherwise, SQLITE_OK is returned. If
+** paBlob is non-NULL, then it is the responsibility of the caller to
+** eventually free the returned buffer.
+**
+** This function may leave an open sqlite3_blob* handle in the
+** Fts3Table.pSegments variable. This handle is reused by subsequent calls
+** to this function. The handle may be closed by calling the
+** sqlite3Fts3SegmentsClose() function. Reusing a blob handle is a handy
+** performance improvement, but the blob handle should always be closed
+** before control is returned to the user (to prevent a lock being held
+** on the database file for longer than necessary). Thus, any virtual table
+** method (xFilter etc.) that may directly or indirectly call this function
+** must call sqlite3Fts3SegmentsClose() before returning.
+*/
+SQLITE_PRIVATE int sqlite3Fts3ReadBlock(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iBlockid,         /* Access the row with blockid=$iBlockid */
+  char **paBlob,                  /* OUT: Blob data in malloc'd buffer */
+  int *pnBlob,                    /* OUT: Size of blob data */
+  int *pnLoad                     /* OUT: Bytes actually loaded */
+){
+  int rc;                         /* Return code */
+
+  /* pnBlob must be non-NULL. paBlob may be NULL or non-NULL. */
+  assert( pnBlob );
+
+  if( p->pSegments ){
+    rc = sqlite3_blob_reopen(p->pSegments, iBlockid);
+  }else{
+    if( 0==p->zSegmentsTbl ){
+      p->zSegmentsTbl = sqlite3_mprintf("%s_segments", p->zName);
+      if( 0==p->zSegmentsTbl ) return SQLITE_NOMEM;
+    }
+    rc = sqlite3_blob_open(
+       p->db, p->zDb, p->zSegmentsTbl, "block", iBlockid, 0, &p->pSegments
+    );
+  }
+
+  if( rc==SQLITE_OK ){
+    int nByte = sqlite3_blob_bytes(p->pSegments);
+    *pnBlob = nByte;
+    if( paBlob ){
+      char *aByte = sqlite3_malloc(nByte + FTS3_NODE_PADDING);
+      if( !aByte ){
+        rc = SQLITE_NOMEM;
+      }else{
+        if( pnLoad && nByte>(FTS3_NODE_CHUNK_THRESHOLD) ){
+          nByte = FTS3_NODE_CHUNKSIZE;
+          *pnLoad = nByte;
+        }
+        rc = sqlite3_blob_read(p->pSegments, aByte, nByte, 0);
+        memset(&aByte[nByte], 0, FTS3_NODE_PADDING);
+        if( rc!=SQLITE_OK ){
+          sqlite3_free(aByte);
+          aByte = 0;
+        }
+      }
+      *paBlob = aByte;
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Close the blob handle at p->pSegments, if it is open. See comments above
+** the sqlite3Fts3ReadBlock() function for details.
+*/
+SQLITE_PRIVATE void sqlite3Fts3SegmentsClose(Fts3Table *p){
+  sqlite3_blob_close(p->pSegments);
+  p->pSegments = 0;
+}
+    
+static int fts3SegReaderIncrRead(Fts3SegReader *pReader){
+  int nRead;                      /* Number of bytes to read */
+  int rc;                         /* Return code */
+
+  nRead = MIN(pReader->nNode - pReader->nPopulate, FTS3_NODE_CHUNKSIZE);
+  rc = sqlite3_blob_read(
+      pReader->pBlob, 
+      &pReader->aNode[pReader->nPopulate],
+      nRead,
+      pReader->nPopulate
+  );
+
+  if( rc==SQLITE_OK ){
+    pReader->nPopulate += nRead;
+    memset(&pReader->aNode[pReader->nPopulate], 0, FTS3_NODE_PADDING);
+    if( pReader->nPopulate==pReader->nNode ){
+      sqlite3_blob_close(pReader->pBlob);
+      pReader->pBlob = 0;
+      pReader->nPopulate = 0;
+    }
+  }
+  return rc;
+}
+
+static int fts3SegReaderRequire(Fts3SegReader *pReader, char *pFrom, int nByte){
+  int rc = SQLITE_OK;
+  assert( !pReader->pBlob 
+       || (pFrom>=pReader->aNode && pFrom<&pReader->aNode[pReader->nNode])
+  );
+  while( pReader->pBlob && rc==SQLITE_OK 
+     &&  (pFrom - pReader->aNode + nByte)>pReader->nPopulate
+  ){
+    rc = fts3SegReaderIncrRead(pReader);
+  }
+  return rc;
+}
+
+/*
+** Set an Fts3SegReader cursor to point at EOF.
+*/
+static void fts3SegReaderSetEof(Fts3SegReader *pSeg){
+  if( !fts3SegReaderIsRootOnly(pSeg) ){
+    sqlite3_free(pSeg->aNode);
+    sqlite3_blob_close(pSeg->pBlob);
+    pSeg->pBlob = 0;
+  }
+  pSeg->aNode = 0;
+}
+
+/*
+** Move the iterator passed as the first argument to the next term in the
+** segment. If successful, SQLITE_OK is returned. If there is no next term,
+** SQLITE_DONE. Otherwise, an SQLite error code.
+*/
+static int fts3SegReaderNext(
+  Fts3Table *p, 
+  Fts3SegReader *pReader,
+  int bIncr
+){
+  int rc;                         /* Return code of various sub-routines */
+  char *pNext;                    /* Cursor variable */
+  int nPrefix;                    /* Number of bytes in term prefix */
+  int nSuffix;                    /* Number of bytes in term suffix */
+
+  if( !pReader->aDoclist ){
+    pNext = pReader->aNode;
+  }else{
+    pNext = &pReader->aDoclist[pReader->nDoclist];
+  }
+
+  if( !pNext || pNext>=&pReader->aNode[pReader->nNode] ){
+
+    if( fts3SegReaderIsPending(pReader) ){
+      Fts3HashElem *pElem = *(pReader->ppNextElem);
+      sqlite3_free(pReader->aNode);
+      pReader->aNode = 0;
+      if( pElem ){
+        char *aCopy;
+        PendingList *pList = (PendingList *)fts3HashData(pElem);
+        int nCopy = pList->nData+1;
+        pReader->zTerm = (char *)fts3HashKey(pElem);
+        pReader->nTerm = fts3HashKeysize(pElem);
+        aCopy = (char*)sqlite3_malloc(nCopy);
+        if( !aCopy ) return SQLITE_NOMEM;
+        memcpy(aCopy, pList->aData, nCopy);
+        pReader->nNode = pReader->nDoclist = nCopy;
+        pReader->aNode = pReader->aDoclist = aCopy;
+        pReader->ppNextElem++;
+        assert( pReader->aNode );
+      }
+      return SQLITE_OK;
+    }
+
+    fts3SegReaderSetEof(pReader);
+
+    /* If iCurrentBlock>=iLeafEndBlock, this is an EOF condition. All leaf 
+    ** blocks have already been traversed.  */
+    assert( pReader->iCurrentBlock<=pReader->iLeafEndBlock );
+    if( pReader->iCurrentBlock>=pReader->iLeafEndBlock ){
+      return SQLITE_OK;
+    }
+
+    rc = sqlite3Fts3ReadBlock(
+        p, ++pReader->iCurrentBlock, &pReader->aNode, &pReader->nNode, 
+        (bIncr ? &pReader->nPopulate : 0)
+    );
+    if( rc!=SQLITE_OK ) return rc;
+    assert( pReader->pBlob==0 );
+    if( bIncr && pReader->nPopulate<pReader->nNode ){
+      pReader->pBlob = p->pSegments;
+      p->pSegments = 0;
+    }
+    pNext = pReader->aNode;
+  }
+
+  assert( !fts3SegReaderIsPending(pReader) );
+
+  rc = fts3SegReaderRequire(pReader, pNext, FTS3_VARINT_MAX*2);
+  if( rc!=SQLITE_OK ) return rc;
+  
+  /* Because of the FTS3_NODE_PADDING bytes of padding, the following is 
+  ** safe (no risk of overread) even if the node data is corrupted. */
+  pNext += fts3GetVarint32(pNext, &nPrefix);
+  pNext += fts3GetVarint32(pNext, &nSuffix);
+  if( nPrefix<0 || nSuffix<=0 
+   || &pNext[nSuffix]>&pReader->aNode[pReader->nNode] 
+  ){
+    return FTS_CORRUPT_VTAB;
+  }
+
+  if( nPrefix+nSuffix>pReader->nTermAlloc ){
+    int nNew = (nPrefix+nSuffix)*2;
+    char *zNew = sqlite3_realloc(pReader->zTerm, nNew);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    pReader->zTerm = zNew;
+    pReader->nTermAlloc = nNew;
+  }
+
+  rc = fts3SegReaderRequire(pReader, pNext, nSuffix+FTS3_VARINT_MAX);
+  if( rc!=SQLITE_OK ) return rc;
+
+  memcpy(&pReader->zTerm[nPrefix], pNext, nSuffix);
+  pReader->nTerm = nPrefix+nSuffix;
+  pNext += nSuffix;
+  pNext += fts3GetVarint32(pNext, &pReader->nDoclist);
+  pReader->aDoclist = pNext;
+  pReader->pOffsetList = 0;
+
+  /* Check that the doclist does not appear to extend past the end of the
+  ** b-tree node. And that the final byte of the doclist is 0x00. If either 
+  ** of these statements is untrue, then the data structure is corrupt.
+  */
+  if( &pReader->aDoclist[pReader->nDoclist]>&pReader->aNode[pReader->nNode] 
+   || (pReader->nPopulate==0 && pReader->aDoclist[pReader->nDoclist-1])
+  ){
+    return FTS_CORRUPT_VTAB;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Set the SegReader to point to the first docid in the doclist associated
+** with the current term.
+*/
+static int fts3SegReaderFirstDocid(Fts3Table *pTab, Fts3SegReader *pReader){
+  int rc = SQLITE_OK;
+  assert( pReader->aDoclist );
+  assert( !pReader->pOffsetList );
+  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
+    u8 bEof = 0;
+    pReader->iDocid = 0;
+    pReader->nOffsetList = 0;
+    sqlite3Fts3DoclistPrev(0,
+        pReader->aDoclist, pReader->nDoclist, &pReader->pOffsetList, 
+        &pReader->iDocid, &pReader->nOffsetList, &bEof
+    );
+  }else{
+    rc = fts3SegReaderRequire(pReader, pReader->aDoclist, FTS3_VARINT_MAX);
+    if( rc==SQLITE_OK ){
+      int n = sqlite3Fts3GetVarint(pReader->aDoclist, &pReader->iDocid);
+      pReader->pOffsetList = &pReader->aDoclist[n];
+    }
+  }
+  return rc;
+}
+
+/*
+** Advance the SegReader to point to the next docid in the doclist
+** associated with the current term.
+** 
+** If arguments ppOffsetList and pnOffsetList are not NULL, then 
+** *ppOffsetList is set to point to the first column-offset list
+** in the doclist entry (i.e. immediately past the docid varint).
+** *pnOffsetList is set to the length of the set of column-offset
+** lists, not including the nul-terminator byte. For example:
+*/
+static int fts3SegReaderNextDocid(
+  Fts3Table *pTab,
+  Fts3SegReader *pReader,         /* Reader to advance to next docid */
+  char **ppOffsetList,            /* OUT: Pointer to current position-list */
+  int *pnOffsetList               /* OUT: Length of *ppOffsetList in bytes */
+){
+  int rc = SQLITE_OK;
+  char *p = pReader->pOffsetList;
+  char c = 0;
+
+  assert( p );
+
+  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
+    /* A pending-terms seg-reader for an FTS4 table that uses order=desc.
+    ** Pending-terms doclists are always built up in ascending order, so
+    ** we have to iterate through them backwards here. */
+    u8 bEof = 0;
+    if( ppOffsetList ){
+      *ppOffsetList = pReader->pOffsetList;
+      *pnOffsetList = pReader->nOffsetList - 1;
+    }
+    sqlite3Fts3DoclistPrev(0,
+        pReader->aDoclist, pReader->nDoclist, &p, &pReader->iDocid,
+        &pReader->nOffsetList, &bEof
+    );
+    if( bEof ){
+      pReader->pOffsetList = 0;
+    }else{
+      pReader->pOffsetList = p;
+    }
+  }else{
+    char *pEnd = &pReader->aDoclist[pReader->nDoclist];
+
+    /* Pointer p currently points at the first byte of an offset list. The
+    ** following block advances it to point one byte past the end of
+    ** the same offset list. */
+    while( 1 ){
+  
+      /* The following line of code (and the "p++" below the while() loop) is
+      ** normally all that is required to move pointer p to the desired 
+      ** position. The exception is if this node is being loaded from disk
+      ** incrementally and pointer "p" now points to the first byte past
+      ** the populated part of pReader->aNode[].
+      */
+      while( *p | c ) c = *p++ & 0x80;
+      assert( *p==0 );
+  
+      if( pReader->pBlob==0 || p<&pReader->aNode[pReader->nPopulate] ) break;
+      rc = fts3SegReaderIncrRead(pReader);
+      if( rc!=SQLITE_OK ) return rc;
+    }
+    p++;
+  
+    /* If required, populate the output variables with a pointer to and the
+    ** size of the previous offset-list.
+    */
+    if( ppOffsetList ){
+      *ppOffsetList = pReader->pOffsetList;
+      *pnOffsetList = (int)(p - pReader->pOffsetList - 1);
+    }
+
+    /* List may have been edited in place by fts3EvalNearTrim() */
+    while( p<pEnd && *p==0 ) p++;
+  
+    /* If there are no more entries in the doclist, set pOffsetList to
+    ** NULL. Otherwise, set Fts3SegReader.iDocid to the next docid and
+    ** Fts3SegReader.pOffsetList to point to the next offset list before
+    ** returning.
+    */
+    if( p>=pEnd ){
+      pReader->pOffsetList = 0;
+    }else{
+      rc = fts3SegReaderRequire(pReader, p, FTS3_VARINT_MAX);
+      if( rc==SQLITE_OK ){
+        sqlite3_int64 iDelta;
+        pReader->pOffsetList = p + sqlite3Fts3GetVarint(p, &iDelta);
+        if( pTab->bDescIdx ){
+          pReader->iDocid -= iDelta;
+        }else{
+          pReader->iDocid += iDelta;
+        }
+      }
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+
+SQLITE_PRIVATE int sqlite3Fts3MsrOvfl(
+  Fts3Cursor *pCsr, 
+  Fts3MultiSegReader *pMsr,
+  int *pnOvfl
+){
+  Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
+  int nOvfl = 0;
+  int ii;
+  int rc = SQLITE_OK;
+  int pgsz = p->nPgsz;
+
+  assert( p->bFts4 );
+  assert( pgsz>0 );
+
+  for(ii=0; rc==SQLITE_OK && ii<pMsr->nSegment; ii++){
+    Fts3SegReader *pReader = pMsr->apSegment[ii];
+    if( !fts3SegReaderIsPending(pReader) 
+     && !fts3SegReaderIsRootOnly(pReader) 
+    ){
+      sqlite3_int64 jj;
+      for(jj=pReader->iStartBlock; jj<=pReader->iLeafEndBlock; jj++){
+        int nBlob;
+        rc = sqlite3Fts3ReadBlock(p, jj, 0, &nBlob, 0);
+        if( rc!=SQLITE_OK ) break;
+        if( (nBlob+35)>pgsz ){
+          nOvfl += (nBlob + 34)/pgsz;
+        }
+      }
+    }
+  }
+  *pnOvfl = nOvfl;
+  return rc;
+}
+
+/*
+** Free all allocations associated with the iterator passed as the 
+** second argument.
+*/
+SQLITE_PRIVATE void sqlite3Fts3SegReaderFree(Fts3SegReader *pReader){
+  if( pReader ){
+    if( !fts3SegReaderIsPending(pReader) ){
+      sqlite3_free(pReader->zTerm);
+    }
+    if( !fts3SegReaderIsRootOnly(pReader) ){
+      sqlite3_free(pReader->aNode);
+    }
+    sqlite3_blob_close(pReader->pBlob);
+  }
+  sqlite3_free(pReader);
+}
+
+/*
+** Allocate a new SegReader object.
+*/
+SQLITE_PRIVATE int sqlite3Fts3SegReaderNew(
+  int iAge,                       /* Segment "age". */
+  int bLookup,                    /* True for a lookup only */
+  sqlite3_int64 iStartLeaf,       /* First leaf to traverse */
+  sqlite3_int64 iEndLeaf,         /* Final leaf to traverse */
+  sqlite3_int64 iEndBlock,        /* Final block of segment */
+  const char *zRoot,              /* Buffer containing root node */
+  int nRoot,                      /* Size of buffer containing root node */
+  Fts3SegReader **ppReader        /* OUT: Allocated Fts3SegReader */
+){
+  Fts3SegReader *pReader;         /* Newly allocated SegReader object */
+  int nExtra = 0;                 /* Bytes to allocate segment root node */
+
+  assert( iStartLeaf<=iEndLeaf );
+  if( iStartLeaf==0 ){
+    nExtra = nRoot + FTS3_NODE_PADDING;
+  }
+
+  pReader = (Fts3SegReader *)sqlite3_malloc(sizeof(Fts3SegReader) + nExtra);
+  if( !pReader ){
+    return SQLITE_NOMEM;
+  }
+  memset(pReader, 0, sizeof(Fts3SegReader));
+  pReader->iIdx = iAge;
+  pReader->bLookup = bLookup!=0;
+  pReader->iStartBlock = iStartLeaf;
+  pReader->iLeafEndBlock = iEndLeaf;
+  pReader->iEndBlock = iEndBlock;
+
+  if( nExtra ){
+    /* The entire segment is stored in the root node. */
+    pReader->aNode = (char *)&pReader[1];
+    pReader->rootOnly = 1;
+    pReader->nNode = nRoot;
+    memcpy(pReader->aNode, zRoot, nRoot);
+    memset(&pReader->aNode[nRoot], 0, FTS3_NODE_PADDING);
+  }else{
+    pReader->iCurrentBlock = iStartLeaf-1;
+  }
+  *ppReader = pReader;
+  return SQLITE_OK;
+}
+
+/*
+** This is a comparison function used as a qsort() callback when sorting
+** an array of pending terms by term. This occurs as part of flushing
+** the contents of the pending-terms hash table to the database.
+*/
+static int SQLITE_CDECL fts3CompareElemByTerm(
+  const void *lhs,
+  const void *rhs
+){
+  char *z1 = fts3HashKey(*(Fts3HashElem **)lhs);
+  char *z2 = fts3HashKey(*(Fts3HashElem **)rhs);
+  int n1 = fts3HashKeysize(*(Fts3HashElem **)lhs);
+  int n2 = fts3HashKeysize(*(Fts3HashElem **)rhs);
+
+  int n = (n1<n2 ? n1 : n2);
+  int c = memcmp(z1, z2, n);
+  if( c==0 ){
+    c = n1 - n2;
+  }
+  return c;
+}
+
+/*
+** This function is used to allocate an Fts3SegReader that iterates through
+** a subset of the terms stored in the Fts3Table.pendingTerms array.
+**
+** If the isPrefixIter parameter is zero, then the returned SegReader iterates
+** through each term in the pending-terms table. Or, if isPrefixIter is
+** non-zero, it iterates through each term and its prefixes. For example, if
+** the pending terms hash table contains the terms "sqlite", "mysql" and
+** "firebird", then the iterator visits the following 'terms' (in the order
+** shown):
+**
+**   f fi fir fire fireb firebi firebir firebird
+**   m my mys mysq mysql
+**   s sq sql sqli sqlit sqlite
+**
+** Whereas if isPrefixIter is zero, the terms visited are:
+**
+**   firebird mysql sqlite
+*/
+SQLITE_PRIVATE int sqlite3Fts3SegReaderPending(
+  Fts3Table *p,                   /* Virtual table handle */
+  int iIndex,                     /* Index for p->aIndex */
+  const char *zTerm,              /* Term to search for */
+  int nTerm,                      /* Size of buffer zTerm */
+  int bPrefix,                    /* True for a prefix iterator */
+  Fts3SegReader **ppReader        /* OUT: SegReader for pending-terms */
+){
+  Fts3SegReader *pReader = 0;     /* Fts3SegReader object to return */
+  Fts3HashElem *pE;               /* Iterator variable */
+  Fts3HashElem **aElem = 0;       /* Array of term hash entries to scan */
+  int nElem = 0;                  /* Size of array at aElem */
+  int rc = SQLITE_OK;             /* Return Code */
+  Fts3Hash *pHash;
+
+  pHash = &p->aIndex[iIndex].hPending;
+  if( bPrefix ){
+    int nAlloc = 0;               /* Size of allocated array at aElem */
+
+    for(pE=fts3HashFirst(pHash); pE; pE=fts3HashNext(pE)){
+      char *zKey = (char *)fts3HashKey(pE);
+      int nKey = fts3HashKeysize(pE);
+      if( nTerm==0 || (nKey>=nTerm && 0==memcmp(zKey, zTerm, nTerm)) ){
+        if( nElem==nAlloc ){
+          Fts3HashElem **aElem2;
+          nAlloc += 16;
+          aElem2 = (Fts3HashElem **)sqlite3_realloc(
+              aElem, nAlloc*sizeof(Fts3HashElem *)
+          );
+          if( !aElem2 ){
+            rc = SQLITE_NOMEM;
+            nElem = 0;
+            break;
+          }
+          aElem = aElem2;
+        }
+
+        aElem[nElem++] = pE;
+      }
+    }
+
+    /* If more than one term matches the prefix, sort the Fts3HashElem
+    ** objects in term order using qsort(). This uses the same comparison
+    ** callback as is used when flushing terms to disk.
+    */
+    if( nElem>1 ){
+      qsort(aElem, nElem, sizeof(Fts3HashElem *), fts3CompareElemByTerm);
+    }
+
+  }else{
+    /* The query is a simple term lookup that matches at most one term in
+    ** the index. All that is required is a straight hash-lookup. 
+    **
+    ** Because the stack address of pE may be accessed via the aElem pointer
+    ** below, the "Fts3HashElem *pE" must be declared so that it is valid
+    ** within this entire function, not just this "else{...}" block.
+    */
+    pE = fts3HashFindElem(pHash, zTerm, nTerm);
+    if( pE ){
+      aElem = &pE;
+      nElem = 1;
+    }
+  }
+
+  if( nElem>0 ){
+    int nByte = sizeof(Fts3SegReader) + (nElem+1)*sizeof(Fts3HashElem *);
+    pReader = (Fts3SegReader *)sqlite3_malloc(nByte);
+    if( !pReader ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memset(pReader, 0, nByte);
+      pReader->iIdx = 0x7FFFFFFF;
+      pReader->ppNextElem = (Fts3HashElem **)&pReader[1];
+      memcpy(pReader->ppNextElem, aElem, nElem*sizeof(Fts3HashElem *));
+    }
+  }
+
+  if( bPrefix ){
+    sqlite3_free(aElem);
+  }
+  *ppReader = pReader;
+  return rc;
+}
+
+/*
+** Compare the entries pointed to by two Fts3SegReader structures. 
+** Comparison is as follows:
+**
+**   1) EOF is greater than not EOF.
+**
+**   2) The current terms (if any) are compared using memcmp(). If one
+**      term is a prefix of another, the longer term is considered the
+**      larger.
+**
+**   3) By segment age. An older segment is considered larger.
+*/
+static int fts3SegReaderCmp(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
+  int rc;
+  if( pLhs->aNode && pRhs->aNode ){
+    int rc2 = pLhs->nTerm - pRhs->nTerm;
+    if( rc2<0 ){
+      rc = memcmp(pLhs->zTerm, pRhs->zTerm, pLhs->nTerm);
+    }else{
+      rc = memcmp(pLhs->zTerm, pRhs->zTerm, pRhs->nTerm);
+    }
+    if( rc==0 ){
+      rc = rc2;
+    }
+  }else{
+    rc = (pLhs->aNode==0) - (pRhs->aNode==0);
+  }
+  if( rc==0 ){
+    rc = pRhs->iIdx - pLhs->iIdx;
+  }
+  assert( rc!=0 );
+  return rc;
+}
+
+/*
+** A different comparison function for SegReader structures. In this
+** version, it is assumed that each SegReader points to an entry in
+** a doclist for identical terms. Comparison is made as follows:
+**
+**   1) EOF (end of doclist in this case) is greater than not EOF.
+**
+**   2) By current docid.
+**
+**   3) By segment age. An older segment is considered larger.
+*/
+static int fts3SegReaderDoclistCmp(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
+  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
+  if( rc==0 ){
+    if( pLhs->iDocid==pRhs->iDocid ){
+      rc = pRhs->iIdx - pLhs->iIdx;
+    }else{
+      rc = (pLhs->iDocid > pRhs->iDocid) ? 1 : -1;
+    }
+  }
+  assert( pLhs->aNode && pRhs->aNode );
+  return rc;
+}
+static int fts3SegReaderDoclistCmpRev(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
+  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
+  if( rc==0 ){
+    if( pLhs->iDocid==pRhs->iDocid ){
+      rc = pRhs->iIdx - pLhs->iIdx;
+    }else{
+      rc = (pLhs->iDocid < pRhs->iDocid) ? 1 : -1;
+    }
+  }
+  assert( pLhs->aNode && pRhs->aNode );
+  return rc;
+}
+
+/*
+** Compare the term that the Fts3SegReader object passed as the first argument
+** points to with the term specified by arguments zTerm and nTerm. 
+**
+** If the pSeg iterator is already at EOF, return 0. Otherwise, return
+** -ve if the pSeg term is less than zTerm/nTerm, 0 if the two terms are
+** equal, or +ve if the pSeg term is greater than zTerm/nTerm.
+*/
+static int fts3SegReaderTermCmp(
+  Fts3SegReader *pSeg,            /* Segment reader object */
+  const char *zTerm,              /* Term to compare to */
+  int nTerm                       /* Size of term zTerm in bytes */
+){
+  int res = 0;
+  if( pSeg->aNode ){
+    if( pSeg->nTerm>nTerm ){
+      res = memcmp(pSeg->zTerm, zTerm, nTerm);
+    }else{
+      res = memcmp(pSeg->zTerm, zTerm, pSeg->nTerm);
+    }
+    if( res==0 ){
+      res = pSeg->nTerm-nTerm;
+    }
+  }
+  return res;
+}
+
+/*
+** Argument apSegment is an array of nSegment elements. It is known that
+** the final (nSegment-nSuspect) members are already in sorted order
+** (according to the comparison function provided). This function shuffles
+** the array around until all entries are in sorted order.
+*/
+static void fts3SegReaderSort(
+  Fts3SegReader **apSegment,                     /* Array to sort entries of */
+  int nSegment,                                  /* Size of apSegment array */
+  int nSuspect,                                  /* Unsorted entry count */
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *)  /* Comparison function */
+){
+  int i;                          /* Iterator variable */
+
+  assert( nSuspect<=nSegment );
+
+  if( nSuspect==nSegment ) nSuspect--;
+  for(i=nSuspect-1; i>=0; i--){
+    int j;
+    for(j=i; j<(nSegment-1); j++){
+      Fts3SegReader *pTmp;
+      if( xCmp(apSegment[j], apSegment[j+1])<0 ) break;
+      pTmp = apSegment[j+1];
+      apSegment[j+1] = apSegment[j];
+      apSegment[j] = pTmp;
+    }
+  }
+
+#ifndef NDEBUG
+  /* Check that the list really is sorted now. */
+  for(i=0; i<(nSuspect-1); i++){
+    assert( xCmp(apSegment[i], apSegment[i+1])<0 );
+  }
+#endif
+}
+
+/* 
+** Insert a record into the %_segments table.
+*/
+static int fts3WriteSegment(
+  Fts3Table *p,                   /* Virtual table handle */
+  sqlite3_int64 iBlock,           /* Block id for new block */
+  char *z,                        /* Pointer to buffer containing block data */
+  int n                           /* Size of buffer z in bytes */
+){
+  sqlite3_stmt *pStmt;
+  int rc = fts3SqlStmt(p, SQL_INSERT_SEGMENTS, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pStmt, 1, iBlock);
+    sqlite3_bind_blob(pStmt, 2, z, n, SQLITE_STATIC);
+    sqlite3_step(pStmt);
+    rc = sqlite3_reset(pStmt);
+  }
+  return rc;
+}
+
+/*
+** Find the largest relative level number in the table. If successful, set
+** *pnMax to this value and return SQLITE_OK. Otherwise, if an error occurs,
+** set *pnMax to zero and return an SQLite error code.
+*/
+SQLITE_PRIVATE int sqlite3Fts3MaxLevel(Fts3Table *p, int *pnMax){
+  int rc;
+  int mxLevel = 0;
+  sqlite3_stmt *pStmt = 0;
+
+  rc = fts3SqlStmt(p, SQL_SELECT_MXLEVEL, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    if( SQLITE_ROW==sqlite3_step(pStmt) ){
+      mxLevel = sqlite3_column_int(pStmt, 0);
+    }
+    rc = sqlite3_reset(pStmt);
+  }
+  *pnMax = mxLevel;
+  return rc;
+}
+
+/* 
+** Insert a record into the %_segdir table.
+*/
+static int fts3WriteSegdir(
+  Fts3Table *p,                   /* Virtual table handle */
+  sqlite3_int64 iLevel,           /* Value for "level" field (absolute level) */
+  int iIdx,                       /* Value for "idx" field */
+  sqlite3_int64 iStartBlock,      /* Value for "start_block" field */
+  sqlite3_int64 iLeafEndBlock,    /* Value for "leaves_end_block" field */
+  sqlite3_int64 iEndBlock,        /* Value for "end_block" field */
+  sqlite3_int64 nLeafData,        /* Bytes of leaf data in segment */
+  char *zRoot,                    /* Blob value for "root" field */
+  int nRoot                       /* Number of bytes in buffer zRoot */
+){
+  sqlite3_stmt *pStmt;
+  int rc = fts3SqlStmt(p, SQL_INSERT_SEGDIR, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pStmt, 1, iLevel);
+    sqlite3_bind_int(pStmt, 2, iIdx);
+    sqlite3_bind_int64(pStmt, 3, iStartBlock);
+    sqlite3_bind_int64(pStmt, 4, iLeafEndBlock);
+    if( nLeafData==0 ){
+      sqlite3_bind_int64(pStmt, 5, iEndBlock);
+    }else{
+      char *zEnd = sqlite3_mprintf("%lld %lld", iEndBlock, nLeafData);
+      if( !zEnd ) return SQLITE_NOMEM;
+      sqlite3_bind_text(pStmt, 5, zEnd, -1, sqlite3_free);
+    }
+    sqlite3_bind_blob(pStmt, 6, zRoot, nRoot, SQLITE_STATIC);
+    sqlite3_step(pStmt);
+    rc = sqlite3_reset(pStmt);
+  }
+  return rc;
+}
+
+/*
+** Return the size of the common prefix (if any) shared by zPrev and
+** zNext, in bytes. For example, 
+**
+**   fts3PrefixCompress("abc", 3, "abcdef", 6)   // returns 3
+**   fts3PrefixCompress("abX", 3, "abcdef", 6)   // returns 2
+**   fts3PrefixCompress("abX", 3, "Xbcdef", 6)   // returns 0
+*/
+static int fts3PrefixCompress(
+  const char *zPrev,              /* Buffer containing previous term */
+  int nPrev,                      /* Size of buffer zPrev in bytes */
+  const char *zNext,              /* Buffer containing next term */
+  int nNext                       /* Size of buffer zNext in bytes */
+){
+  int n;
+  UNUSED_PARAMETER(nNext);
+  for(n=0; n<nPrev && zPrev[n]==zNext[n]; n++);
+  return n;
+}
+
+/*
+** Add term zTerm to the SegmentNode. It is guaranteed that zTerm is larger
+** (according to memcmp) than the previous term.
+*/
+static int fts3NodeAddTerm(
+  Fts3Table *p,                   /* Virtual table handle */
+  SegmentNode **ppTree,           /* IN/OUT: SegmentNode handle */ 
+  int isCopyTerm,                 /* True if zTerm/nTerm is transient */
+  const char *zTerm,              /* Pointer to buffer containing term */
+  int nTerm                       /* Size of term in bytes */
+){
+  SegmentNode *pTree = *ppTree;
+  int rc;
+  SegmentNode *pNew;
+
+  /* First try to append the term to the current node. Return early if 
+  ** this is possible.
+  */
+  if( pTree ){
+    int nData = pTree->nData;     /* Current size of node in bytes */
+    int nReq = nData;             /* Required space after adding zTerm */
+    int nPrefix;                  /* Number of bytes of prefix compression */
+    int nSuffix;                  /* Suffix length */
+
+    nPrefix = fts3PrefixCompress(pTree->zTerm, pTree->nTerm, zTerm, nTerm);
+    nSuffix = nTerm-nPrefix;
+
+    nReq += sqlite3Fts3VarintLen(nPrefix)+sqlite3Fts3VarintLen(nSuffix)+nSuffix;
+    if( nReq<=p->nNodeSize || !pTree->zTerm ){
+
+      if( nReq>p->nNodeSize ){
+        /* An unusual case: this is the first term to be added to the node
+        ** and the static node buffer (p->nNodeSize bytes) is not large
+        ** enough. Use a separately malloced buffer instead This wastes
+        ** p->nNodeSize bytes, but since this scenario only comes about when
+        ** the database contain two terms that share a prefix of almost 2KB, 
+        ** this is not expected to be a serious problem. 
+        */
+        assert( pTree->aData==(char *)&pTree[1] );
+        pTree->aData = (char *)sqlite3_malloc(nReq);
+        if( !pTree->aData ){
+          return SQLITE_NOMEM;
+        }
+      }
+
+      if( pTree->zTerm ){
+        /* There is no prefix-length field for first term in a node */
+        nData += sqlite3Fts3PutVarint(&pTree->aData[nData], nPrefix);
+      }
+
+      nData += sqlite3Fts3PutVarint(&pTree->aData[nData], nSuffix);
+      memcpy(&pTree->aData[nData], &zTerm[nPrefix], nSuffix);
+      pTree->nData = nData + nSuffix;
+      pTree->nEntry++;
+
+      if( isCopyTerm ){
+        if( pTree->nMalloc<nTerm ){
+          char *zNew = sqlite3_realloc(pTree->zMalloc, nTerm*2);
+          if( !zNew ){
+            return SQLITE_NOMEM;
+          }
+          pTree->nMalloc = nTerm*2;
+          pTree->zMalloc = zNew;
+        }
+        pTree->zTerm = pTree->zMalloc;
+        memcpy(pTree->zTerm, zTerm, nTerm);
+        pTree->nTerm = nTerm;
+      }else{
+        pTree->zTerm = (char *)zTerm;
+        pTree->nTerm = nTerm;
+      }
+      return SQLITE_OK;
+    }
+  }
+
+  /* If control flows to here, it was not possible to append zTerm to the
+  ** current node. Create a new node (a right-sibling of the current node).
+  ** If this is the first node in the tree, the term is added to it.
+  **
+  ** Otherwise, the term is not added to the new node, it is left empty for
+  ** now. Instead, the term is inserted into the parent of pTree. If pTree 
+  ** has no parent, one is created here.
+  */
+  pNew = (SegmentNode *)sqlite3_malloc(sizeof(SegmentNode) + p->nNodeSize);
+  if( !pNew ){
+    return SQLITE_NOMEM;
+  }
+  memset(pNew, 0, sizeof(SegmentNode));
+  pNew->nData = 1 + FTS3_VARINT_MAX;
+  pNew->aData = (char *)&pNew[1];
+
+  if( pTree ){
+    SegmentNode *pParent = pTree->pParent;
+    rc = fts3NodeAddTerm(p, &pParent, isCopyTerm, zTerm, nTerm);
+    if( pTree->pParent==0 ){
+      pTree->pParent = pParent;
+    }
+    pTree->pRight = pNew;
+    pNew->pLeftmost = pTree->pLeftmost;
+    pNew->pParent = pParent;
+    pNew->zMalloc = pTree->zMalloc;
+    pNew->nMalloc = pTree->nMalloc;
+    pTree->zMalloc = 0;
+  }else{
+    pNew->pLeftmost = pNew;
+    rc = fts3NodeAddTerm(p, &pNew, isCopyTerm, zTerm, nTerm); 
+  }
+
+  *ppTree = pNew;
+  return rc;
+}
+
+/*
+** Helper function for fts3NodeWrite().
+*/
+static int fts3TreeFinishNode(
+  SegmentNode *pTree, 
+  int iHeight, 
+  sqlite3_int64 iLeftChild
+){
+  int nStart;
+  assert( iHeight>=1 && iHeight<128 );
+  nStart = FTS3_VARINT_MAX - sqlite3Fts3VarintLen(iLeftChild);
+  pTree->aData[nStart] = (char)iHeight;
+  sqlite3Fts3PutVarint(&pTree->aData[nStart+1], iLeftChild);
+  return nStart;
+}
+
+/*
+** Write the buffer for the segment node pTree and all of its peers to the
+** database. Then call this function recursively to write the parent of 
+** pTree and its peers to the database. 
+**
+** Except, if pTree is a root node, do not write it to the database. Instead,
+** set output variables *paRoot and *pnRoot to contain the root node.
+**
+** If successful, SQLITE_OK is returned and output variable *piLast is
+** set to the largest blockid written to the database (or zero if no
+** blocks were written to the db). Otherwise, an SQLite error code is 
+** returned.
+*/
+static int fts3NodeWrite(
+  Fts3Table *p,                   /* Virtual table handle */
+  SegmentNode *pTree,             /* SegmentNode handle */
+  int iHeight,                    /* Height of this node in tree */
+  sqlite3_int64 iLeaf,            /* Block id of first leaf node */
+  sqlite3_int64 iFree,            /* Block id of next free slot in %_segments */
+  sqlite3_int64 *piLast,          /* OUT: Block id of last entry written */
+  char **paRoot,                  /* OUT: Data for root node */
+  int *pnRoot                     /* OUT: Size of root node in bytes */
+){
+  int rc = SQLITE_OK;
+
+  if( !pTree->pParent ){
+    /* Root node of the tree. */
+    int nStart = fts3TreeFinishNode(pTree, iHeight, iLeaf);
+    *piLast = iFree-1;
+    *pnRoot = pTree->nData - nStart;
+    *paRoot = &pTree->aData[nStart];
+  }else{
+    SegmentNode *pIter;
+    sqlite3_int64 iNextFree = iFree;
+    sqlite3_int64 iNextLeaf = iLeaf;
+    for(pIter=pTree->pLeftmost; pIter && rc==SQLITE_OK; pIter=pIter->pRight){
+      int nStart = fts3TreeFinishNode(pIter, iHeight, iNextLeaf);
+      int nWrite = pIter->nData - nStart;
+  
+      rc = fts3WriteSegment(p, iNextFree, &pIter->aData[nStart], nWrite);
+      iNextFree++;
+      iNextLeaf += (pIter->nEntry+1);
+    }
+    if( rc==SQLITE_OK ){
+      assert( iNextLeaf==iFree );
+      rc = fts3NodeWrite(
+          p, pTree->pParent, iHeight+1, iFree, iNextFree, piLast, paRoot, pnRoot
+      );
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Free all memory allocations associated with the tree pTree.
+*/
+static void fts3NodeFree(SegmentNode *pTree){
+  if( pTree ){
+    SegmentNode *p = pTree->pLeftmost;
+    fts3NodeFree(p->pParent);
+    while( p ){
+      SegmentNode *pRight = p->pRight;
+      if( p->aData!=(char *)&p[1] ){
+        sqlite3_free(p->aData);
+      }
+      assert( pRight==0 || p->zMalloc==0 );
+      sqlite3_free(p->zMalloc);
+      sqlite3_free(p);
+      p = pRight;
+    }
+  }
+}
+
+/*
+** Add a term to the segment being constructed by the SegmentWriter object
+** *ppWriter. When adding the first term to a segment, *ppWriter should
+** be passed NULL. This function will allocate a new SegmentWriter object
+** and return it via the input/output variable *ppWriter in this case.
+**
+** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
+*/
+static int fts3SegWriterAdd(
+  Fts3Table *p,                   /* Virtual table handle */
+  SegmentWriter **ppWriter,       /* IN/OUT: SegmentWriter handle */ 
+  int isCopyTerm,                 /* True if buffer zTerm must be copied */
+  const char *zTerm,              /* Pointer to buffer containing term */
+  int nTerm,                      /* Size of term in bytes */
+  const char *aDoclist,           /* Pointer to buffer containing doclist */
+  int nDoclist                    /* Size of doclist in bytes */
+){
+  int nPrefix;                    /* Size of term prefix in bytes */
+  int nSuffix;                    /* Size of term suffix in bytes */
+  int nReq;                       /* Number of bytes required on leaf page */
+  int nData;
+  SegmentWriter *pWriter = *ppWriter;
+
+  if( !pWriter ){
+    int rc;
+    sqlite3_stmt *pStmt;
+
+    /* Allocate the SegmentWriter structure */
+    pWriter = (SegmentWriter *)sqlite3_malloc(sizeof(SegmentWriter));
+    if( !pWriter ) return SQLITE_NOMEM;
+    memset(pWriter, 0, sizeof(SegmentWriter));
+    *ppWriter = pWriter;
+
+    /* Allocate a buffer in which to accumulate data */
+    pWriter->aData = (char *)sqlite3_malloc(p->nNodeSize);
+    if( !pWriter->aData ) return SQLITE_NOMEM;
+    pWriter->nSize = p->nNodeSize;
+
+    /* Find the next free blockid in the %_segments table */
+    rc = fts3SqlStmt(p, SQL_NEXT_SEGMENTS_ID, &pStmt, 0);
+    if( rc!=SQLITE_OK ) return rc;
+    if( SQLITE_ROW==sqlite3_step(pStmt) ){
+      pWriter->iFree = sqlite3_column_int64(pStmt, 0);
+      pWriter->iFirst = pWriter->iFree;
+    }
+    rc = sqlite3_reset(pStmt);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  nData = pWriter->nData;
+
+  nPrefix = fts3PrefixCompress(pWriter->zTerm, pWriter->nTerm, zTerm, nTerm);
+  nSuffix = nTerm-nPrefix;
+
+  /* Figure out how many bytes are required by this new entry */
+  nReq = sqlite3Fts3VarintLen(nPrefix) +    /* varint containing prefix size */
+    sqlite3Fts3VarintLen(nSuffix) +         /* varint containing suffix size */
+    nSuffix +                               /* Term suffix */
+    sqlite3Fts3VarintLen(nDoclist) +        /* Size of doclist */
+    nDoclist;                               /* Doclist data */
+
+  if( nData>0 && nData+nReq>p->nNodeSize ){
+    int rc;
+
+    /* The current leaf node is full. Write it out to the database. */
+    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, nData);
+    if( rc!=SQLITE_OK ) return rc;
+    p->nLeafAdd++;
+
+    /* Add the current term to the interior node tree. The term added to
+    ** the interior tree must:
+    **
+    **   a) be greater than the largest term on the leaf node just written
+    **      to the database (still available in pWriter->zTerm), and
+    **
+    **   b) be less than or equal to the term about to be added to the new
+    **      leaf node (zTerm/nTerm).
+    **
+    ** In other words, it must be the prefix of zTerm 1 byte longer than
+    ** the common prefix (if any) of zTerm and pWriter->zTerm.
+    */
+    assert( nPrefix<nTerm );
+    rc = fts3NodeAddTerm(p, &pWriter->pTree, isCopyTerm, zTerm, nPrefix+1);
+    if( rc!=SQLITE_OK ) return rc;
+
+    nData = 0;
+    pWriter->nTerm = 0;
+
+    nPrefix = 0;
+    nSuffix = nTerm;
+    nReq = 1 +                              /* varint containing prefix size */
+      sqlite3Fts3VarintLen(nTerm) +         /* varint containing suffix size */
+      nTerm +                               /* Term suffix */
+      sqlite3Fts3VarintLen(nDoclist) +      /* Size of doclist */
+      nDoclist;                             /* Doclist data */
+  }
+
+  /* Increase the total number of bytes written to account for the new entry. */
+  pWriter->nLeafData += nReq;
+
+  /* If the buffer currently allocated is too small for this entry, realloc
+  ** the buffer to make it large enough.
+  */
+  if( nReq>pWriter->nSize ){
+    char *aNew = sqlite3_realloc(pWriter->aData, nReq);
+    if( !aNew ) return SQLITE_NOMEM;
+    pWriter->aData = aNew;
+    pWriter->nSize = nReq;
+  }
+  assert( nData+nReq<=pWriter->nSize );
+
+  /* Append the prefix-compressed term and doclist to the buffer. */
+  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nPrefix);
+  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nSuffix);
+  memcpy(&pWriter->aData[nData], &zTerm[nPrefix], nSuffix);
+  nData += nSuffix;
+  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nDoclist);
+  memcpy(&pWriter->aData[nData], aDoclist, nDoclist);
+  pWriter->nData = nData + nDoclist;
+
+  /* Save the current term so that it can be used to prefix-compress the next.
+  ** If the isCopyTerm parameter is true, then the buffer pointed to by
+  ** zTerm is transient, so take a copy of the term data. Otherwise, just
+  ** store a copy of the pointer.
+  */
+  if( isCopyTerm ){
+    if( nTerm>pWriter->nMalloc ){
+      char *zNew = sqlite3_realloc(pWriter->zMalloc, nTerm*2);
+      if( !zNew ){
+        return SQLITE_NOMEM;
+      }
+      pWriter->nMalloc = nTerm*2;
+      pWriter->zMalloc = zNew;
+      pWriter->zTerm = zNew;
+    }
+    assert( pWriter->zTerm==pWriter->zMalloc );
+    memcpy(pWriter->zTerm, zTerm, nTerm);
+  }else{
+    pWriter->zTerm = (char *)zTerm;
+  }
+  pWriter->nTerm = nTerm;
+
+  return SQLITE_OK;
+}
+
+/*
+** Flush all data associated with the SegmentWriter object pWriter to the
+** database. This function must be called after all terms have been added
+** to the segment using fts3SegWriterAdd(). If successful, SQLITE_OK is
+** returned. Otherwise, an SQLite error code.
+*/
+static int fts3SegWriterFlush(
+  Fts3Table *p,                   /* Virtual table handle */
+  SegmentWriter *pWriter,         /* SegmentWriter to flush to the db */
+  sqlite3_int64 iLevel,           /* Value for 'level' column of %_segdir */
+  int iIdx                        /* Value for 'idx' column of %_segdir */
+){
+  int rc;                         /* Return code */
+  if( pWriter->pTree ){
+    sqlite3_int64 iLast = 0;      /* Largest block id written to database */
+    sqlite3_int64 iLastLeaf;      /* Largest leaf block id written to db */
+    char *zRoot = NULL;           /* Pointer to buffer containing root node */
+    int nRoot = 0;                /* Size of buffer zRoot */
+
+    iLastLeaf = pWriter->iFree;
+    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, pWriter->nData);
+    if( rc==SQLITE_OK ){
+      rc = fts3NodeWrite(p, pWriter->pTree, 1,
+          pWriter->iFirst, pWriter->iFree, &iLast, &zRoot, &nRoot);
+    }
+    if( rc==SQLITE_OK ){
+      rc = fts3WriteSegdir(p, iLevel, iIdx, 
+          pWriter->iFirst, iLastLeaf, iLast, pWriter->nLeafData, zRoot, nRoot);
+    }
+  }else{
+    /* The entire tree fits on the root node. Write it to the segdir table. */
+    rc = fts3WriteSegdir(p, iLevel, iIdx, 
+        0, 0, 0, pWriter->nLeafData, pWriter->aData, pWriter->nData);
+  }
+  p->nLeafAdd++;
+  return rc;
+}
+
+/*
+** Release all memory held by the SegmentWriter object passed as the 
+** first argument.
+*/
+static void fts3SegWriterFree(SegmentWriter *pWriter){
+  if( pWriter ){
+    sqlite3_free(pWriter->aData);
+    sqlite3_free(pWriter->zMalloc);
+    fts3NodeFree(pWriter->pTree);
+    sqlite3_free(pWriter);
+  }
+}
+
+/*
+** The first value in the apVal[] array is assumed to contain an integer.
+** This function tests if there exist any documents with docid values that
+** are different from that integer. i.e. if deleting the document with docid
+** pRowid would mean the FTS3 table were empty.
+**
+** If successful, *pisEmpty is set to true if the table is empty except for
+** document pRowid, or false otherwise, and SQLITE_OK is returned. If an
+** error occurs, an SQLite error code is returned.
+*/
+static int fts3IsEmpty(Fts3Table *p, sqlite3_value *pRowid, int *pisEmpty){
+  sqlite3_stmt *pStmt;
+  int rc;
+  if( p->zContentTbl ){
+    /* If using the content=xxx option, assume the table is never empty */
+    *pisEmpty = 0;
+    rc = SQLITE_OK;
+  }else{
+    rc = fts3SqlStmt(p, SQL_IS_EMPTY, &pStmt, &pRowid);
+    if( rc==SQLITE_OK ){
+      if( SQLITE_ROW==sqlite3_step(pStmt) ){
+        *pisEmpty = sqlite3_column_int(pStmt, 0);
+      }
+      rc = sqlite3_reset(pStmt);
+    }
+  }
+  return rc;
+}
+
+/*
+** Set *pnMax to the largest segment level in the database for the index
+** iIndex.
+**
+** Segment levels are stored in the 'level' column of the %_segdir table.
+**
+** Return SQLITE_OK if successful, or an SQLite error code if not.
+*/
+static int fts3SegmentMaxLevel(
+  Fts3Table *p, 
+  int iLangid,
+  int iIndex, 
+  sqlite3_int64 *pnMax
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  assert( iIndex>=0 && iIndex<p->nIndex );
+
+  /* Set pStmt to the compiled version of:
+  **
+  **   SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?
+  **
+  ** (1024 is actually the value of macro FTS3_SEGDIR_PREFIXLEVEL_STR).
+  */
+  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR_MAX_LEVEL, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+  sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
+  sqlite3_bind_int64(pStmt, 2, 
+      getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
+  );
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    *pnMax = sqlite3_column_int64(pStmt, 0);
+  }
+  return sqlite3_reset(pStmt);
+}
+
+/*
+** iAbsLevel is an absolute level that may be assumed to exist within
+** the database. This function checks if it is the largest level number
+** within its index. Assuming no error occurs, *pbMax is set to 1 if
+** iAbsLevel is indeed the largest level, or 0 otherwise, and SQLITE_OK
+** is returned. If an error occurs, an error code is returned and the
+** final value of *pbMax is undefined.
+*/
+static int fts3SegmentIsMaxLevel(Fts3Table *p, i64 iAbsLevel, int *pbMax){
+
+  /* Set pStmt to the compiled version of:
+  **
+  **   SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?
+  **
+  ** (1024 is actually the value of macro FTS3_SEGDIR_PREFIXLEVEL_STR).
+  */
+  sqlite3_stmt *pStmt;
+  int rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR_MAX_LEVEL, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+  sqlite3_bind_int64(pStmt, 1, iAbsLevel+1);
+  sqlite3_bind_int64(pStmt, 2, 
+      ((iAbsLevel/FTS3_SEGDIR_MAXLEVEL)+1) * FTS3_SEGDIR_MAXLEVEL
+  );
+
+  *pbMax = 0;
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    *pbMax = sqlite3_column_type(pStmt, 0)==SQLITE_NULL;
+  }
+  return sqlite3_reset(pStmt);
+}
+
+/*
+** Delete all entries in the %_segments table associated with the segment
+** opened with seg-reader pSeg. This function does not affect the contents
+** of the %_segdir table.
+*/
+static int fts3DeleteSegment(
+  Fts3Table *p,                   /* FTS table handle */
+  Fts3SegReader *pSeg             /* Segment to delete */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  if( pSeg->iStartBlock ){
+    sqlite3_stmt *pDelete;        /* SQL statement to delete rows */
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGMENTS_RANGE, &pDelete, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pDelete, 1, pSeg->iStartBlock);
+      sqlite3_bind_int64(pDelete, 2, pSeg->iEndBlock);
+      sqlite3_step(pDelete);
+      rc = sqlite3_reset(pDelete);
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is used after merging multiple segments into a single large
+** segment to delete the old, now redundant, segment b-trees. Specifically,
+** it:
+** 
+**   1) Deletes all %_segments entries for the segments associated with 
+**      each of the SegReader objects in the array passed as the third 
+**      argument, and
+**
+**   2) deletes all %_segdir entries with level iLevel, or all %_segdir
+**      entries regardless of level if (iLevel<0).
+**
+** SQLITE_OK is returned if successful, otherwise an SQLite error code.
+*/
+static int fts3DeleteSegdir(
+  Fts3Table *p,                   /* Virtual table handle */
+  int iLangid,                    /* Language id */
+  int iIndex,                     /* Index for p->aIndex */
+  int iLevel,                     /* Level of %_segdir entries to delete */
+  Fts3SegReader **apSegment,      /* Array of SegReader objects */
+  int nReader                     /* Size of array apSegment */
+){
+  int rc = SQLITE_OK;             /* Return Code */
+  int i;                          /* Iterator variable */
+  sqlite3_stmt *pDelete = 0;      /* SQL statement to delete rows */
+
+  for(i=0; rc==SQLITE_OK && i<nReader; i++){
+    rc = fts3DeleteSegment(p, apSegment[i]);
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  assert( iLevel>=0 || iLevel==FTS3_SEGCURSOR_ALL );
+  if( iLevel==FTS3_SEGCURSOR_ALL ){
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_RANGE, &pDelete, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pDelete, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
+      sqlite3_bind_int64(pDelete, 2, 
+          getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
+      );
+    }
+  }else{
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_LEVEL, &pDelete, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(
+          pDelete, 1, getAbsoluteLevel(p, iLangid, iIndex, iLevel)
+      );
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    sqlite3_step(pDelete);
+    rc = sqlite3_reset(pDelete);
+  }
+
+  return rc;
+}
+
+/*
+** When this function is called, buffer *ppList (size *pnList bytes) contains 
+** a position list that may (or may not) feature multiple columns. This
+** function adjusts the pointer *ppList and the length *pnList so that they
+** identify the subset of the position list that corresponds to column iCol.
+**
+** If there are no entries in the input position list for column iCol, then
+** *pnList is set to zero before returning.
+**
+** If parameter bZero is non-zero, then any part of the input list following
+** the end of the output list is zeroed before returning.
+*/
+static void fts3ColumnFilter(
+  int iCol,                       /* Column to filter on */
+  int bZero,                      /* Zero out anything following *ppList */
+  char **ppList,                  /* IN/OUT: Pointer to position list */
+  int *pnList                     /* IN/OUT: Size of buffer *ppList in bytes */
+){
+  char *pList = *ppList;
+  int nList = *pnList;
+  char *pEnd = &pList[nList];
+  int iCurrent = 0;
+  char *p = pList;
+
+  assert( iCol>=0 );
+  while( 1 ){
+    char c = 0;
+    while( p<pEnd && (c | *p)&0xFE ) c = *p++ & 0x80;
+  
+    if( iCol==iCurrent ){
+      nList = (int)(p - pList);
+      break;
+    }
+
+    nList -= (int)(p - pList);
+    pList = p;
+    if( nList==0 ){
+      break;
+    }
+    p = &pList[1];
+    p += fts3GetVarint32(p, &iCurrent);
+  }
+
+  if( bZero && &pList[nList]!=pEnd ){
+    memset(&pList[nList], 0, pEnd - &pList[nList]);
+  }
+  *ppList = pList;
+  *pnList = nList;
+}
+
+/*
+** Cache data in the Fts3MultiSegReader.aBuffer[] buffer (overwriting any
+** existing data). Grow the buffer if required.
+**
+** If successful, return SQLITE_OK. Otherwise, if an OOM error is encountered
+** trying to resize the buffer, return SQLITE_NOMEM.
+*/
+static int fts3MsrBufferData(
+  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
+  char *pList,
+  int nList
+){
+  if( nList>pMsr->nBuffer ){
+    char *pNew;
+    pMsr->nBuffer = nList*2;
+    pNew = (char *)sqlite3_realloc(pMsr->aBuffer, pMsr->nBuffer);
+    if( !pNew ) return SQLITE_NOMEM;
+    pMsr->aBuffer = pNew;
+  }
+
+  memcpy(pMsr->aBuffer, pList, nList);
+  return SQLITE_OK;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrNext(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
+  sqlite3_int64 *piDocid,         /* OUT: Docid value */
+  char **paPoslist,               /* OUT: Pointer to position list */
+  int *pnPoslist                  /* OUT: Size of position list in bytes */
+){
+  int nMerge = pMsr->nAdvance;
+  Fts3SegReader **apSegment = pMsr->apSegment;
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
+    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
+  );
+
+  if( nMerge==0 ){
+    *paPoslist = 0;
+    return SQLITE_OK;
+  }
+
+  while( 1 ){
+    Fts3SegReader *pSeg;
+    pSeg = pMsr->apSegment[0];
+
+    if( pSeg->pOffsetList==0 ){
+      *paPoslist = 0;
+      break;
+    }else{
+      int rc;
+      char *pList;
+      int nList;
+      int j;
+      sqlite3_int64 iDocid = apSegment[0]->iDocid;
+
+      rc = fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
+      j = 1;
+      while( rc==SQLITE_OK 
+        && j<nMerge
+        && apSegment[j]->pOffsetList
+        && apSegment[j]->iDocid==iDocid
+      ){
+        rc = fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
+        j++;
+      }
+      if( rc!=SQLITE_OK ) return rc;
+      fts3SegReaderSort(pMsr->apSegment, nMerge, j, xCmp);
+
+      if( nList>0 && fts3SegReaderIsPending(apSegment[0]) ){
+        rc = fts3MsrBufferData(pMsr, pList, nList+1);
+        if( rc!=SQLITE_OK ) return rc;
+        assert( (pMsr->aBuffer[nList] & 0xFE)==0x00 );
+        pList = pMsr->aBuffer;
+      }
+
+      if( pMsr->iColFilter>=0 ){
+        fts3ColumnFilter(pMsr->iColFilter, 1, &pList, &nList);
+      }
+
+      if( nList>0 ){
+        *paPoslist = pList;
+        *piDocid = iDocid;
+        *pnPoslist = nList;
+        break;
+      }
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+static int fts3SegReaderStart(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr,       /* Cursor object */
+  const char *zTerm,              /* Term searched for (or NULL) */
+  int nTerm                       /* Length of zTerm in bytes */
+){
+  int i;
+  int nSeg = pCsr->nSegment;
+
+  /* If the Fts3SegFilter defines a specific term (or term prefix) to search 
+  ** for, then advance each segment iterator until it points to a term of
+  ** equal or greater value than the specified term. This prevents many
+  ** unnecessary merge/sort operations for the case where single segment
+  ** b-tree leaf nodes contain more than one term.
+  */
+  for(i=0; pCsr->bRestart==0 && i<pCsr->nSegment; i++){
+    int res = 0;
+    Fts3SegReader *pSeg = pCsr->apSegment[i];
+    do {
+      int rc = fts3SegReaderNext(p, pSeg, 0);
+      if( rc!=SQLITE_OK ) return rc;
+    }while( zTerm && (res = fts3SegReaderTermCmp(pSeg, zTerm, nTerm))<0 );
+
+    if( pSeg->bLookup && res!=0 ){
+      fts3SegReaderSetEof(pSeg);
+    }
+  }
+  fts3SegReaderSort(pCsr->apSegment, nSeg, nSeg, fts3SegReaderCmp);
+
+  return SQLITE_OK;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3SegReaderStart(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr,       /* Cursor object */
+  Fts3SegFilter *pFilter          /* Restrictions on range of iteration */
+){
+  pCsr->pFilter = pFilter;
+  return fts3SegReaderStart(p, pCsr, pFilter->zTerm, pFilter->nTerm);
+}
+
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrStart(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr,       /* Cursor object */
+  int iCol,                       /* Column to match on. */
+  const char *zTerm,              /* Term to iterate through a doclist for */
+  int nTerm                       /* Number of bytes in zTerm */
+){
+  int i;
+  int rc;
+  int nSegment = pCsr->nSegment;
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
+    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
+  );
+
+  assert( pCsr->pFilter==0 );
+  assert( zTerm && nTerm>0 );
+
+  /* Advance each segment iterator until it points to the term zTerm/nTerm. */
+  rc = fts3SegReaderStart(p, pCsr, zTerm, nTerm);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Determine how many of the segments actually point to zTerm/nTerm. */
+  for(i=0; i<nSegment; i++){
+    Fts3SegReader *pSeg = pCsr->apSegment[i];
+    if( !pSeg->aNode || fts3SegReaderTermCmp(pSeg, zTerm, nTerm) ){
+      break;
+    }
+  }
+  pCsr->nAdvance = i;
+
+  /* Advance each of the segments to point to the first docid. */
+  for(i=0; i<pCsr->nAdvance; i++){
+    rc = fts3SegReaderFirstDocid(p, pCsr->apSegment[i]);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  fts3SegReaderSort(pCsr->apSegment, i, i, xCmp);
+
+  assert( iCol<0 || iCol<p->nColumn );
+  pCsr->iColFilter = iCol;
+
+  return SQLITE_OK;
+}
+
+/*
+** This function is called on a MultiSegReader that has been started using
+** sqlite3Fts3MsrIncrStart(). One or more calls to MsrIncrNext() may also
+** have been made. Calling this function puts the MultiSegReader in such
+** a state that if the next two calls are:
+**
+**   sqlite3Fts3SegReaderStart()
+**   sqlite3Fts3SegReaderStep()
+**
+** then the entire doclist for the term is available in 
+** MultiSegReader.aDoclist/nDoclist.
+*/
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrRestart(Fts3MultiSegReader *pCsr){
+  int i;                          /* Used to iterate through segment-readers */
+
+  assert( pCsr->zTerm==0 );
+  assert( pCsr->nTerm==0 );
+  assert( pCsr->aDoclist==0 );
+  assert( pCsr->nDoclist==0 );
+
+  pCsr->nAdvance = 0;
+  pCsr->bRestart = 1;
+  for(i=0; i<pCsr->nSegment; i++){
+    pCsr->apSegment[i]->pOffsetList = 0;
+    pCsr->apSegment[i]->nOffsetList = 0;
+    pCsr->apSegment[i]->iDocid = 0;
+  }
+
+  return SQLITE_OK;
+}
+
+
+SQLITE_PRIVATE int sqlite3Fts3SegReaderStep(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr        /* Cursor object */
+){
+  int rc = SQLITE_OK;
+
+  int isIgnoreEmpty =  (pCsr->pFilter->flags & FTS3_SEGMENT_IGNORE_EMPTY);
+  int isRequirePos =   (pCsr->pFilter->flags & FTS3_SEGMENT_REQUIRE_POS);
+  int isColFilter =    (pCsr->pFilter->flags & FTS3_SEGMENT_COLUMN_FILTER);
+  int isPrefix =       (pCsr->pFilter->flags & FTS3_SEGMENT_PREFIX);
+  int isScan =         (pCsr->pFilter->flags & FTS3_SEGMENT_SCAN);
+  int isFirst =        (pCsr->pFilter->flags & FTS3_SEGMENT_FIRST);
+
+  Fts3SegReader **apSegment = pCsr->apSegment;
+  int nSegment = pCsr->nSegment;
+  Fts3SegFilter *pFilter = pCsr->pFilter;
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
+    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
+  );
+
+  if( pCsr->nSegment==0 ) return SQLITE_OK;
+
+  do {
+    int nMerge;
+    int i;
+  
+    /* Advance the first pCsr->nAdvance entries in the apSegment[] array
+    ** forward. Then sort the list in order of current term again.  
+    */
+    for(i=0; i<pCsr->nAdvance; i++){
+      Fts3SegReader *pSeg = apSegment[i];
+      if( pSeg->bLookup ){
+        fts3SegReaderSetEof(pSeg);
+      }else{
+        rc = fts3SegReaderNext(p, pSeg, 0);
+      }
+      if( rc!=SQLITE_OK ) return rc;
+    }
+    fts3SegReaderSort(apSegment, nSegment, pCsr->nAdvance, fts3SegReaderCmp);
+    pCsr->nAdvance = 0;
+
+    /* If all the seg-readers are at EOF, we're finished. return SQLITE_OK. */
+    assert( rc==SQLITE_OK );
+    if( apSegment[0]->aNode==0 ) break;
+
+    pCsr->nTerm = apSegment[0]->nTerm;
+    pCsr->zTerm = apSegment[0]->zTerm;
+
+    /* If this is a prefix-search, and if the term that apSegment[0] points
+    ** to does not share a suffix with pFilter->zTerm/nTerm, then all 
+    ** required callbacks have been made. In this case exit early.
+    **
+    ** Similarly, if this is a search for an exact match, and the first term
+    ** of segment apSegment[0] is not a match, exit early.
+    */
+    if( pFilter->zTerm && !isScan ){
+      if( pCsr->nTerm<pFilter->nTerm 
+       || (!isPrefix && pCsr->nTerm>pFilter->nTerm)
+       || memcmp(pCsr->zTerm, pFilter->zTerm, pFilter->nTerm) 
+      ){
+        break;
+      }
+    }
+
+    nMerge = 1;
+    while( nMerge<nSegment 
+        && apSegment[nMerge]->aNode
+        && apSegment[nMerge]->nTerm==pCsr->nTerm 
+        && 0==memcmp(pCsr->zTerm, apSegment[nMerge]->zTerm, pCsr->nTerm)
+    ){
+      nMerge++;
+    }
+
+    assert( isIgnoreEmpty || (isRequirePos && !isColFilter) );
+    if( nMerge==1 
+     && !isIgnoreEmpty 
+     && !isFirst 
+     && (p->bDescIdx==0 || fts3SegReaderIsPending(apSegment[0])==0)
+    ){
+      pCsr->nDoclist = apSegment[0]->nDoclist;
+      if( fts3SegReaderIsPending(apSegment[0]) ){
+        rc = fts3MsrBufferData(pCsr, apSegment[0]->aDoclist, pCsr->nDoclist);
+        pCsr->aDoclist = pCsr->aBuffer;
+      }else{
+        pCsr->aDoclist = apSegment[0]->aDoclist;
+      }
+      if( rc==SQLITE_OK ) rc = SQLITE_ROW;
+    }else{
+      int nDoclist = 0;           /* Size of doclist */
+      sqlite3_int64 iPrev = 0;    /* Previous docid stored in doclist */
+
+      /* The current term of the first nMerge entries in the array
+      ** of Fts3SegReader objects is the same. The doclists must be merged
+      ** and a single term returned with the merged doclist.
+      */
+      for(i=0; i<nMerge; i++){
+        fts3SegReaderFirstDocid(p, apSegment[i]);
+      }
+      fts3SegReaderSort(apSegment, nMerge, nMerge, xCmp);
+      while( apSegment[0]->pOffsetList ){
+        int j;                    /* Number of segments that share a docid */
+        char *pList = 0;
+        int nList = 0;
+        int nByte;
+        sqlite3_int64 iDocid = apSegment[0]->iDocid;
+        fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
+        j = 1;
+        while( j<nMerge
+            && apSegment[j]->pOffsetList
+            && apSegment[j]->iDocid==iDocid
+        ){
+          fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
+          j++;
+        }
+
+        if( isColFilter ){
+          fts3ColumnFilter(pFilter->iCol, 0, &pList, &nList);
+        }
+
+        if( !isIgnoreEmpty || nList>0 ){
+
+          /* Calculate the 'docid' delta value to write into the merged 
+          ** doclist. */
+          sqlite3_int64 iDelta;
+          if( p->bDescIdx && nDoclist>0 ){
+            iDelta = iPrev - iDocid;
+          }else{
+            iDelta = iDocid - iPrev;
+          }
+          assert( iDelta>0 || (nDoclist==0 && iDelta==iDocid) );
+          assert( nDoclist>0 || iDelta==iDocid );
+
+          nByte = sqlite3Fts3VarintLen(iDelta) + (isRequirePos?nList+1:0);
+          if( nDoclist+nByte>pCsr->nBuffer ){
+            char *aNew;
+            pCsr->nBuffer = (nDoclist+nByte)*2;
+            aNew = sqlite3_realloc(pCsr->aBuffer, pCsr->nBuffer);
+            if( !aNew ){
+              return SQLITE_NOMEM;
+            }
+            pCsr->aBuffer = aNew;
+          }
+
+          if( isFirst ){
+            char *a = &pCsr->aBuffer[nDoclist];
+            int nWrite;
+           
+            nWrite = sqlite3Fts3FirstFilter(iDelta, pList, nList, a);
+            if( nWrite ){
+              iPrev = iDocid;
+              nDoclist += nWrite;
+            }
+          }else{
+            nDoclist += sqlite3Fts3PutVarint(&pCsr->aBuffer[nDoclist], iDelta);
+            iPrev = iDocid;
+            if( isRequirePos ){
+              memcpy(&pCsr->aBuffer[nDoclist], pList, nList);
+              nDoclist += nList;
+              pCsr->aBuffer[nDoclist++] = '\0';
+            }
+          }
+        }
+
+        fts3SegReaderSort(apSegment, nMerge, j, xCmp);
+      }
+      if( nDoclist>0 ){
+        pCsr->aDoclist = pCsr->aBuffer;
+        pCsr->nDoclist = nDoclist;
+        rc = SQLITE_ROW;
+      }
+    }
+    pCsr->nAdvance = nMerge;
+  }while( rc==SQLITE_OK );
+
+  return rc;
+}
+
+
+SQLITE_PRIVATE void sqlite3Fts3SegReaderFinish(
+  Fts3MultiSegReader *pCsr       /* Cursor object */
+){
+  if( pCsr ){
+    int i;
+    for(i=0; i<pCsr->nSegment; i++){
+      sqlite3Fts3SegReaderFree(pCsr->apSegment[i]);
+    }
+    sqlite3_free(pCsr->apSegment);
+    sqlite3_free(pCsr->aBuffer);
+
+    pCsr->nSegment = 0;
+    pCsr->apSegment = 0;
+    pCsr->aBuffer = 0;
+  }
+}
+
+/*
+** Decode the "end_block" field, selected by column iCol of the SELECT 
+** statement passed as the first argument. 
+**
+** The "end_block" field may contain either an integer, or a text field
+** containing the text representation of two non-negative integers separated 
+** by one or more space (0x20) characters. In the first case, set *piEndBlock 
+** to the integer value and *pnByte to zero before returning. In the second, 
+** set *piEndBlock to the first value and *pnByte to the second.
+*/
+static void fts3ReadEndBlockField(
+  sqlite3_stmt *pStmt, 
+  int iCol, 
+  i64 *piEndBlock,
+  i64 *pnByte
+){
+  const unsigned char *zText = sqlite3_column_text(pStmt, iCol);
+  if( zText ){
+    int i;
+    int iMul = 1;
+    i64 iVal = 0;
+    for(i=0; zText[i]>='0' && zText[i]<='9'; i++){
+      iVal = iVal*10 + (zText[i] - '0');
+    }
+    *piEndBlock = iVal;
+    while( zText[i]==' ' ) i++;
+    iVal = 0;
+    if( zText[i]=='-' ){
+      i++;
+      iMul = -1;
+    }
+    for(/* no-op */; zText[i]>='0' && zText[i]<='9'; i++){
+      iVal = iVal*10 + (zText[i] - '0');
+    }
+    *pnByte = (iVal * (i64)iMul);
+  }
+}
+
+
+/*
+** A segment of size nByte bytes has just been written to absolute level
+** iAbsLevel. Promote any segments that should be promoted as a result.
+*/
+static int fts3PromoteSegments(
+  Fts3Table *p,                   /* FTS table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level just updated */
+  sqlite3_int64 nByte             /* Size of new segment at iAbsLevel */
+){
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pRange;
+
+  rc = fts3SqlStmt(p, SQL_SELECT_LEVEL_RANGE2, &pRange, 0);
+
+  if( rc==SQLITE_OK ){
+    int bOk = 0;
+    i64 iLast = (iAbsLevel/FTS3_SEGDIR_MAXLEVEL + 1) * FTS3_SEGDIR_MAXLEVEL - 1;
+    i64 nLimit = (nByte*3)/2;
+
+    /* Loop through all entries in the %_segdir table corresponding to 
+    ** segments in this index on levels greater than iAbsLevel. If there is
+    ** at least one such segment, and it is possible to determine that all 
+    ** such segments are smaller than nLimit bytes in size, they will be 
+    ** promoted to level iAbsLevel.  */
+    sqlite3_bind_int64(pRange, 1, iAbsLevel+1);
+    sqlite3_bind_int64(pRange, 2, iLast);
+    while( SQLITE_ROW==sqlite3_step(pRange) ){
+      i64 nSize = 0, dummy;
+      fts3ReadEndBlockField(pRange, 2, &dummy, &nSize);
+      if( nSize<=0 || nSize>nLimit ){
+        /* If nSize==0, then the %_segdir.end_block field does not not 
+        ** contain a size value. This happens if it was written by an
+        ** old version of FTS. In this case it is not possible to determine
+        ** the size of the segment, and so segment promotion does not
+        ** take place.  */
+        bOk = 0;
+        break;
+      }
+      bOk = 1;
+    }
+    rc = sqlite3_reset(pRange);
+
+    if( bOk ){
+      int iIdx = 0;
+      sqlite3_stmt *pUpdate1 = 0;
+      sqlite3_stmt *pUpdate2 = 0;
+
+      if( rc==SQLITE_OK ){
+        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL_IDX, &pUpdate1, 0);
+      }
+      if( rc==SQLITE_OK ){
+        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL, &pUpdate2, 0);
+      }
+
+      if( rc==SQLITE_OK ){
+
+        /* Loop through all %_segdir entries for segments in this index with
+        ** levels equal to or greater than iAbsLevel. As each entry is visited,
+        ** updated it to set (level = -1) and (idx = N), where N is 0 for the
+        ** oldest segment in the range, 1 for the next oldest, and so on.
+        **
+        ** In other words, move all segments being promoted to level -1,
+        ** setting the "idx" fields as appropriate to keep them in the same
+        ** order. The contents of level -1 (which is never used, except
+        ** transiently here), will be moved back to level iAbsLevel below.  */
+        sqlite3_bind_int64(pRange, 1, iAbsLevel);
+        while( SQLITE_ROW==sqlite3_step(pRange) ){
+          sqlite3_bind_int(pUpdate1, 1, iIdx++);
+          sqlite3_bind_int(pUpdate1, 2, sqlite3_column_int(pRange, 0));
+          sqlite3_bind_int(pUpdate1, 3, sqlite3_column_int(pRange, 1));
+          sqlite3_step(pUpdate1);
+          rc = sqlite3_reset(pUpdate1);
+          if( rc!=SQLITE_OK ){
+            sqlite3_reset(pRange);
+            break;
+          }
+        }
+      }
+      if( rc==SQLITE_OK ){
+        rc = sqlite3_reset(pRange);
+      }
+
+      /* Move level -1 to level iAbsLevel */
+      if( rc==SQLITE_OK ){
+        sqlite3_bind_int64(pUpdate2, 1, iAbsLevel);
+        sqlite3_step(pUpdate2);
+        rc = sqlite3_reset(pUpdate2);
+      }
+    }
+  }
+
+
+  return rc;
+}
+
+/*
+** Merge all level iLevel segments in the database into a single 
+** iLevel+1 segment. Or, if iLevel<0, merge all segments into a
+** single segment with a level equal to the numerically largest level 
+** currently present in the database.
+**
+** If this function is called with iLevel<0, but there is only one
+** segment in the database, SQLITE_DONE is returned immediately. 
+** Otherwise, if successful, SQLITE_OK is returned. If an error occurs, 
+** an SQLite error code is returned.
+*/
+static int fts3SegmentMerge(
+  Fts3Table *p, 
+  int iLangid,                    /* Language id to merge */
+  int iIndex,                     /* Index in p->aIndex[] to merge */
+  int iLevel                      /* Level to merge */
+){
+  int rc;                         /* Return code */
+  int iIdx = 0;                   /* Index of new segment */
+  sqlite3_int64 iNewLevel = 0;    /* Level/index to create new segment at */
+  SegmentWriter *pWriter = 0;     /* Used to write the new, merged, segment */
+  Fts3SegFilter filter;           /* Segment term filter condition */
+  Fts3MultiSegReader csr;         /* Cursor to iterate through level(s) */
+  int bIgnoreEmpty = 0;           /* True to ignore empty segments */
+  i64 iMaxLevel = 0;              /* Max level number for this index/langid */
+
+  assert( iLevel==FTS3_SEGCURSOR_ALL
+       || iLevel==FTS3_SEGCURSOR_PENDING
+       || iLevel>=0
+  );
+  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
+  assert( iIndex>=0 && iIndex<p->nIndex );
+
+  rc = sqlite3Fts3SegReaderCursor(p, iLangid, iIndex, iLevel, 0, 0, 1, 0, &csr);
+  if( rc!=SQLITE_OK || csr.nSegment==0 ) goto finished;
+
+  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
+    rc = fts3SegmentMaxLevel(p, iLangid, iIndex, &iMaxLevel);
+    if( rc!=SQLITE_OK ) goto finished;
+  }
+
+  if( iLevel==FTS3_SEGCURSOR_ALL ){
+    /* This call is to merge all segments in the database to a single
+    ** segment. The level of the new segment is equal to the numerically
+    ** greatest segment level currently present in the database for this
+    ** index. The idx of the new segment is always 0.  */
+    if( csr.nSegment==1 && 0==fts3SegReaderIsPending(csr.apSegment[0]) ){
+      rc = SQLITE_DONE;
+      goto finished;
+    }
+    iNewLevel = iMaxLevel;
+    bIgnoreEmpty = 1;
+
+  }else{
+    /* This call is to merge all segments at level iLevel. find the next
+    ** available segment index at level iLevel+1. The call to
+    ** fts3AllocateSegdirIdx() will merge the segments at level iLevel+1 to 
+    ** a single iLevel+2 segment if necessary.  */
+    assert( FTS3_SEGCURSOR_PENDING==-1 );
+    iNewLevel = getAbsoluteLevel(p, iLangid, iIndex, iLevel+1);
+    rc = fts3AllocateSegdirIdx(p, iLangid, iIndex, iLevel+1, &iIdx);
+    bIgnoreEmpty = (iLevel!=FTS3_SEGCURSOR_PENDING) && (iNewLevel>iMaxLevel);
+  }
+  if( rc!=SQLITE_OK ) goto finished;
+
+  assert( csr.nSegment>0 );
+  assert( iNewLevel>=getAbsoluteLevel(p, iLangid, iIndex, 0) );
+  assert( iNewLevel<getAbsoluteLevel(p, iLangid, iIndex,FTS3_SEGDIR_MAXLEVEL) );
+
+  memset(&filter, 0, sizeof(Fts3SegFilter));
+  filter.flags = FTS3_SEGMENT_REQUIRE_POS;
+  filter.flags |= (bIgnoreEmpty ? FTS3_SEGMENT_IGNORE_EMPTY : 0);
+
+  rc = sqlite3Fts3SegReaderStart(p, &csr, &filter);
+  while( SQLITE_OK==rc ){
+    rc = sqlite3Fts3SegReaderStep(p, &csr);
+    if( rc!=SQLITE_ROW ) break;
+    rc = fts3SegWriterAdd(p, &pWriter, 1, 
+        csr.zTerm, csr.nTerm, csr.aDoclist, csr.nDoclist);
+  }
+  if( rc!=SQLITE_OK ) goto finished;
+  assert( pWriter || bIgnoreEmpty );
+
+  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
+    rc = fts3DeleteSegdir(
+        p, iLangid, iIndex, iLevel, csr.apSegment, csr.nSegment
+    );
+    if( rc!=SQLITE_OK ) goto finished;
+  }
+  if( pWriter ){
+    rc = fts3SegWriterFlush(p, pWriter, iNewLevel, iIdx);
+    if( rc==SQLITE_OK ){
+      if( iLevel==FTS3_SEGCURSOR_PENDING || iNewLevel<iMaxLevel ){
+        rc = fts3PromoteSegments(p, iNewLevel, pWriter->nLeafData);
+      }
+    }
+  }
+
+ finished:
+  fts3SegWriterFree(pWriter);
+  sqlite3Fts3SegReaderFinish(&csr);
+  return rc;
+}
+
+
+/* 
+** Flush the contents of pendingTerms to level 0 segments. 
+*/
+SQLITE_PRIVATE int sqlite3Fts3PendingTermsFlush(Fts3Table *p){
+  int rc = SQLITE_OK;
+  int i;
+        
+  for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
+    rc = fts3SegmentMerge(p, p->iPrevLangid, i, FTS3_SEGCURSOR_PENDING);
+    if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+  }
+  sqlite3Fts3PendingTermsClear(p);
+
+  /* Determine the auto-incr-merge setting if unknown.  If enabled,
+  ** estimate the number of leaf blocks of content to be written
+  */
+  if( rc==SQLITE_OK && p->bHasStat
+   && p->nAutoincrmerge==0xff && p->nLeafAdd>0
+  ){
+    sqlite3_stmt *pStmt = 0;
+    rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int(pStmt, 1, FTS_STAT_AUTOINCRMERGE);
+      rc = sqlite3_step(pStmt);
+      if( rc==SQLITE_ROW ){
+        p->nAutoincrmerge = sqlite3_column_int(pStmt, 0);
+        if( p->nAutoincrmerge==1 ) p->nAutoincrmerge = 8;
+      }else if( rc==SQLITE_DONE ){
+        p->nAutoincrmerge = 0;
+      }
+      rc = sqlite3_reset(pStmt);
+    }
+  }
+  return rc;
+}
+
+/*
+** Encode N integers as varints into a blob.
+*/
+static void fts3EncodeIntArray(
+  int N,             /* The number of integers to encode */
+  u32 *a,            /* The integer values */
+  char *zBuf,        /* Write the BLOB here */
+  int *pNBuf         /* Write number of bytes if zBuf[] used here */
+){
+  int i, j;
+  for(i=j=0; i<N; i++){
+    j += sqlite3Fts3PutVarint(&zBuf[j], (sqlite3_int64)a[i]);
+  }
+  *pNBuf = j;
+}
+
+/*
+** Decode a blob of varints into N integers
+*/
+static void fts3DecodeIntArray(
+  int N,             /* The number of integers to decode */
+  u32 *a,            /* Write the integer values */
+  const char *zBuf,  /* The BLOB containing the varints */
+  int nBuf           /* size of the BLOB */
+){
+  int i, j;
+  UNUSED_PARAMETER(nBuf);
+  for(i=j=0; i<N; i++){
+    sqlite3_int64 x;
+    j += sqlite3Fts3GetVarint(&zBuf[j], &x);
+    assert(j<=nBuf);
+    a[i] = (u32)(x & 0xffffffff);
+  }
+}
+
+/*
+** Insert the sizes (in tokens) for each column of the document
+** with docid equal to p->iPrevDocid.  The sizes are encoded as
+** a blob of varints.
+*/
+static void fts3InsertDocsize(
+  int *pRC,                       /* Result code */
+  Fts3Table *p,                   /* Table into which to insert */
+  u32 *aSz                        /* Sizes of each column, in tokens */
+){
+  char *pBlob;             /* The BLOB encoding of the document size */
+  int nBlob;               /* Number of bytes in the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement used to insert the encoding */
+  int rc;                  /* Result code from subfunctions */
+
+  if( *pRC ) return;
+  pBlob = sqlite3_malloc( 10*p->nColumn );
+  if( pBlob==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  fts3EncodeIntArray(p->nColumn, aSz, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_DOCSIZE, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(pBlob);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_int64(pStmt, 1, p->iPrevDocid);
+  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, sqlite3_free);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+}
+
+/*
+** Record 0 of the %_stat table contains a blob consisting of N varints,
+** where N is the number of user defined columns in the fts3 table plus
+** two. If nCol is the number of user defined columns, then values of the 
+** varints are set as follows:
+**
+**   Varint 0:       Total number of rows in the table.
+**
+**   Varint 1..nCol: For each column, the total number of tokens stored in
+**                   the column for all rows of the table.
+**
+**   Varint 1+nCol:  The total size, in bytes, of all text values in all
+**                   columns of all rows of the table.
+**
+*/
+static void fts3UpdateDocTotals(
+  int *pRC,                       /* The result code */
+  Fts3Table *p,                   /* Table being updated */
+  u32 *aSzIns,                    /* Size increases */
+  u32 *aSzDel,                    /* Size decreases */
+  int nChng                       /* Change in the number of documents */
+){
+  char *pBlob;             /* Storage for BLOB written into %_stat */
+  int nBlob;               /* Size of BLOB written into %_stat */
+  u32 *a;                  /* Array of integers that becomes the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i;                   /* Loop counter */
+  int rc;                  /* Result code from subfunctions */
+
+  const int nStat = p->nColumn+2;
+
+  if( *pRC ) return;
+  a = sqlite3_malloc( (sizeof(u32)+10)*nStat );
+  if( a==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  pBlob = (char*)&a[nStat];
+  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    fts3DecodeIntArray(nStat, a,
+         sqlite3_column_blob(pStmt, 0),
+         sqlite3_column_bytes(pStmt, 0));
+  }else{
+    memset(a, 0, sizeof(u32)*(nStat) );
+  }
+  rc = sqlite3_reset(pStmt);
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  if( nChng<0 && a[0]<(u32)(-nChng) ){
+    a[0] = 0;
+  }else{
+    a[0] += nChng;
+  }
+  for(i=0; i<p->nColumn+1; i++){
+    u32 x = a[i+1];
+    if( x+aSzIns[i] < aSzDel[i] ){
+      x = 0;
+    }else{
+      x = x + aSzIns[i] - aSzDel[i];
+    }
+    a[i+1] = x;
+  }
+  fts3EncodeIntArray(nStat, a, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
+  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, SQLITE_STATIC);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+  sqlite3_free(a);
+}
+
+/*
+** Merge the entire database so that there is one segment for each 
+** iIndex/iLangid combination.
+*/
+static int fts3DoOptimize(Fts3Table *p, int bReturnDone){
+  int bSeenDone = 0;
+  int rc;
+  sqlite3_stmt *pAllLangid = 0;
+
+  rc = fts3SqlStmt(p, SQL_SELECT_ALL_LANGID, &pAllLangid, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;
+    sqlite3_bind_int(pAllLangid, 1, p->iPrevLangid);
+    sqlite3_bind_int(pAllLangid, 2, p->nIndex);
+    while( sqlite3_step(pAllLangid)==SQLITE_ROW ){
+      int i;
+      int iLangid = sqlite3_column_int(pAllLangid, 0);
+      for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
+        rc = fts3SegmentMerge(p, iLangid, i, FTS3_SEGCURSOR_ALL);
+        if( rc==SQLITE_DONE ){
+          bSeenDone = 1;
+          rc = SQLITE_OK;
+        }
+      }
+    }
+    rc2 = sqlite3_reset(pAllLangid);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  sqlite3Fts3SegmentsClose(p);
+  sqlite3Fts3PendingTermsClear(p);
+
+  return (rc==SQLITE_OK && bReturnDone && bSeenDone) ? SQLITE_DONE : rc;
+}
+
+/*
+** This function is called when the user executes the following statement:
+**
+**     INSERT INTO <tbl>(<tbl>) VALUES('rebuild');
+**
+** The entire FTS index is discarded and rebuilt. If the table is one 
+** created using the content=xxx option, then the new index is based on
+** the current contents of the xxx table. Otherwise, it is rebuilt based
+** on the contents of the %_content table.
+*/
+static int fts3DoRebuild(Fts3Table *p){
+  int rc;                         /* Return Code */
+
+  rc = fts3DeleteAll(p, 0);
+  if( rc==SQLITE_OK ){
+    u32 *aSz = 0;
+    u32 *aSzIns = 0;
+    u32 *aSzDel = 0;
+    sqlite3_stmt *pStmt = 0;
+    int nEntry = 0;
+
+    /* Compose and prepare an SQL statement to loop through the content table */
+    char *zSql = sqlite3_mprintf("SELECT %s" , p->zReadExprlist);
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+      sqlite3_free(zSql);
+    }
+
+    if( rc==SQLITE_OK ){
+      int nByte = sizeof(u32) * (p->nColumn+1)*3;
+      aSz = (u32 *)sqlite3_malloc(nByte);
+      if( aSz==0 ){
+        rc = SQLITE_NOMEM;
+      }else{
+        memset(aSz, 0, nByte);
+        aSzIns = &aSz[p->nColumn+1];
+        aSzDel = &aSzIns[p->nColumn+1];
+      }
+    }
+
+    while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      int iCol;
+      int iLangid = langidFromSelect(p, pStmt);
+      rc = fts3PendingTermsDocid(p, 0, iLangid, sqlite3_column_int64(pStmt, 0));
+      memset(aSz, 0, sizeof(aSz[0]) * (p->nColumn+1));
+      for(iCol=0; rc==SQLITE_OK && iCol<p->nColumn; iCol++){
+        if( p->abNotindexed[iCol]==0 ){
+          const char *z = (const char *) sqlite3_column_text(pStmt, iCol+1);
+          rc = fts3PendingTermsAdd(p, iLangid, z, iCol, &aSz[iCol]);
+          aSz[p->nColumn] += sqlite3_column_bytes(pStmt, iCol+1);
+        }
+      }
+      if( p->bHasDocsize ){
+        fts3InsertDocsize(&rc, p, aSz);
+      }
+      if( rc!=SQLITE_OK ){
+        sqlite3_finalize(pStmt);
+        pStmt = 0;
+      }else{
+        nEntry++;
+        for(iCol=0; iCol<=p->nColumn; iCol++){
+          aSzIns[iCol] += aSz[iCol];
+        }
+      }
+    }
+    if( p->bFts4 ){
+      fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nEntry);
+    }
+    sqlite3_free(aSz);
+
+    if( pStmt ){
+      int rc2 = sqlite3_finalize(pStmt);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
+  }
+
+  return rc;
+}
+
+
+/*
+** This function opens a cursor used to read the input data for an 
+** incremental merge operation. Specifically, it opens a cursor to scan
+** the oldest nSeg segments (idx=0 through idx=(nSeg-1)) in absolute 
+** level iAbsLevel.
+*/
+static int fts3IncrmergeCsr(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level to open */
+  int nSeg,                       /* Number of segments to merge */
+  Fts3MultiSegReader *pCsr        /* Cursor object to populate */
+){
+  int rc;                         /* Return Code */
+  sqlite3_stmt *pStmt = 0;        /* Statement used to read %_segdir entry */  
+  int nByte;                      /* Bytes allocated at pCsr->apSegment[] */
+
+  /* Allocate space for the Fts3MultiSegReader.aCsr[] array */
+  memset(pCsr, 0, sizeof(*pCsr));
+  nByte = sizeof(Fts3SegReader *) * nSeg;
+  pCsr->apSegment = (Fts3SegReader **)sqlite3_malloc(nByte);
+
+  if( pCsr->apSegment==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    memset(pCsr->apSegment, 0, nByte);
+    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL, &pStmt, 0);
+  }
+  if( rc==SQLITE_OK ){
+    int i;
+    int rc2;
+    sqlite3_bind_int64(pStmt, 1, iAbsLevel);
+    assert( pCsr->nSegment==0 );
+    for(i=0; rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW && i<nSeg; i++){
+      rc = sqlite3Fts3SegReaderNew(i, 0,
+          sqlite3_column_int64(pStmt, 1),        /* segdir.start_block */
+          sqlite3_column_int64(pStmt, 2),        /* segdir.leaves_end_block */
+          sqlite3_column_int64(pStmt, 3),        /* segdir.end_block */
+          sqlite3_column_blob(pStmt, 4),         /* segdir.root */
+          sqlite3_column_bytes(pStmt, 4),        /* segdir.root */
+          &pCsr->apSegment[i]
+      );
+      pCsr->nSegment++;
+    }
+    rc2 = sqlite3_reset(pStmt);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  return rc;
+}
+
+typedef struct IncrmergeWriter IncrmergeWriter;
+typedef struct NodeWriter NodeWriter;
+typedef struct Blob Blob;
+typedef struct NodeReader NodeReader;
+
+/*
+** An instance of the following structure is used as a dynamic buffer
+** to build up nodes or other blobs of data in.
+**
+** The function blobGrowBuffer() is used to extend the allocation.
+*/
+struct Blob {
+  char *a;                        /* Pointer to allocation */
+  int n;                          /* Number of valid bytes of data in a[] */
+  int nAlloc;                     /* Allocated size of a[] (nAlloc>=n) */
+};
+
+/*
+** This structure is used to build up buffers containing segment b-tree 
+** nodes (blocks).
+*/
+struct NodeWriter {
+  sqlite3_int64 iBlock;           /* Current block id */
+  Blob key;                       /* Last key written to the current block */
+  Blob block;                     /* Current block image */
+};
+
+/*
+** An object of this type contains the state required to create or append
+** to an appendable b-tree segment.
+*/
+struct IncrmergeWriter {
+  int nLeafEst;                   /* Space allocated for leaf blocks */
+  int nWork;                      /* Number of leaf pages flushed */
+  sqlite3_int64 iAbsLevel;        /* Absolute level of input segments */
+  int iIdx;                       /* Index of *output* segment in iAbsLevel+1 */
+  sqlite3_int64 iStart;           /* Block number of first allocated block */
+  sqlite3_int64 iEnd;             /* Block number of last allocated block */
+  sqlite3_int64 nLeafData;        /* Bytes of leaf page data so far */
+  u8 bNoLeafData;                 /* If true, store 0 for segment size */
+  NodeWriter aNodeWriter[FTS_MAX_APPENDABLE_HEIGHT];
+};
+
+/*
+** An object of the following type is used to read data from a single
+** FTS segment node. See the following functions:
+**
+**     nodeReaderInit()
+**     nodeReaderNext()
+**     nodeReaderRelease()
+*/
+struct NodeReader {
+  const char *aNode;
+  int nNode;
+  int iOff;                       /* Current offset within aNode[] */
+
+  /* Output variables. Containing the current node entry. */
+  sqlite3_int64 iChild;           /* Pointer to child node */
+  Blob term;                      /* Current term */
+  const char *aDoclist;           /* Pointer to doclist */
+  int nDoclist;                   /* Size of doclist in bytes */
+};
+
+/*
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
+** Otherwise, if the allocation at pBlob->a is not already at least nMin
+** bytes in size, extend (realloc) it to be so.
+**
+** If an OOM error occurs, set *pRc to SQLITE_NOMEM and leave pBlob->a
+** unmodified. Otherwise, if the allocation succeeds, update pBlob->nAlloc
+** to reflect the new size of the pBlob->a[] buffer.
+*/
+static void blobGrowBuffer(Blob *pBlob, int nMin, int *pRc){
+  if( *pRc==SQLITE_OK && nMin>pBlob->nAlloc ){
+    int nAlloc = nMin;
+    char *a = (char *)sqlite3_realloc(pBlob->a, nAlloc);
+    if( a ){
+      pBlob->nAlloc = nAlloc;
+      pBlob->a = a;
+    }else{
+      *pRc = SQLITE_NOMEM;
+    }
+  }
+}
+
+/*
+** Attempt to advance the node-reader object passed as the first argument to
+** the next entry on the node. 
+**
+** Return an error code if an error occurs (SQLITE_NOMEM is possible). 
+** Otherwise return SQLITE_OK. If there is no next entry on the node
+** (e.g. because the current entry is the last) set NodeReader->aNode to
+** NULL to indicate EOF. Otherwise, populate the NodeReader structure output 
+** variables for the new entry.
+*/
+static int nodeReaderNext(NodeReader *p){
+  int bFirst = (p->term.n==0);    /* True for first term on the node */
+  int nPrefix = 0;                /* Bytes to copy from previous term */
+  int nSuffix = 0;                /* Bytes to append to the prefix */
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( p->aNode );
+  if( p->iChild && bFirst==0 ) p->iChild++;
+  if( p->iOff>=p->nNode ){
+    /* EOF */
+    p->aNode = 0;
+  }else{
+    if( bFirst==0 ){
+      p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nPrefix);
+    }
+    p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nSuffix);
+
+    blobGrowBuffer(&p->term, nPrefix+nSuffix, &rc);
+    if( rc==SQLITE_OK ){
+      memcpy(&p->term.a[nPrefix], &p->aNode[p->iOff], nSuffix);
+      p->term.n = nPrefix+nSuffix;
+      p->iOff += nSuffix;
+      if( p->iChild==0 ){
+        p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &p->nDoclist);
+        p->aDoclist = &p->aNode[p->iOff];
+        p->iOff += p->nDoclist;
+      }
+    }
+  }
+
+  assert( p->iOff<=p->nNode );
+
+  return rc;
+}
+
+/*
+** Release all dynamic resources held by node-reader object *p.
+*/
+static void nodeReaderRelease(NodeReader *p){
+  sqlite3_free(p->term.a);
+}
+
+/*
+** Initialize a node-reader object to read the node in buffer aNode/nNode.
+**
+** If successful, SQLITE_OK is returned and the NodeReader object set to 
+** point to the first entry on the node (if any). Otherwise, an SQLite
+** error code is returned.
+*/
+static int nodeReaderInit(NodeReader *p, const char *aNode, int nNode){
+  memset(p, 0, sizeof(NodeReader));
+  p->aNode = aNode;
+  p->nNode = nNode;
+
+  /* Figure out if this is a leaf or an internal node. */
+  if( p->aNode[0] ){
+    /* An internal node. */
+    p->iOff = 1 + sqlite3Fts3GetVarint(&p->aNode[1], &p->iChild);
+  }else{
+    p->iOff = 1;
+  }
+
+  return nodeReaderNext(p);
+}
+
+/*
+** This function is called while writing an FTS segment each time a leaf o
+** node is finished and written to disk. The key (zTerm/nTerm) is guaranteed
+** to be greater than the largest key on the node just written, but smaller
+** than or equal to the first key that will be written to the next leaf
+** node.
+**
+** The block id of the leaf node just written to disk may be found in
+** (pWriter->aNodeWriter[0].iBlock) when this function is called.
+*/
+static int fts3IncrmergePush(
+  Fts3Table *p,                   /* Fts3 table handle */
+  IncrmergeWriter *pWriter,       /* Writer object */
+  const char *zTerm,              /* Term to write to internal node */
+  int nTerm                       /* Bytes at zTerm */
+){
+  sqlite3_int64 iPtr = pWriter->aNodeWriter[0].iBlock;
+  int iLayer;
+
+  assert( nTerm>0 );
+  for(iLayer=1; ALWAYS(iLayer<FTS_MAX_APPENDABLE_HEIGHT); iLayer++){
+    sqlite3_int64 iNextPtr = 0;
+    NodeWriter *pNode = &pWriter->aNodeWriter[iLayer];
+    int rc = SQLITE_OK;
+    int nPrefix;
+    int nSuffix;
+    int nSpace;
+
+    /* Figure out how much space the key will consume if it is written to
+    ** the current node of layer iLayer. Due to the prefix compression, 
+    ** the space required changes depending on which node the key is to
+    ** be added to.  */
+    nPrefix = fts3PrefixCompress(pNode->key.a, pNode->key.n, zTerm, nTerm);
+    nSuffix = nTerm - nPrefix;
+    nSpace  = sqlite3Fts3VarintLen(nPrefix);
+    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
+
+    if( pNode->key.n==0 || (pNode->block.n + nSpace)<=p->nNodeSize ){ 
+      /* If the current node of layer iLayer contains zero keys, or if adding
+      ** the key to it will not cause it to grow to larger than nNodeSize 
+      ** bytes in size, write the key here.  */
+
+      Blob *pBlk = &pNode->block;
+      if( pBlk->n==0 ){
+        blobGrowBuffer(pBlk, p->nNodeSize, &rc);
+        if( rc==SQLITE_OK ){
+          pBlk->a[0] = (char)iLayer;
+          pBlk->n = 1 + sqlite3Fts3PutVarint(&pBlk->a[1], iPtr);
+        }
+      }
+      blobGrowBuffer(pBlk, pBlk->n + nSpace, &rc);
+      blobGrowBuffer(&pNode->key, nTerm, &rc);
+
+      if( rc==SQLITE_OK ){
+        if( pNode->key.n ){
+          pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nPrefix);
+        }
+        pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nSuffix);
+        memcpy(&pBlk->a[pBlk->n], &zTerm[nPrefix], nSuffix);
+        pBlk->n += nSuffix;
+
+        memcpy(pNode->key.a, zTerm, nTerm);
+        pNode->key.n = nTerm;
+      }
+    }else{
+      /* Otherwise, flush the current node of layer iLayer to disk.
+      ** Then allocate a new, empty sibling node. The key will be written
+      ** into the parent of this node. */
+      rc = fts3WriteSegment(p, pNode->iBlock, pNode->block.a, pNode->block.n);
+
+      assert( pNode->block.nAlloc>=p->nNodeSize );
+      pNode->block.a[0] = (char)iLayer;
+      pNode->block.n = 1 + sqlite3Fts3PutVarint(&pNode->block.a[1], iPtr+1);
+
+      iNextPtr = pNode->iBlock;
+      pNode->iBlock++;
+      pNode->key.n = 0;
+    }
+
+    if( rc!=SQLITE_OK || iNextPtr==0 ) return rc;
+    iPtr = iNextPtr;
+  }
+
+  assert( 0 );
+  return 0;
+}
+
+/*
+** Append a term and (optionally) doclist to the FTS segment node currently
+** stored in blob *pNode. The node need not contain any terms, but the
+** header must be written before this function is called.
+**
+** A node header is a single 0x00 byte for a leaf node, or a height varint
+** followed by the left-hand-child varint for an internal node.
+**
+** The term to be appended is passed via arguments zTerm/nTerm. For a 
+** leaf node, the doclist is passed as aDoclist/nDoclist. For an internal
+** node, both aDoclist and nDoclist must be passed 0.
+**
+** If the size of the value in blob pPrev is zero, then this is the first
+** term written to the node. Otherwise, pPrev contains a copy of the 
+** previous term. Before this function returns, it is updated to contain a
+** copy of zTerm/nTerm.
+**
+** It is assumed that the buffer associated with pNode is already large
+** enough to accommodate the new entry. The buffer associated with pPrev
+** is extended by this function if requrired.
+**
+** If an error (i.e. OOM condition) occurs, an SQLite error code is
+** returned. Otherwise, SQLITE_OK.
+*/
+static int fts3AppendToNode(
+  Blob *pNode,                    /* Current node image to append to */
+  Blob *pPrev,                    /* Buffer containing previous term written */
+  const char *zTerm,              /* New term to write */
+  int nTerm,                      /* Size of zTerm in bytes */
+  const char *aDoclist,           /* Doclist (or NULL) to write */
+  int nDoclist                    /* Size of aDoclist in bytes */ 
+){
+  int rc = SQLITE_OK;             /* Return code */
+  int bFirst = (pPrev->n==0);     /* True if this is the first term written */
+  int nPrefix;                    /* Size of term prefix in bytes */
+  int nSuffix;                    /* Size of term suffix in bytes */
+
+  /* Node must have already been started. There must be a doclist for a
+  ** leaf node, and there must not be a doclist for an internal node.  */
+  assert( pNode->n>0 );
+  assert( (pNode->a[0]=='\0')==(aDoclist!=0) );
+
+  blobGrowBuffer(pPrev, nTerm, &rc);
+  if( rc!=SQLITE_OK ) return rc;
+
+  nPrefix = fts3PrefixCompress(pPrev->a, pPrev->n, zTerm, nTerm);
+  nSuffix = nTerm - nPrefix;
+  memcpy(pPrev->a, zTerm, nTerm);
+  pPrev->n = nTerm;
+
+  if( bFirst==0 ){
+    pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nPrefix);
+  }
+  pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nSuffix);
+  memcpy(&pNode->a[pNode->n], &zTerm[nPrefix], nSuffix);
+  pNode->n += nSuffix;
+
+  if( aDoclist ){
+    pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nDoclist);
+    memcpy(&pNode->a[pNode->n], aDoclist, nDoclist);
+    pNode->n += nDoclist;
+  }
+
+  assert( pNode->n<=pNode->nAlloc );
+
+  return SQLITE_OK;
+}
+
+/*
+** Append the current term and doclist pointed to by cursor pCsr to the
+** appendable b-tree segment opened for writing by pWriter.
+**
+** Return SQLITE_OK if successful, or an SQLite error code otherwise.
+*/
+static int fts3IncrmergeAppend(
+  Fts3Table *p,                   /* Fts3 table handle */
+  IncrmergeWriter *pWriter,       /* Writer object */
+  Fts3MultiSegReader *pCsr        /* Cursor containing term and doclist */
+){
+  const char *zTerm = pCsr->zTerm;
+  int nTerm = pCsr->nTerm;
+  const char *aDoclist = pCsr->aDoclist;
+  int nDoclist = pCsr->nDoclist;
+  int rc = SQLITE_OK;           /* Return code */
+  int nSpace;                   /* Total space in bytes required on leaf */
+  int nPrefix;                  /* Size of prefix shared with previous term */
+  int nSuffix;                  /* Size of suffix (nTerm - nPrefix) */
+  NodeWriter *pLeaf;            /* Object used to write leaf nodes */
+
+  pLeaf = &pWriter->aNodeWriter[0];
+  nPrefix = fts3PrefixCompress(pLeaf->key.a, pLeaf->key.n, zTerm, nTerm);
+  nSuffix = nTerm - nPrefix;
+
+  nSpace  = sqlite3Fts3VarintLen(nPrefix);
+  nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
+  nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
+
+  /* If the current block is not empty, and if adding this term/doclist
+  ** to the current block would make it larger than Fts3Table.nNodeSize
+  ** bytes, write this block out to the database. */
+  if( pLeaf->block.n>0 && (pLeaf->block.n + nSpace)>p->nNodeSize ){
+    rc = fts3WriteSegment(p, pLeaf->iBlock, pLeaf->block.a, pLeaf->block.n);
+    pWriter->nWork++;
+
+    /* Add the current term to the parent node. The term added to the 
+    ** parent must:
+    **
+    **   a) be greater than the largest term on the leaf node just written
+    **      to the database (still available in pLeaf->key), and
+    **
+    **   b) be less than or equal to the term about to be added to the new
+    **      leaf node (zTerm/nTerm).
+    **
+    ** In other words, it must be the prefix of zTerm 1 byte longer than
+    ** the common prefix (if any) of zTerm and pWriter->zTerm.
+    */
+    if( rc==SQLITE_OK ){
+      rc = fts3IncrmergePush(p, pWriter, zTerm, nPrefix+1);
+    }
+
+    /* Advance to the next output block */
+    pLeaf->iBlock++;
+    pLeaf->key.n = 0;
+    pLeaf->block.n = 0;
+
+    nSuffix = nTerm;
+    nSpace  = 1;
+    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
+    nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
+  }
+
+  pWriter->nLeafData += nSpace;
+  blobGrowBuffer(&pLeaf->block, pLeaf->block.n + nSpace, &rc);
+  if( rc==SQLITE_OK ){
+    if( pLeaf->block.n==0 ){
+      pLeaf->block.n = 1;
+      pLeaf->block.a[0] = '\0';
+    }
+    rc = fts3AppendToNode(
+        &pLeaf->block, &pLeaf->key, zTerm, nTerm, aDoclist, nDoclist
+    );
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to release all dynamic resources held by the
+** merge-writer object pWriter, and if no error has occurred, to flush
+** all outstanding node buffers held by pWriter to disk.
+**
+** If *pRc is not SQLITE_OK when this function is called, then no attempt
+** is made to write any data to disk. Instead, this function serves only
+** to release outstanding resources.
+**
+** Otherwise, if *pRc is initially SQLITE_OK and an error occurs while
+** flushing buffers to disk, *pRc is set to an SQLite error code before
+** returning.
+*/
+static void fts3IncrmergeRelease(
+  Fts3Table *p,                   /* FTS3 table handle */
+  IncrmergeWriter *pWriter,       /* Merge-writer object */
+  int *pRc                        /* IN/OUT: Error code */
+){
+  int i;                          /* Used to iterate through non-root layers */
+  int iRoot;                      /* Index of root in pWriter->aNodeWriter */
+  NodeWriter *pRoot;              /* NodeWriter for root node */
+  int rc = *pRc;                  /* Error code */
+
+  /* Set iRoot to the index in pWriter->aNodeWriter[] of the output segment 
+  ** root node. If the segment fits entirely on a single leaf node, iRoot
+  ** will be set to 0. If the root node is the parent of the leaves, iRoot
+  ** will be 1. And so on.  */
+  for(iRoot=FTS_MAX_APPENDABLE_HEIGHT-1; iRoot>=0; iRoot--){
+    NodeWriter *pNode = &pWriter->aNodeWriter[iRoot];
+    if( pNode->block.n>0 ) break;
+    assert( *pRc || pNode->block.nAlloc==0 );
+    assert( *pRc || pNode->key.nAlloc==0 );
+    sqlite3_free(pNode->block.a);
+    sqlite3_free(pNode->key.a);
+  }
+
+  /* Empty output segment. This is a no-op. */
+  if( iRoot<0 ) return;
+
+  /* The entire output segment fits on a single node. Normally, this means
+  ** the node would be stored as a blob in the "root" column of the %_segdir
+  ** table. However, this is not permitted in this case. The problem is that 
+  ** space has already been reserved in the %_segments table, and so the 
+  ** start_block and end_block fields of the %_segdir table must be populated. 
+  ** And, by design or by accident, released versions of FTS cannot handle 
+  ** segments that fit entirely on the root node with start_block!=0.
+  **
+  ** Instead, create a synthetic root node that contains nothing but a 
+  ** pointer to the single content node. So that the segment consists of a
+  ** single leaf and a single interior (root) node.
+  **
+  ** Todo: Better might be to defer allocating space in the %_segments 
+  ** table until we are sure it is needed.
+  */
+  if( iRoot==0 ){
+    Blob *pBlock = &pWriter->aNodeWriter[1].block;
+    blobGrowBuffer(pBlock, 1 + FTS3_VARINT_MAX, &rc);
+    if( rc==SQLITE_OK ){
+      pBlock->a[0] = 0x01;
+      pBlock->n = 1 + sqlite3Fts3PutVarint(
+          &pBlock->a[1], pWriter->aNodeWriter[0].iBlock
+      );
+    }
+    iRoot = 1;
+  }
+  pRoot = &pWriter->aNodeWriter[iRoot];
+
+  /* Flush all currently outstanding nodes to disk. */
+  for(i=0; i<iRoot; i++){
+    NodeWriter *pNode = &pWriter->aNodeWriter[i];
+    if( pNode->block.n>0 && rc==SQLITE_OK ){
+      rc = fts3WriteSegment(p, pNode->iBlock, pNode->block.a, pNode->block.n);
+    }
+    sqlite3_free(pNode->block.a);
+    sqlite3_free(pNode->key.a);
+  }
+
+  /* Write the %_segdir record. */
+  if( rc==SQLITE_OK ){
+    rc = fts3WriteSegdir(p, 
+        pWriter->iAbsLevel+1,               /* level */
+        pWriter->iIdx,                      /* idx */
+        pWriter->iStart,                    /* start_block */
+        pWriter->aNodeWriter[0].iBlock,     /* leaves_end_block */
+        pWriter->iEnd,                      /* end_block */
+        (pWriter->bNoLeafData==0 ? pWriter->nLeafData : 0),   /* end_block */
+        pRoot->block.a, pRoot->block.n      /* root */
+    );
+  }
+  sqlite3_free(pRoot->block.a);
+  sqlite3_free(pRoot->key.a);
+
+  *pRc = rc;
+}
+
+/*
+** Compare the term in buffer zLhs (size in bytes nLhs) with that in
+** zRhs (size in bytes nRhs) using memcmp. If one term is a prefix of
+** the other, it is considered to be smaller than the other.
+**
+** Return -ve if zLhs is smaller than zRhs, 0 if it is equal, or +ve
+** if it is greater.
+*/
+static int fts3TermCmp(
+  const char *zLhs, int nLhs,     /* LHS of comparison */
+  const char *zRhs, int nRhs      /* RHS of comparison */
+){
+  int nCmp = MIN(nLhs, nRhs);
+  int res;
+
+  res = memcmp(zLhs, zRhs, nCmp);
+  if( res==0 ) res = nLhs - nRhs;
+
+  return res;
+}
+
+
+/*
+** Query to see if the entry in the %_segments table with blockid iEnd is 
+** NULL. If no error occurs and the entry is NULL, set *pbRes 1 before
+** returning. Otherwise, set *pbRes to 0. 
+**
+** Or, if an error occurs while querying the database, return an SQLite 
+** error code. The final value of *pbRes is undefined in this case.
+**
+** This is used to test if a segment is an "appendable" segment. If it
+** is, then a NULL entry has been inserted into the %_segments table
+** with blockid %_segdir.end_block.
+*/
+static int fts3IsAppendable(Fts3Table *p, sqlite3_int64 iEnd, int *pbRes){
+  int bRes = 0;                   /* Result to set *pbRes to */
+  sqlite3_stmt *pCheck = 0;       /* Statement to query database with */
+  int rc;                         /* Return code */
+
+  rc = fts3SqlStmt(p, SQL_SEGMENT_IS_APPENDABLE, &pCheck, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pCheck, 1, iEnd);
+    if( SQLITE_ROW==sqlite3_step(pCheck) ) bRes = 1;
+    rc = sqlite3_reset(pCheck);
+  }
+  
+  *pbRes = bRes;
+  return rc;
+}
+
+/*
+** This function is called when initializing an incremental-merge operation.
+** It checks if the existing segment with index value iIdx at absolute level 
+** (iAbsLevel+1) can be appended to by the incremental merge. If it can, the
+** merge-writer object *pWriter is initialized to write to it.
+**
+** An existing segment can be appended to by an incremental merge if:
+**
+**   * It was initially created as an appendable segment (with all required
+**     space pre-allocated), and
+**
+**   * The first key read from the input (arguments zKey and nKey) is 
+**     greater than the largest key currently stored in the potential
+**     output segment.
+*/
+static int fts3IncrmergeLoad(
+  Fts3Table *p,                   /* Fts3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level of input segments */
+  int iIdx,                       /* Index of candidate output segment */
+  const char *zKey,               /* First key to write */
+  int nKey,                       /* Number of bytes in nKey */
+  IncrmergeWriter *pWriter        /* Populate this object */
+){
+  int rc;                         /* Return code */
+  sqlite3_stmt *pSelect = 0;      /* SELECT to read %_segdir entry */
+
+  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR, &pSelect, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_int64 iStart = 0;     /* Value of %_segdir.start_block */
+    sqlite3_int64 iLeafEnd = 0;   /* Value of %_segdir.leaves_end_block */
+    sqlite3_int64 iEnd = 0;       /* Value of %_segdir.end_block */
+    const char *aRoot = 0;        /* Pointer to %_segdir.root buffer */
+    int nRoot = 0;                /* Size of aRoot[] in bytes */
+    int rc2;                      /* Return code from sqlite3_reset() */
+    int bAppendable = 0;          /* Set to true if segment is appendable */
+
+    /* Read the %_segdir entry for index iIdx absolute level (iAbsLevel+1) */
+    sqlite3_bind_int64(pSelect, 1, iAbsLevel+1);
+    sqlite3_bind_int(pSelect, 2, iIdx);
+    if( sqlite3_step(pSelect)==SQLITE_ROW ){
+      iStart = sqlite3_column_int64(pSelect, 1);
+      iLeafEnd = sqlite3_column_int64(pSelect, 2);
+      fts3ReadEndBlockField(pSelect, 3, &iEnd, &pWriter->nLeafData);
+      if( pWriter->nLeafData<0 ){
+        pWriter->nLeafData = pWriter->nLeafData * -1;
+      }
+      pWriter->bNoLeafData = (pWriter->nLeafData==0);
+      nRoot = sqlite3_column_bytes(pSelect, 4);
+      aRoot = sqlite3_column_blob(pSelect, 4);
+    }else{
+      return sqlite3_reset(pSelect);
+    }
+
+    /* Check for the zero-length marker in the %_segments table */
+    rc = fts3IsAppendable(p, iEnd, &bAppendable);
+
+    /* Check that zKey/nKey is larger than the largest key the candidate */
+    if( rc==SQLITE_OK && bAppendable ){
+      char *aLeaf = 0;
+      int nLeaf = 0;
+
+      rc = sqlite3Fts3ReadBlock(p, iLeafEnd, &aLeaf, &nLeaf, 0);
+      if( rc==SQLITE_OK ){
+        NodeReader reader;
+        for(rc = nodeReaderInit(&reader, aLeaf, nLeaf);
+            rc==SQLITE_OK && reader.aNode;
+            rc = nodeReaderNext(&reader)
+        ){
+          assert( reader.aNode );
+        }
+        if( fts3TermCmp(zKey, nKey, reader.term.a, reader.term.n)<=0 ){
+          bAppendable = 0;
+        }
+        nodeReaderRelease(&reader);
+      }
+      sqlite3_free(aLeaf);
+    }
+
+    if( rc==SQLITE_OK && bAppendable ){
+      /* It is possible to append to this segment. Set up the IncrmergeWriter
+      ** object to do so.  */
+      int i;
+      int nHeight = (int)aRoot[0];
+      NodeWriter *pNode;
+
+      pWriter->nLeafEst = (int)((iEnd - iStart) + 1)/FTS_MAX_APPENDABLE_HEIGHT;
+      pWriter->iStart = iStart;
+      pWriter->iEnd = iEnd;
+      pWriter->iAbsLevel = iAbsLevel;
+      pWriter->iIdx = iIdx;
+
+      for(i=nHeight+1; i<FTS_MAX_APPENDABLE_HEIGHT; i++){
+        pWriter->aNodeWriter[i].iBlock = pWriter->iStart + i*pWriter->nLeafEst;
+      }
+
+      pNode = &pWriter->aNodeWriter[nHeight];
+      pNode->iBlock = pWriter->iStart + pWriter->nLeafEst*nHeight;
+      blobGrowBuffer(&pNode->block, MAX(nRoot, p->nNodeSize), &rc);
+      if( rc==SQLITE_OK ){
+        memcpy(pNode->block.a, aRoot, nRoot);
+        pNode->block.n = nRoot;
+      }
+
+      for(i=nHeight; i>=0 && rc==SQLITE_OK; i--){
+        NodeReader reader;
+        pNode = &pWriter->aNodeWriter[i];
+
+        rc = nodeReaderInit(&reader, pNode->block.a, pNode->block.n);
+        while( reader.aNode && rc==SQLITE_OK ) rc = nodeReaderNext(&reader);
+        blobGrowBuffer(&pNode->key, reader.term.n, &rc);
+        if( rc==SQLITE_OK ){
+          memcpy(pNode->key.a, reader.term.a, reader.term.n);
+          pNode->key.n = reader.term.n;
+          if( i>0 ){
+            char *aBlock = 0;
+            int nBlock = 0;
+            pNode = &pWriter->aNodeWriter[i-1];
+            pNode->iBlock = reader.iChild;
+            rc = sqlite3Fts3ReadBlock(p, reader.iChild, &aBlock, &nBlock, 0);
+            blobGrowBuffer(&pNode->block, MAX(nBlock, p->nNodeSize), &rc);
+            if( rc==SQLITE_OK ){
+              memcpy(pNode->block.a, aBlock, nBlock);
+              pNode->block.n = nBlock;
+            }
+            sqlite3_free(aBlock);
+          }
+        }
+        nodeReaderRelease(&reader);
+      }
+    }
+
+    rc2 = sqlite3_reset(pSelect);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  return rc;
+}
+
+/*
+** Determine the largest segment index value that exists within absolute
+** level iAbsLevel+1. If no error occurs, set *piIdx to this value plus
+** one before returning SQLITE_OK. Or, if there are no segments at all 
+** within level iAbsLevel, set *piIdx to zero.
+**
+** If an error occurs, return an SQLite error code. The final value of
+** *piIdx is undefined in this case.
+*/
+static int fts3IncrmergeOutputIdx( 
+  Fts3Table *p,                   /* FTS Table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute index of input segments */
+  int *piIdx                      /* OUT: Next free index at iAbsLevel+1 */
+){
+  int rc;
+  sqlite3_stmt *pOutputIdx = 0;   /* SQL used to find output index */
+
+  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENT_INDEX, &pOutputIdx, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pOutputIdx, 1, iAbsLevel+1);
+    sqlite3_step(pOutputIdx);
+    *piIdx = sqlite3_column_int(pOutputIdx, 0);
+    rc = sqlite3_reset(pOutputIdx);
+  }
+
+  return rc;
+}
+
+/* 
+** Allocate an appendable output segment on absolute level iAbsLevel+1
+** with idx value iIdx.
+**
+** In the %_segdir table, a segment is defined by the values in three
+** columns:
+**
+**     start_block
+**     leaves_end_block
+**     end_block
+**
+** When an appendable segment is allocated, it is estimated that the
+** maximum number of leaf blocks that may be required is the sum of the
+** number of leaf blocks consumed by the input segments, plus the number
+** of input segments, multiplied by two. This value is stored in stack 
+** variable nLeafEst.
+**
+** A total of 16*nLeafEst blocks are allocated when an appendable segment
+** is created ((1 + end_block - start_block)==16*nLeafEst). The contiguous
+** array of leaf nodes starts at the first block allocated. The array
+** of interior nodes that are parents of the leaf nodes start at block
+** (start_block + (1 + end_block - start_block) / 16). And so on.
+**
+** In the actual code below, the value "16" is replaced with the 
+** pre-processor macro FTS_MAX_APPENDABLE_HEIGHT.
+*/
+static int fts3IncrmergeWriter( 
+  Fts3Table *p,                   /* Fts3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level of input segments */
+  int iIdx,                       /* Index of new output segment */
+  Fts3MultiSegReader *pCsr,       /* Cursor that data will be read from */
+  IncrmergeWriter *pWriter        /* Populate this object */
+){
+  int rc;                         /* Return Code */
+  int i;                          /* Iterator variable */
+  int nLeafEst = 0;               /* Blocks allocated for leaf nodes */
+  sqlite3_stmt *pLeafEst = 0;     /* SQL used to determine nLeafEst */
+  sqlite3_stmt *pFirstBlock = 0;  /* SQL used to determine first block */
+
+  /* Calculate nLeafEst. */
+  rc = fts3SqlStmt(p, SQL_MAX_LEAF_NODE_ESTIMATE, &pLeafEst, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pLeafEst, 1, iAbsLevel);
+    sqlite3_bind_int64(pLeafEst, 2, pCsr->nSegment);
+    if( SQLITE_ROW==sqlite3_step(pLeafEst) ){
+      nLeafEst = sqlite3_column_int(pLeafEst, 0);
+    }
+    rc = sqlite3_reset(pLeafEst);
+  }
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Calculate the first block to use in the output segment */
+  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENTS_ID, &pFirstBlock, 0);
+  if( rc==SQLITE_OK ){
+    if( SQLITE_ROW==sqlite3_step(pFirstBlock) ){
+      pWriter->iStart = sqlite3_column_int64(pFirstBlock, 0);
+      pWriter->iEnd = pWriter->iStart - 1;
+      pWriter->iEnd += nLeafEst * FTS_MAX_APPENDABLE_HEIGHT;
+    }
+    rc = sqlite3_reset(pFirstBlock);
+  }
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Insert the marker in the %_segments table to make sure nobody tries
+  ** to steal the space just allocated. This is also used to identify 
+  ** appendable segments.  */
+  rc = fts3WriteSegment(p, pWriter->iEnd, 0, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  pWriter->iAbsLevel = iAbsLevel;
+  pWriter->nLeafEst = nLeafEst;
+  pWriter->iIdx = iIdx;
+
+  /* Set up the array of NodeWriter objects */
+  for(i=0; i<FTS_MAX_APPENDABLE_HEIGHT; i++){
+    pWriter->aNodeWriter[i].iBlock = pWriter->iStart + i*pWriter->nLeafEst;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Remove an entry from the %_segdir table. This involves running the 
+** following two statements:
+**
+**   DELETE FROM %_segdir WHERE level = :iAbsLevel AND idx = :iIdx
+**   UPDATE %_segdir SET idx = idx - 1 WHERE level = :iAbsLevel AND idx > :iIdx
+**
+** The DELETE statement removes the specific %_segdir level. The UPDATE 
+** statement ensures that the remaining segments have contiguously allocated
+** idx values.
+*/
+static int fts3RemoveSegdirEntry(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level to delete from */
+  int iIdx                        /* Index of %_segdir entry to delete */
+){
+  int rc;                         /* Return code */
+  sqlite3_stmt *pDelete = 0;      /* DELETE statement */
+
+  rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_ENTRY, &pDelete, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pDelete, 1, iAbsLevel);
+    sqlite3_bind_int(pDelete, 2, iIdx);
+    sqlite3_step(pDelete);
+    rc = sqlite3_reset(pDelete);
+  }
+
+  return rc;
+}
+
+/*
+** One or more segments have just been removed from absolute level iAbsLevel.
+** Update the 'idx' values of the remaining segments in the level so that
+** the idx values are a contiguous sequence starting from 0.
+*/
+static int fts3RepackSegdirLevel(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel         /* Absolute level to repack */
+){
+  int rc;                         /* Return code */
+  int *aIdx = 0;                  /* Array of remaining idx values */
+  int nIdx = 0;                   /* Valid entries in aIdx[] */
+  int nAlloc = 0;                 /* Allocated size of aIdx[] */
+  int i;                          /* Iterator variable */
+  sqlite3_stmt *pSelect = 0;      /* Select statement to read idx values */
+  sqlite3_stmt *pUpdate = 0;      /* Update statement to modify idx values */
+
+  rc = fts3SqlStmt(p, SQL_SELECT_INDEXES, &pSelect, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;
+    sqlite3_bind_int64(pSelect, 1, iAbsLevel);
+    while( SQLITE_ROW==sqlite3_step(pSelect) ){
+      if( nIdx>=nAlloc ){
+        int *aNew;
+        nAlloc += 16;
+        aNew = sqlite3_realloc(aIdx, nAlloc*sizeof(int));
+        if( !aNew ){
+          rc = SQLITE_NOMEM;
+          break;
+        }
+        aIdx = aNew;
+      }
+      aIdx[nIdx++] = sqlite3_column_int(pSelect, 0);
+    }
+    rc2 = sqlite3_reset(pSelect);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = fts3SqlStmt(p, SQL_SHIFT_SEGDIR_ENTRY, &pUpdate, 0);
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pUpdate, 2, iAbsLevel);
+  }
+
+  assert( p->bIgnoreSavepoint==0 );
+  p->bIgnoreSavepoint = 1;
+  for(i=0; rc==SQLITE_OK && i<nIdx; i++){
+    if( aIdx[i]!=i ){
+      sqlite3_bind_int(pUpdate, 3, aIdx[i]);
+      sqlite3_bind_int(pUpdate, 1, i);
+      sqlite3_step(pUpdate);
+      rc = sqlite3_reset(pUpdate);
+    }
+  }
+  p->bIgnoreSavepoint = 0;
+
+  sqlite3_free(aIdx);
+  return rc;
+}
+
+static void fts3StartNode(Blob *pNode, int iHeight, sqlite3_int64 iChild){
+  pNode->a[0] = (char)iHeight;
+  if( iChild ){
+    assert( pNode->nAlloc>=1+sqlite3Fts3VarintLen(iChild) );
+    pNode->n = 1 + sqlite3Fts3PutVarint(&pNode->a[1], iChild);
+  }else{
+    assert( pNode->nAlloc>=1 );
+    pNode->n = 1;
+  }
+}
+
+/*
+** The first two arguments are a pointer to and the size of a segment b-tree
+** node. The node may be a leaf or an internal node.
+**
+** This function creates a new node image in blob object *pNew by copying
+** all terms that are greater than or equal to zTerm/nTerm (for leaf nodes)
+** or greater than zTerm/nTerm (for internal nodes) from aNode/nNode.
+*/
+static int fts3TruncateNode(
+  const char *aNode,              /* Current node image */
+  int nNode,                      /* Size of aNode in bytes */
+  Blob *pNew,                     /* OUT: Write new node image here */
+  const char *zTerm,              /* Omit all terms smaller than this */
+  int nTerm,                      /* Size of zTerm in bytes */
+  sqlite3_int64 *piBlock          /* OUT: Block number in next layer down */
+){
+  NodeReader reader;              /* Reader object */
+  Blob prev = {0, 0, 0};          /* Previous term written to new node */
+  int rc = SQLITE_OK;             /* Return code */
+  int bLeaf = aNode[0]=='\0';     /* True for a leaf node */
+
+  /* Allocate required output space */
+  blobGrowBuffer(pNew, nNode, &rc);
+  if( rc!=SQLITE_OK ) return rc;
+  pNew->n = 0;
+
+  /* Populate new node buffer */
+  for(rc = nodeReaderInit(&reader, aNode, nNode); 
+      rc==SQLITE_OK && reader.aNode; 
+      rc = nodeReaderNext(&reader)
+  ){
+    if( pNew->n==0 ){
+      int res = fts3TermCmp(reader.term.a, reader.term.n, zTerm, nTerm);
+      if( res<0 || (bLeaf==0 && res==0) ) continue;
+      fts3StartNode(pNew, (int)aNode[0], reader.iChild);
+      *piBlock = reader.iChild;
+    }
+    rc = fts3AppendToNode(
+        pNew, &prev, reader.term.a, reader.term.n,
+        reader.aDoclist, reader.nDoclist
+    );
+    if( rc!=SQLITE_OK ) break;
+  }
+  if( pNew->n==0 ){
+    fts3StartNode(pNew, (int)aNode[0], reader.iChild);
+    *piBlock = reader.iChild;
+  }
+  assert( pNew->n<=pNew->nAlloc );
+
+  nodeReaderRelease(&reader);
+  sqlite3_free(prev.a);
+  return rc;
+}
+
+/*
+** Remove all terms smaller than zTerm/nTerm from segment iIdx in absolute 
+** level iAbsLevel. This may involve deleting entries from the %_segments
+** table, and modifying existing entries in both the %_segments and %_segdir
+** tables.
+**
+** SQLITE_OK is returned if the segment is updated successfully. Or an
+** SQLite error code otherwise.
+*/
+static int fts3TruncateSegment(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level of segment to modify */
+  int iIdx,                       /* Index within level of segment to modify */
+  const char *zTerm,              /* Remove terms smaller than this */
+  int nTerm                      /* Number of bytes in buffer zTerm */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  Blob root = {0,0,0};            /* New root page image */
+  Blob block = {0,0,0};           /* Buffer used for any other block */
+  sqlite3_int64 iBlock = 0;       /* Block id */
+  sqlite3_int64 iNewStart = 0;    /* New value for iStartBlock */
+  sqlite3_int64 iOldStart = 0;    /* Old value for iStartBlock */
+  sqlite3_stmt *pFetch = 0;       /* Statement used to fetch segdir */
+
+  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR, &pFetch, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;                      /* sqlite3_reset() return code */
+    sqlite3_bind_int64(pFetch, 1, iAbsLevel);
+    sqlite3_bind_int(pFetch, 2, iIdx);
+    if( SQLITE_ROW==sqlite3_step(pFetch) ){
+      const char *aRoot = sqlite3_column_blob(pFetch, 4);
+      int nRoot = sqlite3_column_bytes(pFetch, 4);
+      iOldStart = sqlite3_column_int64(pFetch, 1);
+      rc = fts3TruncateNode(aRoot, nRoot, &root, zTerm, nTerm, &iBlock);
+    }
+    rc2 = sqlite3_reset(pFetch);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  while( rc==SQLITE_OK && iBlock ){
+    char *aBlock = 0;
+    int nBlock = 0;
+    iNewStart = iBlock;
+
+    rc = sqlite3Fts3ReadBlock(p, iBlock, &aBlock, &nBlock, 0);
+    if( rc==SQLITE_OK ){
+      rc = fts3TruncateNode(aBlock, nBlock, &block, zTerm, nTerm, &iBlock);
+    }
+    if( rc==SQLITE_OK ){
+      rc = fts3WriteSegment(p, iNewStart, block.a, block.n);
+    }
+    sqlite3_free(aBlock);
+  }
+
+  /* Variable iNewStart now contains the first valid leaf node. */
+  if( rc==SQLITE_OK && iNewStart ){
+    sqlite3_stmt *pDel = 0;
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGMENTS_RANGE, &pDel, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pDel, 1, iOldStart);
+      sqlite3_bind_int64(pDel, 2, iNewStart-1);
+      sqlite3_step(pDel);
+      rc = sqlite3_reset(pDel);
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    sqlite3_stmt *pChomp = 0;
+    rc = fts3SqlStmt(p, SQL_CHOMP_SEGDIR, &pChomp, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pChomp, 1, iNewStart);
+      sqlite3_bind_blob(pChomp, 2, root.a, root.n, SQLITE_STATIC);
+      sqlite3_bind_int64(pChomp, 3, iAbsLevel);
+      sqlite3_bind_int(pChomp, 4, iIdx);
+      sqlite3_step(pChomp);
+      rc = sqlite3_reset(pChomp);
+    }
+  }
+
+  sqlite3_free(root.a);
+  sqlite3_free(block.a);
+  return rc;
+}
+
+/*
+** This function is called after an incrmental-merge operation has run to
+** merge (or partially merge) two or more segments from absolute level
+** iAbsLevel.
+**
+** Each input segment is either removed from the db completely (if all of
+** its data was copied to the output segment by the incrmerge operation)
+** or modified in place so that it no longer contains those entries that
+** have been duplicated in the output segment.
+*/
+static int fts3IncrmergeChomp(
+  Fts3Table *p,                   /* FTS table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level containing segments */
+  Fts3MultiSegReader *pCsr,       /* Chomp all segments opened by this cursor */
+  int *pnRem                      /* Number of segments not deleted */
+){
+  int i;
+  int nRem = 0;
+  int rc = SQLITE_OK;
+
+  for(i=pCsr->nSegment-1; i>=0 && rc==SQLITE_OK; i--){
+    Fts3SegReader *pSeg = 0;
+    int j;
+
+    /* Find the Fts3SegReader object with Fts3SegReader.iIdx==i. It is hiding
+    ** somewhere in the pCsr->apSegment[] array.  */
+    for(j=0; ALWAYS(j<pCsr->nSegment); j++){
+      pSeg = pCsr->apSegment[j];
+      if( pSeg->iIdx==i ) break;
+    }
+    assert( j<pCsr->nSegment && pSeg->iIdx==i );
+
+    if( pSeg->aNode==0 ){
+      /* Seg-reader is at EOF. Remove the entire input segment. */
+      rc = fts3DeleteSegment(p, pSeg);
+      if( rc==SQLITE_OK ){
+        rc = fts3RemoveSegdirEntry(p, iAbsLevel, pSeg->iIdx);
+      }
+      *pnRem = 0;
+    }else{
+      /* The incremental merge did not copy all the data from this 
+      ** segment to the upper level. The segment is modified in place
+      ** so that it contains no keys smaller than zTerm/nTerm. */ 
+      const char *zTerm = pSeg->zTerm;
+      int nTerm = pSeg->nTerm;
+      rc = fts3TruncateSegment(p, iAbsLevel, pSeg->iIdx, zTerm, nTerm);
+      nRem++;
+    }
+  }
+
+  if( rc==SQLITE_OK && nRem!=pCsr->nSegment ){
+    rc = fts3RepackSegdirLevel(p, iAbsLevel);
+  }
+
+  *pnRem = nRem;
+  return rc;
+}
+
+/*
+** Store an incr-merge hint in the database.
+*/
+static int fts3IncrmergeHintStore(Fts3Table *p, Blob *pHint){
+  sqlite3_stmt *pReplace = 0;
+  int rc;                         /* Return code */
+
+  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pReplace, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int(pReplace, 1, FTS_STAT_INCRMERGEHINT);
+    sqlite3_bind_blob(pReplace, 2, pHint->a, pHint->n, SQLITE_STATIC);
+    sqlite3_step(pReplace);
+    rc = sqlite3_reset(pReplace);
+  }
+
+  return rc;
+}
+
+/*
+** Load an incr-merge hint from the database. The incr-merge hint, if one 
+** exists, is stored in the rowid==1 row of the %_stat table.
+**
+** If successful, populate blob *pHint with the value read from the %_stat
+** table and return SQLITE_OK. Otherwise, if an error occurs, return an
+** SQLite error code.
+*/
+static int fts3IncrmergeHintLoad(Fts3Table *p, Blob *pHint){
+  sqlite3_stmt *pSelect = 0;
+  int rc;
+
+  pHint->n = 0;
+  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pSelect, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;
+    sqlite3_bind_int(pSelect, 1, FTS_STAT_INCRMERGEHINT);
+    if( SQLITE_ROW==sqlite3_step(pSelect) ){
+      const char *aHint = sqlite3_column_blob(pSelect, 0);
+      int nHint = sqlite3_column_bytes(pSelect, 0);
+      if( aHint ){
+        blobGrowBuffer(pHint, nHint, &rc);
+        if( rc==SQLITE_OK ){
+          memcpy(pHint->a, aHint, nHint);
+          pHint->n = nHint;
+        }
+      }
+    }
+    rc2 = sqlite3_reset(pSelect);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  return rc;
+}
+
+/*
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
+** Otherwise, append an entry to the hint stored in blob *pHint. Each entry
+** consists of two varints, the absolute level number of the input segments 
+** and the number of input segments.
+**
+** If successful, leave *pRc set to SQLITE_OK and return. If an error occurs,
+** set *pRc to an SQLite error code before returning.
+*/
+static void fts3IncrmergeHintPush(
+  Blob *pHint,                    /* Hint blob to append to */
+  i64 iAbsLevel,                  /* First varint to store in hint */
+  int nInput,                     /* Second varint to store in hint */
+  int *pRc                        /* IN/OUT: Error code */
+){
+  blobGrowBuffer(pHint, pHint->n + 2*FTS3_VARINT_MAX, pRc);
+  if( *pRc==SQLITE_OK ){
+    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], iAbsLevel);
+    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], (i64)nInput);
+  }
+}
+
+/*
+** Read the last entry (most recently pushed) from the hint blob *pHint
+** and then remove the entry. Write the two values read to *piAbsLevel and 
+** *pnInput before returning.
+**
+** If no error occurs, return SQLITE_OK. If the hint blob in *pHint does
+** not contain at least two valid varints, return SQLITE_CORRUPT_VTAB.
+*/
+static int fts3IncrmergeHintPop(Blob *pHint, i64 *piAbsLevel, int *pnInput){
+  const int nHint = pHint->n;
+  int i;
+
+  i = pHint->n-2;
+  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;
+  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;
+
+  pHint->n = i;
+  i += sqlite3Fts3GetVarint(&pHint->a[i], piAbsLevel);
+  i += fts3GetVarint32(&pHint->a[i], pnInput);
+  if( i!=nHint ) return FTS_CORRUPT_VTAB;
+
+  return SQLITE_OK;
+}
+
+
+/*
+** Attempt an incremental merge that writes nMerge leaf blocks.
+**
+** Incremental merges happen nMin segments at a time. The segments 
+** to be merged are the nMin oldest segments (the ones with the smallest 
+** values for the _segdir.idx field) in the highest level that contains 
+** at least nMin segments. Multiple merges might occur in an attempt to 
+** write the quota of nMerge leaf blocks.
+*/
+SQLITE_PRIVATE int sqlite3Fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
+  int rc;                         /* Return code */
+  int nRem = nMerge;              /* Number of leaf pages yet to  be written */
+  Fts3MultiSegReader *pCsr;       /* Cursor used to read input data */
+  Fts3SegFilter *pFilter;         /* Filter used with cursor pCsr */
+  IncrmergeWriter *pWriter;       /* Writer object */
+  int nSeg = 0;                   /* Number of input segments */
+  sqlite3_int64 iAbsLevel = 0;    /* Absolute level number to work on */
+  Blob hint = {0, 0, 0};          /* Hint read from %_stat table */
+  int bDirtyHint = 0;             /* True if blob 'hint' has been modified */
+
+  /* Allocate space for the cursor, filter and writer objects */
+  const int nAlloc = sizeof(*pCsr) + sizeof(*pFilter) + sizeof(*pWriter);
+  pWriter = (IncrmergeWriter *)sqlite3_malloc(nAlloc);
+  if( !pWriter ) return SQLITE_NOMEM;
+  pFilter = (Fts3SegFilter *)&pWriter[1];
+  pCsr = (Fts3MultiSegReader *)&pFilter[1];
+
+  rc = fts3IncrmergeHintLoad(p, &hint);
+  while( rc==SQLITE_OK && nRem>0 ){
+    const i64 nMod = FTS3_SEGDIR_MAXLEVEL * p->nIndex;
+    sqlite3_stmt *pFindLevel = 0; /* SQL used to determine iAbsLevel */
+    int bUseHint = 0;             /* True if attempting to append */
+    int iIdx = 0;                 /* Largest idx in level (iAbsLevel+1) */
+
+    /* Search the %_segdir table for the absolute level with the smallest
+    ** relative level number that contains at least nMin segments, if any.
+    ** If one is found, set iAbsLevel to the absolute level number and
+    ** nSeg to nMin. If no level with at least nMin segments can be found, 
+    ** set nSeg to -1.
+    */
+    rc = fts3SqlStmt(p, SQL_FIND_MERGE_LEVEL, &pFindLevel, 0);
+    sqlite3_bind_int(pFindLevel, 1, MAX(2, nMin));
+    if( sqlite3_step(pFindLevel)==SQLITE_ROW ){
+      iAbsLevel = sqlite3_column_int64(pFindLevel, 0);
+      nSeg = sqlite3_column_int(pFindLevel, 1);
+      assert( nSeg>=2 );
+    }else{
+      nSeg = -1;
+    }
+    rc = sqlite3_reset(pFindLevel);
+
+    /* If the hint read from the %_stat table is not empty, check if the
+    ** last entry in it specifies a relative level smaller than or equal
+    ** to the level identified by the block above (if any). If so, this 
+    ** iteration of the loop will work on merging at the hinted level.
+    */
+    if( rc==SQLITE_OK && hint.n ){
+      int nHint = hint.n;
+      sqlite3_int64 iHintAbsLevel = 0;      /* Hint level */
+      int nHintSeg = 0;                     /* Hint number of segments */
+
+      rc = fts3IncrmergeHintPop(&hint, &iHintAbsLevel, &nHintSeg);
+      if( nSeg<0 || (iAbsLevel % nMod) >= (iHintAbsLevel % nMod) ){
+        iAbsLevel = iHintAbsLevel;
+        nSeg = nHintSeg;
+        bUseHint = 1;
+        bDirtyHint = 1;
+      }else{
+        /* This undoes the effect of the HintPop() above - so that no entry
+        ** is removed from the hint blob.  */
+        hint.n = nHint;
+      }
+    }
+
+    /* If nSeg is less that zero, then there is no level with at least
+    ** nMin segments and no hint in the %_stat table. No work to do.
+    ** Exit early in this case.  */
+    if( nSeg<0 ) break;
+
+    /* Open a cursor to iterate through the contents of the oldest nSeg 
+    ** indexes of absolute level iAbsLevel. If this cursor is opened using 
+    ** the 'hint' parameters, it is possible that there are less than nSeg
+    ** segments available in level iAbsLevel. In this case, no work is
+    ** done on iAbsLevel - fall through to the next iteration of the loop 
+    ** to start work on some other level.  */
+    memset(pWriter, 0, nAlloc);
+    pFilter->flags = FTS3_SEGMENT_REQUIRE_POS;
+
+    if( rc==SQLITE_OK ){
+      rc = fts3IncrmergeOutputIdx(p, iAbsLevel, &iIdx);
+      assert( bUseHint==1 || bUseHint==0 );
+      if( iIdx==0 || (bUseHint && iIdx==1) ){
+        int bIgnore = 0;
+        rc = fts3SegmentIsMaxLevel(p, iAbsLevel+1, &bIgnore);
+        if( bIgnore ){
+          pFilter->flags |= FTS3_SEGMENT_IGNORE_EMPTY;
+        }
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      rc = fts3IncrmergeCsr(p, iAbsLevel, nSeg, pCsr);
+    }
+    if( SQLITE_OK==rc && pCsr->nSegment==nSeg
+     && SQLITE_OK==(rc = sqlite3Fts3SegReaderStart(p, pCsr, pFilter))
+     && SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, pCsr))
+    ){
+      if( bUseHint && iIdx>0 ){
+        const char *zKey = pCsr->zTerm;
+        int nKey = pCsr->nTerm;
+        rc = fts3IncrmergeLoad(p, iAbsLevel, iIdx-1, zKey, nKey, pWriter);
+      }else{
+        rc = fts3IncrmergeWriter(p, iAbsLevel, iIdx, pCsr, pWriter);
+      }
+
+      if( rc==SQLITE_OK && pWriter->nLeafEst ){
+        fts3LogMerge(nSeg, iAbsLevel);
+        do {
+          rc = fts3IncrmergeAppend(p, pWriter, pCsr);
+          if( rc==SQLITE_OK ) rc = sqlite3Fts3SegReaderStep(p, pCsr);
+          if( pWriter->nWork>=nRem && rc==SQLITE_ROW ) rc = SQLITE_OK;
+        }while( rc==SQLITE_ROW );
+
+        /* Update or delete the input segments */
+        if( rc==SQLITE_OK ){
+          nRem -= (1 + pWriter->nWork);
+          rc = fts3IncrmergeChomp(p, iAbsLevel, pCsr, &nSeg);
+          if( nSeg!=0 ){
+            bDirtyHint = 1;
+            fts3IncrmergeHintPush(&hint, iAbsLevel, nSeg, &rc);
+          }
+        }
+      }
+
+      if( nSeg!=0 ){
+        pWriter->nLeafData = pWriter->nLeafData * -1;
+      }
+      fts3IncrmergeRelease(p, pWriter, &rc);
+      if( nSeg==0 && pWriter->bNoLeafData==0 ){
+        fts3PromoteSegments(p, iAbsLevel+1, pWriter->nLeafData);
+      }
+    }
+
+    sqlite3Fts3SegReaderFinish(pCsr);
+  }
+
+  /* Write the hint values into the %_stat table for the next incr-merger */
+  if( bDirtyHint && rc==SQLITE_OK ){
+    rc = fts3IncrmergeHintStore(p, &hint);
+  }
+
+  sqlite3_free(pWriter);
+  sqlite3_free(hint.a);
+  return rc;
+}
+
+/*
+** Convert the text beginning at *pz into an integer and return
+** its value.  Advance *pz to point to the first character past
+** the integer.
+*/
+static int fts3Getint(const char **pz){
+  const char *z = *pz;
+  int i = 0;
+  while( (*z)>='0' && (*z)<='9' ) i = 10*i + *(z++) - '0';
+  *pz = z;
+  return i;
+}
+
+/*
+** Process statements of the form:
+**
+**    INSERT INTO table(table) VALUES('merge=A,B');
+**
+** A and B are integers that decode to be the number of leaf pages
+** written for the merge, and the minimum number of segments on a level
+** before it will be selected for a merge, respectively.
+*/
+static int fts3DoIncrmerge(
+  Fts3Table *p,                   /* FTS3 table handle */
+  const char *zParam              /* Nul-terminated string containing "A,B" */
+){
+  int rc;
+  int nMin = (FTS3_MERGE_COUNT / 2);
+  int nMerge = 0;
+  const char *z = zParam;
+
+  /* Read the first integer value */
+  nMerge = fts3Getint(&z);
+
+  /* If the first integer value is followed by a ',',  read the second
+  ** integer value. */
+  if( z[0]==',' && z[1]!='\0' ){
+    z++;
+    nMin = fts3Getint(&z);
+  }
+
+  if( z[0]!='\0' || nMin<2 ){
+    rc = SQLITE_ERROR;
+  }else{
+    rc = SQLITE_OK;
+    if( !p->bHasStat ){
+      assert( p->bFts4==0 );
+      sqlite3Fts3CreateStatTable(&rc, p);
+    }
+    if( rc==SQLITE_OK ){
+      rc = sqlite3Fts3Incrmerge(p, nMerge, nMin);
+    }
+    sqlite3Fts3SegmentsClose(p);
+  }
+  return rc;
+}
+
+/*
+** Process statements of the form:
+**
+**    INSERT INTO table(table) VALUES('automerge=X');
+**
+** where X is an integer.  X==0 means to turn automerge off.  X!=0 means
+** turn it on.  The setting is persistent.
+*/
+static int fts3DoAutoincrmerge(
+  Fts3Table *p,                   /* FTS3 table handle */
+  const char *zParam              /* Nul-terminated string containing boolean */
+){
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pStmt = 0;
+  p->nAutoincrmerge = fts3Getint(&zParam);
+  if( p->nAutoincrmerge==1 || p->nAutoincrmerge>FTS3_MERGE_COUNT ){
+    p->nAutoincrmerge = 8;
+  }
+  if( !p->bHasStat ){
+    assert( p->bFts4==0 );
+    sqlite3Fts3CreateStatTable(&rc, p);
+    if( rc ) return rc;
+  }
+  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pStmt, 0);
+  if( rc ) return rc;
+  sqlite3_bind_int(pStmt, 1, FTS_STAT_AUTOINCRMERGE);
+  sqlite3_bind_int(pStmt, 2, p->nAutoincrmerge);
+  sqlite3_step(pStmt);
+  rc = sqlite3_reset(pStmt);
+  return rc;
+}
+
+/*
+** Return a 64-bit checksum for the FTS index entry specified by the
+** arguments to this function.
+*/
+static u64 fts3ChecksumEntry(
+  const char *zTerm,              /* Pointer to buffer containing term */
+  int nTerm,                      /* Size of zTerm in bytes */
+  int iLangid,                    /* Language id for current row */
+  int iIndex,                     /* Index (0..Fts3Table.nIndex-1) */
+  i64 iDocid,                     /* Docid for current row. */
+  int iCol,                       /* Column number */
+  int iPos                        /* Position */
+){
+  int i;
+  u64 ret = (u64)iDocid;
+
+  ret += (ret<<3) + iLangid;
+  ret += (ret<<3) + iIndex;
+  ret += (ret<<3) + iCol;
+  ret += (ret<<3) + iPos;
+  for(i=0; i<nTerm; i++) ret += (ret<<3) + zTerm[i];
+
+  return ret;
+}
+
+/*
+** Return a checksum of all entries in the FTS index that correspond to
+** language id iLangid. The checksum is calculated by XORing the checksums
+** of each individual entry (see fts3ChecksumEntry()) together.
+**
+** If successful, the checksum value is returned and *pRc set to SQLITE_OK.
+** Otherwise, if an error occurs, *pRc is set to an SQLite error code. The
+** return value is undefined in this case.
+*/
+static u64 fts3ChecksumIndex(
+  Fts3Table *p,                   /* FTS3 table handle */
+  int iLangid,                    /* Language id to return cksum for */
+  int iIndex,                     /* Index to cksum (0..p->nIndex-1) */
+  int *pRc                        /* OUT: Return code */
+){
+  Fts3SegFilter filter;
+  Fts3MultiSegReader csr;
+  int rc;
+  u64 cksum = 0;
+
+  assert( *pRc==SQLITE_OK );
+
+  memset(&filter, 0, sizeof(filter));
+  memset(&csr, 0, sizeof(csr));
+  filter.flags =  FTS3_SEGMENT_REQUIRE_POS|FTS3_SEGMENT_IGNORE_EMPTY;
+  filter.flags |= FTS3_SEGMENT_SCAN;
+
+  rc = sqlite3Fts3SegReaderCursor(
+      p, iLangid, iIndex, FTS3_SEGCURSOR_ALL, 0, 0, 0, 1,&csr
+  );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3Fts3SegReaderStart(p, &csr, &filter);
+  }
+
+  if( rc==SQLITE_OK ){
+    while( SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, &csr)) ){
+      char *pCsr = csr.aDoclist;
+      char *pEnd = &pCsr[csr.nDoclist];
+
+      i64 iDocid = 0;
+      i64 iCol = 0;
+      i64 iPos = 0;
+
+      pCsr += sqlite3Fts3GetVarint(pCsr, &iDocid);
+      while( pCsr<pEnd ){
+        i64 iVal = 0;
+        pCsr += sqlite3Fts3GetVarint(pCsr, &iVal);
+        if( pCsr<pEnd ){
+          if( iVal==0 || iVal==1 ){
+            iCol = 0;
+            iPos = 0;
+            if( iVal ){
+              pCsr += sqlite3Fts3GetVarint(pCsr, &iCol);
+            }else{
+              pCsr += sqlite3Fts3GetVarint(pCsr, &iVal);
+              iDocid += iVal;
+            }
+          }else{
+            iPos += (iVal - 2);
+            cksum = cksum ^ fts3ChecksumEntry(
+                csr.zTerm, csr.nTerm, iLangid, iIndex, iDocid,
+                (int)iCol, (int)iPos
+            );
+          }
+        }
+      }
+    }
+  }
+  sqlite3Fts3SegReaderFinish(&csr);
+
+  *pRc = rc;
+  return cksum;
+}
+
+/*
+** Check if the contents of the FTS index match the current contents of the
+** content table. If no error occurs and the contents do match, set *pbOk
+** to true and return SQLITE_OK. Or if the contents do not match, set *pbOk
+** to false before returning.
+**
+** If an error occurs (e.g. an OOM or IO error), return an SQLite error 
+** code. The final value of *pbOk is undefined in this case.
+*/
+static int fts3IntegrityCheck(Fts3Table *p, int *pbOk){
+  int rc = SQLITE_OK;             /* Return code */
+  u64 cksum1 = 0;                 /* Checksum based on FTS index contents */
+  u64 cksum2 = 0;                 /* Checksum based on %_content contents */
+  sqlite3_stmt *pAllLangid = 0;   /* Statement to return all language-ids */
+
+  /* This block calculates the checksum according to the FTS index. */
+  rc = fts3SqlStmt(p, SQL_SELECT_ALL_LANGID, &pAllLangid, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;
+    sqlite3_bind_int(pAllLangid, 1, p->iPrevLangid);
+    sqlite3_bind_int(pAllLangid, 2, p->nIndex);
+    while( rc==SQLITE_OK && sqlite3_step(pAllLangid)==SQLITE_ROW ){
+      int iLangid = sqlite3_column_int(pAllLangid, 0);
+      int i;
+      for(i=0; i<p->nIndex; i++){
+        cksum1 = cksum1 ^ fts3ChecksumIndex(p, iLangid, i, &rc);
+      }
+    }
+    rc2 = sqlite3_reset(pAllLangid);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  /* This block calculates the checksum according to the %_content table */
+  if( rc==SQLITE_OK ){
+    sqlite3_tokenizer_module const *pModule = p->pTokenizer->pModule;
+    sqlite3_stmt *pStmt = 0;
+    char *zSql;
+   
+    zSql = sqlite3_mprintf("SELECT %s" , p->zReadExprlist);
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+      sqlite3_free(zSql);
+    }
+
+    while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      i64 iDocid = sqlite3_column_int64(pStmt, 0);
+      int iLang = langidFromSelect(p, pStmt);
+      int iCol;
+
+      for(iCol=0; rc==SQLITE_OK && iCol<p->nColumn; iCol++){
+        if( p->abNotindexed[iCol]==0 ){
+          const char *zText = (const char *)sqlite3_column_text(pStmt, iCol+1);
+          int nText = sqlite3_column_bytes(pStmt, iCol+1);
+          sqlite3_tokenizer_cursor *pT = 0;
+
+          rc = sqlite3Fts3OpenTokenizer(p->pTokenizer, iLang, zText, nText,&pT);
+          while( rc==SQLITE_OK ){
+            char const *zToken;       /* Buffer containing token */
+            int nToken = 0;           /* Number of bytes in token */
+            int iDum1 = 0, iDum2 = 0; /* Dummy variables */
+            int iPos = 0;             /* Position of token in zText */
+
+            rc = pModule->xNext(pT, &zToken, &nToken, &iDum1, &iDum2, &iPos);
+            if( rc==SQLITE_OK ){
+              int i;
+              cksum2 = cksum2 ^ fts3ChecksumEntry(
+                  zToken, nToken, iLang, 0, iDocid, iCol, iPos
+              );
+              for(i=1; i<p->nIndex; i++){
+                if( p->aIndex[i].nPrefix<=nToken ){
+                  cksum2 = cksum2 ^ fts3ChecksumEntry(
+                      zToken, p->aIndex[i].nPrefix, iLang, i, iDocid, iCol, iPos
+                  );
+                }
+              }
+            }
+          }
+          if( pT ) pModule->xClose(pT);
+          if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+        }
+      }
+    }
+
+    sqlite3_finalize(pStmt);
+  }
+
+  *pbOk = (cksum1==cksum2);
+  return rc;
+}
+
+/*
+** Run the integrity-check. If no error occurs and the current contents of
+** the FTS index are correct, return SQLITE_OK. Or, if the contents of the
+** FTS index are incorrect, return SQLITE_CORRUPT_VTAB.
+**
+** Or, if an error (e.g. an OOM or IO error) occurs, return an SQLite 
+** error code.
+**
+** The integrity-check works as follows. For each token and indexed token
+** prefix in the document set, a 64-bit checksum is calculated (by code
+** in fts3ChecksumEntry()) based on the following:
+**
+**     + The index number (0 for the main index, 1 for the first prefix
+**       index etc.),
+**     + The token (or token prefix) text itself, 
+**     + The language-id of the row it appears in,
+**     + The docid of the row it appears in,
+**     + The column it appears in, and
+**     + The tokens position within that column.
+**
+** The checksums for all entries in the index are XORed together to create
+** a single checksum for the entire index.
+**
+** The integrity-check code calculates the same checksum in two ways:
+**
+**     1. By scanning the contents of the FTS index, and 
+**     2. By scanning and tokenizing the content table.
+**
+** If the two checksums are identical, the integrity-check is deemed to have
+** passed.
+*/
+static int fts3DoIntegrityCheck(
+  Fts3Table *p                    /* FTS3 table handle */
+){
+  int rc;
+  int bOk = 0;
+  rc = fts3IntegrityCheck(p, &bOk);
+  if( rc==SQLITE_OK && bOk==0 ) rc = FTS_CORRUPT_VTAB;
+  return rc;
+}
+
+/*
+** Handle a 'special' INSERT of the form:
+**
+**   "INSERT INTO tbl(tbl) VALUES(<expr>)"
+**
+** Argument pVal contains the result of <expr>. Currently the only 
+** meaningful value to insert is the text 'optimize'.
+*/
+static int fts3SpecialInsert(Fts3Table *p, sqlite3_value *pVal){
+  int rc;                         /* Return Code */
+  const char *zVal = (const char *)sqlite3_value_text(pVal);
+  int nVal = sqlite3_value_bytes(pVal);
+
+  if( !zVal ){
+    return SQLITE_NOMEM;
+  }else if( nVal==8 && 0==sqlite3_strnicmp(zVal, "optimize", 8) ){
+    rc = fts3DoOptimize(p, 0);
+  }else if( nVal==7 && 0==sqlite3_strnicmp(zVal, "rebuild", 7) ){
+    rc = fts3DoRebuild(p);
+  }else if( nVal==15 && 0==sqlite3_strnicmp(zVal, "integrity-check", 15) ){
+    rc = fts3DoIntegrityCheck(p);
+  }else if( nVal>6 && 0==sqlite3_strnicmp(zVal, "merge=", 6) ){
+    rc = fts3DoIncrmerge(p, &zVal[6]);
+  }else if( nVal>10 && 0==sqlite3_strnicmp(zVal, "automerge=", 10) ){
+    rc = fts3DoAutoincrmerge(p, &zVal[10]);
+#ifdef SQLITE_TEST
+  }else if( nVal>9 && 0==sqlite3_strnicmp(zVal, "nodesize=", 9) ){
+    p->nNodeSize = atoi(&zVal[9]);
+    rc = SQLITE_OK;
+  }else if( nVal>11 && 0==sqlite3_strnicmp(zVal, "maxpending=", 9) ){
+    p->nMaxPendingData = atoi(&zVal[11]);
+    rc = SQLITE_OK;
+  }else if( nVal>21 && 0==sqlite3_strnicmp(zVal, "test-no-incr-doclist=", 21) ){
+    p->bNoIncrDoclist = atoi(&zVal[21]);
+    rc = SQLITE_OK;
+#endif
+  }else{
+    rc = SQLITE_ERROR;
+  }
+
+  return rc;
+}
+
+#ifndef SQLITE_DISABLE_FTS4_DEFERRED
+/*
+** Delete all cached deferred doclists. Deferred doclists are cached
+** (allocated) by the sqlite3Fts3CacheDeferredDoclists() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *pCsr){
+  Fts3DeferredToken *pDef;
+  for(pDef=pCsr->pDeferred; pDef; pDef=pDef->pNext){
+    fts3PendingListDelete(pDef->pList);
+    pDef->pList = 0;
+  }
+}
+
+/*
+** Free all entries in the pCsr->pDeffered list. Entries are added to 
+** this list using sqlite3Fts3DeferToken().
+*/
+SQLITE_PRIVATE void sqlite3Fts3FreeDeferredTokens(Fts3Cursor *pCsr){
+  Fts3DeferredToken *pDef;
+  Fts3DeferredToken *pNext;
+  for(pDef=pCsr->pDeferred; pDef; pDef=pNext){
+    pNext = pDef->pNext;
+    fts3PendingListDelete(pDef->pList);
+    sqlite3_free(pDef);
+  }
+  pCsr->pDeferred = 0;
+}
+
+/*
+** Generate deferred-doclists for all tokens in the pCsr->pDeferred list
+** based on the row that pCsr currently points to.
+**
+** A deferred-doclist is like any other doclist with position information
+** included, except that it only contains entries for a single row of the
+** table, not for all rows.
+*/
+SQLITE_PRIVATE int sqlite3Fts3CacheDeferredDoclists(Fts3Cursor *pCsr){
+  int rc = SQLITE_OK;             /* Return code */
+  if( pCsr->pDeferred ){
+    int i;                        /* Used to iterate through table columns */
+    sqlite3_int64 iDocid;         /* Docid of the row pCsr points to */
+    Fts3DeferredToken *pDef;      /* Used to iterate through deferred tokens */
+  
+    Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
+    sqlite3_tokenizer *pT = p->pTokenizer;
+    sqlite3_tokenizer_module const *pModule = pT->pModule;
+   
+    assert( pCsr->isRequireSeek==0 );
+    iDocid = sqlite3_column_int64(pCsr->pStmt, 0);
+  
+    for(i=0; i<p->nColumn && rc==SQLITE_OK; i++){
+      if( p->abNotindexed[i]==0 ){
+        const char *zText = (const char *)sqlite3_column_text(pCsr->pStmt, i+1);
+        sqlite3_tokenizer_cursor *pTC = 0;
+
+        rc = sqlite3Fts3OpenTokenizer(pT, pCsr->iLangid, zText, -1, &pTC);
+        while( rc==SQLITE_OK ){
+          char const *zToken;       /* Buffer containing token */
+          int nToken = 0;           /* Number of bytes in token */
+          int iDum1 = 0, iDum2 = 0; /* Dummy variables */
+          int iPos = 0;             /* Position of token in zText */
+
+          rc = pModule->xNext(pTC, &zToken, &nToken, &iDum1, &iDum2, &iPos);
+          for(pDef=pCsr->pDeferred; pDef && rc==SQLITE_OK; pDef=pDef->pNext){
+            Fts3PhraseToken *pPT = pDef->pToken;
+            if( (pDef->iCol>=p->nColumn || pDef->iCol==i)
+                && (pPT->bFirst==0 || iPos==0)
+                && (pPT->n==nToken || (pPT->isPrefix && pPT->n<nToken))
+                && (0==memcmp(zToken, pPT->z, pPT->n))
+              ){
+              fts3PendingListAppend(&pDef->pList, iDocid, i, iPos, &rc);
+            }
+          }
+        }
+        if( pTC ) pModule->xClose(pTC);
+        if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+      }
+    }
+
+    for(pDef=pCsr->pDeferred; pDef && rc==SQLITE_OK; pDef=pDef->pNext){
+      if( pDef->pList ){
+        rc = fts3PendingListAppendVarint(&pDef->pList, 0);
+      }
+    }
+  }
+
+  return rc;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3DeferredTokenList(
+  Fts3DeferredToken *p, 
+  char **ppData, 
+  int *pnData
+){
+  char *pRet;
+  int nSkip;
+  sqlite3_int64 dummy;
+
+  *ppData = 0;
+  *pnData = 0;
+
+  if( p->pList==0 ){
+    return SQLITE_OK;
+  }
+
+  pRet = (char *)sqlite3_malloc(p->pList->nData);
+  if( !pRet ) return SQLITE_NOMEM;
+
+  nSkip = sqlite3Fts3GetVarint(p->pList->aData, &dummy);
+  *pnData = p->pList->nData - nSkip;
+  *ppData = pRet;
+  
+  memcpy(pRet, &p->pList->aData[nSkip], *pnData);
+  return SQLITE_OK;
+}
+
+/*
+** Add an entry for token pToken to the pCsr->pDeferred list.
+*/
+SQLITE_PRIVATE int sqlite3Fts3DeferToken(
+  Fts3Cursor *pCsr,               /* Fts3 table cursor */
+  Fts3PhraseToken *pToken,        /* Token to defer */
+  int iCol                        /* Column that token must appear in (or -1) */
+){
+  Fts3DeferredToken *pDeferred;
+  pDeferred = sqlite3_malloc(sizeof(*pDeferred));
+  if( !pDeferred ){
+    return SQLITE_NOMEM;
+  }
+  memset(pDeferred, 0, sizeof(*pDeferred));
+  pDeferred->pToken = pToken;
+  pDeferred->pNext = pCsr->pDeferred; 
+  pDeferred->iCol = iCol;
+  pCsr->pDeferred = pDeferred;
+
+  assert( pToken->pDeferred==0 );
+  pToken->pDeferred = pDeferred;
+
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** SQLite value pRowid contains the rowid of a row that may or may not be
+** present in the FTS3 table. If it is, delete it and adjust the contents
+** of subsiduary data structures accordingly.
+*/
+static int fts3DeleteByRowid(
+  Fts3Table *p, 
+  sqlite3_value *pRowid, 
+  int *pnChng,                    /* IN/OUT: Decrement if row is deleted */
+  u32 *aSzDel
+){
+  int rc = SQLITE_OK;             /* Return code */
+  int bFound = 0;                 /* True if *pRowid really is in the table */
+
+  fts3DeleteTerms(&rc, p, pRowid, aSzDel, &bFound);
+  if( bFound && rc==SQLITE_OK ){
+    int isEmpty = 0;              /* Deleting *pRowid leaves the table empty */
+    rc = fts3IsEmpty(p, pRowid, &isEmpty);
+    if( rc==SQLITE_OK ){
+      if( isEmpty ){
+        /* Deleting this row means the whole table is empty. In this case
+        ** delete the contents of all three tables and throw away any
+        ** data in the pendingTerms hash table.  */
+        rc = fts3DeleteAll(p, 1);
+        *pnChng = 0;
+        memset(aSzDel, 0, sizeof(u32) * (p->nColumn+1) * 2);
+      }else{
+        *pnChng = *pnChng - 1;
+        if( p->zContentTbl==0 ){
+          fts3SqlExec(&rc, p, SQL_DELETE_CONTENT, &pRowid);
+        }
+        if( p->bHasDocsize ){
+          fts3SqlExec(&rc, p, SQL_DELETE_DOCSIZE, &pRowid);
+        }
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function does the work for the xUpdate method of FTS3 virtual
+** tables. The schema of the virtual table being:
+**
+**     CREATE TABLE <table name>( 
+**       <user columns>,
+**       <table name> HIDDEN, 
+**       docid HIDDEN, 
+**       <langid> HIDDEN
+**     );
+**
+** 
+*/
+SQLITE_PRIVATE int sqlite3Fts3UpdateMethod(
+  sqlite3_vtab *pVtab,            /* FTS3 vtab object */
+  int nArg,                       /* Size of argument array */
+  sqlite3_value **apVal,          /* Array of arguments */
+  sqlite_int64 *pRowid            /* OUT: The affected (or effected) rowid */
+){
+  Fts3Table *p = (Fts3Table *)pVtab;
+  int rc = SQLITE_OK;             /* Return Code */
+  int isRemove = 0;               /* True for an UPDATE or DELETE */
+  u32 *aSzIns = 0;                /* Sizes of inserted documents */
+  u32 *aSzDel = 0;                /* Sizes of deleted documents */
+  int nChng = 0;                  /* Net change in number of documents */
+  int bInsertDone = 0;
+
+  /* At this point it must be known if the %_stat table exists or not.
+  ** So bHasStat may not be 2.  */
+  assert( p->bHasStat==0 || p->bHasStat==1 );
+
+  assert( p->pSegments==0 );
+  assert( 
+      nArg==1                     /* DELETE operations */
+   || nArg==(2 + p->nColumn + 3)  /* INSERT or UPDATE operations */
+  );
+
+  /* Check for a "special" INSERT operation. One of the form:
+  **
+  **   INSERT INTO xyz(xyz) VALUES('command');
+  */
+  if( nArg>1 
+   && sqlite3_value_type(apVal[0])==SQLITE_NULL 
+   && sqlite3_value_type(apVal[p->nColumn+2])!=SQLITE_NULL 
+  ){
+    rc = fts3SpecialInsert(p, apVal[p->nColumn+2]);
+    goto update_out;
+  }
+
+  if( nArg>1 && sqlite3_value_int(apVal[2 + p->nColumn + 2])<0 ){
+    rc = SQLITE_CONSTRAINT;
+    goto update_out;
+  }
+
+  /* Allocate space to hold the change in document sizes */
+  aSzDel = sqlite3_malloc( sizeof(aSzDel[0])*(p->nColumn+1)*2 );
+  if( aSzDel==0 ){
+    rc = SQLITE_NOMEM;
+    goto update_out;
+  }
+  aSzIns = &aSzDel[p->nColumn+1];
+  memset(aSzDel, 0, sizeof(aSzDel[0])*(p->nColumn+1)*2);
+
+  rc = fts3Writelock(p);
+  if( rc!=SQLITE_OK ) goto update_out;
+
+  /* If this is an INSERT operation, or an UPDATE that modifies the rowid
+  ** value, then this operation requires constraint handling.
+  **
+  ** If the on-conflict mode is REPLACE, this means that the existing row
+  ** should be deleted from the database before inserting the new row. Or,
+  ** if the on-conflict mode is other than REPLACE, then this method must
+  ** detect the conflict and return SQLITE_CONSTRAINT before beginning to
+  ** modify the database file.
+  */
+  if( nArg>1 && p->zContentTbl==0 ){
+    /* Find the value object that holds the new rowid value. */
+    sqlite3_value *pNewRowid = apVal[3+p->nColumn];
+    if( sqlite3_value_type(pNewRowid)==SQLITE_NULL ){
+      pNewRowid = apVal[1];
+    }
+
+    if( sqlite3_value_type(pNewRowid)!=SQLITE_NULL && ( 
+        sqlite3_value_type(apVal[0])==SQLITE_NULL
+     || sqlite3_value_int64(apVal[0])!=sqlite3_value_int64(pNewRowid)
+    )){
+      /* The new rowid is not NULL (in this case the rowid will be
+      ** automatically assigned and there is no chance of a conflict), and 
+      ** the statement is either an INSERT or an UPDATE that modifies the
+      ** rowid column. So if the conflict mode is REPLACE, then delete any
+      ** existing row with rowid=pNewRowid. 
+      **
+      ** Or, if the conflict mode is not REPLACE, insert the new record into 
+      ** the %_content table. If we hit the duplicate rowid constraint (or any
+      ** other error) while doing so, return immediately.
+      **
+      ** This branch may also run if pNewRowid contains a value that cannot
+      ** be losslessly converted to an integer. In this case, the eventual 
+      ** call to fts3InsertData() (either just below or further on in this
+      ** function) will return SQLITE_MISMATCH. If fts3DeleteByRowid is 
+      ** invoked, it will delete zero rows (since no row will have
+      ** docid=$pNewRowid if $pNewRowid is not an integer value).
+      */
+      if( sqlite3_vtab_on_conflict(p->db)==SQLITE_REPLACE ){
+        rc = fts3DeleteByRowid(p, pNewRowid, &nChng, aSzDel);
+      }else{
+        rc = fts3InsertData(p, apVal, pRowid);
+        bInsertDone = 1;
+      }
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    goto update_out;
+  }
+
+  /* If this is a DELETE or UPDATE operation, remove the old record. */
+  if( sqlite3_value_type(apVal[0])!=SQLITE_NULL ){
+    assert( sqlite3_value_type(apVal[0])==SQLITE_INTEGER );
+    rc = fts3DeleteByRowid(p, apVal[0], &nChng, aSzDel);
+    isRemove = 1;
+  }
+  
+  /* If this is an INSERT or UPDATE operation, insert the new record. */
+  if( nArg>1 && rc==SQLITE_OK ){
+    int iLangid = sqlite3_value_int(apVal[2 + p->nColumn + 2]);
+    if( bInsertDone==0 ){
+      rc = fts3InsertData(p, apVal, pRowid);
+      if( rc==SQLITE_CONSTRAINT && p->zContentTbl==0 ){
+        rc = FTS_CORRUPT_VTAB;
+      }
+    }
+    if( rc==SQLITE_OK && (!isRemove || *pRowid!=p->iPrevDocid ) ){
+      rc = fts3PendingTermsDocid(p, 0, iLangid, *pRowid);
+    }
+    if( rc==SQLITE_OK ){
+      assert( p->iPrevDocid==*pRowid );
+      rc = fts3InsertTerms(p, iLangid, apVal, aSzIns);
+    }
+    if( p->bHasDocsize ){
+      fts3InsertDocsize(&rc, p, aSzIns);
+    }
+    nChng++;
+  }
+
+  if( p->bFts4 ){
+    fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nChng);
+  }
+
+ update_out:
+  sqlite3_free(aSzDel);
+  sqlite3Fts3SegmentsClose(p);
+  return rc;
+}
+
+/* 
+** Flush any data in the pending-terms hash table to disk. If successful,
+** merge all segments in the database (including the new segment, if 
+** there was any data to flush) into a single segment. 
+*/
+SQLITE_PRIVATE int sqlite3Fts3Optimize(Fts3Table *p){
+  int rc;
+  rc = sqlite3_exec(p->db, "SAVEPOINT fts3", 0, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = fts3DoOptimize(p, 1);
+    if( rc==SQLITE_OK || rc==SQLITE_DONE ){
+      int rc2 = sqlite3_exec(p->db, "RELEASE fts3", 0, 0, 0);
+      if( rc2!=SQLITE_OK ) rc = rc2;
+    }else{
+      sqlite3_exec(p->db, "ROLLBACK TO fts3", 0, 0, 0);
+      sqlite3_exec(p->db, "RELEASE fts3", 0, 0, 0);
+    }
+  }
+  sqlite3Fts3SegmentsClose(p);
+  return rc;
+}
+
+#endif
+
+/************** End of fts3_write.c ******************************************/
+/************** Begin file fts3_snippet.c ************************************/
+/*
+** 2009 Oct 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+*/
+
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <string.h> */
+/* #include <assert.h> */
+
+/*
+** Characters that may appear in the second argument to matchinfo().
+*/
+#define FTS3_MATCHINFO_NPHRASE   'p'        /* 1 value */
+#define FTS3_MATCHINFO_NCOL      'c'        /* 1 value */
+#define FTS3_MATCHINFO_NDOC      'n'        /* 1 value */
+#define FTS3_MATCHINFO_AVGLENGTH 'a'        /* nCol values */
+#define FTS3_MATCHINFO_LENGTH    'l'        /* nCol values */
+#define FTS3_MATCHINFO_LCS       's'        /* nCol values */
+#define FTS3_MATCHINFO_HITS      'x'        /* 3*nCol*nPhrase values */
+#define FTS3_MATCHINFO_LHITS     'y'        /* nCol*nPhrase values */
+#define FTS3_MATCHINFO_LHITS_BM  'b'        /* nCol*nPhrase values */
+
+/*
+** The default value for the second argument to matchinfo(). 
+*/
+#define FTS3_MATCHINFO_DEFAULT   "pcx"
+
+
+/*
+** Used as an fts3ExprIterate() context when loading phrase doclists to
+** Fts3Expr.aDoclist[]/nDoclist.
+*/
+typedef struct LoadDoclistCtx LoadDoclistCtx;
+struct LoadDoclistCtx {
+  Fts3Cursor *pCsr;               /* FTS3 Cursor */
+  int nPhrase;                    /* Number of phrases seen so far */
+  int nToken;                     /* Number of tokens seen so far */
+};
+
+/*
+** The following types are used as part of the implementation of the 
+** fts3BestSnippet() routine.
+*/
+typedef struct SnippetIter SnippetIter;
+typedef struct SnippetPhrase SnippetPhrase;
+typedef struct SnippetFragment SnippetFragment;
+
+struct SnippetIter {
+  Fts3Cursor *pCsr;               /* Cursor snippet is being generated from */
+  int iCol;                       /* Extract snippet from this column */
+  int nSnippet;                   /* Requested snippet length (in tokens) */
+  int nPhrase;                    /* Number of phrases in query */
+  SnippetPhrase *aPhrase;         /* Array of size nPhrase */
+  int iCurrent;                   /* First token of current snippet */
+};
+
+struct SnippetPhrase {
+  int nToken;                     /* Number of tokens in phrase */
+  char *pList;                    /* Pointer to start of phrase position list */
+  int iHead;                      /* Next value in position list */
+  char *pHead;                    /* Position list data following iHead */
+  int iTail;                      /* Next value in trailing position list */
+  char *pTail;                    /* Position list data following iTail */
+};
+
+struct SnippetFragment {
+  int iCol;                       /* Column snippet is extracted from */
+  int iPos;                       /* Index of first token in snippet */
+  u64 covered;                    /* Mask of query phrases covered */
+  u64 hlmask;                     /* Mask of snippet terms to highlight */
+};
+
+/*
+** This type is used as an fts3ExprIterate() context object while 
+** accumulating the data returned by the matchinfo() function.
+*/
+typedef struct MatchInfo MatchInfo;
+struct MatchInfo {
+  Fts3Cursor *pCursor;            /* FTS3 Cursor */
+  int nCol;                       /* Number of columns in table */
+  int nPhrase;                    /* Number of matchable phrases in query */
+  sqlite3_int64 nDoc;             /* Number of docs in database */
+  char flag;
+  u32 *aMatchinfo;                /* Pre-allocated buffer */
+};
+
+/*
+** An instance of this structure is used to manage a pair of buffers, each
+** (nElem * sizeof(u32)) bytes in size. See the MatchinfoBuffer code below
+** for details.
+*/
+struct MatchinfoBuffer {
+  u8 aRef[3];
+  int nElem;
+  int bGlobal;                    /* Set if global data is loaded */
+  char *zMatchinfo;
+  u32 aMatchinfo[1];
+};
+
+
+/*
+** The snippet() and offsets() functions both return text values. An instance
+** of the following structure is used to accumulate those values while the
+** functions are running. See fts3StringAppend() for details.
+*/
+typedef struct StrBuffer StrBuffer;
+struct StrBuffer {
+  char *z;                        /* Pointer to buffer containing string */
+  int n;                          /* Length of z in bytes (excl. nul-term) */
+  int nAlloc;                     /* Allocated size of buffer z in bytes */
+};
+
+
+/*************************************************************************
+** Start of MatchinfoBuffer code.
+*/
+
+/*
+** Allocate a two-slot MatchinfoBuffer object.
+*/
+static MatchinfoBuffer *fts3MIBufferNew(int nElem, const char *zMatchinfo){
+  MatchinfoBuffer *pRet;
+  int nByte = sizeof(u32) * (2*nElem + 1) + sizeof(MatchinfoBuffer);
+  int nStr = (int)strlen(zMatchinfo);
+
+  pRet = sqlite3_malloc(nByte + nStr+1);
+  if( pRet ){
+    memset(pRet, 0, nByte);
+    pRet->aMatchinfo[0] = (u8*)(&pRet->aMatchinfo[1]) - (u8*)pRet;
+    pRet->aMatchinfo[1+nElem] = pRet->aMatchinfo[0] + sizeof(u32)*(nElem+1);
+    pRet->nElem = nElem;
+    pRet->zMatchinfo = ((char*)pRet) + nByte;
+    memcpy(pRet->zMatchinfo, zMatchinfo, nStr+1);
+    pRet->aRef[0] = 1;
+  }
+
+  return pRet;
+}
+
+static void fts3MIBufferFree(void *p){
+  MatchinfoBuffer *pBuf = (MatchinfoBuffer*)((u8*)p - ((u32*)p)[-1]);
+
+  assert( (u32*)p==&pBuf->aMatchinfo[1] 
+       || (u32*)p==&pBuf->aMatchinfo[pBuf->nElem+2] 
+  );
+  if( (u32*)p==&pBuf->aMatchinfo[1] ){
+    pBuf->aRef[1] = 0;
+  }else{
+    pBuf->aRef[2] = 0;
+  }
+
+  if( pBuf->aRef[0]==0 && pBuf->aRef[1]==0 && pBuf->aRef[2]==0 ){
+    sqlite3_free(pBuf);
+  }
+}
+
+static void (*fts3MIBufferAlloc(MatchinfoBuffer *p, u32 **paOut))(void*){
+  void (*xRet)(void*) = 0;
+  u32 *aOut = 0;
+
+  if( p->aRef[1]==0 ){
+    p->aRef[1] = 1;
+    aOut = &p->aMatchinfo[1];
+    xRet = fts3MIBufferFree;
+  }
+  else if( p->aRef[2]==0 ){
+    p->aRef[2] = 1;
+    aOut = &p->aMatchinfo[p->nElem+2];
+    xRet = fts3MIBufferFree;
+  }else{
+    aOut = (u32*)sqlite3_malloc(p->nElem * sizeof(u32));
+    if( aOut ){
+      xRet = sqlite3_free;
+      if( p->bGlobal ) memcpy(aOut, &p->aMatchinfo[1], p->nElem*sizeof(u32));
+    }
+  }
+
+  *paOut = aOut;
+  return xRet;
+}
+
+static void fts3MIBufferSetGlobal(MatchinfoBuffer *p){
+  p->bGlobal = 1;
+  memcpy(&p->aMatchinfo[2+p->nElem], &p->aMatchinfo[1], p->nElem*sizeof(u32));
+}
+
+/*
+** Free a MatchinfoBuffer object allocated using fts3MIBufferNew()
+*/
+SQLITE_PRIVATE void sqlite3Fts3MIBufferFree(MatchinfoBuffer *p){
+  if( p ){
+    assert( p->aRef[0]==1 );
+    p->aRef[0] = 0;
+    if( p->aRef[0]==0 && p->aRef[1]==0 && p->aRef[2]==0 ){
+      sqlite3_free(p);
+    }
+  }
+}
+
+/* 
+** End of MatchinfoBuffer code.
+*************************************************************************/
+
+
+/*
+** This function is used to help iterate through a position-list. A position
+** list is a list of unique integers, sorted from smallest to largest. Each
+** element of the list is represented by an FTS3 varint that takes the value
+** of the difference between the current element and the previous one plus
+** two. For example, to store the position-list:
+**
+**     4 9 113
+**
+** the three varints:
+**
+**     6 7 106
+**
+** are encoded.
+**
+** When this function is called, *pp points to the start of an element of
+** the list. *piPos contains the value of the previous entry in the list.
+** After it returns, *piPos contains the value of the next element of the
+** list and *pp is advanced to the following varint.
+*/
+static void fts3GetDeltaPosition(char **pp, int *piPos){
+  int iVal;
+  *pp += fts3GetVarint32(*pp, &iVal);
+  *piPos += (iVal-2);
+}
+
+/*
+** Helper function for fts3ExprIterate() (see below).
+*/
+static int fts3ExprIterate2(
+  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
+  int *piPhrase,                  /* Pointer to phrase counter */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
+  void *pCtx                      /* Second argument to pass to callback */
+){
+  int rc;                         /* Return code */
+  int eType = pExpr->eType;     /* Type of expression node pExpr */
+
+  if( eType!=FTSQUERY_PHRASE ){
+    assert( pExpr->pLeft && pExpr->pRight );
+    rc = fts3ExprIterate2(pExpr->pLeft, piPhrase, x, pCtx);
+    if( rc==SQLITE_OK && eType!=FTSQUERY_NOT ){
+      rc = fts3ExprIterate2(pExpr->pRight, piPhrase, x, pCtx);
+    }
+  }else{
+    rc = x(pExpr, *piPhrase, pCtx);
+    (*piPhrase)++;
+  }
+  return rc;
+}
+
+/*
+** Iterate through all phrase nodes in an FTS3 query, except those that
+** are part of a sub-tree that is the right-hand-side of a NOT operator.
+** For each phrase node found, the supplied callback function is invoked.
+**
+** If the callback function returns anything other than SQLITE_OK, 
+** the iteration is abandoned and the error code returned immediately.
+** Otherwise, SQLITE_OK is returned after a callback has been made for
+** all eligible phrase nodes.
+*/
+static int fts3ExprIterate(
+  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
+  void *pCtx                      /* Second argument to pass to callback */
+){
+  int iPhrase = 0;                /* Variable used as the phrase counter */
+  return fts3ExprIterate2(pExpr, &iPhrase, x, pCtx);
+}
+
+
+/*
+** This is an fts3ExprIterate() callback used while loading the doclists
+** for each phrase into Fts3Expr.aDoclist[]/nDoclist. See also
+** fts3ExprLoadDoclists().
+*/
+static int fts3ExprLoadDoclistsCb(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  int rc = SQLITE_OK;
+  Fts3Phrase *pPhrase = pExpr->pPhrase;
+  LoadDoclistCtx *p = (LoadDoclistCtx *)ctx;
+
+  UNUSED_PARAMETER(iPhrase);
+
+  p->nPhrase++;
+  p->nToken += pPhrase->nToken;
+
+  return rc;
+}
+
+/*
+** Load the doclists for each phrase in the query associated with FTS3 cursor
+** pCsr. 
+**
+** If pnPhrase is not NULL, then *pnPhrase is set to the number of matchable 
+** phrases in the expression (all phrases except those directly or 
+** indirectly descended from the right-hand-side of a NOT operator). If 
+** pnToken is not NULL, then it is set to the number of tokens in all
+** matchable phrases of the expression.
+*/
+static int fts3ExprLoadDoclists(
+  Fts3Cursor *pCsr,               /* Fts3 cursor for current query */
+  int *pnPhrase,                  /* OUT: Number of phrases in query */
+  int *pnToken                    /* OUT: Number of tokens in query */
+){
+  int rc;                         /* Return Code */
+  LoadDoclistCtx sCtx = {0,0,0};  /* Context for fts3ExprIterate() */
+  sCtx.pCsr = pCsr;
+  rc = fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb, (void *)&sCtx);
+  if( pnPhrase ) *pnPhrase = sCtx.nPhrase;
+  if( pnToken ) *pnToken = sCtx.nToken;
+  return rc;
+}
+
+static int fts3ExprPhraseCountCb(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  (*(int *)ctx)++;
+  pExpr->iPhrase = iPhrase;
+  return SQLITE_OK;
+}
+static int fts3ExprPhraseCount(Fts3Expr *pExpr){
+  int nPhrase = 0;
+  (void)fts3ExprIterate(pExpr, fts3ExprPhraseCountCb, (void *)&nPhrase);
+  return nPhrase;
+}
+
+/*
+** Advance the position list iterator specified by the first two 
+** arguments so that it points to the first element with a value greater
+** than or equal to parameter iNext.
+*/
+static void fts3SnippetAdvance(char **ppIter, int *piIter, int iNext){
+  char *pIter = *ppIter;
+  if( pIter ){
+    int iIter = *piIter;
+
+    while( iIter<iNext ){
+      if( 0==(*pIter & 0xFE) ){
+        iIter = -1;
+        pIter = 0;
+        break;
+      }
+      fts3GetDeltaPosition(&pIter, &iIter);
+    }
+
+    *piIter = iIter;
+    *ppIter = pIter;
+  }
+}
+
+/*
+** Advance the snippet iterator to the next candidate snippet.
+*/
+static int fts3SnippetNextCandidate(SnippetIter *pIter){
+  int i;                          /* Loop counter */
+
+  if( pIter->iCurrent<0 ){
+    /* The SnippetIter object has just been initialized. The first snippet
+    ** candidate always starts at offset 0 (even if this candidate has a
+    ** score of 0.0).
+    */
+    pIter->iCurrent = 0;
+
+    /* Advance the 'head' iterator of each phrase to the first offset that
+    ** is greater than or equal to (iNext+nSnippet).
+    */
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, pIter->nSnippet);
+    }
+  }else{
+    int iStart;
+    int iEnd = 0x7FFFFFFF;
+
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      if( pPhrase->pHead && pPhrase->iHead<iEnd ){
+        iEnd = pPhrase->iHead;
+      }
+    }
+    if( iEnd==0x7FFFFFFF ){
+      return 1;
+    }
+
+    pIter->iCurrent = iStart = iEnd - pIter->nSnippet + 1;
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, iEnd+1);
+      fts3SnippetAdvance(&pPhrase->pTail, &pPhrase->iTail, iStart);
+    }
+  }
+
+  return 0;
+}
+
+/*
+** Retrieve information about the current candidate snippet of snippet 
+** iterator pIter.
+*/
+static void fts3SnippetDetails(
+  SnippetIter *pIter,             /* Snippet iterator */
+  u64 mCovered,                   /* Bitmask of phrases already covered */
+  int *piToken,                   /* OUT: First token of proposed snippet */
+  int *piScore,                   /* OUT: "Score" for this snippet */
+  u64 *pmCover,                   /* OUT: Bitmask of phrases covered */
+  u64 *pmHighlight                /* OUT: Bitmask of terms to highlight */
+){
+  int iStart = pIter->iCurrent;   /* First token of snippet */
+  int iScore = 0;                 /* Score of this snippet */
+  int i;                          /* Loop counter */
+  u64 mCover = 0;                 /* Mask of phrases covered by this snippet */
+  u64 mHighlight = 0;             /* Mask of tokens to highlight in snippet */
+
+  for(i=0; i<pIter->nPhrase; i++){
+    SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+    if( pPhrase->pTail ){
+      char *pCsr = pPhrase->pTail;
+      int iCsr = pPhrase->iTail;
+
+      while( iCsr<(iStart+pIter->nSnippet) ){
+        int j;
+        u64 mPhrase = (u64)1 << i;
+        u64 mPos = (u64)1 << (iCsr - iStart);
+        assert( iCsr>=iStart );
+        if( (mCover|mCovered)&mPhrase ){
+          iScore++;
+        }else{
+          iScore += 1000;
+        }
+        mCover |= mPhrase;
+
+        for(j=0; j<pPhrase->nToken; j++){
+          mHighlight |= (mPos>>j);
+        }
+
+        if( 0==(*pCsr & 0x0FE) ) break;
+        fts3GetDeltaPosition(&pCsr, &iCsr);
+      }
+    }
+  }
+
+  /* Set the output variables before returning. */
+  *piToken = iStart;
+  *piScore = iScore;
+  *pmCover = mCover;
+  *pmHighlight = mHighlight;
+}
+
+/*
+** This function is an fts3ExprIterate() callback used by fts3BestSnippet().
+** Each invocation populates an element of the SnippetIter.aPhrase[] array.
+*/
+static int fts3SnippetFindPositions(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  SnippetIter *p = (SnippetIter *)ctx;
+  SnippetPhrase *pPhrase = &p->aPhrase[iPhrase];
+  char *pCsr;
+  int rc;
+
+  pPhrase->nToken = pExpr->pPhrase->nToken;
+  rc = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->iCol, &pCsr);
+  assert( rc==SQLITE_OK || pCsr==0 );
+  if( pCsr ){
+    int iFirst = 0;
+    pPhrase->pList = pCsr;
+    fts3GetDeltaPosition(&pCsr, &iFirst);
+    assert( iFirst>=0 );
+    pPhrase->pHead = pCsr;
+    pPhrase->pTail = pCsr;
+    pPhrase->iHead = iFirst;
+    pPhrase->iTail = iFirst;
+  }else{
+    assert( rc!=SQLITE_OK || (
+       pPhrase->pList==0 && pPhrase->pHead==0 && pPhrase->pTail==0 
+    ));
+  }
+
+  return rc;
+}
+
+/*
+** Select the fragment of text consisting of nFragment contiguous tokens 
+** from column iCol that represent the "best" snippet. The best snippet
+** is the snippet with the highest score, where scores are calculated
+** by adding:
+**
+**   (a) +1 point for each occurrence of a matchable phrase in the snippet.
+**
+**   (b) +1000 points for the first occurrence of each matchable phrase in 
+**       the snippet for which the corresponding mCovered bit is not set.
+**
+** The selected snippet parameters are stored in structure *pFragment before
+** returning. The score of the selected snippet is stored in *piScore
+** before returning.
+*/
+static int fts3BestSnippet(
+  int nSnippet,                   /* Desired snippet length */
+  Fts3Cursor *pCsr,               /* Cursor to create snippet for */
+  int iCol,                       /* Index of column to create snippet from */
+  u64 mCovered,                   /* Mask of phrases already covered */
+  u64 *pmSeen,                    /* IN/OUT: Mask of phrases seen */
+  SnippetFragment *pFragment,     /* OUT: Best snippet found */
+  int *piScore                    /* OUT: Score of snippet pFragment */
+){
+  int rc;                         /* Return Code */
+  int nList;                      /* Number of phrases in expression */
+  SnippetIter sIter;              /* Iterates through snippet candidates */
+  int nByte;                      /* Number of bytes of space to allocate */
+  int iBestScore = -1;            /* Best snippet score found so far */
+  int i;                          /* Loop counter */
+
+  memset(&sIter, 0, sizeof(sIter));
+
+  /* Iterate through the phrases in the expression to count them. The same
+  ** callback makes sure the doclists are loaded for each phrase.
+  */
+  rc = fts3ExprLoadDoclists(pCsr, &nList, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* Now that it is known how many phrases there are, allocate and zero
+  ** the required space using malloc().
+  */
+  nByte = sizeof(SnippetPhrase) * nList;
+  sIter.aPhrase = (SnippetPhrase *)sqlite3_malloc(nByte);
+  if( !sIter.aPhrase ){
+    return SQLITE_NOMEM;
+  }
+  memset(sIter.aPhrase, 0, nByte);
+
+  /* Initialize the contents of the SnippetIter object. Then iterate through
+  ** the set of phrases in the expression to populate the aPhrase[] array.
+  */
+  sIter.pCsr = pCsr;
+  sIter.iCol = iCol;
+  sIter.nSnippet = nSnippet;
+  sIter.nPhrase = nList;
+  sIter.iCurrent = -1;
+  rc = fts3ExprIterate(pCsr->pExpr, fts3SnippetFindPositions, (void*)&sIter);
+  if( rc==SQLITE_OK ){
+
+    /* Set the *pmSeen output variable. */
+    for(i=0; i<nList; i++){
+      if( sIter.aPhrase[i].pHead ){
+        *pmSeen |= (u64)1 << i;
+      }
+    }
+
+    /* Loop through all candidate snippets. Store the best snippet in 
+     ** *pFragment. Store its associated 'score' in iBestScore.
+     */
+    pFragment->iCol = iCol;
+    while( !fts3SnippetNextCandidate(&sIter) ){
+      int iPos;
+      int iScore;
+      u64 mCover;
+      u64 mHighlite;
+      fts3SnippetDetails(&sIter, mCovered, &iPos, &iScore, &mCover,&mHighlite);
+      assert( iScore>=0 );
+      if( iScore>iBestScore ){
+        pFragment->iPos = iPos;
+        pFragment->hlmask = mHighlite;
+        pFragment->covered = mCover;
+        iBestScore = iScore;
+      }
+    }
+
+    *piScore = iBestScore;
+  }
+  sqlite3_free(sIter.aPhrase);
+  return rc;
+}
+
+
+/*
+** Append a string to the string-buffer passed as the first argument.
+**
+** If nAppend is negative, then the length of the string zAppend is
+** determined using strlen().
+*/
+static int fts3StringAppend(
+  StrBuffer *pStr,                /* Buffer to append to */
+  const char *zAppend,            /* Pointer to data to append to buffer */
+  int nAppend                     /* Size of zAppend in bytes (or -1) */
+){
+  if( nAppend<0 ){
+    nAppend = (int)strlen(zAppend);
+  }
+
+  /* If there is insufficient space allocated at StrBuffer.z, use realloc()
+  ** to grow the buffer until so that it is big enough to accomadate the
+  ** appended data.
+  */
+  if( pStr->n+nAppend+1>=pStr->nAlloc ){
+    int nAlloc = pStr->nAlloc+nAppend+100;
+    char *zNew = sqlite3_realloc(pStr->z, nAlloc);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    pStr->z = zNew;
+    pStr->nAlloc = nAlloc;
+  }
+  assert( pStr->z!=0 && (pStr->nAlloc >= pStr->n+nAppend+1) );
+
+  /* Append the data to the string buffer. */
+  memcpy(&pStr->z[pStr->n], zAppend, nAppend);
+  pStr->n += nAppend;
+  pStr->z[pStr->n] = '\0';
+
+  return SQLITE_OK;
+}
+
+/*
+** The fts3BestSnippet() function often selects snippets that end with a
+** query term. That is, the final term of the snippet is always a term
+** that requires highlighting. For example, if 'X' is a highlighted term
+** and '.' is a non-highlighted term, BestSnippet() may select:
+**
+**     ........X.....X
+**
+** This function "shifts" the beginning of the snippet forward in the 
+** document so that there are approximately the same number of 
+** non-highlighted terms to the right of the final highlighted term as there
+** are to the left of the first highlighted term. For example, to this:
+**
+**     ....X.....X....
+**
+** This is done as part of extracting the snippet text, not when selecting
+** the snippet. Snippet selection is done based on doclists only, so there
+** is no way for fts3BestSnippet() to know whether or not the document 
+** actually contains terms that follow the final highlighted term. 
+*/
+static int fts3SnippetShift(
+  Fts3Table *pTab,                /* FTS3 table snippet comes from */
+  int iLangid,                    /* Language id to use in tokenizing */
+  int nSnippet,                   /* Number of tokens desired for snippet */
+  const char *zDoc,               /* Document text to extract snippet from */
+  int nDoc,                       /* Size of buffer zDoc in bytes */
+  int *piPos,                     /* IN/OUT: First token of snippet */
+  u64 *pHlmask                    /* IN/OUT: Mask of tokens to highlight */
+){
+  u64 hlmask = *pHlmask;          /* Local copy of initial highlight-mask */
+
+  if( hlmask ){
+    int nLeft;                    /* Tokens to the left of first highlight */
+    int nRight;                   /* Tokens to the right of last highlight */
+    int nDesired;                 /* Ideal number of tokens to shift forward */
+
+    for(nLeft=0; !(hlmask & ((u64)1 << nLeft)); nLeft++);
+    for(nRight=0; !(hlmask & ((u64)1 << (nSnippet-1-nRight))); nRight++);
+    nDesired = (nLeft-nRight)/2;
+
+    /* Ideally, the start of the snippet should be pushed forward in the
+    ** document nDesired tokens. This block checks if there are actually
+    ** nDesired tokens to the right of the snippet. If so, *piPos and
+    ** *pHlMask are updated to shift the snippet nDesired tokens to the
+    ** right. Otherwise, the snippet is shifted by the number of tokens
+    ** available.
+    */
+    if( nDesired>0 ){
+      int nShift;                 /* Number of tokens to shift snippet by */
+      int iCurrent = 0;           /* Token counter */
+      int rc;                     /* Return Code */
+      sqlite3_tokenizer_module *pMod;
+      sqlite3_tokenizer_cursor *pC;
+      pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
+
+      /* Open a cursor on zDoc/nDoc. Check if there are (nSnippet+nDesired)
+      ** or more tokens in zDoc/nDoc.
+      */
+      rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, iLangid, zDoc, nDoc, &pC);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      while( rc==SQLITE_OK && iCurrent<(nSnippet+nDesired) ){
+        const char *ZDUMMY; int DUMMY1 = 0, DUMMY2 = 0, DUMMY3 = 0;
+        rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
+      }
+      pMod->xClose(pC);
+      if( rc!=SQLITE_OK && rc!=SQLITE_DONE ){ return rc; }
+
+      nShift = (rc==SQLITE_DONE)+iCurrent-nSnippet;
+      assert( nShift<=nDesired );
+      if( nShift>0 ){
+        *piPos += nShift;
+        *pHlmask = hlmask >> nShift;
+      }
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Extract the snippet text for fragment pFragment from cursor pCsr and
+** append it to string buffer pOut.
+*/
+static int fts3SnippetText(
+  Fts3Cursor *pCsr,               /* FTS3 Cursor */
+  SnippetFragment *pFragment,     /* Snippet to extract */
+  int iFragment,                  /* Fragment number */
+  int isLast,                     /* True for final fragment in snippet */
+  int nSnippet,                   /* Number of tokens in extracted snippet */
+  const char *zOpen,              /* String inserted before highlighted term */
+  const char *zClose,             /* String inserted after highlighted term */
+  const char *zEllipsis,          /* String inserted between snippets */
+  StrBuffer *pOut                 /* Write output here */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc;                         /* Return code */
+  const char *zDoc;               /* Document text to extract snippet from */
+  int nDoc;                       /* Size of zDoc in bytes */
+  int iCurrent = 0;               /* Current token number of document */
+  int iEnd = 0;                   /* Byte offset of end of current token */
+  int isShiftDone = 0;            /* True after snippet is shifted */
+  int iPos = pFragment->iPos;     /* First token of snippet */
+  u64 hlmask = pFragment->hlmask; /* Highlight-mask for snippet */
+  int iCol = pFragment->iCol+1;   /* Query column to extract text from */
+  sqlite3_tokenizer_module *pMod; /* Tokenizer module methods object */
+  sqlite3_tokenizer_cursor *pC;   /* Tokenizer cursor open on zDoc/nDoc */
+  
+  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol);
+  if( zDoc==0 ){
+    if( sqlite3_column_type(pCsr->pStmt, iCol)!=SQLITE_NULL ){
+      return SQLITE_NOMEM;
+    }
+    return SQLITE_OK;
+  }
+  nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol);
+
+  /* Open a token cursor on the document. */
+  pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
+  rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, pCsr->iLangid, zDoc,nDoc,&pC);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  while( rc==SQLITE_OK ){
+    const char *ZDUMMY;           /* Dummy argument used with tokenizer */
+    int DUMMY1 = -1;              /* Dummy argument used with tokenizer */
+    int iBegin = 0;               /* Offset in zDoc of start of token */
+    int iFin = 0;                 /* Offset in zDoc of end of token */
+    int isHighlight = 0;          /* True for highlighted terms */
+
+    /* Variable DUMMY1 is initialized to a negative value above. Elsewhere
+    ** in the FTS code the variable that the third argument to xNext points to
+    ** is initialized to zero before the first (*but not necessarily
+    ** subsequent*) call to xNext(). This is done for a particular application
+    ** that needs to know whether or not the tokenizer is being used for
+    ** snippet generation or for some other purpose.
+    **
+    ** Extreme care is required when writing code to depend on this
+    ** initialization. It is not a documented part of the tokenizer interface.
+    ** If a tokenizer is used directly by any code outside of FTS, this
+    ** convention might not be respected.  */
+    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_DONE ){
+        /* Special case - the last token of the snippet is also the last token
+        ** of the column. Append any punctuation that occurred between the end
+        ** of the previous token and the end of the document to the output. 
+        ** Then break out of the loop. */
+        rc = fts3StringAppend(pOut, &zDoc[iEnd], -1);
+      }
+      break;
+    }
+    if( iCurrent<iPos ){ continue; }
+
+    if( !isShiftDone ){
+      int n = nDoc - iBegin;
+      rc = fts3SnippetShift(
+          pTab, pCsr->iLangid, nSnippet, &zDoc[iBegin], n, &iPos, &hlmask
+      );
+      isShiftDone = 1;
+
+      /* Now that the shift has been done, check if the initial "..." are
+      ** required. They are required if (a) this is not the first fragment,
+      ** or (b) this fragment does not begin at position 0 of its column. 
+      */
+      if( rc==SQLITE_OK ){
+        if( iPos>0 || iFragment>0 ){
+          rc = fts3StringAppend(pOut, zEllipsis, -1);
+        }else if( iBegin ){
+          rc = fts3StringAppend(pOut, zDoc, iBegin);
+        }
+      }
+      if( rc!=SQLITE_OK || iCurrent<iPos ) continue;
+    }
+
+    if( iCurrent>=(iPos+nSnippet) ){
+      if( isLast ){
+        rc = fts3StringAppend(pOut, zEllipsis, -1);
+      }
+      break;
+    }
+
+    /* Set isHighlight to true if this term should be highlighted. */
+    isHighlight = (hlmask & ((u64)1 << (iCurrent-iPos)))!=0;
+
+    if( iCurrent>iPos ) rc = fts3StringAppend(pOut, &zDoc[iEnd], iBegin-iEnd);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zOpen, -1);
+    if( rc==SQLITE_OK ) rc = fts3StringAppend(pOut, &zDoc[iBegin], iFin-iBegin);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zClose, -1);
+
+    iEnd = iFin;
+  }
+
+  pMod->xClose(pC);
+  return rc;
+}
+
+
+/*
+** This function is used to count the entries in a column-list (a 
+** delta-encoded list of term offsets within a single column of a single 
+** row). When this function is called, *ppCollist should point to the
+** beginning of the first varint in the column-list (the varint that
+** contains the position of the first matching term in the column data).
+** Before returning, *ppCollist is set to point to the first byte after
+** the last varint in the column-list (either the 0x00 signifying the end
+** of the position-list, or the 0x01 that precedes the column number of
+** the next column in the position-list).
+**
+** The number of elements in the column-list is returned.
+*/
+static int fts3ColumnlistCount(char **ppCollist){
+  char *pEnd = *ppCollist;
+  char c = 0;
+  int nEntry = 0;
+
+  /* A column-list is terminated by either a 0x01 or 0x00. */
+  while( 0xFE & (*pEnd | c) ){
+    c = *pEnd++ & 0x80;
+    if( !c ) nEntry++;
+  }
+
+  *ppCollist = pEnd;
+  return nEntry;
+}
+
+/*
+** This function gathers 'y' or 'b' data for a single phrase.
+*/
+static void fts3ExprLHits(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  MatchInfo *p                    /* Matchinfo context */
+){
+  Fts3Table *pTab = (Fts3Table *)p->pCursor->base.pVtab;
+  int iStart;
+  Fts3Phrase *pPhrase = pExpr->pPhrase;
+  char *pIter = pPhrase->doclist.pList;
+  int iCol = 0;
+
+  assert( p->flag==FTS3_MATCHINFO_LHITS_BM || p->flag==FTS3_MATCHINFO_LHITS );
+  if( p->flag==FTS3_MATCHINFO_LHITS ){
+    iStart = pExpr->iPhrase * p->nCol;
+  }else{
+    iStart = pExpr->iPhrase * ((p->nCol + 31) / 32);
+  }
+
+  while( 1 ){
+    int nHit = fts3ColumnlistCount(&pIter);
+    if( (pPhrase->iColumn>=pTab->nColumn || pPhrase->iColumn==iCol) ){
+      if( p->flag==FTS3_MATCHINFO_LHITS ){
+        p->aMatchinfo[iStart + iCol] = (u32)nHit;
+      }else if( nHit ){
+        p->aMatchinfo[iStart + (iCol+1)/32] |= (1 << (iCol&0x1F));
+      }
+    }
+    assert( *pIter==0x00 || *pIter==0x01 );
+    if( *pIter!=0x01 ) break;
+    pIter++;
+    pIter += fts3GetVarint32(pIter, &iCol);
+  }
+}
+
+/*
+** Gather the results for matchinfo directives 'y' and 'b'.
+*/
+static void fts3ExprLHitGather(
+  Fts3Expr *pExpr,
+  MatchInfo *p
+){
+  assert( (pExpr->pLeft==0)==(pExpr->pRight==0) );
+  if( pExpr->bEof==0 && pExpr->iDocid==p->pCursor->iPrevId ){
+    if( pExpr->pLeft ){
+      fts3ExprLHitGather(pExpr->pLeft, p);
+      fts3ExprLHitGather(pExpr->pRight, p);
+    }else{
+      fts3ExprLHits(pExpr, p);
+    }
+  }
+}
+
+/*
+** fts3ExprIterate() callback used to collect the "global" matchinfo stats
+** for a single query. 
+**
+** fts3ExprIterate() callback to load the 'global' elements of a
+** FTS3_MATCHINFO_HITS matchinfo array. The global stats are those elements 
+** of the matchinfo array that are constant for all rows returned by the 
+** current query.
+**
+** Argument pCtx is actually a pointer to a struct of type MatchInfo. This
+** function populates Matchinfo.aMatchinfo[] as follows:
+**
+**   for(iCol=0; iCol<nCol; iCol++){
+**     aMatchinfo[3*iPhrase*nCol + 3*iCol + 1] = X;
+**     aMatchinfo[3*iPhrase*nCol + 3*iCol + 2] = Y;
+**   }
+**
+** where X is the number of matches for phrase iPhrase is column iCol of all
+** rows of the table. Y is the number of rows for which column iCol contains
+** at least one instance of phrase iPhrase.
+**
+** If the phrase pExpr consists entirely of deferred tokens, then all X and
+** Y values are set to nDoc, where nDoc is the number of documents in the 
+** file system. This is done because the full-text index doclist is required
+** to calculate these values properly, and the full-text index doclist is
+** not available for deferred tokens.
+*/
+static int fts3ExprGlobalHitsCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number (numbered from zero) */
+  void *pCtx                      /* Pointer to MatchInfo structure */
+){
+  MatchInfo *p = (MatchInfo *)pCtx;
+  return sqlite3Fts3EvalPhraseStats(
+      p->pCursor, pExpr, &p->aMatchinfo[3*iPhrase*p->nCol]
+  );
+}
+
+/*
+** fts3ExprIterate() callback used to collect the "local" part of the
+** FTS3_MATCHINFO_HITS array. The local stats are those elements of the 
+** array that are different for each row returned by the query.
+*/
+static int fts3ExprLocalHitsCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number */
+  void *pCtx                      /* Pointer to MatchInfo structure */
+){
+  int rc = SQLITE_OK;
+  MatchInfo *p = (MatchInfo *)pCtx;
+  int iStart = iPhrase * p->nCol * 3;
+  int i;
+
+  for(i=0; i<p->nCol && rc==SQLITE_OK; i++){
+    char *pCsr;
+    rc = sqlite3Fts3EvalPhrasePoslist(p->pCursor, pExpr, i, &pCsr);
+    if( pCsr ){
+      p->aMatchinfo[iStart+i*3] = fts3ColumnlistCount(&pCsr);
+    }else{
+      p->aMatchinfo[iStart+i*3] = 0;
+    }
+  }
+
+  return rc;
+}
+
+static int fts3MatchinfoCheck(
+  Fts3Table *pTab, 
+  char cArg,
+  char **pzErr
+){
+  if( (cArg==FTS3_MATCHINFO_NPHRASE)
+   || (cArg==FTS3_MATCHINFO_NCOL)
+   || (cArg==FTS3_MATCHINFO_NDOC && pTab->bFts4)
+   || (cArg==FTS3_MATCHINFO_AVGLENGTH && pTab->bFts4)
+   || (cArg==FTS3_MATCHINFO_LENGTH && pTab->bHasDocsize)
+   || (cArg==FTS3_MATCHINFO_LCS)
+   || (cArg==FTS3_MATCHINFO_HITS)
+   || (cArg==FTS3_MATCHINFO_LHITS)
+   || (cArg==FTS3_MATCHINFO_LHITS_BM)
+  ){
+    return SQLITE_OK;
+  }
+  sqlite3Fts3ErrMsg(pzErr, "unrecognized matchinfo request: %c", cArg);
+  return SQLITE_ERROR;
+}
+
+static int fts3MatchinfoSize(MatchInfo *pInfo, char cArg){
+  int nVal;                       /* Number of integers output by cArg */
+
+  switch( cArg ){
+    case FTS3_MATCHINFO_NDOC:
+    case FTS3_MATCHINFO_NPHRASE: 
+    case FTS3_MATCHINFO_NCOL: 
+      nVal = 1;
+      break;
+
+    case FTS3_MATCHINFO_AVGLENGTH:
+    case FTS3_MATCHINFO_LENGTH:
+    case FTS3_MATCHINFO_LCS:
+      nVal = pInfo->nCol;
+      break;
+
+    case FTS3_MATCHINFO_LHITS:
+      nVal = pInfo->nCol * pInfo->nPhrase;
+      break;
+
+    case FTS3_MATCHINFO_LHITS_BM:
+      nVal = pInfo->nPhrase * ((pInfo->nCol + 31) / 32);
+      break;
+
+    default:
+      assert( cArg==FTS3_MATCHINFO_HITS );
+      nVal = pInfo->nCol * pInfo->nPhrase * 3;
+      break;
+  }
+
+  return nVal;
+}
+
+static int fts3MatchinfoSelectDoctotal(
+  Fts3Table *pTab,
+  sqlite3_stmt **ppStmt,
+  sqlite3_int64 *pnDoc,
+  const char **paLen
+){
+  sqlite3_stmt *pStmt;
+  const char *a;
+  sqlite3_int64 nDoc;
+
+  if( !*ppStmt ){
+    int rc = sqlite3Fts3SelectDoctotal(pTab, ppStmt);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  pStmt = *ppStmt;
+  assert( sqlite3_data_count(pStmt)==1 );
+
+  a = sqlite3_column_blob(pStmt, 0);
+  a += sqlite3Fts3GetVarint(a, &nDoc);
+  if( nDoc==0 ) return FTS_CORRUPT_VTAB;
+  *pnDoc = (u32)nDoc;
+
+  if( paLen ) *paLen = a;
+  return SQLITE_OK;
+}
+
+/*
+** An instance of the following structure is used to store state while 
+** iterating through a multi-column position-list corresponding to the
+** hits for a single phrase on a single row in order to calculate the
+** values for a matchinfo() FTS3_MATCHINFO_LCS request.
+*/
+typedef struct LcsIterator LcsIterator;
+struct LcsIterator {
+  Fts3Expr *pExpr;                /* Pointer to phrase expression */
+  int iPosOffset;                 /* Tokens count up to end of this phrase */
+  char *pRead;                    /* Cursor used to iterate through aDoclist */
+  int iPos;                       /* Current position */
+};
+
+/* 
+** If LcsIterator.iCol is set to the following value, the iterator has
+** finished iterating through all offsets for all columns.
+*/
+#define LCS_ITERATOR_FINISHED 0x7FFFFFFF;
+
+static int fts3MatchinfoLcsCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number (numbered from zero) */
+  void *pCtx                      /* Pointer to MatchInfo structure */
+){
+  LcsIterator *aIter = (LcsIterator *)pCtx;
+  aIter[iPhrase].pExpr = pExpr;
+  return SQLITE_OK;
+}
+
+/*
+** Advance the iterator passed as an argument to the next position. Return
+** 1 if the iterator is at EOF or if it now points to the start of the
+** position list for the next column.
+*/
+static int fts3LcsIteratorAdvance(LcsIterator *pIter){
+  char *pRead = pIter->pRead;
+  sqlite3_int64 iRead;
+  int rc = 0;
+
+  pRead += sqlite3Fts3GetVarint(pRead, &iRead);
+  if( iRead==0 || iRead==1 ){
+    pRead = 0;
+    rc = 1;
+  }else{
+    pIter->iPos += (int)(iRead-2);
+  }
+
+  pIter->pRead = pRead;
+  return rc;
+}
+  
+/*
+** This function implements the FTS3_MATCHINFO_LCS matchinfo() flag. 
+**
+** If the call is successful, the longest-common-substring lengths for each
+** column are written into the first nCol elements of the pInfo->aMatchinfo[] 
+** array before returning. SQLITE_OK is returned in this case.
+**
+** Otherwise, if an error occurs, an SQLite error code is returned and the
+** data written to the first nCol elements of pInfo->aMatchinfo[] is 
+** undefined.
+*/
+static int fts3MatchinfoLcs(Fts3Cursor *pCsr, MatchInfo *pInfo){
+  LcsIterator *aIter;
+  int i;
+  int iCol;
+  int nToken = 0;
+
+  /* Allocate and populate the array of LcsIterator objects. The array
+  ** contains one element for each matchable phrase in the query.
+  **/
+  aIter = sqlite3_malloc(sizeof(LcsIterator) * pCsr->nPhrase);
+  if( !aIter ) return SQLITE_NOMEM;
+  memset(aIter, 0, sizeof(LcsIterator) * pCsr->nPhrase);
+  (void)fts3ExprIterate(pCsr->pExpr, fts3MatchinfoLcsCb, (void*)aIter);
+
+  for(i=0; i<pInfo->nPhrase; i++){
+    LcsIterator *pIter = &aIter[i];
+    nToken -= pIter->pExpr->pPhrase->nToken;
+    pIter->iPosOffset = nToken;
+  }
+
+  for(iCol=0; iCol<pInfo->nCol; iCol++){
+    int nLcs = 0;                 /* LCS value for this column */
+    int nLive = 0;                /* Number of iterators in aIter not at EOF */
+
+    for(i=0; i<pInfo->nPhrase; i++){
+      int rc;
+      LcsIterator *pIt = &aIter[i];
+      rc = sqlite3Fts3EvalPhrasePoslist(pCsr, pIt->pExpr, iCol, &pIt->pRead);
+      if( rc!=SQLITE_OK ) return rc;
+      if( pIt->pRead ){
+        pIt->iPos = pIt->iPosOffset;
+        fts3LcsIteratorAdvance(&aIter[i]);
+        nLive++;
+      }
+    }
+
+    while( nLive>0 ){
+      LcsIterator *pAdv = 0;      /* The iterator to advance by one position */
+      int nThisLcs = 0;           /* LCS for the current iterator positions */
+
+      for(i=0; i<pInfo->nPhrase; i++){
+        LcsIterator *pIter = &aIter[i];
+        if( pIter->pRead==0 ){
+          /* This iterator is already at EOF for this column. */
+          nThisLcs = 0;
+        }else{
+          if( pAdv==0 || pIter->iPos<pAdv->iPos ){
+            pAdv = pIter;
+          }
+          if( nThisLcs==0 || pIter->iPos==pIter[-1].iPos ){
+            nThisLcs++;
+          }else{
+            nThisLcs = 1;
+          }
+          if( nThisLcs>nLcs ) nLcs = nThisLcs;
+        }
+      }
+      if( fts3LcsIteratorAdvance(pAdv) ) nLive--;
+    }
+
+    pInfo->aMatchinfo[iCol] = nLcs;
+  }
+
+  sqlite3_free(aIter);
+  return SQLITE_OK;
+}
+
+/*
+** Populate the buffer pInfo->aMatchinfo[] with an array of integers to
+** be returned by the matchinfo() function. Argument zArg contains the 
+** format string passed as the second argument to matchinfo (or the
+** default value "pcx" if no second argument was specified). The format
+** string has already been validated and the pInfo->aMatchinfo[] array
+** is guaranteed to be large enough for the output.
+**
+** If bGlobal is true, then populate all fields of the matchinfo() output.
+** If it is false, then assume that those fields that do not change between
+** rows (i.e. FTS3_MATCHINFO_NPHRASE, NCOL, NDOC, AVGLENGTH and part of HITS)
+** have already been populated.
+**
+** Return SQLITE_OK if successful, or an SQLite error code if an error 
+** occurs. If a value other than SQLITE_OK is returned, the state the
+** pInfo->aMatchinfo[] buffer is left in is undefined.
+*/
+static int fts3MatchinfoValues(
+  Fts3Cursor *pCsr,               /* FTS3 cursor object */
+  int bGlobal,                    /* True to grab the global stats */
+  MatchInfo *pInfo,               /* Matchinfo context object */
+  const char *zArg                /* Matchinfo format string */
+){
+  int rc = SQLITE_OK;
+  int i;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  sqlite3_stmt *pSelect = 0;
+
+  for(i=0; rc==SQLITE_OK && zArg[i]; i++){
+    pInfo->flag = zArg[i];
+    switch( zArg[i] ){
+      case FTS3_MATCHINFO_NPHRASE:
+        if( bGlobal ) pInfo->aMatchinfo[0] = pInfo->nPhrase;
+        break;
+
+      case FTS3_MATCHINFO_NCOL:
+        if( bGlobal ) pInfo->aMatchinfo[0] = pInfo->nCol;
+        break;
+        
+      case FTS3_MATCHINFO_NDOC:
+        if( bGlobal ){
+          sqlite3_int64 nDoc = 0;
+          rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &nDoc, 0);
+          pInfo->aMatchinfo[0] = (u32)nDoc;
+        }
+        break;
+
+      case FTS3_MATCHINFO_AVGLENGTH: 
+        if( bGlobal ){
+          sqlite3_int64 nDoc;     /* Number of rows in table */
+          const char *a;          /* Aggregate column length array */
+
+          rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &nDoc, &a);
+          if( rc==SQLITE_OK ){
+            int iCol;
+            for(iCol=0; iCol<pInfo->nCol; iCol++){
+              u32 iVal;
+              sqlite3_int64 nToken;
+              a += sqlite3Fts3GetVarint(a, &nToken);
+              iVal = (u32)(((u32)(nToken&0xffffffff)+nDoc/2)/nDoc);
+              pInfo->aMatchinfo[iCol] = iVal;
+            }
+          }
+        }
+        break;
+
+      case FTS3_MATCHINFO_LENGTH: {
+        sqlite3_stmt *pSelectDocsize = 0;
+        rc = sqlite3Fts3SelectDocsize(pTab, pCsr->iPrevId, &pSelectDocsize);
+        if( rc==SQLITE_OK ){
+          int iCol;
+          const char *a = sqlite3_column_blob(pSelectDocsize, 0);
+          for(iCol=0; iCol<pInfo->nCol; iCol++){
+            sqlite3_int64 nToken;
+            a += sqlite3Fts3GetVarint(a, &nToken);
+            pInfo->aMatchinfo[iCol] = (u32)nToken;
+          }
+        }
+        sqlite3_reset(pSelectDocsize);
+        break;
+      }
+
+      case FTS3_MATCHINFO_LCS:
+        rc = fts3ExprLoadDoclists(pCsr, 0, 0);
+        if( rc==SQLITE_OK ){
+          rc = fts3MatchinfoLcs(pCsr, pInfo);
+        }
+        break;
+
+      case FTS3_MATCHINFO_LHITS_BM:
+      case FTS3_MATCHINFO_LHITS: {
+        int nZero = fts3MatchinfoSize(pInfo, zArg[i]) * sizeof(u32);
+        memset(pInfo->aMatchinfo, 0, nZero);
+        fts3ExprLHitGather(pCsr->pExpr, pInfo);
+        break;
+      }
+
+      default: {
+        Fts3Expr *pExpr;
+        assert( zArg[i]==FTS3_MATCHINFO_HITS );
+        pExpr = pCsr->pExpr;
+        rc = fts3ExprLoadDoclists(pCsr, 0, 0);
+        if( rc!=SQLITE_OK ) break;
+        if( bGlobal ){
+          if( pCsr->pDeferred ){
+            rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &pInfo->nDoc, 0);
+            if( rc!=SQLITE_OK ) break;
+          }
+          rc = fts3ExprIterate(pExpr, fts3ExprGlobalHitsCb,(void*)pInfo);
+          sqlite3Fts3EvalTestDeferred(pCsr, &rc);
+          if( rc!=SQLITE_OK ) break;
+        }
+        (void)fts3ExprIterate(pExpr, fts3ExprLocalHitsCb,(void*)pInfo);
+        break;
+      }
+    }
+
+    pInfo->aMatchinfo += fts3MatchinfoSize(pInfo, zArg[i]);
+  }
+
+  sqlite3_reset(pSelect);
+  return rc;
+}
+
+
+/*
+** Populate pCsr->aMatchinfo[] with data for the current row. The 
+** 'matchinfo' data is an array of 32-bit unsigned integers (C type u32).
+*/
+static void fts3GetMatchinfo(
+  sqlite3_context *pCtx,        /* Return results here */
+  Fts3Cursor *pCsr,               /* FTS3 Cursor object */
+  const char *zArg                /* Second argument to matchinfo() function */
+){
+  MatchInfo sInfo;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+  int bGlobal = 0;                /* Collect 'global' stats as well as local */
+
+  u32 *aOut = 0;
+  void (*xDestroyOut)(void*) = 0;
+
+  memset(&sInfo, 0, sizeof(MatchInfo));
+  sInfo.pCursor = pCsr;
+  sInfo.nCol = pTab->nColumn;
+
+  /* If there is cached matchinfo() data, but the format string for the 
+  ** cache does not match the format string for this request, discard 
+  ** the cached data. */
+  if( pCsr->pMIBuffer && strcmp(pCsr->pMIBuffer->zMatchinfo, zArg) ){
+    sqlite3Fts3MIBufferFree(pCsr->pMIBuffer);
+    pCsr->pMIBuffer = 0;
+  }
+
+  /* If Fts3Cursor.pMIBuffer is NULL, then this is the first time the
+  ** matchinfo function has been called for this query. In this case 
+  ** allocate the array used to accumulate the matchinfo data and
+  ** initialize those elements that are constant for every row.
+  */
+  if( pCsr->pMIBuffer==0 ){
+    int nMatchinfo = 0;           /* Number of u32 elements in match-info */
+    int i;                        /* Used to iterate through zArg */
+
+    /* Determine the number of phrases in the query */
+    pCsr->nPhrase = fts3ExprPhraseCount(pCsr->pExpr);
+    sInfo.nPhrase = pCsr->nPhrase;
+
+    /* Determine the number of integers in the buffer returned by this call. */
+    for(i=0; zArg[i]; i++){
+      char *zErr = 0;
+      if( fts3MatchinfoCheck(pTab, zArg[i], &zErr) ){
+        sqlite3_result_error(pCtx, zErr, -1);
+        sqlite3_free(zErr);
+        return;
+      }
+      nMatchinfo += fts3MatchinfoSize(&sInfo, zArg[i]);
+    }
+
+    /* Allocate space for Fts3Cursor.aMatchinfo[] and Fts3Cursor.zMatchinfo. */
+    pCsr->pMIBuffer = fts3MIBufferNew(nMatchinfo, zArg);
+    if( !pCsr->pMIBuffer ) rc = SQLITE_NOMEM;
+
+    pCsr->isMatchinfoNeeded = 1;
+    bGlobal = 1;
+  }
+
+  if( rc==SQLITE_OK ){
+    xDestroyOut = fts3MIBufferAlloc(pCsr->pMIBuffer, &aOut);
+    if( xDestroyOut==0 ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    sInfo.aMatchinfo = aOut;
+    sInfo.nPhrase = pCsr->nPhrase;
+    rc = fts3MatchinfoValues(pCsr, bGlobal, &sInfo, zArg);
+    if( bGlobal ){
+      fts3MIBufferSetGlobal(pCsr->pMIBuffer);
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx, rc);
+    if( xDestroyOut ) xDestroyOut(aOut);
+  }else{
+    int n = pCsr->pMIBuffer->nElem * sizeof(u32);
+    sqlite3_result_blob(pCtx, aOut, n, xDestroyOut);
+  }
+}
+
+/*
+** Implementation of snippet() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3Snippet(
+  sqlite3_context *pCtx,          /* SQLite function call context */
+  Fts3Cursor *pCsr,               /* Cursor object */
+  const char *zStart,             /* Snippet start text - "<b>" */
+  const char *zEnd,               /* Snippet end text - "</b>" */
+  const char *zEllipsis,          /* Snippet ellipsis text - "<b>...</b>" */
+  int iCol,                       /* Extract snippet from this column */
+  int nToken                      /* Approximate number of tokens in snippet */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+  int i;
+  StrBuffer res = {0, 0, 0};
+
+  /* The returned text includes up to four fragments of text extracted from
+  ** the data in the current row. The first iteration of the for(...) loop
+  ** below attempts to locate a single fragment of text nToken tokens in 
+  ** size that contains at least one instance of all phrases in the query
+  ** expression that appear in the current row. If such a fragment of text
+  ** cannot be found, the second iteration of the loop attempts to locate
+  ** a pair of fragments, and so on.
+  */
+  int nSnippet = 0;               /* Number of fragments in this snippet */
+  SnippetFragment aSnippet[4];    /* Maximum of 4 fragments per snippet */
+  int nFToken = -1;               /* Number of tokens in each fragment */
+
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
+  }
+
+  for(nSnippet=1; 1; nSnippet++){
+
+    int iSnip;                    /* Loop counter 0..nSnippet-1 */
+    u64 mCovered = 0;             /* Bitmask of phrases covered by snippet */
+    u64 mSeen = 0;                /* Bitmask of phrases seen by BestSnippet() */
+
+    if( nToken>=0 ){
+      nFToken = (nToken+nSnippet-1) / nSnippet;
+    }else{
+      nFToken = -1 * nToken;
+    }
+
+    for(iSnip=0; iSnip<nSnippet; iSnip++){
+      int iBestScore = -1;        /* Best score of columns checked so far */
+      int iRead;                  /* Used to iterate through columns */
+      SnippetFragment *pFragment = &aSnippet[iSnip];
+
+      memset(pFragment, 0, sizeof(*pFragment));
+
+      /* Loop through all columns of the table being considered for snippets.
+      ** If the iCol argument to this function was negative, this means all
+      ** columns of the FTS3 table. Otherwise, only column iCol is considered.
+      */
+      for(iRead=0; iRead<pTab->nColumn; iRead++){
+        SnippetFragment sF = {0, 0, 0, 0};
+        int iS = 0;
+        if( iCol>=0 && iRead!=iCol ) continue;
+
+        /* Find the best snippet of nFToken tokens in column iRead. */
+        rc = fts3BestSnippet(nFToken, pCsr, iRead, mCovered, &mSeen, &sF, &iS);
+        if( rc!=SQLITE_OK ){
+          goto snippet_out;
+        }
+        if( iS>iBestScore ){
+          *pFragment = sF;
+          iBestScore = iS;
+        }
+      }
+
+      mCovered |= pFragment->covered;
+    }
+
+    /* If all query phrases seen by fts3BestSnippet() are present in at least
+    ** one of the nSnippet snippet fragments, break out of the loop.
+    */
+    assert( (mCovered&mSeen)==mCovered );
+    if( mSeen==mCovered || nSnippet==SizeofArray(aSnippet) ) break;
+  }
+
+  assert( nFToken>0 );
+
+  for(i=0; i<nSnippet && rc==SQLITE_OK; i++){
+    rc = fts3SnippetText(pCsr, &aSnippet[i], 
+        i, (i==nSnippet-1), nFToken, zStart, zEnd, zEllipsis, &res
+    );
+  }
+
+ snippet_out:
+  sqlite3Fts3SegmentsClose(pTab);
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx, rc);
+    sqlite3_free(res.z);
+  }else{
+    sqlite3_result_text(pCtx, res.z, -1, sqlite3_free);
+  }
+}
+
+
+typedef struct TermOffset TermOffset;
+typedef struct TermOffsetCtx TermOffsetCtx;
+
+struct TermOffset {
+  char *pList;                    /* Position-list */
+  int iPos;                       /* Position just read from pList */
+  int iOff;                       /* Offset of this term from read positions */
+};
+
+struct TermOffsetCtx {
+  Fts3Cursor *pCsr;
+  int iCol;                       /* Column of table to populate aTerm for */
+  int iTerm;
+  sqlite3_int64 iDocid;
+  TermOffset *aTerm;
+};
+
+/*
+** This function is an fts3ExprIterate() callback used by sqlite3Fts3Offsets().
+*/
+static int fts3ExprTermOffsetInit(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  TermOffsetCtx *p = (TermOffsetCtx *)ctx;
+  int nTerm;                      /* Number of tokens in phrase */
+  int iTerm;                      /* For looping through nTerm phrase terms */
+  char *pList;                    /* Pointer to position list for phrase */
+  int iPos = 0;                   /* First position in position-list */
+  int rc;
+
+  UNUSED_PARAMETER(iPhrase);
+  rc = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->iCol, &pList);
+  nTerm = pExpr->pPhrase->nToken;
+  if( pList ){
+    fts3GetDeltaPosition(&pList, &iPos);
+    assert( iPos>=0 );
+  }
+
+  for(iTerm=0; iTerm<nTerm; iTerm++){
+    TermOffset *pT = &p->aTerm[p->iTerm++];
+    pT->iOff = nTerm-iTerm-1;
+    pT->pList = pList;
+    pT->iPos = iPos;
+  }
+
+  return rc;
+}
+
+/*
+** Implementation of offsets() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3Offsets(
+  sqlite3_context *pCtx,          /* SQLite function call context */
+  Fts3Cursor *pCsr                /* Cursor object */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  sqlite3_tokenizer_module const *pMod = pTab->pTokenizer->pModule;
+  int rc;                         /* Return Code */
+  int nToken;                     /* Number of tokens in query */
+  int iCol;                       /* Column currently being processed */
+  StrBuffer res = {0, 0, 0};      /* Result string */
+  TermOffsetCtx sCtx;             /* Context for fts3ExprTermOffsetInit() */
+
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
+  }
+
+  memset(&sCtx, 0, sizeof(sCtx));
+  assert( pCsr->isRequireSeek==0 );
+
+  /* Count the number of terms in the query */
+  rc = fts3ExprLoadDoclists(pCsr, 0, &nToken);
+  if( rc!=SQLITE_OK ) goto offsets_out;
+
+  /* Allocate the array of TermOffset iterators. */
+  sCtx.aTerm = (TermOffset *)sqlite3_malloc(sizeof(TermOffset)*nToken);
+  if( 0==sCtx.aTerm ){
+    rc = SQLITE_NOMEM;
+    goto offsets_out;
+  }
+  sCtx.iDocid = pCsr->iPrevId;
+  sCtx.pCsr = pCsr;
+
+  /* Loop through the table columns, appending offset information to 
+  ** string-buffer res for each column.
+  */
+  for(iCol=0; iCol<pTab->nColumn; iCol++){
+    sqlite3_tokenizer_cursor *pC; /* Tokenizer cursor */
+    const char *ZDUMMY;           /* Dummy argument used with xNext() */
+    int NDUMMY = 0;               /* Dummy argument used with xNext() */
+    int iStart = 0;
+    int iEnd = 0;
+    int iCurrent = 0;
+    const char *zDoc;
+    int nDoc;
+
+    /* Initialize the contents of sCtx.aTerm[] for column iCol. There is 
+    ** no way that this operation can fail, so the return code from
+    ** fts3ExprIterate() can be discarded.
+    */
+    sCtx.iCol = iCol;
+    sCtx.iTerm = 0;
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprTermOffsetInit, (void*)&sCtx);
+
+    /* Retreive the text stored in column iCol. If an SQL NULL is stored 
+    ** in column iCol, jump immediately to the next iteration of the loop.
+    ** If an OOM occurs while retrieving the data (this can happen if SQLite
+    ** needs to transform the data from utf-16 to utf-8), return SQLITE_NOMEM 
+    ** to the caller. 
+    */
+    zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol+1);
+    nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol+1);
+    if( zDoc==0 ){
+      if( sqlite3_column_type(pCsr->pStmt, iCol+1)==SQLITE_NULL ){
+        continue;
+      }
+      rc = SQLITE_NOMEM;
+      goto offsets_out;
+    }
+
+    /* Initialize a tokenizer iterator to iterate through column iCol. */
+    rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, pCsr->iLangid,
+        zDoc, nDoc, &pC
+    );
+    if( rc!=SQLITE_OK ) goto offsets_out;
+
+    rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+    while( rc==SQLITE_OK ){
+      int i;                      /* Used to loop through terms */
+      int iMinPos = 0x7FFFFFFF;   /* Position of next token */
+      TermOffset *pTerm = 0;      /* TermOffset associated with next token */
+
+      for(i=0; i<nToken; i++){
+        TermOffset *pT = &sCtx.aTerm[i];
+        if( pT->pList && (pT->iPos-pT->iOff)<iMinPos ){
+          iMinPos = pT->iPos-pT->iOff;
+          pTerm = pT;
+        }
+      }
+
+      if( !pTerm ){
+        /* All offsets for this column have been gathered. */
+        rc = SQLITE_DONE;
+      }else{
+        assert( iCurrent<=iMinPos );
+        if( 0==(0xFE&*pTerm->pList) ){
+          pTerm->pList = 0;
+        }else{
+          fts3GetDeltaPosition(&pTerm->pList, &pTerm->iPos);
+        }
+        while( rc==SQLITE_OK && iCurrent<iMinPos ){
+          rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+        }
+        if( rc==SQLITE_OK ){
+          char aBuffer[64];
+          sqlite3_snprintf(sizeof(aBuffer), aBuffer, 
+              "%d %d %d %d ", iCol, pTerm-sCtx.aTerm, iStart, iEnd-iStart
+          );
+          rc = fts3StringAppend(&res, aBuffer, -1);
+        }else if( rc==SQLITE_DONE && pTab->zContentTbl==0 ){
+          rc = FTS_CORRUPT_VTAB;
+        }
+      }
+    }
+    if( rc==SQLITE_DONE ){
+      rc = SQLITE_OK;
+    }
+
+    pMod->xClose(pC);
+    if( rc!=SQLITE_OK ) goto offsets_out;
+  }
+
+ offsets_out:
+  sqlite3_free(sCtx.aTerm);
+  assert( rc!=SQLITE_DONE );
+  sqlite3Fts3SegmentsClose(pTab);
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx,  rc);
+    sqlite3_free(res.z);
+  }else{
+    sqlite3_result_text(pCtx, res.z, res.n-1, sqlite3_free);
+  }
+  return;
+}
+
+/*
+** Implementation of matchinfo() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3Matchinfo(
+  sqlite3_context *pContext,      /* Function call context */
+  Fts3Cursor *pCsr,               /* FTS3 table cursor */
+  const char *zArg                /* Second arg to matchinfo() function */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  const char *zFormat;
+
+  if( zArg ){
+    zFormat = zArg;
+  }else{
+    zFormat = FTS3_MATCHINFO_DEFAULT;
+  }
+
+  if( !pCsr->pExpr ){
+    sqlite3_result_blob(pContext, "", 0, SQLITE_STATIC);
+    return;
+  }else{
+    /* Retrieve matchinfo() data. */
+    fts3GetMatchinfo(pContext, pCsr, zFormat);
+    sqlite3Fts3SegmentsClose(pTab);
+  }
+}
+
+#endif
+
+/************** End of fts3_snippet.c ****************************************/
+/************** Begin file fts3_unicode.c ************************************/
+/*
+** 2012 May 24
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** Implementation of the "unicode" full-text-search tokenizer.
+*/
+
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <stdio.h> */
+/* #include <string.h> */
+
+/* #include "fts3_tokenizer.h" */
+
+/*
+** The following two macros - READ_UTF8 and WRITE_UTF8 - have been copied
+** from the sqlite3 source file utf.c. If this file is compiled as part
+** of the amalgamation, they are not required.
+*/
+#ifndef SQLITE_AMALGAMATION
+
+static const unsigned char sqlite3Utf8Trans1[] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00,
+};
+
+#define READ_UTF8(zIn, zTerm, c)                           \
+  c = *(zIn++);                                            \
+  if( c>=0xc0 ){                                           \
+    c = sqlite3Utf8Trans1[c-0xc0];                         \
+    while( zIn!=zTerm && (*zIn & 0xc0)==0x80 ){            \
+      c = (c<<6) + (0x3f & *(zIn++));                      \
+    }                                                      \
+    if( c<0x80                                             \
+        || (c&0xFFFFF800)==0xD800                          \
+        || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }        \
+  }
+
+#define WRITE_UTF8(zOut, c) {                          \
+  if( c<0x00080 ){                                     \
+    *zOut++ = (u8)(c&0xFF);                            \
+  }                                                    \
+  else if( c<0x00800 ){                                \
+    *zOut++ = 0xC0 + (u8)((c>>6)&0x1F);                \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+  else if( c<0x10000 ){                                \
+    *zOut++ = 0xE0 + (u8)((c>>12)&0x0F);               \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }else{                                               \
+    *zOut++ = 0xF0 + (u8)((c>>18) & 0x07);             \
+    *zOut++ = 0x80 + (u8)((c>>12) & 0x3F);             \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+}
+
+#endif /* ifndef SQLITE_AMALGAMATION */
+
+typedef struct unicode_tokenizer unicode_tokenizer;
+typedef struct unicode_cursor unicode_cursor;
+
+struct unicode_tokenizer {
+  sqlite3_tokenizer base;
+  int bRemoveDiacritic;
+  int nException;
+  int *aiException;
+};
+
+struct unicode_cursor {
+  sqlite3_tokenizer_cursor base;
+  const unsigned char *aInput;    /* Input text being tokenized */
+  int nInput;                     /* Size of aInput[] in bytes */
+  int iOff;                       /* Current offset within aInput[] */
+  int iToken;                     /* Index of next token to be returned */
+  char *zToken;                   /* storage for current token */
+  int nAlloc;                     /* space allocated at zToken */
+};
+
+
+/*
+** Destroy a tokenizer allocated by unicodeCreate().
+*/
+static int unicodeDestroy(sqlite3_tokenizer *pTokenizer){
+  if( pTokenizer ){
+    unicode_tokenizer *p = (unicode_tokenizer *)pTokenizer;
+    sqlite3_free(p->aiException);
+    sqlite3_free(p);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** As part of a tokenchars= or separators= option, the CREATE VIRTUAL TABLE
+** statement has specified that the tokenizer for this table shall consider
+** all characters in string zIn/nIn to be separators (if bAlnum==0) or
+** token characters (if bAlnum==1).
+**
+** For each codepoint in the zIn/nIn string, this function checks if the
+** sqlite3FtsUnicodeIsalnum() function already returns the desired result.
+** If so, no action is taken. Otherwise, the codepoint is added to the 
+** unicode_tokenizer.aiException[] array. For the purposes of tokenization,
+** the return value of sqlite3FtsUnicodeIsalnum() is inverted for all
+** codepoints in the aiException[] array.
+**
+** If a standalone diacritic mark (one that sqlite3FtsUnicodeIsdiacritic()
+** identifies as a diacritic) occurs in the zIn/nIn string it is ignored.
+** It is not possible to change the behavior of the tokenizer with respect
+** to these codepoints.
+*/
+static int unicodeAddExceptions(
+  unicode_tokenizer *p,           /* Tokenizer to add exceptions to */
+  int bAlnum,                     /* Replace Isalnum() return value with this */
+  const char *zIn,                /* Array of characters to make exceptions */
+  int nIn                         /* Length of z in bytes */
+){
+  const unsigned char *z = (const unsigned char *)zIn;
+  const unsigned char *zTerm = &z[nIn];
+  int iCode;
+  int nEntry = 0;
+
+  assert( bAlnum==0 || bAlnum==1 );
+
+  while( z<zTerm ){
+    READ_UTF8(z, zTerm, iCode);
+    assert( (sqlite3FtsUnicodeIsalnum(iCode) & 0xFFFFFFFE)==0 );
+    if( sqlite3FtsUnicodeIsalnum(iCode)!=bAlnum 
+     && sqlite3FtsUnicodeIsdiacritic(iCode)==0 
+    ){
+      nEntry++;
+    }
+  }
+
+  if( nEntry ){
+    int *aNew;                    /* New aiException[] array */
+    int nNew;                     /* Number of valid entries in array aNew[] */
+
+    aNew = sqlite3_realloc(p->aiException, (p->nException+nEntry)*sizeof(int));
+    if( aNew==0 ) return SQLITE_NOMEM;
+    nNew = p->nException;
+
+    z = (const unsigned char *)zIn;
+    while( z<zTerm ){
+      READ_UTF8(z, zTerm, iCode);
+      if( sqlite3FtsUnicodeIsalnum(iCode)!=bAlnum 
+       && sqlite3FtsUnicodeIsdiacritic(iCode)==0
+      ){
+        int i, j;
+        for(i=0; i<nNew && aNew[i]<iCode; i++);
+        for(j=nNew; j>i; j--) aNew[j] = aNew[j-1];
+        aNew[i] = iCode;
+        nNew++;
+      }
+    }
+    p->aiException = aNew;
+    p->nException = nNew;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Return true if the p->aiException[] array contains the value iCode.
+*/
+static int unicodeIsException(unicode_tokenizer *p, int iCode){
+  if( p->nException>0 ){
+    int *a = p->aiException;
+    int iLo = 0;
+    int iHi = p->nException-1;
+
+    while( iHi>=iLo ){
+      int iTest = (iHi + iLo) / 2;
+      if( iCode==a[iTest] ){
+        return 1;
+      }else if( iCode>a[iTest] ){
+        iLo = iTest+1;
+      }else{
+        iHi = iTest-1;
+      }
+    }
+  }
+
+  return 0;
+}
+
+/*
+** Return true if, for the purposes of tokenization, codepoint iCode is
+** considered a token character (not a separator).
+*/
+static int unicodeIsAlnum(unicode_tokenizer *p, int iCode){
+  assert( (sqlite3FtsUnicodeIsalnum(iCode) & 0xFFFFFFFE)==0 );
+  return sqlite3FtsUnicodeIsalnum(iCode) ^ unicodeIsException(p, iCode);
+}
+
+/*
+** Create a new tokenizer instance.
+*/
+static int unicodeCreate(
+  int nArg,                       /* Size of array argv[] */
+  const char * const *azArg,      /* Tokenizer creation arguments */
+  sqlite3_tokenizer **pp          /* OUT: New tokenizer handle */
+){
+  unicode_tokenizer *pNew;        /* New tokenizer object */
+  int i;
+  int rc = SQLITE_OK;
+
+  pNew = (unicode_tokenizer *) sqlite3_malloc(sizeof(unicode_tokenizer));
+  if( pNew==NULL ) return SQLITE_NOMEM;
+  memset(pNew, 0, sizeof(unicode_tokenizer));
+  pNew->bRemoveDiacritic = 1;
+
+  for(i=0; rc==SQLITE_OK && i<nArg; i++){
+    const char *z = azArg[i];
+    int n = (int)strlen(z);
+
+    if( n==19 && memcmp("remove_diacritics=1", z, 19)==0 ){
+      pNew->bRemoveDiacritic = 1;
+    }
+    else if( n==19 && memcmp("remove_diacritics=0", z, 19)==0 ){
+      pNew->bRemoveDiacritic = 0;
+    }
+    else if( n>=11 && memcmp("tokenchars=", z, 11)==0 ){
+      rc = unicodeAddExceptions(pNew, 1, &z[11], n-11);
+    }
+    else if( n>=11 && memcmp("separators=", z, 11)==0 ){
+      rc = unicodeAddExceptions(pNew, 0, &z[11], n-11);
+    }
+    else{
+      /* Unrecognized argument */
+      rc  = SQLITE_ERROR;
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    unicodeDestroy((sqlite3_tokenizer *)pNew);
+    pNew = 0;
+  }
+  *pp = (sqlite3_tokenizer *)pNew;
+  return rc;
+}
+
+/*
+** Prepare to begin tokenizing a particular string.  The input
+** string to be tokenized is pInput[0..nBytes-1].  A cursor
+** used to incrementally tokenize this string is returned in 
+** *ppCursor.
+*/
+static int unicodeOpen(
+  sqlite3_tokenizer *p,           /* The tokenizer */
+  const char *aInput,             /* Input string */
+  int nInput,                     /* Size of string aInput in bytes */
+  sqlite3_tokenizer_cursor **pp   /* OUT: New cursor object */
+){
+  unicode_cursor *pCsr;
+
+  pCsr = (unicode_cursor *)sqlite3_malloc(sizeof(unicode_cursor));
+  if( pCsr==0 ){
+    return SQLITE_NOMEM;
+  }
+  memset(pCsr, 0, sizeof(unicode_cursor));
+
+  pCsr->aInput = (const unsigned char *)aInput;
+  if( aInput==0 ){
+    pCsr->nInput = 0;
+  }else if( nInput<0 ){
+    pCsr->nInput = (int)strlen(aInput);
+  }else{
+    pCsr->nInput = nInput;
+  }
+
+  *pp = &pCsr->base;
+  UNUSED_PARAMETER(p);
+  return SQLITE_OK;
+}
+
+/*
+** Close a tokenization cursor previously opened by a call to
+** simpleOpen() above.
+*/
+static int unicodeClose(sqlite3_tokenizer_cursor *pCursor){
+  unicode_cursor *pCsr = (unicode_cursor *) pCursor;
+  sqlite3_free(pCsr->zToken);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/*
+** Extract the next token from a tokenization cursor.  The cursor must
+** have been opened by a prior call to simpleOpen().
+*/
+static int unicodeNext(
+  sqlite3_tokenizer_cursor *pC,   /* Cursor returned by simpleOpen */
+  const char **paToken,           /* OUT: Token text */
+  int *pnToken,                   /* OUT: Number of bytes at *paToken */
+  int *piStart,                   /* OUT: Starting offset of token */
+  int *piEnd,                     /* OUT: Ending offset of token */
+  int *piPos                      /* OUT: Position integer of token */
+){
+  unicode_cursor *pCsr = (unicode_cursor *)pC;
+  unicode_tokenizer *p = ((unicode_tokenizer *)pCsr->base.pTokenizer);
+  int iCode = 0;
+  char *zOut;
+  const unsigned char *z = &pCsr->aInput[pCsr->iOff];
+  const unsigned char *zStart = z;
+  const unsigned char *zEnd;
+  const unsigned char *zTerm = &pCsr->aInput[pCsr->nInput];
+
+  /* Scan past any delimiter characters before the start of the next token.
+  ** Return SQLITE_DONE early if this takes us all the way to the end of 
+  ** the input.  */
+  while( z<zTerm ){
+    READ_UTF8(z, zTerm, iCode);
+    if( unicodeIsAlnum(p, iCode) ) break;
+    zStart = z;
+  }
+  if( zStart>=zTerm ) return SQLITE_DONE;
+
+  zOut = pCsr->zToken;
+  do {
+    int iOut;
+
+    /* Grow the output buffer if required. */
+    if( (zOut-pCsr->zToken)>=(pCsr->nAlloc-4) ){
+      char *zNew = sqlite3_realloc(pCsr->zToken, pCsr->nAlloc+64);
+      if( !zNew ) return SQLITE_NOMEM;
+      zOut = &zNew[zOut - pCsr->zToken];
+      pCsr->zToken = zNew;
+      pCsr->nAlloc += 64;
+    }
+
+    /* Write the folded case of the last character read to the output */
+    zEnd = z;
+    iOut = sqlite3FtsUnicodeFold(iCode, p->bRemoveDiacritic);
+    if( iOut ){
+      WRITE_UTF8(zOut, iOut);
+    }
+
+    /* If the cursor is not at EOF, read the next character */
+    if( z>=zTerm ) break;
+    READ_UTF8(z, zTerm, iCode);
+  }while( unicodeIsAlnum(p, iCode) 
+       || sqlite3FtsUnicodeIsdiacritic(iCode)
+  );
+
+  /* Set the output variables and return. */
+  pCsr->iOff = (int)(z - pCsr->aInput);
+  *paToken = pCsr->zToken;
+  *pnToken = (int)(zOut - pCsr->zToken);
+  *piStart = (int)(zStart - pCsr->aInput);
+  *piEnd = (int)(zEnd - pCsr->aInput);
+  *piPos = pCsr->iToken++;
+  return SQLITE_OK;
+}
+
+/*
+** Set *ppModule to a pointer to the sqlite3_tokenizer_module 
+** structure for the unicode tokenizer.
+*/
+SQLITE_PRIVATE void sqlite3Fts3UnicodeTokenizer(sqlite3_tokenizer_module const **ppModule){
+  static const sqlite3_tokenizer_module module = {
+    0,
+    unicodeCreate,
+    unicodeDestroy,
+    unicodeOpen,
+    unicodeClose,
+    unicodeNext,
+    0,
+  };
+  *ppModule = &module;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+#endif /* ifndef SQLITE_DISABLE_FTS3_UNICODE */
+
+/************** End of fts3_unicode.c ****************************************/
+/************** Begin file fts3_unicode2.c ***********************************/
+/*
+** 2012 May 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+*/
+
+/*
+** DO NOT EDIT THIS MACHINE GENERATED FILE.
+*/
+
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+#if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
+
+/* #include <assert.h> */
+
+/*
+** Return true if the argument corresponds to a unicode codepoint
+** classified as either a letter or a number. Otherwise false.
+**
+** The results are undefined if the value passed to this function
+** is less than zero.
+*/
+SQLITE_PRIVATE int sqlite3FtsUnicodeIsalnum(int c){
+  /* Each unsigned integer in the following array corresponds to a contiguous
+  ** range of unicode codepoints that are not either letters or numbers (i.e.
+  ** codepoints for which this function should return 0).
+  **
+  ** The most significant 22 bits in each 32-bit value contain the first 
+  ** codepoint in the range. The least significant 10 bits are used to store
+  ** the size of the range (always at least 1). In other words, the value 
+  ** ((C<<22) + N) represents a range of N codepoints starting with codepoint 
+  ** C. It is not possible to represent a range larger than 1023 codepoints 
+  ** using this format.
+  */
+  static const unsigned int aEntry[] = {
+    0x00000030, 0x0000E807, 0x00016C06, 0x0001EC2F, 0x0002AC07,
+    0x0002D001, 0x0002D803, 0x0002EC01, 0x0002FC01, 0x00035C01,
+    0x0003DC01, 0x000B0804, 0x000B480E, 0x000B9407, 0x000BB401,
+    0x000BBC81, 0x000DD401, 0x000DF801, 0x000E1002, 0x000E1C01,
+    0x000FD801, 0x00120808, 0x00156806, 0x00162402, 0x00163C01,
+    0x00164437, 0x0017CC02, 0x00180005, 0x00181816, 0x00187802,
+    0x00192C15, 0x0019A804, 0x0019C001, 0x001B5001, 0x001B580F,
+    0x001B9C07, 0x001BF402, 0x001C000E, 0x001C3C01, 0x001C4401,
+    0x001CC01B, 0x001E980B, 0x001FAC09, 0x001FD804, 0x00205804,
+    0x00206C09, 0x00209403, 0x0020A405, 0x0020C00F, 0x00216403,
+    0x00217801, 0x0023901B, 0x00240004, 0x0024E803, 0x0024F812,
+    0x00254407, 0x00258804, 0x0025C001, 0x00260403, 0x0026F001,
+    0x0026F807, 0x00271C02, 0x00272C03, 0x00275C01, 0x00278802,
+    0x0027C802, 0x0027E802, 0x00280403, 0x0028F001, 0x0028F805,
+    0x00291C02, 0x00292C03, 0x00294401, 0x0029C002, 0x0029D401,
+    0x002A0403, 0x002AF001, 0x002AF808, 0x002B1C03, 0x002B2C03,
+    0x002B8802, 0x002BC002, 0x002C0403, 0x002CF001, 0x002CF807,
+    0x002D1C02, 0x002D2C03, 0x002D5802, 0x002D8802, 0x002DC001,
+    0x002E0801, 0x002EF805, 0x002F1803, 0x002F2804, 0x002F5C01,
+    0x002FCC08, 0x00300403, 0x0030F807, 0x00311803, 0x00312804,
+    0x00315402, 0x00318802, 0x0031FC01, 0x00320802, 0x0032F001,
+    0x0032F807, 0x00331803, 0x00332804, 0x00335402, 0x00338802,
+    0x00340802, 0x0034F807, 0x00351803, 0x00352804, 0x00355C01,
+    0x00358802, 0x0035E401, 0x00360802, 0x00372801, 0x00373C06,
+    0x00375801, 0x00376008, 0x0037C803, 0x0038C401, 0x0038D007,
+    0x0038FC01, 0x00391C09, 0x00396802, 0x003AC401, 0x003AD006,
+    0x003AEC02, 0x003B2006, 0x003C041F, 0x003CD00C, 0x003DC417,
+    0x003E340B, 0x003E6424, 0x003EF80F, 0x003F380D, 0x0040AC14,
+    0x00412806, 0x00415804, 0x00417803, 0x00418803, 0x00419C07,
+    0x0041C404, 0x0042080C, 0x00423C01, 0x00426806, 0x0043EC01,
+    0x004D740C, 0x004E400A, 0x00500001, 0x0059B402, 0x005A0001,
+    0x005A6C02, 0x005BAC03, 0x005C4803, 0x005CC805, 0x005D4802,
+    0x005DC802, 0x005ED023, 0x005F6004, 0x005F7401, 0x0060000F,
+    0x0062A401, 0x0064800C, 0x0064C00C, 0x00650001, 0x00651002,
+    0x0066C011, 0x00672002, 0x00677822, 0x00685C05, 0x00687802,
+    0x0069540A, 0x0069801D, 0x0069FC01, 0x006A8007, 0x006AA006,
+    0x006C0005, 0x006CD011, 0x006D6823, 0x006E0003, 0x006E840D,
+    0x006F980E, 0x006FF004, 0x00709014, 0x0070EC05, 0x0071F802,
+    0x00730008, 0x00734019, 0x0073B401, 0x0073C803, 0x00770027,
+    0x0077F004, 0x007EF401, 0x007EFC03, 0x007F3403, 0x007F7403,
+    0x007FB403, 0x007FF402, 0x00800065, 0x0081A806, 0x0081E805,
+    0x00822805, 0x0082801A, 0x00834021, 0x00840002, 0x00840C04,
+    0x00842002, 0x00845001, 0x00845803, 0x00847806, 0x00849401,
+    0x00849C01, 0x0084A401, 0x0084B801, 0x0084E802, 0x00850005,
+    0x00852804, 0x00853C01, 0x00864264, 0x00900027, 0x0091000B,
+    0x0092704E, 0x00940200, 0x009C0475, 0x009E53B9, 0x00AD400A,
+    0x00B39406, 0x00B3BC03, 0x00B3E404, 0x00B3F802, 0x00B5C001,
+    0x00B5FC01, 0x00B7804F, 0x00B8C00C, 0x00BA001A, 0x00BA6C59,
+    0x00BC00D6, 0x00BFC00C, 0x00C00005, 0x00C02019, 0x00C0A807,
+    0x00C0D802, 0x00C0F403, 0x00C26404, 0x00C28001, 0x00C3EC01,
+    0x00C64002, 0x00C6580A, 0x00C70024, 0x00C8001F, 0x00C8A81E,
+    0x00C94001, 0x00C98020, 0x00CA2827, 0x00CB003F, 0x00CC0100,
+    0x01370040, 0x02924037, 0x0293F802, 0x02983403, 0x0299BC10,
+    0x029A7C01, 0x029BC008, 0x029C0017, 0x029C8002, 0x029E2402,
+    0x02A00801, 0x02A01801, 0x02A02C01, 0x02A08C09, 0x02A0D804,
+    0x02A1D004, 0x02A20002, 0x02A2D011, 0x02A33802, 0x02A38012,
+    0x02A3E003, 0x02A4980A, 0x02A51C0D, 0x02A57C01, 0x02A60004,
+    0x02A6CC1B, 0x02A77802, 0x02A8A40E, 0x02A90C01, 0x02A93002,
+    0x02A97004, 0x02A9DC03, 0x02A9EC01, 0x02AAC001, 0x02AAC803,
+    0x02AADC02, 0x02AAF802, 0x02AB0401, 0x02AB7802, 0x02ABAC07,
+    0x02ABD402, 0x02AF8C0B, 0x03600001, 0x036DFC02, 0x036FFC02,
+    0x037FFC01, 0x03EC7801, 0x03ECA401, 0x03EEC810, 0x03F4F802,
+    0x03F7F002, 0x03F8001A, 0x03F88007, 0x03F8C023, 0x03F95013,
+    0x03F9A004, 0x03FBFC01, 0x03FC040F, 0x03FC6807, 0x03FCEC06,
+    0x03FD6C0B, 0x03FF8007, 0x03FFA007, 0x03FFE405, 0x04040003,
+    0x0404DC09, 0x0405E411, 0x0406400C, 0x0407402E, 0x040E7C01,
+    0x040F4001, 0x04215C01, 0x04247C01, 0x0424FC01, 0x04280403,
+    0x04281402, 0x04283004, 0x0428E003, 0x0428FC01, 0x04294009,
+    0x0429FC01, 0x042CE407, 0x04400003, 0x0440E016, 0x04420003,
+    0x0442C012, 0x04440003, 0x04449C0E, 0x04450004, 0x04460003,
+    0x0446CC0E, 0x04471404, 0x045AAC0D, 0x0491C004, 0x05BD442E,
+    0x05BE3C04, 0x074000F6, 0x07440027, 0x0744A4B5, 0x07480046,
+    0x074C0057, 0x075B0401, 0x075B6C01, 0x075BEC01, 0x075C5401,
+    0x075CD401, 0x075D3C01, 0x075DBC01, 0x075E2401, 0x075EA401,
+    0x075F0C01, 0x07BBC002, 0x07C0002C, 0x07C0C064, 0x07C2800F,
+    0x07C2C40E, 0x07C3040F, 0x07C3440F, 0x07C4401F, 0x07C4C03C,
+    0x07C5C02B, 0x07C7981D, 0x07C8402B, 0x07C90009, 0x07C94002,
+    0x07CC0021, 0x07CCC006, 0x07CCDC46, 0x07CE0014, 0x07CE8025,
+    0x07CF1805, 0x07CF8011, 0x07D0003F, 0x07D10001, 0x07D108B6,
+    0x07D3E404, 0x07D4003E, 0x07D50004, 0x07D54018, 0x07D7EC46,
+    0x07D9140B, 0x07DA0046, 0x07DC0074, 0x38000401, 0x38008060,
+    0x380400F0,
+  };
+  static const unsigned int aAscii[4] = {
+    0xFFFFFFFF, 0xFC00FFFF, 0xF8000001, 0xF8000001,
+  };
+
+  if( c<128 ){
+    return ( (aAscii[c >> 5] & (1 << (c & 0x001F)))==0 );
+  }else if( c<(1<<22) ){
+    unsigned int key = (((unsigned int)c)<<10) | 0x000003FF;
+    int iRes = 0;
+    int iHi = sizeof(aEntry)/sizeof(aEntry[0]) - 1;
+    int iLo = 0;
+    while( iHi>=iLo ){
+      int iTest = (iHi + iLo) / 2;
+      if( key >= aEntry[iTest] ){
+        iRes = iTest;
+        iLo = iTest+1;
+      }else{
+        iHi = iTest-1;
+      }
+    }
+    assert( aEntry[0]<key );
+    assert( key>=aEntry[iRes] );
+    return (((unsigned int)c) >= ((aEntry[iRes]>>10) + (aEntry[iRes]&0x3FF)));
+  }
+  return 1;
+}
+
+
+/*
+** If the argument is a codepoint corresponding to a lowercase letter
+** in the ASCII range with a diacritic added, return the codepoint
+** of the ASCII letter only. For example, if passed 235 - "LATIN
+** SMALL LETTER E WITH DIAERESIS" - return 65 ("LATIN SMALL LETTER
+** E"). The resuls of passing a codepoint that corresponds to an
+** uppercase letter are undefined.
+*/
+static int remove_diacritic(int c){
+  unsigned short aDia[] = {
+        0,  1797,  1848,  1859,  1891,  1928,  1940,  1995, 
+     2024,  2040,  2060,  2110,  2168,  2206,  2264,  2286, 
+     2344,  2383,  2472,  2488,  2516,  2596,  2668,  2732, 
+     2782,  2842,  2894,  2954,  2984,  3000,  3028,  3336, 
+     3456,  3696,  3712,  3728,  3744,  3896,  3912,  3928, 
+     3968,  4008,  4040,  4106,  4138,  4170,  4202,  4234, 
+     4266,  4296,  4312,  4344,  4408,  4424,  4472,  4504, 
+     6148,  6198,  6264,  6280,  6360,  6429,  6505,  6529, 
+    61448, 61468, 61534, 61592, 61642, 61688, 61704, 61726, 
+    61784, 61800, 61836, 61880, 61914, 61948, 61998, 62122, 
+    62154, 62200, 62218, 62302, 62364, 62442, 62478, 62536, 
+    62554, 62584, 62604, 62640, 62648, 62656, 62664, 62730, 
+    62924, 63050, 63082, 63274, 63390, 
+  };
+  char aChar[] = {
+    '\0', 'a',  'c',  'e',  'i',  'n',  'o',  'u',  'y',  'y',  'a',  'c',  
+    'd',  'e',  'e',  'g',  'h',  'i',  'j',  'k',  'l',  'n',  'o',  'r',  
+    's',  't',  'u',  'u',  'w',  'y',  'z',  'o',  'u',  'a',  'i',  'o',  
+    'u',  'g',  'k',  'o',  'j',  'g',  'n',  'a',  'e',  'i',  'o',  'r',  
+    'u',  's',  't',  'h',  'a',  'e',  'o',  'y',  '\0', '\0', '\0', '\0', 
+    '\0', '\0', '\0', '\0', 'a',  'b',  'd',  'd',  'e',  'f',  'g',  'h',  
+    'h',  'i',  'k',  'l',  'l',  'm',  'n',  'p',  'r',  'r',  's',  't',  
+    'u',  'v',  'w',  'w',  'x',  'y',  'z',  'h',  't',  'w',  'y',  'a',  
+    'e',  'i',  'o',  'u',  'y',  
+  };
+
+  unsigned int key = (((unsigned int)c)<<3) | 0x00000007;
+  int iRes = 0;
+  int iHi = sizeof(aDia)/sizeof(aDia[0]) - 1;
+  int iLo = 0;
+  while( iHi>=iLo ){
+    int iTest = (iHi + iLo) / 2;
+    if( key >= aDia[iTest] ){
+      iRes = iTest;
+      iLo = iTest+1;
+    }else{
+      iHi = iTest-1;
+    }
+  }
+  assert( key>=aDia[iRes] );
+  return ((c > (aDia[iRes]>>3) + (aDia[iRes]&0x07)) ? c : (int)aChar[iRes]);
+}
+
+
+/*
+** Return true if the argument interpreted as a unicode codepoint
+** is a diacritical modifier character.
+*/
+SQLITE_PRIVATE int sqlite3FtsUnicodeIsdiacritic(int c){
+  unsigned int mask0 = 0x08029FDF;
+  unsigned int mask1 = 0x000361F8;
+  if( c<768 || c>817 ) return 0;
+  return (c < 768+32) ?
+      (mask0 & (1 << (c-768))) :
+      (mask1 & (1 << (c-768-32)));
+}
+
+
+/*
+** Interpret the argument as a unicode codepoint. If the codepoint
+** is an upper case character that has a lower case equivalent,
+** return the codepoint corresponding to the lower case version.
+** Otherwise, return a copy of the argument.
+**
+** The results are undefined if the value passed to this function
+** is less than zero.
+*/
+SQLITE_PRIVATE int sqlite3FtsUnicodeFold(int c, int bRemoveDiacritic){
+  /* Each entry in the following array defines a rule for folding a range
+  ** of codepoints to lower case. The rule applies to a range of nRange
+  ** codepoints starting at codepoint iCode.
+  **
+  ** If the least significant bit in flags is clear, then the rule applies
+  ** to all nRange codepoints (i.e. all nRange codepoints are upper case and
+  ** need to be folded). Or, if it is set, then the rule only applies to
+  ** every second codepoint in the range, starting with codepoint C.
+  **
+  ** The 7 most significant bits in flags are an index into the aiOff[]
+  ** array. If a specific codepoint C does require folding, then its lower
+  ** case equivalent is ((C + aiOff[flags>>1]) & 0xFFFF).
+  **
+  ** The contents of this array are generated by parsing the CaseFolding.txt
+  ** file distributed as part of the "Unicode Character Database". See
+  ** http://www.unicode.org for details.
+  */
+  static const struct TableEntry {
+    unsigned short iCode;
+    unsigned char flags;
+    unsigned char nRange;
+  } aEntry[] = {
+    {65, 14, 26},          {181, 64, 1},          {192, 14, 23},
+    {216, 14, 7},          {256, 1, 48},          {306, 1, 6},
+    {313, 1, 16},          {330, 1, 46},          {376, 116, 1},
+    {377, 1, 6},           {383, 104, 1},         {385, 50, 1},
+    {386, 1, 4},           {390, 44, 1},          {391, 0, 1},
+    {393, 42, 2},          {395, 0, 1},           {398, 32, 1},
+    {399, 38, 1},          {400, 40, 1},          {401, 0, 1},
+    {403, 42, 1},          {404, 46, 1},          {406, 52, 1},
+    {407, 48, 1},          {408, 0, 1},           {412, 52, 1},
+    {413, 54, 1},          {415, 56, 1},          {416, 1, 6},
+    {422, 60, 1},          {423, 0, 1},           {425, 60, 1},
+    {428, 0, 1},           {430, 60, 1},          {431, 0, 1},
+    {433, 58, 2},          {435, 1, 4},           {439, 62, 1},
+    {440, 0, 1},           {444, 0, 1},           {452, 2, 1},
+    {453, 0, 1},           {455, 2, 1},           {456, 0, 1},
+    {458, 2, 1},           {459, 1, 18},          {478, 1, 18},
+    {497, 2, 1},           {498, 1, 4},           {502, 122, 1},
+    {503, 134, 1},         {504, 1, 40},          {544, 110, 1},
+    {546, 1, 18},          {570, 70, 1},          {571, 0, 1},
+    {573, 108, 1},         {574, 68, 1},          {577, 0, 1},
+    {579, 106, 1},         {580, 28, 1},          {581, 30, 1},
+    {582, 1, 10},          {837, 36, 1},          {880, 1, 4},
+    {886, 0, 1},           {902, 18, 1},          {904, 16, 3},
+    {908, 26, 1},          {910, 24, 2},          {913, 14, 17},
+    {931, 14, 9},          {962, 0, 1},           {975, 4, 1},
+    {976, 140, 1},         {977, 142, 1},         {981, 146, 1},
+    {982, 144, 1},         {984, 1, 24},          {1008, 136, 1},
+    {1009, 138, 1},        {1012, 130, 1},        {1013, 128, 1},
+    {1015, 0, 1},          {1017, 152, 1},        {1018, 0, 1},
+    {1021, 110, 3},        {1024, 34, 16},        {1040, 14, 32},
+    {1120, 1, 34},         {1162, 1, 54},         {1216, 6, 1},
+    {1217, 1, 14},         {1232, 1, 88},         {1329, 22, 38},
+    {4256, 66, 38},        {4295, 66, 1},         {4301, 66, 1},
+    {7680, 1, 150},        {7835, 132, 1},        {7838, 96, 1},
+    {7840, 1, 96},         {7944, 150, 8},        {7960, 150, 6},
+    {7976, 150, 8},        {7992, 150, 8},        {8008, 150, 6},
+    {8025, 151, 8},        {8040, 150, 8},        {8072, 150, 8},
+    {8088, 150, 8},        {8104, 150, 8},        {8120, 150, 2},
+    {8122, 126, 2},        {8124, 148, 1},        {8126, 100, 1},
+    {8136, 124, 4},        {8140, 148, 1},        {8152, 150, 2},
+    {8154, 120, 2},        {8168, 150, 2},        {8170, 118, 2},
+    {8172, 152, 1},        {8184, 112, 2},        {8186, 114, 2},
+    {8188, 148, 1},        {8486, 98, 1},         {8490, 92, 1},
+    {8491, 94, 1},         {8498, 12, 1},         {8544, 8, 16},
+    {8579, 0, 1},          {9398, 10, 26},        {11264, 22, 47},
+    {11360, 0, 1},         {11362, 88, 1},        {11363, 102, 1},
+    {11364, 90, 1},        {11367, 1, 6},         {11373, 84, 1},
+    {11374, 86, 1},        {11375, 80, 1},        {11376, 82, 1},
+    {11378, 0, 1},         {11381, 0, 1},         {11390, 78, 2},
+    {11392, 1, 100},       {11499, 1, 4},         {11506, 0, 1},
+    {42560, 1, 46},        {42624, 1, 24},        {42786, 1, 14},
+    {42802, 1, 62},        {42873, 1, 4},         {42877, 76, 1},
+    {42878, 1, 10},        {42891, 0, 1},         {42893, 74, 1},
+    {42896, 1, 4},         {42912, 1, 10},        {42922, 72, 1},
+    {65313, 14, 26},       
+  };
+  static const unsigned short aiOff[] = {
+   1,     2,     8,     15,    16,    26,    28,    32,    
+   37,    38,    40,    48,    63,    64,    69,    71,    
+   79,    80,    116,   202,   203,   205,   206,   207,   
+   209,   210,   211,   213,   214,   217,   218,   219,   
+   775,   7264,  10792, 10795, 23228, 23256, 30204, 54721, 
+   54753, 54754, 54756, 54787, 54793, 54809, 57153, 57274, 
+   57921, 58019, 58363, 61722, 65268, 65341, 65373, 65406, 
+   65408, 65410, 65415, 65424, 65436, 65439, 65450, 65462, 
+   65472, 65476, 65478, 65480, 65482, 65488, 65506, 65511, 
+   65514, 65521, 65527, 65528, 65529, 
+  };
+
+  int ret = c;
+
+  assert( c>=0 );
+  assert( sizeof(unsigned short)==2 && sizeof(unsigned char)==1 );
+
+  if( c<128 ){
+    if( c>='A' && c<='Z' ) ret = c + ('a' - 'A');
+  }else if( c<65536 ){
+    int iHi = sizeof(aEntry)/sizeof(aEntry[0]) - 1;
+    int iLo = 0;
+    int iRes = -1;
+
+    while( iHi>=iLo ){
+      int iTest = (iHi + iLo) / 2;
+      int cmp = (c - aEntry[iTest].iCode);
+      if( cmp>=0 ){
+        iRes = iTest;
+        iLo = iTest+1;
+      }else{
+        iHi = iTest-1;
+      }
+    }
+    assert( iRes<0 || c>=aEntry[iRes].iCode );
+
+    if( iRes>=0 ){
+      const struct TableEntry *p = &aEntry[iRes];
+      if( c<(p->iCode + p->nRange) && 0==(0x01 & p->flags & (p->iCode ^ c)) ){
+        ret = (c + (aiOff[p->flags>>1])) & 0x0000FFFF;
+        assert( ret>0 );
+      }
+    }
+
+    if( bRemoveDiacritic ) ret = remove_diacritic(ret);
+  }
+  
+  else if( c>=66560 && c<66600 ){
+    ret = c + 40;
+  }
+
+  return ret;
+}
+#endif /* defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4) */
+#endif /* !defined(SQLITE_DISABLE_FTS3_UNICODE) */
+
+/************** End of fts3_unicode2.c ***************************************/
+/************** Begin file rtree.c *******************************************/
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code for implementations of the r-tree and r*-tree
+** algorithms packaged as an SQLite virtual table module.
+*/
+
+/*
+** Database Format of R-Tree Tables
+** --------------------------------
+**
+** The data structure for a single virtual r-tree table is stored in three 
+** native SQLite tables declared as follows. In each case, the '%' character
+** in the table name is replaced with the user-supplied name of the r-tree
+** table.
+**
+**   CREATE TABLE %_node(nodeno INTEGER PRIMARY KEY, data BLOB)
+**   CREATE TABLE %_parent(nodeno INTEGER PRIMARY KEY, parentnode INTEGER)
+**   CREATE TABLE %_rowid(rowid INTEGER PRIMARY KEY, nodeno INTEGER)
+**
+** The data for each node of the r-tree structure is stored in the %_node
+** table. For each node that is not the root node of the r-tree, there is
+** an entry in the %_parent table associating the node with its parent.
+** And for each row of data in the table, there is an entry in the %_rowid
+** table that maps from the entries rowid to the id of the node that it
+** is stored on.
+**
+** The root node of an r-tree always exists, even if the r-tree table is
+** empty. The nodeno of the root node is always 1. All other nodes in the
+** table must be the same size as the root node. The content of each node
+** is formatted as follows:
+**
+**   1. If the node is the root node (node 1), then the first 2 bytes
+**      of the node contain the tree depth as a big-endian integer.
+**      For non-root nodes, the first 2 bytes are left unused.
+**
+**   2. The next 2 bytes contain the number of entries currently 
+**      stored in the node.
+**
+**   3. The remainder of the node contains the node entries. Each entry
+**      consists of a single 8-byte integer followed by an even number
+**      of 4-byte coordinates. For leaf nodes the integer is the rowid
+**      of a record. For internal nodes it is the node number of a
+**      child page.
+*/
+
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RTREE)
+
+#ifndef SQLITE_CORE
+/*   #include "sqlite3ext.h" */
+  SQLITE_EXTENSION_INIT1
+#else
+/*   #include "sqlite3.h" */
+#endif
+
+/* #include <string.h> */
+/* #include <assert.h> */
+/* #include <stdio.h> */
+
+#ifndef SQLITE_AMALGAMATION
+#include "sqlite3rtree.h"
+typedef sqlite3_int64 i64;
+typedef sqlite3_uint64 u64;
+typedef unsigned char u8;
+typedef unsigned short u16;
+typedef unsigned int u32;
+#endif
+
+/*  The following macro is used to suppress compiler warnings.
+*/
+#ifndef UNUSED_PARAMETER
+# define UNUSED_PARAMETER(x) (void)(x)
+#endif
+
+typedef struct Rtree Rtree;
+typedef struct RtreeCursor RtreeCursor;
+typedef struct RtreeNode RtreeNode;
+typedef struct RtreeCell RtreeCell;
+typedef struct RtreeConstraint RtreeConstraint;
+typedef struct RtreeMatchArg RtreeMatchArg;
+typedef struct RtreeGeomCallback RtreeGeomCallback;
+typedef union RtreeCoord RtreeCoord;
+typedef struct RtreeSearchPoint RtreeSearchPoint;
+
+/* The rtree may have between 1 and RTREE_MAX_DIMENSIONS dimensions. */
+#define RTREE_MAX_DIMENSIONS 5
+
+/* Size of hash table Rtree.aHash. This hash table is not expected to
+** ever contain very many entries, so a fixed number of buckets is 
+** used.
+*/
+#define HASHSIZE 97
+
+/* The xBestIndex method of this virtual table requires an estimate of
+** the number of rows in the virtual table to calculate the costs of
+** various strategies. If possible, this estimate is loaded from the
+** sqlite_stat1 table (with RTREE_MIN_ROWEST as a hard-coded minimum).
+** Otherwise, if no sqlite_stat1 entry is available, use 
+** RTREE_DEFAULT_ROWEST.
+*/
+#define RTREE_DEFAULT_ROWEST 1048576
+#define RTREE_MIN_ROWEST         100
+
+/* 
+** An rtree virtual-table object.
+*/
+struct Rtree {
+  sqlite3_vtab base;          /* Base class.  Must be first */
+  sqlite3 *db;                /* Host database connection */
+  int iNodeSize;              /* Size in bytes of each node in the node table */
+  u8 nDim;                    /* Number of dimensions */
+  u8 nDim2;                   /* Twice the number of dimensions */
+  u8 eCoordType;              /* RTREE_COORD_REAL32 or RTREE_COORD_INT32 */
+  u8 nBytesPerCell;           /* Bytes consumed per cell */
+  u8 inWrTrans;               /* True if inside write transaction */
+  int iDepth;                 /* Current depth of the r-tree structure */
+  char *zDb;                  /* Name of database containing r-tree table */
+  char *zName;                /* Name of r-tree table */ 
+  u32 nBusy;                  /* Current number of users of this structure */
+  i64 nRowEst;                /* Estimated number of rows in this table */
+  u32 nCursor;                /* Number of open cursors */
+
+  /* List of nodes removed during a CondenseTree operation. List is
+  ** linked together via the pointer normally used for hash chains -
+  ** RtreeNode.pNext. RtreeNode.iNode stores the depth of the sub-tree 
+  ** headed by the node (leaf nodes have RtreeNode.iNode==0).
+  */
+  RtreeNode *pDeleted;
+  int iReinsertHeight;        /* Height of sub-trees Reinsert() has run on */
+
+  /* Blob I/O on xxx_node */
+  sqlite3_blob *pNodeBlob;
+
+  /* Statements to read/write/delete a record from xxx_node */
+  sqlite3_stmt *pWriteNode;
+  sqlite3_stmt *pDeleteNode;
+
+  /* Statements to read/write/delete a record from xxx_rowid */
+  sqlite3_stmt *pReadRowid;
+  sqlite3_stmt *pWriteRowid;
+  sqlite3_stmt *pDeleteRowid;
+
+  /* Statements to read/write/delete a record from xxx_parent */
+  sqlite3_stmt *pReadParent;
+  sqlite3_stmt *pWriteParent;
+  sqlite3_stmt *pDeleteParent;
+
+  RtreeNode *aHash[HASHSIZE]; /* Hash table of in-memory nodes. */ 
+};
+
+/* Possible values for Rtree.eCoordType: */
+#define RTREE_COORD_REAL32 0
+#define RTREE_COORD_INT32  1
+
+/*
+** If SQLITE_RTREE_INT_ONLY is defined, then this virtual table will
+** only deal with integer coordinates.  No floating point operations
+** will be done.
+*/
+#ifdef SQLITE_RTREE_INT_ONLY
+  typedef sqlite3_int64 RtreeDValue;       /* High accuracy coordinate */
+  typedef int RtreeValue;                  /* Low accuracy coordinate */
+# define RTREE_ZERO 0
+#else
+  typedef double RtreeDValue;              /* High accuracy coordinate */
+  typedef float RtreeValue;                /* Low accuracy coordinate */
+# define RTREE_ZERO 0.0
+#endif
+
+/*
+** When doing a search of an r-tree, instances of the following structure
+** record intermediate results from the tree walk.
+**
+** The id is always a node-id.  For iLevel>=1 the id is the node-id of
+** the node that the RtreeSearchPoint represents.  When iLevel==0, however,
+** the id is of the parent node and the cell that RtreeSearchPoint
+** represents is the iCell-th entry in the parent node.
+*/
+struct RtreeSearchPoint {
+  RtreeDValue rScore;    /* The score for this node.  Smallest goes first. */
+  sqlite3_int64 id;      /* Node ID */
+  u8 iLevel;             /* 0=entries.  1=leaf node.  2+ for higher */
+  u8 eWithin;            /* PARTLY_WITHIN or FULLY_WITHIN */
+  u8 iCell;              /* Cell index within the node */
+};
+
+/*
+** The minimum number of cells allowed for a node is a third of the 
+** maximum. In Gutman's notation:
+**
+**     m = M/3
+**
+** If an R*-tree "Reinsert" operation is required, the same number of
+** cells are removed from the overfull node and reinserted into the tree.
+*/
+#define RTREE_MINCELLS(p) ((((p)->iNodeSize-4)/(p)->nBytesPerCell)/3)
+#define RTREE_REINSERT(p) RTREE_MINCELLS(p)
+#define RTREE_MAXCELLS 51
+
+/*
+** The smallest possible node-size is (512-64)==448 bytes. And the largest
+** supported cell size is 48 bytes (8 byte rowid + ten 4 byte coordinates).
+** Therefore all non-root nodes must contain at least 3 entries. Since 
+** 2^40 is greater than 2^64, an r-tree structure always has a depth of
+** 40 or less.
+*/
+#define RTREE_MAX_DEPTH 40
+
+
+/*
+** Number of entries in the cursor RtreeNode cache.  The first entry is
+** used to cache the RtreeNode for RtreeCursor.sPoint.  The remaining
+** entries cache the RtreeNode for the first elements of the priority queue.
+*/
+#define RTREE_CACHE_SZ  5
+
+/* 
+** An rtree cursor object.
+*/
+struct RtreeCursor {
+  sqlite3_vtab_cursor base;         /* Base class.  Must be first */
+  u8 atEOF;                         /* True if at end of search */
+  u8 bPoint;                        /* True if sPoint is valid */
+  int iStrategy;                    /* Copy of idxNum search parameter */
+  int nConstraint;                  /* Number of entries in aConstraint */
+  RtreeConstraint *aConstraint;     /* Search constraints. */
+  int nPointAlloc;                  /* Number of slots allocated for aPoint[] */
+  int nPoint;                       /* Number of slots used in aPoint[] */
+  int mxLevel;                      /* iLevel value for root of the tree */
+  RtreeSearchPoint *aPoint;         /* Priority queue for search points */
+  RtreeSearchPoint sPoint;          /* Cached next search point */
+  RtreeNode *aNode[RTREE_CACHE_SZ]; /* Rtree node cache */
+  u32 anQueue[RTREE_MAX_DEPTH+1];   /* Number of queued entries by iLevel */
+};
+
+/* Return the Rtree of a RtreeCursor */
+#define RTREE_OF_CURSOR(X)   ((Rtree*)((X)->base.pVtab))
+
+/*
+** A coordinate can be either a floating point number or a integer.  All
+** coordinates within a single R-Tree are always of the same time.
+*/
+union RtreeCoord {
+  RtreeValue f;      /* Floating point value */
+  int i;             /* Integer value */
+  u32 u;             /* Unsigned for byte-order conversions */
+};
+
+/*
+** The argument is an RtreeCoord. Return the value stored within the RtreeCoord
+** formatted as a RtreeDValue (double or int64). This macro assumes that local
+** variable pRtree points to the Rtree structure associated with the
+** RtreeCoord.
+*/
+#ifdef SQLITE_RTREE_INT_ONLY
+# define DCOORD(coord) ((RtreeDValue)coord.i)
+#else
+# define DCOORD(coord) (                           \
+    (pRtree->eCoordType==RTREE_COORD_REAL32) ?      \
+      ((double)coord.f) :                           \
+      ((double)coord.i)                             \
+  )
+#endif
+
+/*
+** A search constraint.
+*/
+struct RtreeConstraint {
+  int iCoord;                     /* Index of constrained coordinate */
+  int op;                         /* Constraining operation */
+  union {
+    RtreeDValue rValue;             /* Constraint value. */
+    int (*xGeom)(sqlite3_rtree_geometry*,int,RtreeDValue*,int*);
+    int (*xQueryFunc)(sqlite3_rtree_query_info*);
+  } u;
+  sqlite3_rtree_query_info *pInfo;  /* xGeom and xQueryFunc argument */
+};
+
+/* Possible values for RtreeConstraint.op */
+#define RTREE_EQ    0x41  /* A */
+#define RTREE_LE    0x42  /* B */
+#define RTREE_LT    0x43  /* C */
+#define RTREE_GE    0x44  /* D */
+#define RTREE_GT    0x45  /* E */
+#define RTREE_MATCH 0x46  /* F: Old-style sqlite3_rtree_geometry_callback() */
+#define RTREE_QUERY 0x47  /* G: New-style sqlite3_rtree_query_callback() */
+
+
+/* 
+** An rtree structure node.
+*/
+struct RtreeNode {
+  RtreeNode *pParent;         /* Parent node */
+  i64 iNode;                  /* The node number */
+  int nRef;                   /* Number of references to this node */
+  int isDirty;                /* True if the node needs to be written to disk */
+  u8 *zData;                  /* Content of the node, as should be on disk */
+  RtreeNode *pNext;           /* Next node in this hash collision chain */
+};
+
+/* Return the number of cells in a node  */
+#define NCELL(pNode) readInt16(&(pNode)->zData[2])
+
+/* 
+** A single cell from a node, deserialized
+*/
+struct RtreeCell {
+  i64 iRowid;                                 /* Node or entry ID */
+  RtreeCoord aCoord[RTREE_MAX_DIMENSIONS*2];  /* Bounding box coordinates */
+};
+
+
+/*
+** This object becomes the sqlite3_user_data() for the SQL functions
+** that are created by sqlite3_rtree_geometry_callback() and
+** sqlite3_rtree_query_callback() and which appear on the right of MATCH
+** operators in order to constrain a search.
+**
+** xGeom and xQueryFunc are the callback functions.  Exactly one of 
+** xGeom and xQueryFunc fields is non-NULL, depending on whether the
+** SQL function was created using sqlite3_rtree_geometry_callback() or
+** sqlite3_rtree_query_callback().
+** 
+** This object is deleted automatically by the destructor mechanism in
+** sqlite3_create_function_v2().
+*/
+struct RtreeGeomCallback {
+  int (*xGeom)(sqlite3_rtree_geometry*, int, RtreeDValue*, int*);
+  int (*xQueryFunc)(sqlite3_rtree_query_info*);
+  void (*xDestructor)(void*);
+  void *pContext;
+};
+
+
+/*
+** Value for the first field of every RtreeMatchArg object. The MATCH
+** operator tests that the first field of a blob operand matches this
+** value to avoid operating on invalid blobs (which could cause a segfault).
+*/
+#define RTREE_GEOMETRY_MAGIC 0x891245AB
+
+/*
+** An instance of this structure (in the form of a BLOB) is returned by
+** the SQL functions that sqlite3_rtree_geometry_callback() and
+** sqlite3_rtree_query_callback() create, and is read as the right-hand
+** operand to the MATCH operator of an R-Tree.
+*/
+struct RtreeMatchArg {
+  u32 magic;                  /* Always RTREE_GEOMETRY_MAGIC */
+  RtreeGeomCallback cb;       /* Info about the callback functions */
+  int nParam;                 /* Number of parameters to the SQL function */
+  sqlite3_value **apSqlParam; /* Original SQL parameter values */
+  RtreeDValue aParam[1];      /* Values for parameters to the SQL function */
+};
+
+#ifndef MAX
+# define MAX(x,y) ((x) < (y) ? (y) : (x))
+#endif
+#ifndef MIN
+# define MIN(x,y) ((x) > (y) ? (y) : (x))
+#endif
+
+/* What version of GCC is being used.  0 means GCC is not being used */
+#ifndef GCC_VERSION
+#if defined(__GNUC__) && !defined(SQLITE_DISABLE_INTRINSIC)
+# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
+#else
+# define GCC_VERSION 0
+#endif
+#endif
+
+/* What version of CLANG is being used.  0 means CLANG is not being used */
+#ifndef CLANG_VERSION
+#if defined(__clang__) && !defined(_WIN32) && !defined(SQLITE_DISABLE_INTRINSIC)
+# define CLANG_VERSION \
+            (__clang_major__*1000000+__clang_minor__*1000+__clang_patchlevel__)
+#else
+# define CLANG_VERSION 0
+#endif
+#endif
+
+/* The testcase() macro should already be defined in the amalgamation.  If
+** it is not, make it a no-op.
+*/
+#ifndef SQLITE_AMALGAMATION
+# define testcase(X)
+#endif
+
+/*
+** Macros to determine whether the machine is big or little endian,
+** and whether or not that determination is run-time or compile-time.
+**
+** For best performance, an attempt is made to guess at the byte-order
+** using C-preprocessor macros.  If that is unsuccessful, or if
+** -DSQLITE_RUNTIME_BYTEORDER=1 is set, then byte-order is determined
+** at run-time.
+*/
+#ifndef SQLITE_BYTEORDER
+#if defined(i386)     || defined(__i386__)   || defined(_M_IX86) ||    \
+    defined(__x86_64) || defined(__x86_64__) || defined(_M_X64)  ||    \
+    defined(_M_AMD64) || defined(_M_ARM)     || defined(__x86)   ||    \
+    defined(__arm__)
+# define SQLITE_BYTEORDER    1234
+#elif defined(sparc)    || defined(__ppc__)
+# define SQLITE_BYTEORDER    4321
+#else
+# define SQLITE_BYTEORDER    0     /* 0 means "unknown at compile-time" */
+#endif
+#endif
+
+
+/* What version of MSVC is being used.  0 means MSVC is not being used */
+#ifndef MSVC_VERSION
+#if defined(_MSC_VER) && !defined(SQLITE_DISABLE_INTRINSIC)
+# define MSVC_VERSION _MSC_VER
+#else
+# define MSVC_VERSION 0
+#endif
+#endif
+
+/*
+** Functions to deserialize a 16 bit integer, 32 bit real number and
+** 64 bit integer. The deserialized value is returned.
+*/
+static int readInt16(u8 *p){
+  return (p[0]<<8) + p[1];
+}
+static void readCoord(u8 *p, RtreeCoord *pCoord){
+  assert( ((((char*)p) - (char*)0)&3)==0 );  /* p is always 4-byte aligned */
+#if SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+  pCoord->u = _byteswap_ulong(*(u32*)p);
+#elif SQLITE_BYTEORDER==1234 && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
+  pCoord->u = __builtin_bswap32(*(u32*)p);
+#elif SQLITE_BYTEORDER==4321
+  pCoord->u = *(u32*)p;
+#else
+  pCoord->u = (
+    (((u32)p[0]) << 24) + 
+    (((u32)p[1]) << 16) + 
+    (((u32)p[2]) <<  8) + 
+    (((u32)p[3]) <<  0)
+  );
+#endif
+}
+static i64 readInt64(u8 *p){
+#if SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+  u64 x;
+  memcpy(&x, p, 8);
+  return (i64)_byteswap_uint64(x);
+#elif SQLITE_BYTEORDER==1234 && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
+  u64 x;
+  memcpy(&x, p, 8);
+  return (i64)__builtin_bswap64(x);
+#elif SQLITE_BYTEORDER==4321
+  i64 x;
+  memcpy(&x, p, 8);
+  return x;
+#else
+  return (
+    (((i64)p[0]) << 56) + 
+    (((i64)p[1]) << 48) + 
+    (((i64)p[2]) << 40) + 
+    (((i64)p[3]) << 32) + 
+    (((i64)p[4]) << 24) + 
+    (((i64)p[5]) << 16) + 
+    (((i64)p[6]) <<  8) + 
+    (((i64)p[7]) <<  0)
+  );
+#endif
+}
+
+/*
+** Functions to serialize a 16 bit integer, 32 bit real number and
+** 64 bit integer. The value returned is the number of bytes written
+** to the argument buffer (always 2, 4 and 8 respectively).
+*/
+static void writeInt16(u8 *p, int i){
+  p[0] = (i>> 8)&0xFF;
+  p[1] = (i>> 0)&0xFF;
+}
+static int writeCoord(u8 *p, RtreeCoord *pCoord){
+  u32 i;
+  assert( ((((char*)p) - (char*)0)&3)==0 );  /* p is always 4-byte aligned */
+  assert( sizeof(RtreeCoord)==4 );
+  assert( sizeof(u32)==4 );
+#if SQLITE_BYTEORDER==1234 && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
+  i = __builtin_bswap32(pCoord->u);
+  memcpy(p, &i, 4);
+#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+  i = _byteswap_ulong(pCoord->u);
+  memcpy(p, &i, 4);
+#elif SQLITE_BYTEORDER==4321
+  i = pCoord->u;
+  memcpy(p, &i, 4);
+#else
+  i = pCoord->u;
+  p[0] = (i>>24)&0xFF;
+  p[1] = (i>>16)&0xFF;
+  p[2] = (i>> 8)&0xFF;
+  p[3] = (i>> 0)&0xFF;
+#endif
+  return 4;
+}
+static int writeInt64(u8 *p, i64 i){
+#if SQLITE_BYTEORDER==1234 && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
+  i = (i64)__builtin_bswap64((u64)i);
+  memcpy(p, &i, 8);
+#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+  i = (i64)_byteswap_uint64((u64)i);
+  memcpy(p, &i, 8);
+#elif SQLITE_BYTEORDER==4321
+  memcpy(p, &i, 8);
+#else
+  p[0] = (i>>56)&0xFF;
+  p[1] = (i>>48)&0xFF;
+  p[2] = (i>>40)&0xFF;
+  p[3] = (i>>32)&0xFF;
+  p[4] = (i>>24)&0xFF;
+  p[5] = (i>>16)&0xFF;
+  p[6] = (i>> 8)&0xFF;
+  p[7] = (i>> 0)&0xFF;
+#endif
+  return 8;
+}
+
+/*
+** Increment the reference count of node p.
+*/
+static void nodeReference(RtreeNode *p){
+  if( p ){
+    p->nRef++;
+  }
+}
+
+/*
+** Clear the content of node p (set all bytes to 0x00).
+*/
+static void nodeZero(Rtree *pRtree, RtreeNode *p){
+  memset(&p->zData[2], 0, pRtree->iNodeSize-2);
+  p->isDirty = 1;
+}
+
+/*
+** Given a node number iNode, return the corresponding key to use
+** in the Rtree.aHash table.
+*/
+static int nodeHash(i64 iNode){
+  return iNode % HASHSIZE;
+}
+
+/*
+** Search the node hash table for node iNode. If found, return a pointer
+** to it. Otherwise, return 0.
+*/
+static RtreeNode *nodeHashLookup(Rtree *pRtree, i64 iNode){
+  RtreeNode *p;
+  for(p=pRtree->aHash[nodeHash(iNode)]; p && p->iNode!=iNode; p=p->pNext);
+  return p;
+}
+
+/*
+** Add node pNode to the node hash table.
+*/
+static void nodeHashInsert(Rtree *pRtree, RtreeNode *pNode){
+  int iHash;
+  assert( pNode->pNext==0 );
+  iHash = nodeHash(pNode->iNode);
+  pNode->pNext = pRtree->aHash[iHash];
+  pRtree->aHash[iHash] = pNode;
+}
+
+/*
+** Remove node pNode from the node hash table.
+*/
+static void nodeHashDelete(Rtree *pRtree, RtreeNode *pNode){
+  RtreeNode **pp;
+  if( pNode->iNode!=0 ){
+    pp = &pRtree->aHash[nodeHash(pNode->iNode)];
+    for( ; (*pp)!=pNode; pp = &(*pp)->pNext){ assert(*pp); }
+    *pp = pNode->pNext;
+    pNode->pNext = 0;
+  }
+}
+
+/*
+** Allocate and return new r-tree node. Initially, (RtreeNode.iNode==0),
+** indicating that node has not yet been assigned a node number. It is
+** assigned a node number when nodeWrite() is called to write the
+** node contents out to the database.
+*/
+static RtreeNode *nodeNew(Rtree *pRtree, RtreeNode *pParent){
+  RtreeNode *pNode;
+  pNode = (RtreeNode *)sqlite3_malloc(sizeof(RtreeNode) + pRtree->iNodeSize);
+  if( pNode ){
+    memset(pNode, 0, sizeof(RtreeNode) + pRtree->iNodeSize);
+    pNode->zData = (u8 *)&pNode[1];
+    pNode->nRef = 1;
+    pNode->pParent = pParent;
+    pNode->isDirty = 1;
+    nodeReference(pParent);
+  }
+  return pNode;
+}
+
+/*
+** Clear the Rtree.pNodeBlob object
+*/
+static void nodeBlobReset(Rtree *pRtree){
+  if( pRtree->pNodeBlob && pRtree->inWrTrans==0 && pRtree->nCursor==0 ){
+    sqlite3_blob *pBlob = pRtree->pNodeBlob;
+    pRtree->pNodeBlob = 0;
+    sqlite3_blob_close(pBlob);
+  }
+}
+
+/*
+** Obtain a reference to an r-tree node.
+*/
+static int nodeAcquire(
+  Rtree *pRtree,             /* R-tree structure */
+  i64 iNode,                 /* Node number to load */
+  RtreeNode *pParent,        /* Either the parent node or NULL */
+  RtreeNode **ppNode         /* OUT: Acquired node */
+){
+  int rc = SQLITE_OK;
+  RtreeNode *pNode = 0;
+
+  /* Check if the requested node is already in the hash table. If so,
+  ** increase its reference count and return it.
+  */
+  if( (pNode = nodeHashLookup(pRtree, iNode)) ){
+    assert( !pParent || !pNode->pParent || pNode->pParent==pParent );
+    if( pParent && !pNode->pParent ){
+      nodeReference(pParent);
+      pNode->pParent = pParent;
+    }
+    pNode->nRef++;
+    *ppNode = pNode;
+    return SQLITE_OK;
+  }
+
+  if( pRtree->pNodeBlob ){
+    sqlite3_blob *pBlob = pRtree->pNodeBlob;
+    pRtree->pNodeBlob = 0;
+    rc = sqlite3_blob_reopen(pBlob, iNode);
+    pRtree->pNodeBlob = pBlob;
+    if( rc ){
+      nodeBlobReset(pRtree);
+      if( rc==SQLITE_NOMEM ) return SQLITE_NOMEM;
+    }
+  }
+  if( pRtree->pNodeBlob==0 ){
+    char *zTab = sqlite3_mprintf("%s_node", pRtree->zName);
+    if( zTab==0 ) return SQLITE_NOMEM;
+    rc = sqlite3_blob_open(pRtree->db, pRtree->zDb, zTab, "data", iNode, 0,
+                           &pRtree->pNodeBlob);
+    sqlite3_free(zTab);
+  }
+  if( rc ){
+    nodeBlobReset(pRtree);
+    *ppNode = 0;
+    /* If unable to open an sqlite3_blob on the desired row, that can only
+    ** be because the shadow tables hold erroneous data. */
+    if( rc==SQLITE_ERROR ) rc = SQLITE_CORRUPT_VTAB;
+  }else if( pRtree->iNodeSize==sqlite3_blob_bytes(pRtree->pNodeBlob) ){
+    pNode = (RtreeNode *)sqlite3_malloc(sizeof(RtreeNode)+pRtree->iNodeSize);
+    if( !pNode ){
+      rc = SQLITE_NOMEM;
+    }else{
+      pNode->pParent = pParent;
+      pNode->zData = (u8 *)&pNode[1];
+      pNode->nRef = 1;
+      pNode->iNode = iNode;
+      pNode->isDirty = 0;
+      pNode->pNext = 0;
+      rc = sqlite3_blob_read(pRtree->pNodeBlob, pNode->zData,
+                             pRtree->iNodeSize, 0);
+      nodeReference(pParent);
+    }
+  }
+
+  /* If the root node was just loaded, set pRtree->iDepth to the height
+  ** of the r-tree structure. A height of zero means all data is stored on
+  ** the root node. A height of one means the children of the root node
+  ** are the leaves, and so on. If the depth as specified on the root node
+  ** is greater than RTREE_MAX_DEPTH, the r-tree structure must be corrupt.
+  */
+  if( pNode && iNode==1 ){
+    pRtree->iDepth = readInt16(pNode->zData);
+    if( pRtree->iDepth>RTREE_MAX_DEPTH ){
+      rc = SQLITE_CORRUPT_VTAB;
+    }
+  }
+
+  /* If no error has occurred so far, check if the "number of entries"
+  ** field on the node is too large. If so, set the return code to 
+  ** SQLITE_CORRUPT_VTAB.
+  */
+  if( pNode && rc==SQLITE_OK ){
+    if( NCELL(pNode)>((pRtree->iNodeSize-4)/pRtree->nBytesPerCell) ){
+      rc = SQLITE_CORRUPT_VTAB;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    if( pNode!=0 ){
+      nodeHashInsert(pRtree, pNode);
+    }else{
+      rc = SQLITE_CORRUPT_VTAB;
+    }
+    *ppNode = pNode;
+  }else{
+    sqlite3_free(pNode);
+    *ppNode = 0;
+  }
+
+  return rc;
+}
+
+/*
+** Overwrite cell iCell of node pNode with the contents of pCell.
+*/
+static void nodeOverwriteCell(
+  Rtree *pRtree,             /* The overall R-Tree */
+  RtreeNode *pNode,          /* The node into which the cell is to be written */
+  RtreeCell *pCell,          /* The cell to write */
+  int iCell                  /* Index into pNode into which pCell is written */
+){
+  int ii;
+  u8 *p = &pNode->zData[4 + pRtree->nBytesPerCell*iCell];
+  p += writeInt64(p, pCell->iRowid);
+  for(ii=0; ii<pRtree->nDim2; ii++){
+    p += writeCoord(p, &pCell->aCoord[ii]);
+  }
+  pNode->isDirty = 1;
+}
+
+/*
+** Remove the cell with index iCell from node pNode.
+*/
+static void nodeDeleteCell(Rtree *pRtree, RtreeNode *pNode, int iCell){
+  u8 *pDst = &pNode->zData[4 + pRtree->nBytesPerCell*iCell];
+  u8 *pSrc = &pDst[pRtree->nBytesPerCell];
+  int nByte = (NCELL(pNode) - iCell - 1) * pRtree->nBytesPerCell;
+  memmove(pDst, pSrc, nByte);
+  writeInt16(&pNode->zData[2], NCELL(pNode)-1);
+  pNode->isDirty = 1;
+}
+
+/*
+** Insert the contents of cell pCell into node pNode. If the insert
+** is successful, return SQLITE_OK.
+**
+** If there is not enough free space in pNode, return SQLITE_FULL.
+*/
+static int nodeInsertCell(
+  Rtree *pRtree,                /* The overall R-Tree */
+  RtreeNode *pNode,             /* Write new cell into this node */
+  RtreeCell *pCell              /* The cell to be inserted */
+){
+  int nCell;                    /* Current number of cells in pNode */
+  int nMaxCell;                 /* Maximum number of cells for pNode */
+
+  nMaxCell = (pRtree->iNodeSize-4)/pRtree->nBytesPerCell;
+  nCell = NCELL(pNode);
+
+  assert( nCell<=nMaxCell );
+  if( nCell<nMaxCell ){
+    nodeOverwriteCell(pRtree, pNode, pCell, nCell);
+    writeInt16(&pNode->zData[2], nCell+1);
+    pNode->isDirty = 1;
+  }
+
+  return (nCell==nMaxCell);
+}
+
+/*
+** If the node is dirty, write it out to the database.
+*/
+static int nodeWrite(Rtree *pRtree, RtreeNode *pNode){
+  int rc = SQLITE_OK;
+  if( pNode->isDirty ){
+    sqlite3_stmt *p = pRtree->pWriteNode;
+    if( pNode->iNode ){
+      sqlite3_bind_int64(p, 1, pNode->iNode);
+    }else{
+      sqlite3_bind_null(p, 1);
+    }
+    sqlite3_bind_blob(p, 2, pNode->zData, pRtree->iNodeSize, SQLITE_STATIC);
+    sqlite3_step(p);
+    pNode->isDirty = 0;
+    rc = sqlite3_reset(p);
+    if( pNode->iNode==0 && rc==SQLITE_OK ){
+      pNode->iNode = sqlite3_last_insert_rowid(pRtree->db);
+      nodeHashInsert(pRtree, pNode);
+    }
+  }
+  return rc;
+}
+
+/*
+** Release a reference to a node. If the node is dirty and the reference
+** count drops to zero, the node data is written to the database.
+*/
+static int nodeRelease(Rtree *pRtree, RtreeNode *pNode){
+  int rc = SQLITE_OK;
+  if( pNode ){
+    assert( pNode->nRef>0 );
+    pNode->nRef--;
+    if( pNode->nRef==0 ){
+      if( pNode->iNode==1 ){
+        pRtree->iDepth = -1;
+      }
+      if( pNode->pParent ){
+        rc = nodeRelease(pRtree, pNode->pParent);
+      }
+      if( rc==SQLITE_OK ){
+        rc = nodeWrite(pRtree, pNode);
+      }
+      nodeHashDelete(pRtree, pNode);
+      sqlite3_free(pNode);
+    }
+  }
+  return rc;
+}
+
+/*
+** Return the 64-bit integer value associated with cell iCell of
+** node pNode. If pNode is a leaf node, this is a rowid. If it is
+** an internal node, then the 64-bit integer is a child page number.
+*/
+static i64 nodeGetRowid(
+  Rtree *pRtree,       /* The overall R-Tree */
+  RtreeNode *pNode,    /* The node from which to extract the ID */
+  int iCell            /* The cell index from which to extract the ID */
+){
+  assert( iCell<NCELL(pNode) );
+  return readInt64(&pNode->zData[4 + pRtree->nBytesPerCell*iCell]);
+}
+
+/*
+** Return coordinate iCoord from cell iCell in node pNode.
+*/
+static void nodeGetCoord(
+  Rtree *pRtree,               /* The overall R-Tree */
+  RtreeNode *pNode,            /* The node from which to extract a coordinate */
+  int iCell,                   /* The index of the cell within the node */
+  int iCoord,                  /* Which coordinate to extract */
+  RtreeCoord *pCoord           /* OUT: Space to write result to */
+){
+  readCoord(&pNode->zData[12 + pRtree->nBytesPerCell*iCell + 4*iCoord], pCoord);
+}
+
+/*
+** Deserialize cell iCell of node pNode. Populate the structure pointed
+** to by pCell with the results.
+*/
+static void nodeGetCell(
+  Rtree *pRtree,               /* The overall R-Tree */
+  RtreeNode *pNode,            /* The node containing the cell to be read */
+  int iCell,                   /* Index of the cell within the node */
+  RtreeCell *pCell             /* OUT: Write the cell contents here */
+){
+  u8 *pData;
+  RtreeCoord *pCoord;
+  int ii = 0;
+  pCell->iRowid = nodeGetRowid(pRtree, pNode, iCell);
+  pData = pNode->zData + (12 + pRtree->nBytesPerCell*iCell);
+  pCoord = pCell->aCoord;
+  do{
+    readCoord(pData, &pCoord[ii]);
+    readCoord(pData+4, &pCoord[ii+1]);
+    pData += 8;
+    ii += 2;
+  }while( ii<pRtree->nDim2 );
+}
+
+
+/* Forward declaration for the function that does the work of
+** the virtual table module xCreate() and xConnect() methods.
+*/
+static int rtreeInit(
+  sqlite3 *, void *, int, const char *const*, sqlite3_vtab **, char **, int
+);
+
+/* 
+** Rtree virtual table module xCreate method.
+*/
+static int rtreeCreate(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  return rtreeInit(db, pAux, argc, argv, ppVtab, pzErr, 1);
+}
+
+/* 
+** Rtree virtual table module xConnect method.
+*/
+static int rtreeConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  return rtreeInit(db, pAux, argc, argv, ppVtab, pzErr, 0);
+}
+
+/*
+** Increment the r-tree reference count.
+*/
+static void rtreeReference(Rtree *pRtree){
+  pRtree->nBusy++;
+}
+
+/*
+** Decrement the r-tree reference count. When the reference count reaches
+** zero the structure is deleted.
+*/
+static void rtreeRelease(Rtree *pRtree){
+  pRtree->nBusy--;
+  if( pRtree->nBusy==0 ){
+    pRtree->inWrTrans = 0;
+    pRtree->nCursor = 0;
+    nodeBlobReset(pRtree);
+    sqlite3_finalize(pRtree->pWriteNode);
+    sqlite3_finalize(pRtree->pDeleteNode);
+    sqlite3_finalize(pRtree->pReadRowid);
+    sqlite3_finalize(pRtree->pWriteRowid);
+    sqlite3_finalize(pRtree->pDeleteRowid);
+    sqlite3_finalize(pRtree->pReadParent);
+    sqlite3_finalize(pRtree->pWriteParent);
+    sqlite3_finalize(pRtree->pDeleteParent);
+    sqlite3_free(pRtree);
+  }
+}
+
+/* 
+** Rtree virtual table module xDisconnect method.
+*/
+static int rtreeDisconnect(sqlite3_vtab *pVtab){
+  rtreeRelease((Rtree *)pVtab);
+  return SQLITE_OK;
+}
+
+/* 
+** Rtree virtual table module xDestroy method.
+*/
+static int rtreeDestroy(sqlite3_vtab *pVtab){
+  Rtree *pRtree = (Rtree *)pVtab;
+  int rc;
+  char *zCreate = sqlite3_mprintf(
+    "DROP TABLE '%q'.'%q_node';"
+    "DROP TABLE '%q'.'%q_rowid';"
+    "DROP TABLE '%q'.'%q_parent';",
+    pRtree->zDb, pRtree->zName, 
+    pRtree->zDb, pRtree->zName,
+    pRtree->zDb, pRtree->zName
+  );
+  if( !zCreate ){
+    rc = SQLITE_NOMEM;
+  }else{
+    nodeBlobReset(pRtree);
+    rc = sqlite3_exec(pRtree->db, zCreate, 0, 0, 0);
+    sqlite3_free(zCreate);
+  }
+  if( rc==SQLITE_OK ){
+    rtreeRelease(pRtree);
+  }
+
+  return rc;
+}
+
+/* 
+** Rtree virtual table module xOpen method.
+*/
+static int rtreeOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  int rc = SQLITE_NOMEM;
+  Rtree *pRtree = (Rtree *)pVTab;
+  RtreeCursor *pCsr;
+
+  pCsr = (RtreeCursor *)sqlite3_malloc(sizeof(RtreeCursor));
+  if( pCsr ){
+    memset(pCsr, 0, sizeof(RtreeCursor));
+    pCsr->base.pVtab = pVTab;
+    rc = SQLITE_OK;
+    pRtree->nCursor++;
+  }
+  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
+
+  return rc;
+}
+
+
+/*
+** Free the RtreeCursor.aConstraint[] array and its contents.
+*/
+static void freeCursorConstraints(RtreeCursor *pCsr){
+  if( pCsr->aConstraint ){
+    int i;                        /* Used to iterate through constraint array */
+    for(i=0; i<pCsr->nConstraint; i++){
+      sqlite3_rtree_query_info *pInfo = pCsr->aConstraint[i].pInfo;
+      if( pInfo ){
+        if( pInfo->xDelUser ) pInfo->xDelUser(pInfo->pUser);
+        sqlite3_free(pInfo);
+      }
+    }
+    sqlite3_free(pCsr->aConstraint);
+    pCsr->aConstraint = 0;
+  }
+}
+
+/* 
+** Rtree virtual table module xClose method.
+*/
+static int rtreeClose(sqlite3_vtab_cursor *cur){
+  Rtree *pRtree = (Rtree *)(cur->pVtab);
+  int ii;
+  RtreeCursor *pCsr = (RtreeCursor *)cur;
+  assert( pRtree->nCursor>0 );
+  freeCursorConstraints(pCsr);
+  sqlite3_free(pCsr->aPoint);
+  for(ii=0; ii<RTREE_CACHE_SZ; ii++) nodeRelease(pRtree, pCsr->aNode[ii]);
+  sqlite3_free(pCsr);
+  pRtree->nCursor--;
+  nodeBlobReset(pRtree);
+  return SQLITE_OK;
+}
+
+/*
+** Rtree virtual table module xEof method.
+**
+** Return non-zero if the cursor does not currently point to a valid 
+** record (i.e if the scan has finished), or zero otherwise.
+*/
+static int rtreeEof(sqlite3_vtab_cursor *cur){
+  RtreeCursor *pCsr = (RtreeCursor *)cur;
+  return pCsr->atEOF;
+}
+
+/*
+** Convert raw bits from the on-disk RTree record into a coordinate value.
+** The on-disk format is big-endian and needs to be converted for little-
+** endian platforms.  The on-disk record stores integer coordinates if
+** eInt is true and it stores 32-bit floating point records if eInt is
+** false.  a[] is the four bytes of the on-disk record to be decoded.
+** Store the results in "r".
+**
+** There are five versions of this macro.  The last one is generic.  The
+** other four are various architectures-specific optimizations.
+*/
+#if SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    c.u = _byteswap_ulong(*(u32*)a);                            \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#elif SQLITE_BYTEORDER==1234 && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    c.u = __builtin_bswap32(*(u32*)a);                          \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#elif SQLITE_BYTEORDER==1234
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    memcpy(&c.u,a,4);                                           \
+    c.u = ((c.u>>24)&0xff)|((c.u>>8)&0xff00)|                   \
+          ((c.u&0xff)<<24)|((c.u&0xff00)<<8);                   \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#elif SQLITE_BYTEORDER==4321
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    memcpy(&c.u,a,4);                                           \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#else
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    c.u = ((u32)a[0]<<24) + ((u32)a[1]<<16)                     \
+           +((u32)a[2]<<8) + a[3];                              \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#endif
+
+/*
+** Check the RTree node or entry given by pCellData and p against the MATCH
+** constraint pConstraint.  
+*/
+static int rtreeCallbackConstraint(
+  RtreeConstraint *pConstraint,  /* The constraint to test */
+  int eInt,                      /* True if RTree holding integer coordinates */
+  u8 *pCellData,                 /* Raw cell content */
+  RtreeSearchPoint *pSearch,     /* Container of this cell */
+  sqlite3_rtree_dbl *prScore,    /* OUT: score for the cell */
+  int *peWithin                  /* OUT: visibility of the cell */
+){
+  sqlite3_rtree_query_info *pInfo = pConstraint->pInfo; /* Callback info */
+  int nCoord = pInfo->nCoord;                           /* No. of coordinates */
+  int rc;                                             /* Callback return code */
+  RtreeCoord c;                                       /* Translator union */
+  sqlite3_rtree_dbl aCoord[RTREE_MAX_DIMENSIONS*2];   /* Decoded coordinates */
+
+  assert( pConstraint->op==RTREE_MATCH || pConstraint->op==RTREE_QUERY );
+  assert( nCoord==2 || nCoord==4 || nCoord==6 || nCoord==8 || nCoord==10 );
+
+  if( pConstraint->op==RTREE_QUERY && pSearch->iLevel==1 ){
+    pInfo->iRowid = readInt64(pCellData);
+  }
+  pCellData += 8;
+#ifndef SQLITE_RTREE_INT_ONLY
+  if( eInt==0 ){
+    switch( nCoord ){
+      case 10:  readCoord(pCellData+36, &c); aCoord[9] = c.f;
+                readCoord(pCellData+32, &c); aCoord[8] = c.f;
+      case 8:   readCoord(pCellData+28, &c); aCoord[7] = c.f;
+                readCoord(pCellData+24, &c); aCoord[6] = c.f;
+      case 6:   readCoord(pCellData+20, &c); aCoord[5] = c.f;
+                readCoord(pCellData+16, &c); aCoord[4] = c.f;
+      case 4:   readCoord(pCellData+12, &c); aCoord[3] = c.f;
+                readCoord(pCellData+8,  &c); aCoord[2] = c.f;
+      default:  readCoord(pCellData+4,  &c); aCoord[1] = c.f;
+                readCoord(pCellData,    &c); aCoord[0] = c.f;
+    }
+  }else
+#endif
+  {
+    switch( nCoord ){
+      case 10:  readCoord(pCellData+36, &c); aCoord[9] = c.i;
+                readCoord(pCellData+32, &c); aCoord[8] = c.i;
+      case 8:   readCoord(pCellData+28, &c); aCoord[7] = c.i;
+                readCoord(pCellData+24, &c); aCoord[6] = c.i;
+      case 6:   readCoord(pCellData+20, &c); aCoord[5] = c.i;
+                readCoord(pCellData+16, &c); aCoord[4] = c.i;
+      case 4:   readCoord(pCellData+12, &c); aCoord[3] = c.i;
+                readCoord(pCellData+8,  &c); aCoord[2] = c.i;
+      default:  readCoord(pCellData+4,  &c); aCoord[1] = c.i;
+                readCoord(pCellData,    &c); aCoord[0] = c.i;
+    }
+  }
+  if( pConstraint->op==RTREE_MATCH ){
+    int eWithin = 0;
+    rc = pConstraint->u.xGeom((sqlite3_rtree_geometry*)pInfo,
+                              nCoord, aCoord, &eWithin);
+    if( eWithin==0 ) *peWithin = NOT_WITHIN;
+    *prScore = RTREE_ZERO;
+  }else{
+    pInfo->aCoord = aCoord;
+    pInfo->iLevel = pSearch->iLevel - 1;
+    pInfo->rScore = pInfo->rParentScore = pSearch->rScore;
+    pInfo->eWithin = pInfo->eParentWithin = pSearch->eWithin;
+    rc = pConstraint->u.xQueryFunc(pInfo);
+    if( pInfo->eWithin<*peWithin ) *peWithin = pInfo->eWithin;
+    if( pInfo->rScore<*prScore || *prScore<RTREE_ZERO ){
+      *prScore = pInfo->rScore;
+    }
+  }
+  return rc;
+}
+
+/* 
+** Check the internal RTree node given by pCellData against constraint p.
+** If this constraint cannot be satisfied by any child within the node,
+** set *peWithin to NOT_WITHIN.
+*/
+static void rtreeNonleafConstraint(
+  RtreeConstraint *p,        /* The constraint to test */
+  int eInt,                  /* True if RTree holds integer coordinates */
+  u8 *pCellData,             /* Raw cell content as appears on disk */
+  int *peWithin              /* Adjust downward, as appropriate */
+){
+  sqlite3_rtree_dbl val;     /* Coordinate value convert to a double */
+
+  /* p->iCoord might point to either a lower or upper bound coordinate
+  ** in a coordinate pair.  But make pCellData point to the lower bound.
+  */
+  pCellData += 8 + 4*(p->iCoord&0xfe);
+
+  assert(p->op==RTREE_LE || p->op==RTREE_LT || p->op==RTREE_GE 
+      || p->op==RTREE_GT || p->op==RTREE_EQ );
+  assert( ((((char*)pCellData) - (char*)0)&3)==0 );  /* 4-byte aligned */
+  switch( p->op ){
+    case RTREE_LE:
+    case RTREE_LT:
+    case RTREE_EQ:
+      RTREE_DECODE_COORD(eInt, pCellData, val);
+      /* val now holds the lower bound of the coordinate pair */
+      if( p->u.rValue>=val ) return;
+      if( p->op!=RTREE_EQ ) break;  /* RTREE_LE and RTREE_LT end here */
+      /* Fall through for the RTREE_EQ case */
+
+    default: /* RTREE_GT or RTREE_GE,  or fallthrough of RTREE_EQ */
+      pCellData += 4;
+      RTREE_DECODE_COORD(eInt, pCellData, val);
+      /* val now holds the upper bound of the coordinate pair */
+      if( p->u.rValue<=val ) return;
+  }
+  *peWithin = NOT_WITHIN;
+}
+
+/*
+** Check the leaf RTree cell given by pCellData against constraint p.
+** If this constraint is not satisfied, set *peWithin to NOT_WITHIN.
+** If the constraint is satisfied, leave *peWithin unchanged.
+**
+** The constraint is of the form:  xN op $val
+**
+** The op is given by p->op.  The xN is p->iCoord-th coordinate in
+** pCellData.  $val is given by p->u.rValue.
+*/
+static void rtreeLeafConstraint(
+  RtreeConstraint *p,        /* The constraint to test */
+  int eInt,                  /* True if RTree holds integer coordinates */
+  u8 *pCellData,             /* Raw cell content as appears on disk */
+  int *peWithin              /* Adjust downward, as appropriate */
+){
+  RtreeDValue xN;      /* Coordinate value converted to a double */
+
+  assert(p->op==RTREE_LE || p->op==RTREE_LT || p->op==RTREE_GE 
+      || p->op==RTREE_GT || p->op==RTREE_EQ );
+  pCellData += 8 + p->iCoord*4;
+  assert( ((((char*)pCellData) - (char*)0)&3)==0 );  /* 4-byte aligned */
+  RTREE_DECODE_COORD(eInt, pCellData, xN);
+  switch( p->op ){
+    case RTREE_LE: if( xN <= p->u.rValue ) return;  break;
+    case RTREE_LT: if( xN <  p->u.rValue ) return;  break;
+    case RTREE_GE: if( xN >= p->u.rValue ) return;  break;
+    case RTREE_GT: if( xN >  p->u.rValue ) return;  break;
+    default:       if( xN == p->u.rValue ) return;  break;
+  }
+  *peWithin = NOT_WITHIN;
+}
+
+/*
+** One of the cells in node pNode is guaranteed to have a 64-bit 
+** integer value equal to iRowid. Return the index of this cell.
+*/
+static int nodeRowidIndex(
+  Rtree *pRtree, 
+  RtreeNode *pNode, 
+  i64 iRowid,
+  int *piIndex
+){
+  int ii;
+  int nCell = NCELL(pNode);
+  assert( nCell<200 );
+  for(ii=0; ii<nCell; ii++){
+    if( nodeGetRowid(pRtree, pNode, ii)==iRowid ){
+      *piIndex = ii;
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_CORRUPT_VTAB;
+}
+
+/*
+** Return the index of the cell containing a pointer to node pNode
+** in its parent. If pNode is the root node, return -1.
+*/
+static int nodeParentIndex(Rtree *pRtree, RtreeNode *pNode, int *piIndex){
+  RtreeNode *pParent = pNode->pParent;
+  if( pParent ){
+    return nodeRowidIndex(pRtree, pParent, pNode->iNode, piIndex);
+  }
+  *piIndex = -1;
+  return SQLITE_OK;
+}
+
+/*
+** Compare two search points.  Return negative, zero, or positive if the first
+** is less than, equal to, or greater than the second.
+**
+** The rScore is the primary key.  Smaller rScore values come first.
+** If the rScore is a tie, then use iLevel as the tie breaker with smaller
+** iLevel values coming first.  In this way, if rScore is the same for all
+** SearchPoints, then iLevel becomes the deciding factor and the result
+** is a depth-first search, which is the desired default behavior.
+*/
+static int rtreeSearchPointCompare(
+  const RtreeSearchPoint *pA,
+  const RtreeSearchPoint *pB
+){
+  if( pA->rScore<pB->rScore ) return -1;
+  if( pA->rScore>pB->rScore ) return +1;
+  if( pA->iLevel<pB->iLevel ) return -1;
+  if( pA->iLevel>pB->iLevel ) return +1;
+  return 0;
+}
+
+/*
+** Interchange two search points in a cursor.
+*/
+static void rtreeSearchPointSwap(RtreeCursor *p, int i, int j){
+  RtreeSearchPoint t = p->aPoint[i];
+  assert( i<j );
+  p->aPoint[i] = p->aPoint[j];
+  p->aPoint[j] = t;
+  i++; j++;
+  if( i<RTREE_CACHE_SZ ){
+    if( j>=RTREE_CACHE_SZ ){
+      nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
+      p->aNode[i] = 0;
+    }else{
+      RtreeNode *pTemp = p->aNode[i];
+      p->aNode[i] = p->aNode[j];
+      p->aNode[j] = pTemp;
+    }
+  }
+}
+
+/*
+** Return the search point with the lowest current score.
+*/
+static RtreeSearchPoint *rtreeSearchPointFirst(RtreeCursor *pCur){
+  return pCur->bPoint ? &pCur->sPoint : pCur->nPoint ? pCur->aPoint : 0;
+}
+
+/*
+** Get the RtreeNode for the search point with the lowest score.
+*/
+static RtreeNode *rtreeNodeOfFirstSearchPoint(RtreeCursor *pCur, int *pRC){
+  sqlite3_int64 id;
+  int ii = 1 - pCur->bPoint;
+  assert( ii==0 || ii==1 );
+  assert( pCur->bPoint || pCur->nPoint );
+  if( pCur->aNode[ii]==0 ){
+    assert( pRC!=0 );
+    id = ii ? pCur->aPoint[0].id : pCur->sPoint.id;
+    *pRC = nodeAcquire(RTREE_OF_CURSOR(pCur), id, 0, &pCur->aNode[ii]);
+  }
+  return pCur->aNode[ii];
+}
+
+/*
+** Push a new element onto the priority queue
+*/
+static RtreeSearchPoint *rtreeEnqueue(
+  RtreeCursor *pCur,    /* The cursor */
+  RtreeDValue rScore,   /* Score for the new search point */
+  u8 iLevel             /* Level for the new search point */
+){
+  int i, j;
+  RtreeSearchPoint *pNew;
+  if( pCur->nPoint>=pCur->nPointAlloc ){
+    int nNew = pCur->nPointAlloc*2 + 8;
+    pNew = sqlite3_realloc(pCur->aPoint, nNew*sizeof(pCur->aPoint[0]));
+    if( pNew==0 ) return 0;
+    pCur->aPoint = pNew;
+    pCur->nPointAlloc = nNew;
+  }
+  i = pCur->nPoint++;
+  pNew = pCur->aPoint + i;
+  pNew->rScore = rScore;
+  pNew->iLevel = iLevel;
+  assert( iLevel<=RTREE_MAX_DEPTH );
+  while( i>0 ){
+    RtreeSearchPoint *pParent;
+    j = (i-1)/2;
+    pParent = pCur->aPoint + j;
+    if( rtreeSearchPointCompare(pNew, pParent)>=0 ) break;
+    rtreeSearchPointSwap(pCur, j, i);
+    i = j;
+    pNew = pParent;
+  }
+  return pNew;
+}
+
+/*
+** Allocate a new RtreeSearchPoint and return a pointer to it.  Return
+** NULL if malloc fails.
+*/
+static RtreeSearchPoint *rtreeSearchPointNew(
+  RtreeCursor *pCur,    /* The cursor */
+  RtreeDValue rScore,   /* Score for the new search point */
+  u8 iLevel             /* Level for the new search point */
+){
+  RtreeSearchPoint *pNew, *pFirst;
+  pFirst = rtreeSearchPointFirst(pCur);
+  pCur->anQueue[iLevel]++;
+  if( pFirst==0
+   || pFirst->rScore>rScore 
+   || (pFirst->rScore==rScore && pFirst->iLevel>iLevel)
+  ){
+    if( pCur->bPoint ){
+      int ii;
+      pNew = rtreeEnqueue(pCur, rScore, iLevel);
+      if( pNew==0 ) return 0;
+      ii = (int)(pNew - pCur->aPoint) + 1;
+      if( ii<RTREE_CACHE_SZ ){
+        assert( pCur->aNode[ii]==0 );
+        pCur->aNode[ii] = pCur->aNode[0];
+       }else{
+        nodeRelease(RTREE_OF_CURSOR(pCur), pCur->aNode[0]);
+      }
+      pCur->aNode[0] = 0;
+      *pNew = pCur->sPoint;
+    }
+    pCur->sPoint.rScore = rScore;
+    pCur->sPoint.iLevel = iLevel;
+    pCur->bPoint = 1;
+    return &pCur->sPoint;
+  }else{
+    return rtreeEnqueue(pCur, rScore, iLevel);
+  }
+}
+
+#if 0
+/* Tracing routines for the RtreeSearchPoint queue */
+static void tracePoint(RtreeSearchPoint *p, int idx, RtreeCursor *pCur){
+  if( idx<0 ){ printf(" s"); }else{ printf("%2d", idx); }
+  printf(" %d.%05lld.%02d %g %d",
+    p->iLevel, p->id, p->iCell, p->rScore, p->eWithin
+  );
+  idx++;
+  if( idx<RTREE_CACHE_SZ ){
+    printf(" %p\n", pCur->aNode[idx]);
+  }else{
+    printf("\n");
+  }
+}
+static void traceQueue(RtreeCursor *pCur, const char *zPrefix){
+  int ii;
+  printf("=== %9s ", zPrefix);
+  if( pCur->bPoint ){
+    tracePoint(&pCur->sPoint, -1, pCur);
+  }
+  for(ii=0; ii<pCur->nPoint; ii++){
+    if( ii>0 || pCur->bPoint ) printf("              ");
+    tracePoint(&pCur->aPoint[ii], ii, pCur);
+  }
+}
+# define RTREE_QUEUE_TRACE(A,B) traceQueue(A,B)
+#else
+# define RTREE_QUEUE_TRACE(A,B)   /* no-op */
+#endif
+
+/* Remove the search point with the lowest current score.
+*/
+static void rtreeSearchPointPop(RtreeCursor *p){
+  int i, j, k, n;
+  i = 1 - p->bPoint;
+  assert( i==0 || i==1 );
+  if( p->aNode[i] ){
+    nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
+    p->aNode[i] = 0;
+  }
+  if( p->bPoint ){
+    p->anQueue[p->sPoint.iLevel]--;
+    p->bPoint = 0;
+  }else if( p->nPoint ){
+    p->anQueue[p->aPoint[0].iLevel]--;
+    n = --p->nPoint;
+    p->aPoint[0] = p->aPoint[n];
+    if( n<RTREE_CACHE_SZ-1 ){
+      p->aNode[1] = p->aNode[n+1];
+      p->aNode[n+1] = 0;
+    }
+    i = 0;
+    while( (j = i*2+1)<n ){
+      k = j+1;
+      if( k<n && rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[j])<0 ){
+        if( rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[i])<0 ){
+          rtreeSearchPointSwap(p, i, k);
+          i = k;
+        }else{
+          break;
+        }
+      }else{
+        if( rtreeSearchPointCompare(&p->aPoint[j], &p->aPoint[i])<0 ){
+          rtreeSearchPointSwap(p, i, j);
+          i = j;
+        }else{
+          break;
+        }
+      }
+    }
+  }
+}
+
+
+/*
+** Continue the search on cursor pCur until the front of the queue
+** contains an entry suitable for returning as a result-set row,
+** or until the RtreeSearchPoint queue is empty, indicating that the
+** query has completed.
+*/
+static int rtreeStepToLeaf(RtreeCursor *pCur){
+  RtreeSearchPoint *p;
+  Rtree *pRtree = RTREE_OF_CURSOR(pCur);
+  RtreeNode *pNode;
+  int eWithin;
+  int rc = SQLITE_OK;
+  int nCell;
+  int nConstraint = pCur->nConstraint;
+  int ii;
+  int eInt;
+  RtreeSearchPoint x;
+
+  eInt = pRtree->eCoordType==RTREE_COORD_INT32;
+  while( (p = rtreeSearchPointFirst(pCur))!=0 && p->iLevel>0 ){
+    pNode = rtreeNodeOfFirstSearchPoint(pCur, &rc);
+    if( rc ) return rc;
+    nCell = NCELL(pNode);
+    assert( nCell<200 );
+    while( p->iCell<nCell ){
+      sqlite3_rtree_dbl rScore = (sqlite3_rtree_dbl)-1;
+      u8 *pCellData = pNode->zData + (4+pRtree->nBytesPerCell*p->iCell);
+      eWithin = FULLY_WITHIN;
+      for(ii=0; ii<nConstraint; ii++){
+        RtreeConstraint *pConstraint = pCur->aConstraint + ii;
+        if( pConstraint->op>=RTREE_MATCH ){
+          rc = rtreeCallbackConstraint(pConstraint, eInt, pCellData, p,
+                                       &rScore, &eWithin);
+          if( rc ) return rc;
+        }else if( p->iLevel==1 ){
+          rtreeLeafConstraint(pConstraint, eInt, pCellData, &eWithin);
+        }else{
+          rtreeNonleafConstraint(pConstraint, eInt, pCellData, &eWithin);
+        }
+        if( eWithin==NOT_WITHIN ) break;
+      }
+      p->iCell++;
+      if( eWithin==NOT_WITHIN ) continue;
+      x.iLevel = p->iLevel - 1;
+      if( x.iLevel ){
+        x.id = readInt64(pCellData);
+        x.iCell = 0;
+      }else{
+        x.id = p->id;
+        x.iCell = p->iCell - 1;
+      }
+      if( p->iCell>=nCell ){
+        RTREE_QUEUE_TRACE(pCur, "POP-S:");
+        rtreeSearchPointPop(pCur);
+      }
+      if( rScore<RTREE_ZERO ) rScore = RTREE_ZERO;
+      p = rtreeSearchPointNew(pCur, rScore, x.iLevel);
+      if( p==0 ) return SQLITE_NOMEM;
+      p->eWithin = (u8)eWithin;
+      p->id = x.id;
+      p->iCell = x.iCell;
+      RTREE_QUEUE_TRACE(pCur, "PUSH-S:");
+      break;
+    }
+    if( p->iCell>=nCell ){
+      RTREE_QUEUE_TRACE(pCur, "POP-Se:");
+      rtreeSearchPointPop(pCur);
+    }
+  }
+  pCur->atEOF = p==0;
+  return SQLITE_OK;
+}
+
+/* 
+** Rtree virtual table module xNext method.
+*/
+static int rtreeNext(sqlite3_vtab_cursor *pVtabCursor){
+  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
+  int rc = SQLITE_OK;
+
+  /* Move to the next entry that matches the configured constraints. */
+  RTREE_QUEUE_TRACE(pCsr, "POP-Nx:");
+  rtreeSearchPointPop(pCsr);
+  rc = rtreeStepToLeaf(pCsr);
+  return rc;
+}
+
+/* 
+** Rtree virtual table module xRowid method.
+*/
+static int rtreeRowid(sqlite3_vtab_cursor *pVtabCursor, sqlite_int64 *pRowid){
+  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
+  RtreeSearchPoint *p = rtreeSearchPointFirst(pCsr);
+  int rc = SQLITE_OK;
+  RtreeNode *pNode = rtreeNodeOfFirstSearchPoint(pCsr, &rc);
+  if( rc==SQLITE_OK && p ){
+    *pRowid = nodeGetRowid(RTREE_OF_CURSOR(pCsr), pNode, p->iCell);
+  }
+  return rc;
+}
+
+/* 
+** Rtree virtual table module xColumn method.
+*/
+static int rtreeColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  Rtree *pRtree = (Rtree *)cur->pVtab;
+  RtreeCursor *pCsr = (RtreeCursor *)cur;
+  RtreeSearchPoint *p = rtreeSearchPointFirst(pCsr);
+  RtreeCoord c;
+  int rc = SQLITE_OK;
+  RtreeNode *pNode = rtreeNodeOfFirstSearchPoint(pCsr, &rc);
+
+  if( rc ) return rc;
+  if( p==0 ) return SQLITE_OK;
+  if( i==0 ){
+    sqlite3_result_int64(ctx, nodeGetRowid(pRtree, pNode, p->iCell));
+  }else{
+    nodeGetCoord(pRtree, pNode, p->iCell, i-1, &c);
+#ifndef SQLITE_RTREE_INT_ONLY
+    if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
+      sqlite3_result_double(ctx, c.f);
+    }else
+#endif
+    {
+      assert( pRtree->eCoordType==RTREE_COORD_INT32 );
+      sqlite3_result_int(ctx, c.i);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/* 
+** Use nodeAcquire() to obtain the leaf node containing the record with 
+** rowid iRowid. If successful, set *ppLeaf to point to the node and
+** return SQLITE_OK. If there is no such record in the table, set
+** *ppLeaf to 0 and return SQLITE_OK. If an error occurs, set *ppLeaf
+** to zero and return an SQLite error code.
+*/
+static int findLeafNode(
+  Rtree *pRtree,              /* RTree to search */
+  i64 iRowid,                 /* The rowid searching for */
+  RtreeNode **ppLeaf,         /* Write the node here */
+  sqlite3_int64 *piNode       /* Write the node-id here */
+){
+  int rc;
+  *ppLeaf = 0;
+  sqlite3_bind_int64(pRtree->pReadRowid, 1, iRowid);
+  if( sqlite3_step(pRtree->pReadRowid)==SQLITE_ROW ){
+    i64 iNode = sqlite3_column_int64(pRtree->pReadRowid, 0);
+    if( piNode ) *piNode = iNode;
+    rc = nodeAcquire(pRtree, iNode, 0, ppLeaf);
+    sqlite3_reset(pRtree->pReadRowid);
+  }else{
+    rc = sqlite3_reset(pRtree->pReadRowid);
+  }
+  return rc;
+}
+
+/*
+** This function is called to configure the RtreeConstraint object passed
+** as the second argument for a MATCH constraint. The value passed as the
+** first argument to this function is the right-hand operand to the MATCH
+** operator.
+*/
+static int deserializeGeometry(sqlite3_value *pValue, RtreeConstraint *pCons){
+  RtreeMatchArg *pBlob;              /* BLOB returned by geometry function */
+  sqlite3_rtree_query_info *pInfo;   /* Callback information */
+  int nBlob;                         /* Size of the geometry function blob */
+  int nExpected;                     /* Expected size of the BLOB */
+
+  /* Check that value is actually a blob. */
+  if( sqlite3_value_type(pValue)!=SQLITE_BLOB ) return SQLITE_ERROR;
+
+  /* Check that the blob is roughly the right size. */
+  nBlob = sqlite3_value_bytes(pValue);
+  if( nBlob<(int)sizeof(RtreeMatchArg) ){
+    return SQLITE_ERROR;
+  }
+
+  pInfo = (sqlite3_rtree_query_info*)sqlite3_malloc( sizeof(*pInfo)+nBlob );
+  if( !pInfo ) return SQLITE_NOMEM;
+  memset(pInfo, 0, sizeof(*pInfo));
+  pBlob = (RtreeMatchArg*)&pInfo[1];
+
+  memcpy(pBlob, sqlite3_value_blob(pValue), nBlob);
+  nExpected = (int)(sizeof(RtreeMatchArg) +
+                    pBlob->nParam*sizeof(sqlite3_value*) +
+                    (pBlob->nParam-1)*sizeof(RtreeDValue));
+  if( pBlob->magic!=RTREE_GEOMETRY_MAGIC || nBlob!=nExpected ){
+    sqlite3_free(pInfo);
+    return SQLITE_ERROR;
+  }
+  pInfo->pContext = pBlob->cb.pContext;
+  pInfo->nParam = pBlob->nParam;
+  pInfo->aParam = pBlob->aParam;
+  pInfo->apSqlParam = pBlob->apSqlParam;
+
+  if( pBlob->cb.xGeom ){
+    pCons->u.xGeom = pBlob->cb.xGeom;
+  }else{
+    pCons->op = RTREE_QUERY;
+    pCons->u.xQueryFunc = pBlob->cb.xQueryFunc;
+  }
+  pCons->pInfo = pInfo;
+  return SQLITE_OK;
+}
+
+/* 
+** Rtree virtual table module xFilter method.
+*/
+static int rtreeFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  Rtree *pRtree = (Rtree *)pVtabCursor->pVtab;
+  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
+  RtreeNode *pRoot = 0;
+  int ii;
+  int rc = SQLITE_OK;
+  int iCell = 0;
+
+  rtreeReference(pRtree);
+
+  /* Reset the cursor to the same state as rtreeOpen() leaves it in. */
+  freeCursorConstraints(pCsr);
+  sqlite3_free(pCsr->aPoint);
+  memset(pCsr, 0, sizeof(RtreeCursor));
+  pCsr->base.pVtab = (sqlite3_vtab*)pRtree;
+
+  pCsr->iStrategy = idxNum;
+  if( idxNum==1 ){
+    /* Special case - lookup by rowid. */
+    RtreeNode *pLeaf;        /* Leaf on which the required cell resides */
+    RtreeSearchPoint *p;     /* Search point for the leaf */
+    i64 iRowid = sqlite3_value_int64(argv[0]);
+    i64 iNode = 0;
+    rc = findLeafNode(pRtree, iRowid, &pLeaf, &iNode);
+    if( rc==SQLITE_OK && pLeaf!=0 ){
+      p = rtreeSearchPointNew(pCsr, RTREE_ZERO, 0);
+      assert( p!=0 );  /* Always returns pCsr->sPoint */
+      pCsr->aNode[0] = pLeaf;
+      p->id = iNode;
+      p->eWithin = PARTLY_WITHIN;
+      rc = nodeRowidIndex(pRtree, pLeaf, iRowid, &iCell);
+      p->iCell = (u8)iCell;
+      RTREE_QUEUE_TRACE(pCsr, "PUSH-F1:");
+    }else{
+      pCsr->atEOF = 1;
+    }
+  }else{
+    /* Normal case - r-tree scan. Set up the RtreeCursor.aConstraint array 
+    ** with the configured constraints. 
+    */
+    rc = nodeAcquire(pRtree, 1, 0, &pRoot);
+    if( rc==SQLITE_OK && argc>0 ){
+      pCsr->aConstraint = sqlite3_malloc(sizeof(RtreeConstraint)*argc);
+      pCsr->nConstraint = argc;
+      if( !pCsr->aConstraint ){
+        rc = SQLITE_NOMEM;
+      }else{
+        memset(pCsr->aConstraint, 0, sizeof(RtreeConstraint)*argc);
+        memset(pCsr->anQueue, 0, sizeof(u32)*(pRtree->iDepth + 1));
+        assert( (idxStr==0 && argc==0)
+                || (idxStr && (int)strlen(idxStr)==argc*2) );
+        for(ii=0; ii<argc; ii++){
+          RtreeConstraint *p = &pCsr->aConstraint[ii];
+          p->op = idxStr[ii*2];
+          p->iCoord = idxStr[ii*2+1]-'0';
+          if( p->op>=RTREE_MATCH ){
+            /* A MATCH operator. The right-hand-side must be a blob that
+            ** can be cast into an RtreeMatchArg object. One created using
+            ** an sqlite3_rtree_geometry_callback() SQL user function.
+            */
+            rc = deserializeGeometry(argv[ii], p);
+            if( rc!=SQLITE_OK ){
+              break;
+            }
+            p->pInfo->nCoord = pRtree->nDim2;
+            p->pInfo->anQueue = pCsr->anQueue;
+            p->pInfo->mxLevel = pRtree->iDepth + 1;
+          }else{
+#ifdef SQLITE_RTREE_INT_ONLY
+            p->u.rValue = sqlite3_value_int64(argv[ii]);
+#else
+            p->u.rValue = sqlite3_value_double(argv[ii]);
+#endif
+          }
+        }
+      }
+    }
+    if( rc==SQLITE_OK ){
+      RtreeSearchPoint *pNew;
+      pNew = rtreeSearchPointNew(pCsr, RTREE_ZERO, (u8)(pRtree->iDepth+1));
+      if( pNew==0 ) return SQLITE_NOMEM;
+      pNew->id = 1;
+      pNew->iCell = 0;
+      pNew->eWithin = PARTLY_WITHIN;
+      assert( pCsr->bPoint==1 );
+      pCsr->aNode[0] = pRoot;
+      pRoot = 0;
+      RTREE_QUEUE_TRACE(pCsr, "PUSH-Fm:");
+      rc = rtreeStepToLeaf(pCsr);
+    }
+  }
+
+  nodeRelease(pRtree, pRoot);
+  rtreeRelease(pRtree);
+  return rc;
+}
+
+/*
+** Rtree virtual table module xBestIndex method. There are three
+** table scan strategies to choose from (in order from most to 
+** least desirable):
+**
+**   idxNum     idxStr        Strategy
+**   ------------------------------------------------
+**     1        Unused        Direct lookup by rowid.
+**     2        See below     R-tree query or full-table scan.
+**   ------------------------------------------------
+**
+** If strategy 1 is used, then idxStr is not meaningful. If strategy
+** 2 is used, idxStr is formatted to contain 2 bytes for each 
+** constraint used. The first two bytes of idxStr correspond to 
+** the constraint in sqlite3_index_info.aConstraintUsage[] with
+** (argvIndex==1) etc.
+**
+** The first of each pair of bytes in idxStr identifies the constraint
+** operator as follows:
+**
+**   Operator    Byte Value
+**   ----------------------
+**      =        0x41 ('A')
+**     <=        0x42 ('B')
+**      <        0x43 ('C')
+**     >=        0x44 ('D')
+**      >        0x45 ('E')
+**   MATCH       0x46 ('F')
+**   ----------------------
+**
+** The second of each pair of bytes identifies the coordinate column
+** to which the constraint applies. The leftmost coordinate column
+** is 'a', the second from the left 'b' etc.
+*/
+static int rtreeBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  Rtree *pRtree = (Rtree*)tab;
+  int rc = SQLITE_OK;
+  int ii;
+  int bMatch = 0;                 /* True if there exists a MATCH constraint */
+  i64 nRow;                       /* Estimated rows returned by this scan */
+
+  int iIdx = 0;
+  char zIdxStr[RTREE_MAX_DIMENSIONS*8+1];
+  memset(zIdxStr, 0, sizeof(zIdxStr));
+
+  /* Check if there exists a MATCH constraint - even an unusable one. If there
+  ** is, do not consider the lookup-by-rowid plan as using such a plan would
+  ** require the VDBE to evaluate the MATCH constraint, which is not currently
+  ** possible. */
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    if( pIdxInfo->aConstraint[ii].op==SQLITE_INDEX_CONSTRAINT_MATCH ){
+      bMatch = 1;
+    }
+  }
+
+  assert( pIdxInfo->idxStr==0 );
+  for(ii=0; ii<pIdxInfo->nConstraint && iIdx<(int)(sizeof(zIdxStr)-1); ii++){
+    struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[ii];
+
+    if( bMatch==0 && p->usable 
+     && p->iColumn==0 && p->op==SQLITE_INDEX_CONSTRAINT_EQ 
+    ){
+      /* We have an equality constraint on the rowid. Use strategy 1. */
+      int jj;
+      for(jj=0; jj<ii; jj++){
+        pIdxInfo->aConstraintUsage[jj].argvIndex = 0;
+        pIdxInfo->aConstraintUsage[jj].omit = 0;
+      }
+      pIdxInfo->idxNum = 1;
+      pIdxInfo->aConstraintUsage[ii].argvIndex = 1;
+      pIdxInfo->aConstraintUsage[jj].omit = 1;
+
+      /* This strategy involves a two rowid lookups on an B-Tree structures
+      ** and then a linear search of an R-Tree node. This should be 
+      ** considered almost as quick as a direct rowid lookup (for which 
+      ** sqlite uses an internal cost of 0.0). It is expected to return
+      ** a single row.
+      */ 
+      pIdxInfo->estimatedCost = 30.0;
+      pIdxInfo->estimatedRows = 1;
+      return SQLITE_OK;
+    }
+
+    if( p->usable && (p->iColumn>0 || p->op==SQLITE_INDEX_CONSTRAINT_MATCH) ){
+      u8 op;
+      switch( p->op ){
+        case SQLITE_INDEX_CONSTRAINT_EQ: op = RTREE_EQ; break;
+        case SQLITE_INDEX_CONSTRAINT_GT: op = RTREE_GT; break;
+        case SQLITE_INDEX_CONSTRAINT_LE: op = RTREE_LE; break;
+        case SQLITE_INDEX_CONSTRAINT_LT: op = RTREE_LT; break;
+        case SQLITE_INDEX_CONSTRAINT_GE: op = RTREE_GE; break;
+        default:
+          assert( p->op==SQLITE_INDEX_CONSTRAINT_MATCH );
+          op = RTREE_MATCH; 
+          break;
+      }
+      zIdxStr[iIdx++] = op;
+      zIdxStr[iIdx++] = (char)(p->iColumn - 1 + '0');
+      pIdxInfo->aConstraintUsage[ii].argvIndex = (iIdx/2);
+      pIdxInfo->aConstraintUsage[ii].omit = 1;
+    }
+  }
+
+  pIdxInfo->idxNum = 2;
+  pIdxInfo->needToFreeIdxStr = 1;
+  if( iIdx>0 && 0==(pIdxInfo->idxStr = sqlite3_mprintf("%s", zIdxStr)) ){
+    return SQLITE_NOMEM;
+  }
+
+  nRow = pRtree->nRowEst >> (iIdx/2);
+  pIdxInfo->estimatedCost = (double)6.0 * (double)nRow;
+  pIdxInfo->estimatedRows = nRow;
+
+  return rc;
+}
+
+/*
+** Return the N-dimensional volumn of the cell stored in *p.
+*/
+static RtreeDValue cellArea(Rtree *pRtree, RtreeCell *p){
+  RtreeDValue area = (RtreeDValue)1;
+  assert( pRtree->nDim>=1 && pRtree->nDim<=5 );
+#ifndef SQLITE_RTREE_INT_ONLY
+  if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
+    switch( pRtree->nDim ){
+      case 5:  area  = p->aCoord[9].f - p->aCoord[8].f;
+      case 4:  area *= p->aCoord[7].f - p->aCoord[6].f;
+      case 3:  area *= p->aCoord[5].f - p->aCoord[4].f;
+      case 2:  area *= p->aCoord[3].f - p->aCoord[2].f;
+      default: area *= p->aCoord[1].f - p->aCoord[0].f;
+    }
+  }else
+#endif
+  {
+    switch( pRtree->nDim ){
+      case 5:  area  = p->aCoord[9].i - p->aCoord[8].i;
+      case 4:  area *= p->aCoord[7].i - p->aCoord[6].i;
+      case 3:  area *= p->aCoord[5].i - p->aCoord[4].i;
+      case 2:  area *= p->aCoord[3].i - p->aCoord[2].i;
+      default: area *= p->aCoord[1].i - p->aCoord[0].i;
+    }
+  }
+  return area;
+}
+
+/*
+** Return the margin length of cell p. The margin length is the sum
+** of the objects size in each dimension.
+*/
+static RtreeDValue cellMargin(Rtree *pRtree, RtreeCell *p){
+  RtreeDValue margin = 0;
+  int ii = pRtree->nDim2 - 2;
+  do{
+    margin += (DCOORD(p->aCoord[ii+1]) - DCOORD(p->aCoord[ii]));
+    ii -= 2;
+  }while( ii>=0 );
+  return margin;
+}
+
+/*
+** Store the union of cells p1 and p2 in p1.
+*/
+static void cellUnion(Rtree *pRtree, RtreeCell *p1, RtreeCell *p2){
+  int ii = 0;
+  if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
+    do{
+      p1->aCoord[ii].f = MIN(p1->aCoord[ii].f, p2->aCoord[ii].f);
+      p1->aCoord[ii+1].f = MAX(p1->aCoord[ii+1].f, p2->aCoord[ii+1].f);
+      ii += 2;
+    }while( ii<pRtree->nDim2 );
+  }else{
+    do{
+      p1->aCoord[ii].i = MIN(p1->aCoord[ii].i, p2->aCoord[ii].i);
+      p1->aCoord[ii+1].i = MAX(p1->aCoord[ii+1].i, p2->aCoord[ii+1].i);
+      ii += 2;
+    }while( ii<pRtree->nDim2 );
+  }
+}
+
+/*
+** Return true if the area covered by p2 is a subset of the area covered
+** by p1. False otherwise.
+*/
+static int cellContains(Rtree *pRtree, RtreeCell *p1, RtreeCell *p2){
+  int ii;
+  int isInt = (pRtree->eCoordType==RTREE_COORD_INT32);
+  for(ii=0; ii<pRtree->nDim2; ii+=2){
+    RtreeCoord *a1 = &p1->aCoord[ii];
+    RtreeCoord *a2 = &p2->aCoord[ii];
+    if( (!isInt && (a2[0].f<a1[0].f || a2[1].f>a1[1].f)) 
+     || ( isInt && (a2[0].i<a1[0].i || a2[1].i>a1[1].i)) 
+    ){
+      return 0;
+    }
+  }
+  return 1;
+}
+
+/*
+** Return the amount cell p would grow by if it were unioned with pCell.
+*/
+static RtreeDValue cellGrowth(Rtree *pRtree, RtreeCell *p, RtreeCell *pCell){
+  RtreeDValue area;
+  RtreeCell cell;
+  memcpy(&cell, p, sizeof(RtreeCell));
+  area = cellArea(pRtree, &cell);
+  cellUnion(pRtree, &cell, pCell);
+  return (cellArea(pRtree, &cell)-area);
+}
+
+static RtreeDValue cellOverlap(
+  Rtree *pRtree, 
+  RtreeCell *p, 
+  RtreeCell *aCell, 
+  int nCell
+){
+  int ii;
+  RtreeDValue overlap = RTREE_ZERO;
+  for(ii=0; ii<nCell; ii++){
+    int jj;
+    RtreeDValue o = (RtreeDValue)1;
+    for(jj=0; jj<pRtree->nDim2; jj+=2){
+      RtreeDValue x1, x2;
+      x1 = MAX(DCOORD(p->aCoord[jj]), DCOORD(aCell[ii].aCoord[jj]));
+      x2 = MIN(DCOORD(p->aCoord[jj+1]), DCOORD(aCell[ii].aCoord[jj+1]));
+      if( x2<x1 ){
+        o = (RtreeDValue)0;
+        break;
+      }else{
+        o = o * (x2-x1);
+      }
+    }
+    overlap += o;
+  }
+  return overlap;
+}
+
+
+/*
+** This function implements the ChooseLeaf algorithm from Gutman[84].
+** ChooseSubTree in r*tree terminology.
+*/
+static int ChooseLeaf(
+  Rtree *pRtree,               /* Rtree table */
+  RtreeCell *pCell,            /* Cell to insert into rtree */
+  int iHeight,                 /* Height of sub-tree rooted at pCell */
+  RtreeNode **ppLeaf           /* OUT: Selected leaf page */
+){
+  int rc;
+  int ii;
+  RtreeNode *pNode;
+  rc = nodeAcquire(pRtree, 1, 0, &pNode);
+
+  for(ii=0; rc==SQLITE_OK && ii<(pRtree->iDepth-iHeight); ii++){
+    int iCell;
+    sqlite3_int64 iBest = 0;
+
+    RtreeDValue fMinGrowth = RTREE_ZERO;
+    RtreeDValue fMinArea = RTREE_ZERO;
+
+    int nCell = NCELL(pNode);
+    RtreeCell cell;
+    RtreeNode *pChild;
+
+    RtreeCell *aCell = 0;
+
+    /* Select the child node which will be enlarged the least if pCell
+    ** is inserted into it. Resolve ties by choosing the entry with
+    ** the smallest area.
+    */
+    for(iCell=0; iCell<nCell; iCell++){
+      int bBest = 0;
+      RtreeDValue growth;
+      RtreeDValue area;
+      nodeGetCell(pRtree, pNode, iCell, &cell);
+      growth = cellGrowth(pRtree, &cell, pCell);
+      area = cellArea(pRtree, &cell);
+      if( iCell==0||growth<fMinGrowth||(growth==fMinGrowth && area<fMinArea) ){
+        bBest = 1;
+      }
+      if( bBest ){
+        fMinGrowth = growth;
+        fMinArea = area;
+        iBest = cell.iRowid;
+      }
+    }
+
+    sqlite3_free(aCell);
+    rc = nodeAcquire(pRtree, iBest, pNode, &pChild);
+    nodeRelease(pRtree, pNode);
+    pNode = pChild;
+  }
+
+  *ppLeaf = pNode;
+  return rc;
+}
+
+/*
+** A cell with the same content as pCell has just been inserted into
+** the node pNode. This function updates the bounding box cells in
+** all ancestor elements.
+*/
+static int AdjustTree(
+  Rtree *pRtree,                    /* Rtree table */
+  RtreeNode *pNode,                 /* Adjust ancestry of this node. */
+  RtreeCell *pCell                  /* This cell was just inserted */
+){
+  RtreeNode *p = pNode;
+  while( p->pParent ){
+    RtreeNode *pParent = p->pParent;
+    RtreeCell cell;
+    int iCell;
+
+    if( nodeParentIndex(pRtree, p, &iCell) ){
+      return SQLITE_CORRUPT_VTAB;
+    }
+
+    nodeGetCell(pRtree, pParent, iCell, &cell);
+    if( !cellContains(pRtree, &cell, pCell) ){
+      cellUnion(pRtree, &cell, pCell);
+      nodeOverwriteCell(pRtree, pParent, &cell, iCell);
+    }
+ 
+    p = pParent;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Write mapping (iRowid->iNode) to the <rtree>_rowid table.
+*/
+static int rowidWrite(Rtree *pRtree, sqlite3_int64 iRowid, sqlite3_int64 iNode){
+  sqlite3_bind_int64(pRtree->pWriteRowid, 1, iRowid);
+  sqlite3_bind_int64(pRtree->pWriteRowid, 2, iNode);
+  sqlite3_step(pRtree->pWriteRowid);
+  return sqlite3_reset(pRtree->pWriteRowid);
+}
+
+/*
+** Write mapping (iNode->iPar) to the <rtree>_parent table.
+*/
+static int parentWrite(Rtree *pRtree, sqlite3_int64 iNode, sqlite3_int64 iPar){
+  sqlite3_bind_int64(pRtree->pWriteParent, 1, iNode);
+  sqlite3_bind_int64(pRtree->pWriteParent, 2, iPar);
+  sqlite3_step(pRtree->pWriteParent);
+  return sqlite3_reset(pRtree->pWriteParent);
+}
+
+static int rtreeInsertCell(Rtree *, RtreeNode *, RtreeCell *, int);
+
+
+/*
+** Arguments aIdx, aDistance and aSpare all point to arrays of size
+** nIdx. The aIdx array contains the set of integers from 0 to 
+** (nIdx-1) in no particular order. This function sorts the values
+** in aIdx according to the indexed values in aDistance. For
+** example, assuming the inputs:
+**
+**   aIdx      = { 0,   1,   2,   3 }
+**   aDistance = { 5.0, 2.0, 7.0, 6.0 }
+**
+** this function sets the aIdx array to contain:
+**
+**   aIdx      = { 0,   1,   2,   3 }
+**
+** The aSpare array is used as temporary working space by the
+** sorting algorithm.
+*/
+static void SortByDistance(
+  int *aIdx, 
+  int nIdx, 
+  RtreeDValue *aDistance, 
+  int *aSpare
+){
+  if( nIdx>1 ){
+    int iLeft = 0;
+    int iRight = 0;
+
+    int nLeft = nIdx/2;
+    int nRight = nIdx-nLeft;
+    int *aLeft = aIdx;
+    int *aRight = &aIdx[nLeft];
+
+    SortByDistance(aLeft, nLeft, aDistance, aSpare);
+    SortByDistance(aRight, nRight, aDistance, aSpare);
+
+    memcpy(aSpare, aLeft, sizeof(int)*nLeft);
+    aLeft = aSpare;
+
+    while( iLeft<nLeft || iRight<nRight ){
+      if( iLeft==nLeft ){
+        aIdx[iLeft+iRight] = aRight[iRight];
+        iRight++;
+      }else if( iRight==nRight ){
+        aIdx[iLeft+iRight] = aLeft[iLeft];
+        iLeft++;
+      }else{
+        RtreeDValue fLeft = aDistance[aLeft[iLeft]];
+        RtreeDValue fRight = aDistance[aRight[iRight]];
+        if( fLeft<fRight ){
+          aIdx[iLeft+iRight] = aLeft[iLeft];
+          iLeft++;
+        }else{
+          aIdx[iLeft+iRight] = aRight[iRight];
+          iRight++;
+        }
+      }
+    }
+
+#if 0
+    /* Check that the sort worked */
+    {
+      int jj;
+      for(jj=1; jj<nIdx; jj++){
+        RtreeDValue left = aDistance[aIdx[jj-1]];
+        RtreeDValue right = aDistance[aIdx[jj]];
+        assert( left<=right );
+      }
+    }
+#endif
+  }
+}
+
+/*
+** Arguments aIdx, aCell and aSpare all point to arrays of size
+** nIdx. The aIdx array contains the set of integers from 0 to 
+** (nIdx-1) in no particular order. This function sorts the values
+** in aIdx according to dimension iDim of the cells in aCell. The
+** minimum value of dimension iDim is considered first, the
+** maximum used to break ties.
+**
+** The aSpare array is used as temporary working space by the
+** sorting algorithm.
+*/
+static void SortByDimension(
+  Rtree *pRtree,
+  int *aIdx, 
+  int nIdx, 
+  int iDim, 
+  RtreeCell *aCell, 
+  int *aSpare
+){
+  if( nIdx>1 ){
+
+    int iLeft = 0;
+    int iRight = 0;
+
+    int nLeft = nIdx/2;
+    int nRight = nIdx-nLeft;
+    int *aLeft = aIdx;
+    int *aRight = &aIdx[nLeft];
+
+    SortByDimension(pRtree, aLeft, nLeft, iDim, aCell, aSpare);
+    SortByDimension(pRtree, aRight, nRight, iDim, aCell, aSpare);
+
+    memcpy(aSpare, aLeft, sizeof(int)*nLeft);
+    aLeft = aSpare;
+    while( iLeft<nLeft || iRight<nRight ){
+      RtreeDValue xleft1 = DCOORD(aCell[aLeft[iLeft]].aCoord[iDim*2]);
+      RtreeDValue xleft2 = DCOORD(aCell[aLeft[iLeft]].aCoord[iDim*2+1]);
+      RtreeDValue xright1 = DCOORD(aCell[aRight[iRight]].aCoord[iDim*2]);
+      RtreeDValue xright2 = DCOORD(aCell[aRight[iRight]].aCoord[iDim*2+1]);
+      if( (iLeft!=nLeft) && ((iRight==nRight)
+       || (xleft1<xright1)
+       || (xleft1==xright1 && xleft2<xright2)
+      )){
+        aIdx[iLeft+iRight] = aLeft[iLeft];
+        iLeft++;
+      }else{
+        aIdx[iLeft+iRight] = aRight[iRight];
+        iRight++;
+      }
+    }
+
+#if 0
+    /* Check that the sort worked */
+    {
+      int jj;
+      for(jj=1; jj<nIdx; jj++){
+        RtreeDValue xleft1 = aCell[aIdx[jj-1]].aCoord[iDim*2];
+        RtreeDValue xleft2 = aCell[aIdx[jj-1]].aCoord[iDim*2+1];
+        RtreeDValue xright1 = aCell[aIdx[jj]].aCoord[iDim*2];
+        RtreeDValue xright2 = aCell[aIdx[jj]].aCoord[iDim*2+1];
+        assert( xleft1<=xright1 && (xleft1<xright1 || xleft2<=xright2) );
+      }
+    }
+#endif
+  }
+}
+
+/*
+** Implementation of the R*-tree variant of SplitNode from Beckman[1990].
+*/
+static int splitNodeStartree(
+  Rtree *pRtree,
+  RtreeCell *aCell,
+  int nCell,
+  RtreeNode *pLeft,
+  RtreeNode *pRight,
+  RtreeCell *pBboxLeft,
+  RtreeCell *pBboxRight
+){
+  int **aaSorted;
+  int *aSpare;
+  int ii;
+
+  int iBestDim = 0;
+  int iBestSplit = 0;
+  RtreeDValue fBestMargin = RTREE_ZERO;
+
+  int nByte = (pRtree->nDim+1)*(sizeof(int*)+nCell*sizeof(int));
+
+  aaSorted = (int **)sqlite3_malloc(nByte);
+  if( !aaSorted ){
+    return SQLITE_NOMEM;
+  }
+
+  aSpare = &((int *)&aaSorted[pRtree->nDim])[pRtree->nDim*nCell];
+  memset(aaSorted, 0, nByte);
+  for(ii=0; ii<pRtree->nDim; ii++){
+    int jj;
+    aaSorted[ii] = &((int *)&aaSorted[pRtree->nDim])[ii*nCell];
+    for(jj=0; jj<nCell; jj++){
+      aaSorted[ii][jj] = jj;
+    }
+    SortByDimension(pRtree, aaSorted[ii], nCell, ii, aCell, aSpare);
+  }
+
+  for(ii=0; ii<pRtree->nDim; ii++){
+    RtreeDValue margin = RTREE_ZERO;
+    RtreeDValue fBestOverlap = RTREE_ZERO;
+    RtreeDValue fBestArea = RTREE_ZERO;
+    int iBestLeft = 0;
+    int nLeft;
+
+    for(
+      nLeft=RTREE_MINCELLS(pRtree); 
+      nLeft<=(nCell-RTREE_MINCELLS(pRtree)); 
+      nLeft++
+    ){
+      RtreeCell left;
+      RtreeCell right;
+      int kk;
+      RtreeDValue overlap;
+      RtreeDValue area;
+
+      memcpy(&left, &aCell[aaSorted[ii][0]], sizeof(RtreeCell));
+      memcpy(&right, &aCell[aaSorted[ii][nCell-1]], sizeof(RtreeCell));
+      for(kk=1; kk<(nCell-1); kk++){
+        if( kk<nLeft ){
+          cellUnion(pRtree, &left, &aCell[aaSorted[ii][kk]]);
+        }else{
+          cellUnion(pRtree, &right, &aCell[aaSorted[ii][kk]]);
+        }
+      }
+      margin += cellMargin(pRtree, &left);
+      margin += cellMargin(pRtree, &right);
+      overlap = cellOverlap(pRtree, &left, &right, 1);
+      area = cellArea(pRtree, &left) + cellArea(pRtree, &right);
+      if( (nLeft==RTREE_MINCELLS(pRtree))
+       || (overlap<fBestOverlap)
+       || (overlap==fBestOverlap && area<fBestArea)
+      ){
+        iBestLeft = nLeft;
+        fBestOverlap = overlap;
+        fBestArea = area;
+      }
+    }
+
+    if( ii==0 || margin<fBestMargin ){
+      iBestDim = ii;
+      fBestMargin = margin;
+      iBestSplit = iBestLeft;
+    }
+  }
+
+  memcpy(pBboxLeft, &aCell[aaSorted[iBestDim][0]], sizeof(RtreeCell));
+  memcpy(pBboxRight, &aCell[aaSorted[iBestDim][iBestSplit]], sizeof(RtreeCell));
+  for(ii=0; ii<nCell; ii++){
+    RtreeNode *pTarget = (ii<iBestSplit)?pLeft:pRight;
+    RtreeCell *pBbox = (ii<iBestSplit)?pBboxLeft:pBboxRight;
+    RtreeCell *pCell = &aCell[aaSorted[iBestDim][ii]];
+    nodeInsertCell(pRtree, pTarget, pCell);
+    cellUnion(pRtree, pBbox, pCell);
+  }
+
+  sqlite3_free(aaSorted);
+  return SQLITE_OK;
+}
+
+
+static int updateMapping(
+  Rtree *pRtree, 
+  i64 iRowid, 
+  RtreeNode *pNode, 
+  int iHeight
+){
+  int (*xSetMapping)(Rtree *, sqlite3_int64, sqlite3_int64);
+  xSetMapping = ((iHeight==0)?rowidWrite:parentWrite);
+  if( iHeight>0 ){
+    RtreeNode *pChild = nodeHashLookup(pRtree, iRowid);
+    if( pChild ){
+      nodeRelease(pRtree, pChild->pParent);
+      nodeReference(pNode);
+      pChild->pParent = pNode;
+    }
+  }
+  return xSetMapping(pRtree, iRowid, pNode->iNode);
+}
+
+static int SplitNode(
+  Rtree *pRtree,
+  RtreeNode *pNode,
+  RtreeCell *pCell,
+  int iHeight
+){
+  int i;
+  int newCellIsRight = 0;
+
+  int rc = SQLITE_OK;
+  int nCell = NCELL(pNode);
+  RtreeCell *aCell;
+  int *aiUsed;
+
+  RtreeNode *pLeft = 0;
+  RtreeNode *pRight = 0;
+
+  RtreeCell leftbbox;
+  RtreeCell rightbbox;
+
+  /* Allocate an array and populate it with a copy of pCell and 
+  ** all cells from node pLeft. Then zero the original node.
+  */
+  aCell = sqlite3_malloc((sizeof(RtreeCell)+sizeof(int))*(nCell+1));
+  if( !aCell ){
+    rc = SQLITE_NOMEM;
+    goto splitnode_out;
+  }
+  aiUsed = (int *)&aCell[nCell+1];
+  memset(aiUsed, 0, sizeof(int)*(nCell+1));
+  for(i=0; i<nCell; i++){
+    nodeGetCell(pRtree, pNode, i, &aCell[i]);
+  }
+  nodeZero(pRtree, pNode);
+  memcpy(&aCell[nCell], pCell, sizeof(RtreeCell));
+  nCell++;
+
+  if( pNode->iNode==1 ){
+    pRight = nodeNew(pRtree, pNode);
+    pLeft = nodeNew(pRtree, pNode);
+    pRtree->iDepth++;
+    pNode->isDirty = 1;
+    writeInt16(pNode->zData, pRtree->iDepth);
+  }else{
+    pLeft = pNode;
+    pRight = nodeNew(pRtree, pLeft->pParent);
+    nodeReference(pLeft);
+  }
+
+  if( !pLeft || !pRight ){
+    rc = SQLITE_NOMEM;
+    goto splitnode_out;
+  }
+
+  memset(pLeft->zData, 0, pRtree->iNodeSize);
+  memset(pRight->zData, 0, pRtree->iNodeSize);
+
+  rc = splitNodeStartree(pRtree, aCell, nCell, pLeft, pRight,
+                         &leftbbox, &rightbbox);
+  if( rc!=SQLITE_OK ){
+    goto splitnode_out;
+  }
+
+  /* Ensure both child nodes have node numbers assigned to them by calling
+  ** nodeWrite(). Node pRight always needs a node number, as it was created
+  ** by nodeNew() above. But node pLeft sometimes already has a node number.
+  ** In this case avoid the all to nodeWrite().
+  */
+  if( SQLITE_OK!=(rc = nodeWrite(pRtree, pRight))
+   || (0==pLeft->iNode && SQLITE_OK!=(rc = nodeWrite(pRtree, pLeft)))
+  ){
+    goto splitnode_out;
+  }
+
+  rightbbox.iRowid = pRight->iNode;
+  leftbbox.iRowid = pLeft->iNode;
+
+  if( pNode->iNode==1 ){
+    rc = rtreeInsertCell(pRtree, pLeft->pParent, &leftbbox, iHeight+1);
+    if( rc!=SQLITE_OK ){
+      goto splitnode_out;
+    }
+  }else{
+    RtreeNode *pParent = pLeft->pParent;
+    int iCell;
+    rc = nodeParentIndex(pRtree, pLeft, &iCell);
+    if( rc==SQLITE_OK ){
+      nodeOverwriteCell(pRtree, pParent, &leftbbox, iCell);
+      rc = AdjustTree(pRtree, pParent, &leftbbox);
+    }
+    if( rc!=SQLITE_OK ){
+      goto splitnode_out;
+    }
+  }
+  if( (rc = rtreeInsertCell(pRtree, pRight->pParent, &rightbbox, iHeight+1)) ){
+    goto splitnode_out;
+  }
+
+  for(i=0; i<NCELL(pRight); i++){
+    i64 iRowid = nodeGetRowid(pRtree, pRight, i);
+    rc = updateMapping(pRtree, iRowid, pRight, iHeight);
+    if( iRowid==pCell->iRowid ){
+      newCellIsRight = 1;
+    }
+    if( rc!=SQLITE_OK ){
+      goto splitnode_out;
+    }
+  }
+  if( pNode->iNode==1 ){
+    for(i=0; i<NCELL(pLeft); i++){
+      i64 iRowid = nodeGetRowid(pRtree, pLeft, i);
+      rc = updateMapping(pRtree, iRowid, pLeft, iHeight);
+      if( rc!=SQLITE_OK ){
+        goto splitnode_out;
+      }
+    }
+  }else if( newCellIsRight==0 ){
+    rc = updateMapping(pRtree, pCell->iRowid, pLeft, iHeight);
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = nodeRelease(pRtree, pRight);
+    pRight = 0;
+  }
+  if( rc==SQLITE_OK ){
+    rc = nodeRelease(pRtree, pLeft);
+    pLeft = 0;
+  }
+
+splitnode_out:
+  nodeRelease(pRtree, pRight);
+  nodeRelease(pRtree, pLeft);
+  sqlite3_free(aCell);
+  return rc;
+}
+
+/*
+** If node pLeaf is not the root of the r-tree and its pParent pointer is 
+** still NULL, load all ancestor nodes of pLeaf into memory and populate
+** the pLeaf->pParent chain all the way up to the root node.
+**
+** This operation is required when a row is deleted (or updated - an update
+** is implemented as a delete followed by an insert). SQLite provides the
+** rowid of the row to delete, which can be used to find the leaf on which
+** the entry resides (argument pLeaf). Once the leaf is located, this 
+** function is called to determine its ancestry.
+*/
+static int fixLeafParent(Rtree *pRtree, RtreeNode *pLeaf){
+  int rc = SQLITE_OK;
+  RtreeNode *pChild = pLeaf;
+  while( rc==SQLITE_OK && pChild->iNode!=1 && pChild->pParent==0 ){
+    int rc2 = SQLITE_OK;          /* sqlite3_reset() return code */
+    sqlite3_bind_int64(pRtree->pReadParent, 1, pChild->iNode);
+    rc = sqlite3_step(pRtree->pReadParent);
+    if( rc==SQLITE_ROW ){
+      RtreeNode *pTest;           /* Used to test for reference loops */
+      i64 iNode;                  /* Node number of parent node */
+
+      /* Before setting pChild->pParent, test that we are not creating a
+      ** loop of references (as we would if, say, pChild==pParent). We don't
+      ** want to do this as it leads to a memory leak when trying to delete
+      ** the referenced counted node structures.
+      */
+      iNode = sqlite3_column_int64(pRtree->pReadParent, 0);
+      for(pTest=pLeaf; pTest && pTest->iNode!=iNode; pTest=pTest->pParent);
+      if( !pTest ){
+        rc2 = nodeAcquire(pRtree, iNode, 0, &pChild->pParent);
+      }
+    }
+    rc = sqlite3_reset(pRtree->pReadParent);
+    if( rc==SQLITE_OK ) rc = rc2;
+    if( rc==SQLITE_OK && !pChild->pParent ) rc = SQLITE_CORRUPT_VTAB;
+    pChild = pChild->pParent;
+  }
+  return rc;
+}
+
+static int deleteCell(Rtree *, RtreeNode *, int, int);
+
+static int removeNode(Rtree *pRtree, RtreeNode *pNode, int iHeight){
+  int rc;
+  int rc2;
+  RtreeNode *pParent = 0;
+  int iCell;
+
+  assert( pNode->nRef==1 );
+
+  /* Remove the entry in the parent cell. */
+  rc = nodeParentIndex(pRtree, pNode, &iCell);
+  if( rc==SQLITE_OK ){
+    pParent = pNode->pParent;
+    pNode->pParent = 0;
+    rc = deleteCell(pRtree, pParent, iCell, iHeight+1);
+  }
+  rc2 = nodeRelease(pRtree, pParent);
+  if( rc==SQLITE_OK ){
+    rc = rc2;
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* Remove the xxx_node entry. */
+  sqlite3_bind_int64(pRtree->pDeleteNode, 1, pNode->iNode);
+  sqlite3_step(pRtree->pDeleteNode);
+  if( SQLITE_OK!=(rc = sqlite3_reset(pRtree->pDeleteNode)) ){
+    return rc;
+  }
+
+  /* Remove the xxx_parent entry. */
+  sqlite3_bind_int64(pRtree->pDeleteParent, 1, pNode->iNode);
+  sqlite3_step(pRtree->pDeleteParent);
+  if( SQLITE_OK!=(rc = sqlite3_reset(pRtree->pDeleteParent)) ){
+    return rc;
+  }
+  
+  /* Remove the node from the in-memory hash table and link it into
+  ** the Rtree.pDeleted list. Its contents will be re-inserted later on.
+  */
+  nodeHashDelete(pRtree, pNode);
+  pNode->iNode = iHeight;
+  pNode->pNext = pRtree->pDeleted;
+  pNode->nRef++;
+  pRtree->pDeleted = pNode;
+
+  return SQLITE_OK;
+}
+
+static int fixBoundingBox(Rtree *pRtree, RtreeNode *pNode){
+  RtreeNode *pParent = pNode->pParent;
+  int rc = SQLITE_OK; 
+  if( pParent ){
+    int ii; 
+    int nCell = NCELL(pNode);
+    RtreeCell box;                            /* Bounding box for pNode */
+    nodeGetCell(pRtree, pNode, 0, &box);
+    for(ii=1; ii<nCell; ii++){
+      RtreeCell cell;
+      nodeGetCell(pRtree, pNode, ii, &cell);
+      cellUnion(pRtree, &box, &cell);
+    }
+    box.iRowid = pNode->iNode;
+    rc = nodeParentIndex(pRtree, pNode, &ii);
+    if( rc==SQLITE_OK ){
+      nodeOverwriteCell(pRtree, pParent, &box, ii);
+      rc = fixBoundingBox(pRtree, pParent);
+    }
+  }
+  return rc;
+}
+
+/*
+** Delete the cell at index iCell of node pNode. After removing the
+** cell, adjust the r-tree data structure if required.
+*/
+static int deleteCell(Rtree *pRtree, RtreeNode *pNode, int iCell, int iHeight){
+  RtreeNode *pParent;
+  int rc;
+
+  if( SQLITE_OK!=(rc = fixLeafParent(pRtree, pNode)) ){
+    return rc;
+  }
+
+  /* Remove the cell from the node. This call just moves bytes around
+  ** the in-memory node image, so it cannot fail.
+  */
+  nodeDeleteCell(pRtree, pNode, iCell);
+
+  /* If the node is not the tree root and now has less than the minimum
+  ** number of cells, remove it from the tree. Otherwise, update the
+  ** cell in the parent node so that it tightly contains the updated
+  ** node.
+  */
+  pParent = pNode->pParent;
+  assert( pParent || pNode->iNode==1 );
+  if( pParent ){
+    if( NCELL(pNode)<RTREE_MINCELLS(pRtree) ){
+      rc = removeNode(pRtree, pNode, iHeight);
+    }else{
+      rc = fixBoundingBox(pRtree, pNode);
+    }
+  }
+
+  return rc;
+}
+
+static int Reinsert(
+  Rtree *pRtree, 
+  RtreeNode *pNode, 
+  RtreeCell *pCell, 
+  int iHeight
+){
+  int *aOrder;
+  int *aSpare;
+  RtreeCell *aCell;
+  RtreeDValue *aDistance;
+  int nCell;
+  RtreeDValue aCenterCoord[RTREE_MAX_DIMENSIONS];
+  int iDim;
+  int ii;
+  int rc = SQLITE_OK;
+  int n;
+
+  memset(aCenterCoord, 0, sizeof(RtreeDValue)*RTREE_MAX_DIMENSIONS);
+
+  nCell = NCELL(pNode)+1;
+  n = (nCell+1)&(~1);
+
+  /* Allocate the buffers used by this operation. The allocation is
+  ** relinquished before this function returns.
+  */
+  aCell = (RtreeCell *)sqlite3_malloc(n * (
+    sizeof(RtreeCell)     +         /* aCell array */
+    sizeof(int)           +         /* aOrder array */
+    sizeof(int)           +         /* aSpare array */
+    sizeof(RtreeDValue)             /* aDistance array */
+  ));
+  if( !aCell ){
+    return SQLITE_NOMEM;
+  }
+  aOrder    = (int *)&aCell[n];
+  aSpare    = (int *)&aOrder[n];
+  aDistance = (RtreeDValue *)&aSpare[n];
+
+  for(ii=0; ii<nCell; ii++){
+    if( ii==(nCell-1) ){
+      memcpy(&aCell[ii], pCell, sizeof(RtreeCell));
+    }else{
+      nodeGetCell(pRtree, pNode, ii, &aCell[ii]);
+    }
+    aOrder[ii] = ii;
+    for(iDim=0; iDim<pRtree->nDim; iDim++){
+      aCenterCoord[iDim] += DCOORD(aCell[ii].aCoord[iDim*2]);
+      aCenterCoord[iDim] += DCOORD(aCell[ii].aCoord[iDim*2+1]);
+    }
+  }
+  for(iDim=0; iDim<pRtree->nDim; iDim++){
+    aCenterCoord[iDim] = (aCenterCoord[iDim]/(nCell*(RtreeDValue)2));
+  }
+
+  for(ii=0; ii<nCell; ii++){
+    aDistance[ii] = RTREE_ZERO;
+    for(iDim=0; iDim<pRtree->nDim; iDim++){
+      RtreeDValue coord = (DCOORD(aCell[ii].aCoord[iDim*2+1]) - 
+                               DCOORD(aCell[ii].aCoord[iDim*2]));
+      aDistance[ii] += (coord-aCenterCoord[iDim])*(coord-aCenterCoord[iDim]);
+    }
+  }
+
+  SortByDistance(aOrder, nCell, aDistance, aSpare);
+  nodeZero(pRtree, pNode);
+
+  for(ii=0; rc==SQLITE_OK && ii<(nCell-(RTREE_MINCELLS(pRtree)+1)); ii++){
+    RtreeCell *p = &aCell[aOrder[ii]];
+    nodeInsertCell(pRtree, pNode, p);
+    if( p->iRowid==pCell->iRowid ){
+      if( iHeight==0 ){
+        rc = rowidWrite(pRtree, p->iRowid, pNode->iNode);
+      }else{
+        rc = parentWrite(pRtree, p->iRowid, pNode->iNode);
+      }
+    }
+  }
+  if( rc==SQLITE_OK ){
+    rc = fixBoundingBox(pRtree, pNode);
+  }
+  for(; rc==SQLITE_OK && ii<nCell; ii++){
+    /* Find a node to store this cell in. pNode->iNode currently contains
+    ** the height of the sub-tree headed by the cell.
+    */
+    RtreeNode *pInsert;
+    RtreeCell *p = &aCell[aOrder[ii]];
+    rc = ChooseLeaf(pRtree, p, iHeight, &pInsert);
+    if( rc==SQLITE_OK ){
+      int rc2;
+      rc = rtreeInsertCell(pRtree, pInsert, p, iHeight);
+      rc2 = nodeRelease(pRtree, pInsert);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
+  }
+
+  sqlite3_free(aCell);
+  return rc;
+}
+
+/*
+** Insert cell pCell into node pNode. Node pNode is the head of a 
+** subtree iHeight high (leaf nodes have iHeight==0).
+*/
+static int rtreeInsertCell(
+  Rtree *pRtree,
+  RtreeNode *pNode,
+  RtreeCell *pCell,
+  int iHeight
+){
+  int rc = SQLITE_OK;
+  if( iHeight>0 ){
+    RtreeNode *pChild = nodeHashLookup(pRtree, pCell->iRowid);
+    if( pChild ){
+      nodeRelease(pRtree, pChild->pParent);
+      nodeReference(pNode);
+      pChild->pParent = pNode;
+    }
+  }
+  if( nodeInsertCell(pRtree, pNode, pCell) ){
+    if( iHeight<=pRtree->iReinsertHeight || pNode->iNode==1){
+      rc = SplitNode(pRtree, pNode, pCell, iHeight);
+    }else{
+      pRtree->iReinsertHeight = iHeight;
+      rc = Reinsert(pRtree, pNode, pCell, iHeight);
+    }
+  }else{
+    rc = AdjustTree(pRtree, pNode, pCell);
+    if( rc==SQLITE_OK ){
+      if( iHeight==0 ){
+        rc = rowidWrite(pRtree, pCell->iRowid, pNode->iNode);
+      }else{
+        rc = parentWrite(pRtree, pCell->iRowid, pNode->iNode);
+      }
+    }
+  }
+  return rc;
+}
+
+static int reinsertNodeContent(Rtree *pRtree, RtreeNode *pNode){
+  int ii;
+  int rc = SQLITE_OK;
+  int nCell = NCELL(pNode);
+
+  for(ii=0; rc==SQLITE_OK && ii<nCell; ii++){
+    RtreeNode *pInsert;
+    RtreeCell cell;
+    nodeGetCell(pRtree, pNode, ii, &cell);
+
+    /* Find a node to store this cell in. pNode->iNode currently contains
+    ** the height of the sub-tree headed by the cell.
+    */
+    rc = ChooseLeaf(pRtree, &cell, (int)pNode->iNode, &pInsert);
+    if( rc==SQLITE_OK ){
+      int rc2;
+      rc = rtreeInsertCell(pRtree, pInsert, &cell, (int)pNode->iNode);
+      rc2 = nodeRelease(pRtree, pInsert);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Select a currently unused rowid for a new r-tree record.
+*/
+static int newRowid(Rtree *pRtree, i64 *piRowid){
+  int rc;
+  sqlite3_bind_null(pRtree->pWriteRowid, 1);
+  sqlite3_bind_null(pRtree->pWriteRowid, 2);
+  sqlite3_step(pRtree->pWriteRowid);
+  rc = sqlite3_reset(pRtree->pWriteRowid);
+  *piRowid = sqlite3_last_insert_rowid(pRtree->db);
+  return rc;
+}
+
+/*
+** Remove the entry with rowid=iDelete from the r-tree structure.
+*/
+static int rtreeDeleteRowid(Rtree *pRtree, sqlite3_int64 iDelete){
+  int rc;                         /* Return code */
+  RtreeNode *pLeaf = 0;           /* Leaf node containing record iDelete */
+  int iCell;                      /* Index of iDelete cell in pLeaf */
+  RtreeNode *pRoot;               /* Root node of rtree structure */
+
+
+  /* Obtain a reference to the root node to initialize Rtree.iDepth */
+  rc = nodeAcquire(pRtree, 1, 0, &pRoot);
+
+  /* Obtain a reference to the leaf node that contains the entry 
+  ** about to be deleted. 
+  */
+  if( rc==SQLITE_OK ){
+    rc = findLeafNode(pRtree, iDelete, &pLeaf, 0);
+  }
+
+  /* Delete the cell in question from the leaf node. */
+  if( rc==SQLITE_OK ){
+    int rc2;
+    rc = nodeRowidIndex(pRtree, pLeaf, iDelete, &iCell);
+    if( rc==SQLITE_OK ){
+      rc = deleteCell(pRtree, pLeaf, iCell, 0);
+    }
+    rc2 = nodeRelease(pRtree, pLeaf);
+    if( rc==SQLITE_OK ){
+      rc = rc2;
+    }
+  }
+
+  /* Delete the corresponding entry in the <rtree>_rowid table. */
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pRtree->pDeleteRowid, 1, iDelete);
+    sqlite3_step(pRtree->pDeleteRowid);
+    rc = sqlite3_reset(pRtree->pDeleteRowid);
+  }
+
+  /* Check if the root node now has exactly one child. If so, remove
+  ** it, schedule the contents of the child for reinsertion and 
+  ** reduce the tree height by one.
+  **
+  ** This is equivalent to copying the contents of the child into
+  ** the root node (the operation that Gutman's paper says to perform 
+  ** in this scenario).
+  */
+  if( rc==SQLITE_OK && pRtree->iDepth>0 && NCELL(pRoot)==1 ){
+    int rc2;
+    RtreeNode *pChild;
+    i64 iChild = nodeGetRowid(pRtree, pRoot, 0);
+    rc = nodeAcquire(pRtree, iChild, pRoot, &pChild);
+    if( rc==SQLITE_OK ){
+      rc = removeNode(pRtree, pChild, pRtree->iDepth-1);
+    }
+    rc2 = nodeRelease(pRtree, pChild);
+    if( rc==SQLITE_OK ) rc = rc2;
+    if( rc==SQLITE_OK ){
+      pRtree->iDepth--;
+      writeInt16(pRoot->zData, pRtree->iDepth);
+      pRoot->isDirty = 1;
+    }
+  }
+
+  /* Re-insert the contents of any underfull nodes removed from the tree. */
+  for(pLeaf=pRtree->pDeleted; pLeaf; pLeaf=pRtree->pDeleted){
+    if( rc==SQLITE_OK ){
+      rc = reinsertNodeContent(pRtree, pLeaf);
+    }
+    pRtree->pDeleted = pLeaf->pNext;
+    sqlite3_free(pLeaf);
+  }
+
+  /* Release the reference to the root node. */
+  if( rc==SQLITE_OK ){
+    rc = nodeRelease(pRtree, pRoot);
+  }else{
+    nodeRelease(pRtree, pRoot);
+  }
+
+  return rc;
+}
+
+/*
+** Rounding constants for float->double conversion.
+*/
+#define RNDTOWARDS  (1.0 - 1.0/8388608.0)  /* Round towards zero */
+#define RNDAWAY     (1.0 + 1.0/8388608.0)  /* Round away from zero */
+
+#if !defined(SQLITE_RTREE_INT_ONLY)
+/*
+** Convert an sqlite3_value into an RtreeValue (presumably a float)
+** while taking care to round toward negative or positive, respectively.
+*/
+static RtreeValue rtreeValueDown(sqlite3_value *v){
+  double d = sqlite3_value_double(v);
+  float f = (float)d;
+  if( f>d ){
+    f = (float)(d*(d<0 ? RNDAWAY : RNDTOWARDS));
+  }
+  return f;
+}
+static RtreeValue rtreeValueUp(sqlite3_value *v){
+  double d = sqlite3_value_double(v);
+  float f = (float)d;
+  if( f<d ){
+    f = (float)(d*(d<0 ? RNDTOWARDS : RNDAWAY));
+  }
+  return f;
+}
+#endif /* !defined(SQLITE_RTREE_INT_ONLY) */
+
+/*
+** A constraint has failed while inserting a row into an rtree table. 
+** Assuming no OOM error occurs, this function sets the error message 
+** (at pRtree->base.zErrMsg) to an appropriate value and returns
+** SQLITE_CONSTRAINT.
+**
+** Parameter iCol is the index of the leftmost column involved in the
+** constraint failure. If it is 0, then the constraint that failed is
+** the unique constraint on the id column. Otherwise, it is the rtree
+** (c1<=c2) constraint on columns iCol and iCol+1 that has failed.
+**
+** If an OOM occurs, SQLITE_NOMEM is returned instead of SQLITE_CONSTRAINT.
+*/
+static int rtreeConstraintError(Rtree *pRtree, int iCol){
+  sqlite3_stmt *pStmt = 0;
+  char *zSql; 
+  int rc;
+
+  assert( iCol==0 || iCol%2 );
+  zSql = sqlite3_mprintf("SELECT * FROM %Q.%Q", pRtree->zDb, pRtree->zName);
+  if( zSql ){
+    rc = sqlite3_prepare_v2(pRtree->db, zSql, -1, &pStmt, 0);
+  }else{
+    rc = SQLITE_NOMEM;
+  }
+  sqlite3_free(zSql);
+
+  if( rc==SQLITE_OK ){
+    if( iCol==0 ){
+      const char *zCol = sqlite3_column_name(pStmt, 0);
+      pRtree->base.zErrMsg = sqlite3_mprintf(
+          "UNIQUE constraint failed: %s.%s", pRtree->zName, zCol
+      );
+    }else{
+      const char *zCol1 = sqlite3_column_name(pStmt, iCol);
+      const char *zCol2 = sqlite3_column_name(pStmt, iCol+1);
+      pRtree->base.zErrMsg = sqlite3_mprintf(
+          "rtree constraint failed: %s.(%s<=%s)", pRtree->zName, zCol1, zCol2
+      );
+    }
+  }
+
+  sqlite3_finalize(pStmt);
+  return (rc==SQLITE_OK ? SQLITE_CONSTRAINT : rc);
+}
+
+
+
+/*
+** The xUpdate method for rtree module virtual tables.
+*/
+static int rtreeUpdate(
+  sqlite3_vtab *pVtab, 
+  int nData, 
+  sqlite3_value **azData, 
+  sqlite_int64 *pRowid
+){
+  Rtree *pRtree = (Rtree *)pVtab;
+  int rc = SQLITE_OK;
+  RtreeCell cell;                 /* New cell to insert if nData>1 */
+  int bHaveRowid = 0;             /* Set to 1 after new rowid is determined */
+
+  rtreeReference(pRtree);
+  assert(nData>=1);
+
+  cell.iRowid = 0;  /* Used only to suppress a compiler warning */
+
+  /* Constraint handling. A write operation on an r-tree table may return
+  ** SQLITE_CONSTRAINT for two reasons:
+  **
+  **   1. A duplicate rowid value, or
+  **   2. The supplied data violates the "x2>=x1" constraint.
+  **
+  ** In the first case, if the conflict-handling mode is REPLACE, then
+  ** the conflicting row can be removed before proceeding. In the second
+  ** case, SQLITE_CONSTRAINT must be returned regardless of the
+  ** conflict-handling mode specified by the user.
+  */
+  if( nData>1 ){
+    int ii;
+
+    /* Populate the cell.aCoord[] array. The first coordinate is azData[3].
+    **
+    ** NB: nData can only be less than nDim*2+3 if the rtree is mis-declared
+    ** with "column" that are interpreted as table constraints.
+    ** Example:  CREATE VIRTUAL TABLE bad USING rtree(x,y,CHECK(y>5));
+    ** This problem was discovered after years of use, so we silently ignore
+    ** these kinds of misdeclared tables to avoid breaking any legacy.
+    */
+    assert( nData<=(pRtree->nDim2 + 3) );
+
+#ifndef SQLITE_RTREE_INT_ONLY
+    if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
+      for(ii=0; ii<nData-4; ii+=2){
+        cell.aCoord[ii].f = rtreeValueDown(azData[ii+3]);
+        cell.aCoord[ii+1].f = rtreeValueUp(azData[ii+4]);
+        if( cell.aCoord[ii].f>cell.aCoord[ii+1].f ){
+          rc = rtreeConstraintError(pRtree, ii+1);
+          goto constraint;
+        }
+      }
+    }else
+#endif
+    {
+      for(ii=0; ii<nData-4; ii+=2){
+        cell.aCoord[ii].i = sqlite3_value_int(azData[ii+3]);
+        cell.aCoord[ii+1].i = sqlite3_value_int(azData[ii+4]);
+        if( cell.aCoord[ii].i>cell.aCoord[ii+1].i ){
+          rc = rtreeConstraintError(pRtree, ii+1);
+          goto constraint;
+        }
+      }
+    }
+
+    /* If a rowid value was supplied, check if it is already present in 
+    ** the table. If so, the constraint has failed. */
+    if( sqlite3_value_type(azData[2])!=SQLITE_NULL ){
+      cell.iRowid = sqlite3_value_int64(azData[2]);
+      if( sqlite3_value_type(azData[0])==SQLITE_NULL
+       || sqlite3_value_int64(azData[0])!=cell.iRowid
+      ){
+        int steprc;
+        sqlite3_bind_int64(pRtree->pReadRowid, 1, cell.iRowid);
+        steprc = sqlite3_step(pRtree->pReadRowid);
+        rc = sqlite3_reset(pRtree->pReadRowid);
+        if( SQLITE_ROW==steprc ){
+          if( sqlite3_vtab_on_conflict(pRtree->db)==SQLITE_REPLACE ){
+            rc = rtreeDeleteRowid(pRtree, cell.iRowid);
+          }else{
+            rc = rtreeConstraintError(pRtree, 0);
+            goto constraint;
+          }
+        }
+      }
+      bHaveRowid = 1;
+    }
+  }
+
+  /* If azData[0] is not an SQL NULL value, it is the rowid of a
+  ** record to delete from the r-tree table. The following block does
+  ** just that.
+  */
+  if( sqlite3_value_type(azData[0])!=SQLITE_NULL ){
+    rc = rtreeDeleteRowid(pRtree, sqlite3_value_int64(azData[0]));
+  }
+
+  /* If the azData[] array contains more than one element, elements
+  ** (azData[2]..azData[argc-1]) contain a new record to insert into
+  ** the r-tree structure.
+  */
+  if( rc==SQLITE_OK && nData>1 ){
+    /* Insert the new record into the r-tree */
+    RtreeNode *pLeaf = 0;
+
+    /* Figure out the rowid of the new row. */
+    if( bHaveRowid==0 ){
+      rc = newRowid(pRtree, &cell.iRowid);
+    }
+    *pRowid = cell.iRowid;
+
+    if( rc==SQLITE_OK ){
+      rc = ChooseLeaf(pRtree, &cell, 0, &pLeaf);
+    }
+    if( rc==SQLITE_OK ){
+      int rc2;
+      pRtree->iReinsertHeight = -1;
+      rc = rtreeInsertCell(pRtree, pLeaf, &cell, 0);
+      rc2 = nodeRelease(pRtree, pLeaf);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
+  }
+
+constraint:
+  rtreeRelease(pRtree);
+  return rc;
+}
+
+/*
+** Called when a transaction starts.
+*/
+static int rtreeBeginTransaction(sqlite3_vtab *pVtab){
+  Rtree *pRtree = (Rtree *)pVtab;
+  assert( pRtree->inWrTrans==0 );
+  pRtree->inWrTrans++;
+  return SQLITE_OK;
+}
+
+/*
+** Called when a transaction completes (either by COMMIT or ROLLBACK).
+** The sqlite3_blob object should be released at this point.
+*/
+static int rtreeEndTransaction(sqlite3_vtab *pVtab){
+  Rtree *pRtree = (Rtree *)pVtab;
+  pRtree->inWrTrans = 0;
+  nodeBlobReset(pRtree);
+  return SQLITE_OK;
+}
+
+/*
+** The xRename method for rtree module virtual tables.
+*/
+static int rtreeRename(sqlite3_vtab *pVtab, const char *zNewName){
+  Rtree *pRtree = (Rtree *)pVtab;
+  int rc = SQLITE_NOMEM;
+  char *zSql = sqlite3_mprintf(
+    "ALTER TABLE %Q.'%q_node'   RENAME TO \"%w_node\";"
+    "ALTER TABLE %Q.'%q_parent' RENAME TO \"%w_parent\";"
+    "ALTER TABLE %Q.'%q_rowid'  RENAME TO \"%w_rowid\";"
+    , pRtree->zDb, pRtree->zName, zNewName 
+    , pRtree->zDb, pRtree->zName, zNewName 
+    , pRtree->zDb, pRtree->zName, zNewName
+  );
+  if( zSql ){
+    rc = sqlite3_exec(pRtree->db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+  return rc;
+}
+
+
+/*
+** This function populates the pRtree->nRowEst variable with an estimate
+** of the number of rows in the virtual table. If possible, this is based
+** on sqlite_stat1 data. Otherwise, use RTREE_DEFAULT_ROWEST.
+*/
+static int rtreeQueryStat1(sqlite3 *db, Rtree *pRtree){
+  const char *zFmt = "SELECT stat FROM %Q.sqlite_stat1 WHERE tbl = '%q_rowid'";
+  char *zSql;
+  sqlite3_stmt *p;
+  int rc;
+  i64 nRow = 0;
+
+  rc = sqlite3_table_column_metadata(
+      db, pRtree->zDb, "sqlite_stat1",0,0,0,0,0,0
+  );
+  if( rc!=SQLITE_OK ){
+    pRtree->nRowEst = RTREE_DEFAULT_ROWEST;
+    return rc==SQLITE_ERROR ? SQLITE_OK : rc;
+  }
+  zSql = sqlite3_mprintf(zFmt, pRtree->zDb, pRtree->zName);
+  if( zSql==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3_prepare_v2(db, zSql, -1, &p, 0);
+    if( rc==SQLITE_OK ){
+      if( sqlite3_step(p)==SQLITE_ROW ) nRow = sqlite3_column_int64(p, 0);
+      rc = sqlite3_finalize(p);
+    }else if( rc!=SQLITE_NOMEM ){
+      rc = SQLITE_OK;
+    }
+
+    if( rc==SQLITE_OK ){
+      if( nRow==0 ){
+        pRtree->nRowEst = RTREE_DEFAULT_ROWEST;
+      }else{
+        pRtree->nRowEst = MAX(nRow, RTREE_MIN_ROWEST);
+      }
+    }
+    sqlite3_free(zSql);
+  }
+
+  return rc;
+}
+
+static sqlite3_module rtreeModule = {
+  0,                          /* iVersion */
+  rtreeCreate,                /* xCreate - create a table */
+  rtreeConnect,               /* xConnect - connect to an existing table */
+  rtreeBestIndex,             /* xBestIndex - Determine search strategy */
+  rtreeDisconnect,            /* xDisconnect - Disconnect from a table */
+  rtreeDestroy,               /* xDestroy - Drop a table */
+  rtreeOpen,                  /* xOpen - open a cursor */
+  rtreeClose,                 /* xClose - close a cursor */
+  rtreeFilter,                /* xFilter - configure scan constraints */
+  rtreeNext,                  /* xNext - advance a cursor */
+  rtreeEof,                   /* xEof */
+  rtreeColumn,                /* xColumn - read data */
+  rtreeRowid,                 /* xRowid - read data */
+  rtreeUpdate,                /* xUpdate - write data */
+  rtreeBeginTransaction,      /* xBegin - begin transaction */
+  rtreeEndTransaction,        /* xSync - sync transaction */
+  rtreeEndTransaction,        /* xCommit - commit transaction */
+  rtreeEndTransaction,        /* xRollback - rollback transaction */
+  0,                          /* xFindFunction - function overloading */
+  rtreeRename,                /* xRename - rename the table */
+  0,                          /* xSavepoint */
+  0,                          /* xRelease */
+  0,                          /* xRollbackTo */
+};
+
+static int rtreeSqlInit(
+  Rtree *pRtree, 
+  sqlite3 *db, 
+  const char *zDb, 
+  const char *zPrefix, 
+  int isCreate
+){
+  int rc = SQLITE_OK;
+
+  #define N_STATEMENT 8
+  static const char *azSql[N_STATEMENT] = {
+    /* Write the xxx_node table */
+    "INSERT OR REPLACE INTO '%q'.'%q_node' VALUES(:1, :2)",
+    "DELETE FROM '%q'.'%q_node' WHERE nodeno = :1",
+
+    /* Read and write the xxx_rowid table */
+    "SELECT nodeno FROM '%q'.'%q_rowid' WHERE rowid = :1",
+    "INSERT OR REPLACE INTO '%q'.'%q_rowid' VALUES(:1, :2)",
+    "DELETE FROM '%q'.'%q_rowid' WHERE rowid = :1",
+
+    /* Read and write the xxx_parent table */
+    "SELECT parentnode FROM '%q'.'%q_parent' WHERE nodeno = :1",
+    "INSERT OR REPLACE INTO '%q'.'%q_parent' VALUES(:1, :2)",
+    "DELETE FROM '%q'.'%q_parent' WHERE nodeno = :1"
+  };
+  sqlite3_stmt **appStmt[N_STATEMENT];
+  int i;
+
+  pRtree->db = db;
+
+  if( isCreate ){
+    char *zCreate = sqlite3_mprintf(
+"CREATE TABLE \"%w\".\"%w_node\"(nodeno INTEGER PRIMARY KEY, data BLOB);"
+"CREATE TABLE \"%w\".\"%w_rowid\"(rowid INTEGER PRIMARY KEY, nodeno INTEGER);"
+"CREATE TABLE \"%w\".\"%w_parent\"(nodeno INTEGER PRIMARY KEY,"
+                                  " parentnode INTEGER);"
+"INSERT INTO '%q'.'%q_node' VALUES(1, zeroblob(%d))",
+      zDb, zPrefix, zDb, zPrefix, zDb, zPrefix, zDb, zPrefix, pRtree->iNodeSize
+    );
+    if( !zCreate ){
+      return SQLITE_NOMEM;
+    }
+    rc = sqlite3_exec(db, zCreate, 0, 0, 0);
+    sqlite3_free(zCreate);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }
+
+  appStmt[0] = &pRtree->pWriteNode;
+  appStmt[1] = &pRtree->pDeleteNode;
+  appStmt[2] = &pRtree->pReadRowid;
+  appStmt[3] = &pRtree->pWriteRowid;
+  appStmt[4] = &pRtree->pDeleteRowid;
+  appStmt[5] = &pRtree->pReadParent;
+  appStmt[6] = &pRtree->pWriteParent;
+  appStmt[7] = &pRtree->pDeleteParent;
+
+  rc = rtreeQueryStat1(db, pRtree);
+  for(i=0; i<N_STATEMENT && rc==SQLITE_OK; i++){
+    char *zSql = sqlite3_mprintf(azSql[i], zDb, zPrefix);
+    if( zSql ){
+      rc = sqlite3_prepare_v2(db, zSql, -1, appStmt[i], 0); 
+    }else{
+      rc = SQLITE_NOMEM;
+    }
+    sqlite3_free(zSql);
+  }
+
+  return rc;
+}
+
+/*
+** The second argument to this function contains the text of an SQL statement
+** that returns a single integer value. The statement is compiled and executed
+** using database connection db. If successful, the integer value returned
+** is written to *piVal and SQLITE_OK returned. Otherwise, an SQLite error
+** code is returned and the value of *piVal after returning is not defined.
+*/
+static int getIntFromStmt(sqlite3 *db, const char *zSql, int *piVal){
+  int rc = SQLITE_NOMEM;
+  if( zSql ){
+    sqlite3_stmt *pStmt = 0;
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      if( SQLITE_ROW==sqlite3_step(pStmt) ){
+        *piVal = sqlite3_column_int(pStmt, 0);
+      }
+      rc = sqlite3_finalize(pStmt);
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is called from within the xConnect() or xCreate() method to
+** determine the node-size used by the rtree table being created or connected
+** to. If successful, pRtree->iNodeSize is populated and SQLITE_OK returned.
+** Otherwise, an SQLite error code is returned.
+**
+** If this function is being called as part of an xConnect(), then the rtree
+** table already exists. In this case the node-size is determined by inspecting
+** the root node of the tree.
+**
+** Otherwise, for an xCreate(), use 64 bytes less than the database page-size. 
+** This ensures that each node is stored on a single database page. If the 
+** database page-size is so large that more than RTREE_MAXCELLS entries 
+** would fit in a single node, use a smaller node-size.
+*/
+static int getNodeSize(
+  sqlite3 *db,                    /* Database handle */
+  Rtree *pRtree,                  /* Rtree handle */
+  int isCreate,                   /* True for xCreate, false for xConnect */
+  char **pzErr                    /* OUT: Error message, if any */
+){
+  int rc;
+  char *zSql;
+  if( isCreate ){
+    int iPageSize = 0;
+    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", pRtree->zDb);
+    rc = getIntFromStmt(db, zSql, &iPageSize);
+    if( rc==SQLITE_OK ){
+      pRtree->iNodeSize = iPageSize-64;
+      if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
+        pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
+      }
+    }else{
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }
+  }else{
+    zSql = sqlite3_mprintf(
+        "SELECT length(data) FROM '%q'.'%q_node' WHERE nodeno = 1",
+        pRtree->zDb, pRtree->zName
+    );
+    rc = getIntFromStmt(db, zSql, &pRtree->iNodeSize);
+    if( rc!=SQLITE_OK ){
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }
+  }
+
+  sqlite3_free(zSql);
+  return rc;
+}
+
+/* 
+** This function is the implementation of both the xConnect and xCreate
+** methods of the r-tree virtual table.
+**
+**   argv[0]   -> module name
+**   argv[1]   -> database name
+**   argv[2]   -> table name
+**   argv[...] -> column names...
+*/
+static int rtreeInit(
+  sqlite3 *db,                        /* Database connection */
+  void *pAux,                         /* One of the RTREE_COORD_* constants */
+  int argc, const char *const*argv,   /* Parameters to CREATE TABLE statement */
+  sqlite3_vtab **ppVtab,              /* OUT: New virtual table */
+  char **pzErr,                       /* OUT: Error message, if any */
+  int isCreate                        /* True for xCreate, false for xConnect */
+){
+  int rc = SQLITE_OK;
+  Rtree *pRtree;
+  int nDb;              /* Length of string argv[1] */
+  int nName;            /* Length of string argv[2] */
+  int eCoordType = (pAux ? RTREE_COORD_INT32 : RTREE_COORD_REAL32);
+
+  const char *aErrMsg[] = {
+    0,                                                    /* 0 */
+    "Wrong number of columns for an rtree table",         /* 1 */
+    "Too few columns for an rtree table",                 /* 2 */
+    "Too many columns for an rtree table"                 /* 3 */
+  };
+
+  int iErr = (argc<6) ? 2 : argc>(RTREE_MAX_DIMENSIONS*2+4) ? 3 : argc%2;
+  if( aErrMsg[iErr] ){
+    *pzErr = sqlite3_mprintf("%s", aErrMsg[iErr]);
+    return SQLITE_ERROR;
+  }
+
+  sqlite3_vtab_config(db, SQLITE_VTAB_CONSTRAINT_SUPPORT, 1);
+
+  /* Allocate the sqlite3_vtab structure */
+  nDb = (int)strlen(argv[1]);
+  nName = (int)strlen(argv[2]);
+  pRtree = (Rtree *)sqlite3_malloc(sizeof(Rtree)+nDb+nName+2);
+  if( !pRtree ){
+    return SQLITE_NOMEM;
+  }
+  memset(pRtree, 0, sizeof(Rtree)+nDb+nName+2);
+  pRtree->nBusy = 1;
+  pRtree->base.pModule = &rtreeModule;
+  pRtree->zDb = (char *)&pRtree[1];
+  pRtree->zName = &pRtree->zDb[nDb+1];
+  pRtree->nDim = (u8)((argc-4)/2);
+  pRtree->nDim2 = pRtree->nDim*2;
+  pRtree->nBytesPerCell = 8 + pRtree->nDim2*4;
+  pRtree->eCoordType = (u8)eCoordType;
+  memcpy(pRtree->zDb, argv[1], nDb);
+  memcpy(pRtree->zName, argv[2], nName);
+
+  /* Figure out the node size to use. */
+  rc = getNodeSize(db, pRtree, isCreate, pzErr);
+
+  /* Create/Connect to the underlying relational database schema. If
+  ** that is successful, call sqlite3_declare_vtab() to configure
+  ** the r-tree table schema.
+  */
+  if( rc==SQLITE_OK ){
+    if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }else{
+      char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
+      char *zTmp;
+      int ii;
+      for(ii=4; zSql && ii<argc; ii++){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
+        sqlite3_free(zTmp);
+      }
+      if( zSql ){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s);", zTmp);
+        sqlite3_free(zTmp);
+      }
+      if( !zSql ){
+        rc = SQLITE_NOMEM;
+      }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
+        *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+      }
+      sqlite3_free(zSql);
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    *ppVtab = (sqlite3_vtab *)pRtree;
+  }else{
+    assert( *ppVtab==0 );
+    assert( pRtree->nBusy==1 );
+    rtreeRelease(pRtree);
+  }
+  return rc;
+}
+
+
+/*
+** Implementation of a scalar function that decodes r-tree nodes to
+** human readable strings. This can be used for debugging and analysis.
+**
+** The scalar function takes two arguments: (1) the number of dimensions
+** to the rtree (between 1 and 5, inclusive) and (2) a blob of data containing
+** an r-tree node.  For a two-dimensional r-tree structure called "rt", to
+** deserialize all nodes, a statement like:
+**
+**   SELECT rtreenode(2, data) FROM rt_node;
+**
+** The human readable string takes the form of a Tcl list with one
+** entry for each cell in the r-tree node. Each entry is itself a
+** list, containing the 8-byte rowid/pageno followed by the 
+** <num-dimension>*2 coordinates.
+*/
+static void rtreenode(sqlite3_context *ctx, int nArg, sqlite3_value **apArg){
+  char *zText = 0;
+  RtreeNode node;
+  Rtree tree;
+  int ii;
+
+  UNUSED_PARAMETER(nArg);
+  memset(&node, 0, sizeof(RtreeNode));
+  memset(&tree, 0, sizeof(Rtree));
+  tree.nDim = (u8)sqlite3_value_int(apArg[0]);
+  tree.nDim2 = tree.nDim*2;
+  tree.nBytesPerCell = 8 + 8 * tree.nDim;
+  node.zData = (u8 *)sqlite3_value_blob(apArg[1]);
+
+  for(ii=0; ii<NCELL(&node); ii++){
+    char zCell[512];
+    int nCell = 0;
+    RtreeCell cell;
+    int jj;
+
+    nodeGetCell(&tree, &node, ii, &cell);
+    sqlite3_snprintf(512-nCell,&zCell[nCell],"%lld", cell.iRowid);
+    nCell = (int)strlen(zCell);
+    for(jj=0; jj<tree.nDim2; jj++){
+#ifndef SQLITE_RTREE_INT_ONLY
+      sqlite3_snprintf(512-nCell,&zCell[nCell], " %g",
+                       (double)cell.aCoord[jj].f);
+#else
+      sqlite3_snprintf(512-nCell,&zCell[nCell], " %d",
+                       cell.aCoord[jj].i);
+#endif
+      nCell = (int)strlen(zCell);
+    }
+
+    if( zText ){
+      char *zTextNew = sqlite3_mprintf("%s {%s}", zText, zCell);
+      sqlite3_free(zText);
+      zText = zTextNew;
+    }else{
+      zText = sqlite3_mprintf("{%s}", zCell);
+    }
+  }
+  
+  sqlite3_result_text(ctx, zText, -1, sqlite3_free);
+}
+
+/* This routine implements an SQL function that returns the "depth" parameter
+** from the front of a blob that is an r-tree node.  For example:
+**
+**     SELECT rtreedepth(data) FROM rt_node WHERE nodeno=1;
+**
+** The depth value is 0 for all nodes other than the root node, and the root
+** node always has nodeno=1, so the example above is the primary use for this
+** routine.  This routine is intended for testing and analysis only.
+*/
+static void rtreedepth(sqlite3_context *ctx, int nArg, sqlite3_value **apArg){
+  UNUSED_PARAMETER(nArg);
+  if( sqlite3_value_type(apArg[0])!=SQLITE_BLOB 
+   || sqlite3_value_bytes(apArg[0])<2
+  ){
+    sqlite3_result_error(ctx, "Invalid argument to rtreedepth()", -1); 
+  }else{
+    u8 *zBlob = (u8 *)sqlite3_value_blob(apArg[0]);
+    sqlite3_result_int(ctx, readInt16(zBlob));
+  }
+}
+
+/*
+** Register the r-tree module with database handle db. This creates the
+** virtual table module "rtree" and the debugging/analysis scalar 
+** function "rtreenode".
+*/
+SQLITE_PRIVATE int sqlite3RtreeInit(sqlite3 *db){
+  const int utf8 = SQLITE_UTF8;
+  int rc;
+
+  rc = sqlite3_create_function(db, "rtreenode", 2, utf8, 0, rtreenode, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "rtreedepth", 1, utf8, 0,rtreedepth, 0, 0);
+  }
+  if( rc==SQLITE_OK ){
+#ifdef SQLITE_RTREE_INT_ONLY
+    void *c = (void *)RTREE_COORD_INT32;
+#else
+    void *c = (void *)RTREE_COORD_REAL32;
+#endif
+    rc = sqlite3_create_module_v2(db, "rtree", &rtreeModule, c, 0);
+  }
+  if( rc==SQLITE_OK ){
+    void *c = (void *)RTREE_COORD_INT32;
+    rc = sqlite3_create_module_v2(db, "rtree_i32", &rtreeModule, c, 0);
+  }
+
+  return rc;
+}
+
+/*
+** This routine deletes the RtreeGeomCallback object that was attached
+** one of the SQL functions create by sqlite3_rtree_geometry_callback()
+** or sqlite3_rtree_query_callback().  In other words, this routine is the
+** destructor for an RtreeGeomCallback objecct.  This routine is called when
+** the corresponding SQL function is deleted.
+*/
+static void rtreeFreeCallback(void *p){
+  RtreeGeomCallback *pInfo = (RtreeGeomCallback*)p;
+  if( pInfo->xDestructor ) pInfo->xDestructor(pInfo->pContext);
+  sqlite3_free(p);
+}
+
+/*
+** This routine frees the BLOB that is returned by geomCallback().
+*/
+static void rtreeMatchArgFree(void *pArg){
+  int i;
+  RtreeMatchArg *p = (RtreeMatchArg*)pArg;
+  for(i=0; i<p->nParam; i++){
+    sqlite3_value_free(p->apSqlParam[i]);
+  }
+  sqlite3_free(p);
+}
+
+/*
+** Each call to sqlite3_rtree_geometry_callback() or
+** sqlite3_rtree_query_callback() creates an ordinary SQLite
+** scalar function that is implemented by this routine.
+**
+** All this function does is construct an RtreeMatchArg object that
+** contains the geometry-checking callback routines and a list of
+** parameters to this function, then return that RtreeMatchArg object
+** as a BLOB.
+**
+** The R-Tree MATCH operator will read the returned BLOB, deserialize
+** the RtreeMatchArg object, and use the RtreeMatchArg object to figure
+** out which elements of the R-Tree should be returned by the query.
+*/
+static void geomCallback(sqlite3_context *ctx, int nArg, sqlite3_value **aArg){
+  RtreeGeomCallback *pGeomCtx = (RtreeGeomCallback *)sqlite3_user_data(ctx);
+  RtreeMatchArg *pBlob;
+  int nBlob;
+  int memErr = 0;
+
+  nBlob = sizeof(RtreeMatchArg) + (nArg-1)*sizeof(RtreeDValue)
+           + nArg*sizeof(sqlite3_value*);
+  pBlob = (RtreeMatchArg *)sqlite3_malloc(nBlob);
+  if( !pBlob ){
+    sqlite3_result_error_nomem(ctx);
+  }else{
+    int i;
+    pBlob->magic = RTREE_GEOMETRY_MAGIC;
+    pBlob->cb = pGeomCtx[0];
+    pBlob->apSqlParam = (sqlite3_value**)&pBlob->aParam[nArg];
+    pBlob->nParam = nArg;
+    for(i=0; i<nArg; i++){
+      pBlob->apSqlParam[i] = sqlite3_value_dup(aArg[i]);
+      if( pBlob->apSqlParam[i]==0 ) memErr = 1;
+#ifdef SQLITE_RTREE_INT_ONLY
+      pBlob->aParam[i] = sqlite3_value_int64(aArg[i]);
+#else
+      pBlob->aParam[i] = sqlite3_value_double(aArg[i]);
+#endif
+    }
+    if( memErr ){
+      sqlite3_result_error_nomem(ctx);
+      rtreeMatchArgFree(pBlob);
+    }else{
+      sqlite3_result_blob(ctx, pBlob, nBlob, rtreeMatchArgFree);
+    }
+  }
+}
+
+/*
+** Register a new geometry function for use with the r-tree MATCH operator.
+*/
+SQLITE_API int sqlite3_rtree_geometry_callback(
+  sqlite3 *db,                  /* Register SQL function on this connection */
+  const char *zGeom,            /* Name of the new SQL function */
+  int (*xGeom)(sqlite3_rtree_geometry*,int,RtreeDValue*,int*), /* Callback */
+  void *pContext                /* Extra data associated with the callback */
+){
+  RtreeGeomCallback *pGeomCtx;      /* Context object for new user-function */
+
+  /* Allocate and populate the context object. */
+  pGeomCtx = (RtreeGeomCallback *)sqlite3_malloc(sizeof(RtreeGeomCallback));
+  if( !pGeomCtx ) return SQLITE_NOMEM;
+  pGeomCtx->xGeom = xGeom;
+  pGeomCtx->xQueryFunc = 0;
+  pGeomCtx->xDestructor = 0;
+  pGeomCtx->pContext = pContext;
+  return sqlite3_create_function_v2(db, zGeom, -1, SQLITE_ANY, 
+      (void *)pGeomCtx, geomCallback, 0, 0, rtreeFreeCallback
+  );
+}
+
+/*
+** Register a new 2nd-generation geometry function for use with the
+** r-tree MATCH operator.
+*/
+SQLITE_API int sqlite3_rtree_query_callback(
+  sqlite3 *db,                 /* Register SQL function on this connection */
+  const char *zQueryFunc,      /* Name of new SQL function */
+  int (*xQueryFunc)(sqlite3_rtree_query_info*), /* Callback */
+  void *pContext,              /* Extra data passed into the callback */
+  void (*xDestructor)(void*)   /* Destructor for the extra data */
+){
+  RtreeGeomCallback *pGeomCtx;      /* Context object for new user-function */
+
+  /* Allocate and populate the context object. */
+  pGeomCtx = (RtreeGeomCallback *)sqlite3_malloc(sizeof(RtreeGeomCallback));
+  if( !pGeomCtx ) return SQLITE_NOMEM;
+  pGeomCtx->xGeom = 0;
+  pGeomCtx->xQueryFunc = xQueryFunc;
+  pGeomCtx->xDestructor = xDestructor;
+  pGeomCtx->pContext = pContext;
+  return sqlite3_create_function_v2(db, zQueryFunc, -1, SQLITE_ANY, 
+      (void *)pGeomCtx, geomCallback, 0, 0, rtreeFreeCallback
+  );
+}
+
+#if !SQLITE_CORE
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+SQLITE_API int sqlite3_rtree_init(
+  sqlite3 *db,
+  char **pzErrMsg,
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi)
+  return sqlite3RtreeInit(db);
+}
+#endif
+
+#endif
+
+/************** End of rtree.c ***********************************************/
+/************** Begin file icu.c *********************************************/
+/*
+** 2007 May 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** $Id: icu.c,v 1.7 2007/12/13 21:54:11 drh Exp $
+**
+** This file implements an integration between the ICU library 
+** ("International Components for Unicode", an open-source library 
+** for handling unicode data) and SQLite. The integration uses 
+** ICU to provide the following to SQLite:
+**
+**   * An implementation of the SQL regexp() function (and hence REGEXP
+**     operator) using the ICU uregex_XX() APIs.
+**
+**   * Implementations of the SQL scalar upper() and lower() functions
+**     for case mapping.
+**
+**   * Integration of ICU and SQLite collation sequences.
+**
+**   * An implementation of the LIKE operator that uses ICU to 
+**     provide case-independent matching.
+*/
+
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ICU)
+
+/* Include ICU headers */
+#include <unicode/utypes.h>
+#include <unicode/uregex.h>
+#include <unicode/ustring.h>
+#include <unicode/ucol.h>
+
+/* #include <assert.h> */
+
+#ifndef SQLITE_CORE
+/*   #include "sqlite3ext.h" */
+  SQLITE_EXTENSION_INIT1
+#else
+/*   #include "sqlite3.h" */
+#endif
+
+/*
+** Maximum length (in bytes) of the pattern in a LIKE or GLOB
+** operator.
+*/
+#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
+# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
+#endif
+
+/*
+** Version of sqlite3_free() that is always a function, never a macro.
+*/
+static void xFree(void *p){
+  sqlite3_free(p);
+}
+
+/*
+** This lookup table is used to help decode the first byte of
+** a multi-byte UTF8 character. It is copied here from SQLite source
+** code file utf8.c.
+*/
+static const unsigned char icuUtf8Trans1[] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00,
+};
+
+#define SQLITE_ICU_READ_UTF8(zIn, c)                       \
+  c = *(zIn++);                                            \
+  if( c>=0xc0 ){                                           \
+    c = icuUtf8Trans1[c-0xc0];                             \
+    while( (*zIn & 0xc0)==0x80 ){                          \
+      c = (c<<6) + (0x3f & *(zIn++));                      \
+    }                                                      \
+  }
+
+#define SQLITE_ICU_SKIP_UTF8(zIn)                          \
+  assert( *zIn );                                          \
+  if( *(zIn++)>=0xc0 ){                                    \
+    while( (*zIn & 0xc0)==0x80 ){zIn++;}                   \
+  }
+
+
+/*
+** Compare two UTF-8 strings for equality where the first string is
+** a "LIKE" expression. Return true (1) if they are the same and 
+** false (0) if they are different.
+*/
+static int icuLikeCompare(
+  const uint8_t *zPattern,   /* LIKE pattern */
+  const uint8_t *zString,    /* The UTF-8 string to compare against */
+  const UChar32 uEsc         /* The escape character */
+){
+  static const int MATCH_ONE = (UChar32)'_';
+  static const int MATCH_ALL = (UChar32)'%';
+
+  int prevEscape = 0;     /* True if the previous character was uEsc */
+
+  while( 1 ){
+
+    /* Read (and consume) the next character from the input pattern. */
+    UChar32 uPattern;
+    SQLITE_ICU_READ_UTF8(zPattern, uPattern);
+    if( uPattern==0 ) break;
+
+    /* There are now 4 possibilities:
+    **
+    **     1. uPattern is an unescaped match-all character "%",
+    **     2. uPattern is an unescaped match-one character "_",
+    **     3. uPattern is an unescaped escape character, or
+    **     4. uPattern is to be handled as an ordinary character
+    */
+    if( !prevEscape && uPattern==MATCH_ALL ){
+      /* Case 1. */
+      uint8_t c;
+
+      /* Skip any MATCH_ALL or MATCH_ONE characters that follow a
+      ** MATCH_ALL. For each MATCH_ONE, skip one character in the 
+      ** test string.
+      */
+      while( (c=*zPattern) == MATCH_ALL || c == MATCH_ONE ){
+        if( c==MATCH_ONE ){
+          if( *zString==0 ) return 0;
+          SQLITE_ICU_SKIP_UTF8(zString);
+        }
+        zPattern++;
+      }
+
+      if( *zPattern==0 ) return 1;
+
+      while( *zString ){
+        if( icuLikeCompare(zPattern, zString, uEsc) ){
+          return 1;
+        }
+        SQLITE_ICU_SKIP_UTF8(zString);
+      }
+      return 0;
+
+    }else if( !prevEscape && uPattern==MATCH_ONE ){
+      /* Case 2. */
+      if( *zString==0 ) return 0;
+      SQLITE_ICU_SKIP_UTF8(zString);
+
+    }else if( !prevEscape && uPattern==uEsc){
+      /* Case 3. */
+      prevEscape = 1;
+
+    }else{
+      /* Case 4. */
+      UChar32 uString;
+      SQLITE_ICU_READ_UTF8(zString, uString);
+      uString = u_foldCase(uString, U_FOLD_CASE_DEFAULT);
+      uPattern = u_foldCase(uPattern, U_FOLD_CASE_DEFAULT);
+      if( uString!=uPattern ){
+        return 0;
+      }
+      prevEscape = 0;
+    }
+  }
+
+  return *zString==0;
+}
+
+/*
+** Implementation of the like() SQL function.  This function implements
+** the build-in LIKE operator.  The first argument to the function is the
+** pattern and the second argument is the string.  So, the SQL statements:
+**
+**       A LIKE B
+**
+** is implemented as like(B, A). If there is an escape character E, 
+**
+**       A LIKE B ESCAPE E
+**
+** is mapped to like(B, A, E).
+*/
+static void icuLikeFunc(
+  sqlite3_context *context, 
+  int argc, 
+  sqlite3_value **argv
+){
+  const unsigned char *zA = sqlite3_value_text(argv[0]);
+  const unsigned char *zB = sqlite3_value_text(argv[1]);
+  UChar32 uEsc = 0;
+
+  /* Limit the length of the LIKE or GLOB pattern to avoid problems
+  ** of deep recursion and N*N behavior in patternCompare().
+  */
+  if( sqlite3_value_bytes(argv[0])>SQLITE_MAX_LIKE_PATTERN_LENGTH ){
+    sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
+    return;
+  }
+
+
+  if( argc==3 ){
+    /* The escape character string must consist of a single UTF-8 character.
+    ** Otherwise, return an error.
+    */
+    int nE= sqlite3_value_bytes(argv[2]);
+    const unsigned char *zE = sqlite3_value_text(argv[2]);
+    int i = 0;
+    if( zE==0 ) return;
+    U8_NEXT(zE, i, nE, uEsc);
+    if( i!=nE){
+      sqlite3_result_error(context, 
+          "ESCAPE expression must be a single character", -1);
+      return;
+    }
+  }
+
+  if( zA && zB ){
+    sqlite3_result_int(context, icuLikeCompare(zA, zB, uEsc));
+  }
+}
+
+/*
+** This function is called when an ICU function called from within
+** the implementation of an SQL scalar function returns an error.
+**
+** The scalar function context passed as the first argument is 
+** loaded with an error message based on the following two args.
+*/
+static void icuFunctionError(
+  sqlite3_context *pCtx,       /* SQLite scalar function context */
+  const char *zName,           /* Name of ICU function that failed */
+  UErrorCode e                 /* Error code returned by ICU function */
+){
+  char zBuf[128];
+  sqlite3_snprintf(128, zBuf, "ICU error: %s(): %s", zName, u_errorName(e));
+  zBuf[127] = '\0';
+  sqlite3_result_error(pCtx, zBuf, -1);
+}
+
+/*
+** Function to delete compiled regexp objects. Registered as
+** a destructor function with sqlite3_set_auxdata().
+*/
+static void icuRegexpDelete(void *p){
+  URegularExpression *pExpr = (URegularExpression *)p;
+  uregex_close(pExpr);
+}
+
+/*
+** Implementation of SQLite REGEXP operator. This scalar function takes
+** two arguments. The first is a regular expression pattern to compile
+** the second is a string to match against that pattern. If either 
+** argument is an SQL NULL, then NULL Is returned. Otherwise, the result
+** is 1 if the string matches the pattern, or 0 otherwise.
+**
+** SQLite maps the regexp() function to the regexp() operator such
+** that the following two are equivalent:
+**
+**     zString REGEXP zPattern
+**     regexp(zPattern, zString)
+**
+** Uses the following ICU regexp APIs:
+**
+**     uregex_open()
+**     uregex_matches()
+**     uregex_close()
+*/
+static void icuRegexpFunc(sqlite3_context *p, int nArg, sqlite3_value **apArg){
+  UErrorCode status = U_ZERO_ERROR;
+  URegularExpression *pExpr;
+  UBool res;
+  const UChar *zString = sqlite3_value_text16(apArg[1]);
+
+  (void)nArg;  /* Unused parameter */
+
+  /* If the left hand side of the regexp operator is NULL, 
+  ** then the result is also NULL. 
+  */
+  if( !zString ){
+    return;
+  }
+
+  pExpr = sqlite3_get_auxdata(p, 0);
+  if( !pExpr ){
+    const UChar *zPattern = sqlite3_value_text16(apArg[0]);
+    if( !zPattern ){
+      return;
+    }
+    pExpr = uregex_open(zPattern, -1, 0, 0, &status);
+
+    if( U_SUCCESS(status) ){
+      sqlite3_set_auxdata(p, 0, pExpr, icuRegexpDelete);
+    }else{
+      assert(!pExpr);
+      icuFunctionError(p, "uregex_open", status);
+      return;
+    }
+  }
+
+  /* Configure the text that the regular expression operates on. */
+  uregex_setText(pExpr, zString, -1, &status);
+  if( !U_SUCCESS(status) ){
+    icuFunctionError(p, "uregex_setText", status);
+    return;
+  }
+
+  /* Attempt the match */
+  res = uregex_matches(pExpr, 0, &status);
+  if( !U_SUCCESS(status) ){
+    icuFunctionError(p, "uregex_matches", status);
+    return;
+  }
+
+  /* Set the text that the regular expression operates on to a NULL
+  ** pointer. This is not really necessary, but it is tidier than 
+  ** leaving the regular expression object configured with an invalid
+  ** pointer after this function returns.
+  */
+  uregex_setText(pExpr, 0, 0, &status);
+
+  /* Return 1 or 0. */
+  sqlite3_result_int(p, res ? 1 : 0);
+}
+
+/*
+** Implementations of scalar functions for case mapping - upper() and 
+** lower(). Function upper() converts its input to upper-case (ABC).
+** Function lower() converts to lower-case (abc).
+**
+** ICU provides two types of case mapping, "general" case mapping and
+** "language specific". Refer to ICU documentation for the differences
+** between the two.
+**
+** To utilise "general" case mapping, the upper() or lower() scalar 
+** functions are invoked with one argument:
+**
+**     upper('ABC') -> 'abc'
+**     lower('abc') -> 'ABC'
+**
+** To access ICU "language specific" case mapping, upper() or lower()
+** should be invoked with two arguments. The second argument is the name
+** of the locale to use. Passing an empty string ("") or SQL NULL value
+** as the second argument is the same as invoking the 1 argument version
+** of upper() or lower().
+**
+**     lower('I', 'en_us') -> 'i'
+**     lower('I', 'tr_tr') -> '\u131' (small dotless i)
+**
+** http://www.icu-project.org/userguide/posix.html#case_mappings
+*/
+static void icuCaseFunc16(sqlite3_context *p, int nArg, sqlite3_value **apArg){
+  const UChar *zInput;            /* Pointer to input string */
+  UChar *zOutput = 0;             /* Pointer to output buffer */
+  int nInput;                     /* Size of utf-16 input string in bytes */
+  int nOut;                       /* Size of output buffer in bytes */
+  int cnt;
+  int bToUpper;                   /* True for toupper(), false for tolower() */
+  UErrorCode status;
+  const char *zLocale = 0;
+
+  assert(nArg==1 || nArg==2);
+  bToUpper = (sqlite3_user_data(p)!=0);
+  if( nArg==2 ){
+    zLocale = (const char *)sqlite3_value_text(apArg[1]);
+  }
+
+  zInput = sqlite3_value_text16(apArg[0]);
+  if( !zInput ){
+    return;
+  }
+  nOut = nInput = sqlite3_value_bytes16(apArg[0]);
+  if( nOut==0 ){
+    sqlite3_result_text16(p, "", 0, SQLITE_STATIC);
+    return;
+  }
+
+  for(cnt=0; cnt<2; cnt++){
+    UChar *zNew = sqlite3_realloc(zOutput, nOut);
+    if( zNew==0 ){
+      sqlite3_free(zOutput);
+      sqlite3_result_error_nomem(p);
+      return;
+    }
+    zOutput = zNew;
+    status = U_ZERO_ERROR;
+    if( bToUpper ){
+      nOut = 2*u_strToUpper(zOutput,nOut/2,zInput,nInput/2,zLocale,&status);
+    }else{
+      nOut = 2*u_strToLower(zOutput,nOut/2,zInput,nInput/2,zLocale,&status);
+    }
+
+    if( U_SUCCESS(status) ){
+      sqlite3_result_text16(p, zOutput, nOut, xFree);
+    }else if( status==U_BUFFER_OVERFLOW_ERROR ){
+      assert( cnt==0 );
+      continue;
+    }else{
+      icuFunctionError(p, bToUpper ? "u_strToUpper" : "u_strToLower", status);
+    }
+    return;
+  }
+  assert( 0 );     /* Unreachable */
+}
+
+/*
+** Collation sequence destructor function. The pCtx argument points to
+** a UCollator structure previously allocated using ucol_open().
+*/
+static void icuCollationDel(void *pCtx){
+  UCollator *p = (UCollator *)pCtx;
+  ucol_close(p);
+}
+
+/*
+** Collation sequence comparison function. The pCtx argument points to
+** a UCollator structure previously allocated using ucol_open().
+*/
+static int icuCollationColl(
+  void *pCtx,
+  int nLeft,
+  const void *zLeft,
+  int nRight,
+  const void *zRight
+){
+  UCollationResult res;
+  UCollator *p = (UCollator *)pCtx;
+  res = ucol_strcoll(p, (UChar *)zLeft, nLeft/2, (UChar *)zRight, nRight/2);
+  switch( res ){
+    case UCOL_LESS:    return -1;
+    case UCOL_GREATER: return +1;
+    case UCOL_EQUAL:   return 0;
+  }
+  assert(!"Unexpected return value from ucol_strcoll()");
+  return 0;
+}
+
+/*
+** Implementation of the scalar function icu_load_collation().
+**
+** This scalar function is used to add ICU collation based collation 
+** types to an SQLite database connection. It is intended to be called
+** as follows:
+**
+**     SELECT icu_load_collation(<locale>, <collation-name>);
+**
+** Where <locale> is a string containing an ICU locale identifier (i.e.
+** "en_AU", "tr_TR" etc.) and <collation-name> is the name of the
+** collation sequence to create.
+*/
+static void icuLoadCollation(
+  sqlite3_context *p, 
+  int nArg, 
+  sqlite3_value **apArg
+){
+  sqlite3 *db = (sqlite3 *)sqlite3_user_data(p);
+  UErrorCode status = U_ZERO_ERROR;
+  const char *zLocale;      /* Locale identifier - (eg. "jp_JP") */
+  const char *zName;        /* SQL Collation sequence name (eg. "japanese") */
+  UCollator *pUCollator;    /* ICU library collation object */
+  int rc;                   /* Return code from sqlite3_create_collation_x() */
+
+  assert(nArg==2);
+  (void)nArg; /* Unused parameter */
+  zLocale = (const char *)sqlite3_value_text(apArg[0]);
+  zName = (const char *)sqlite3_value_text(apArg[1]);
+
+  if( !zLocale || !zName ){
+    return;
+  }
+
+  pUCollator = ucol_open(zLocale, &status);
+  if( !U_SUCCESS(status) ){
+    icuFunctionError(p, "ucol_open", status);
+    return;
+  }
+  assert(p);
+
+  rc = sqlite3_create_collation_v2(db, zName, SQLITE_UTF16, (void *)pUCollator, 
+      icuCollationColl, icuCollationDel
+  );
+  if( rc!=SQLITE_OK ){
+    ucol_close(pUCollator);
+    sqlite3_result_error(p, "Error registering collation function", -1);
+  }
+}
+
+/*
+** Register the ICU extension functions with database db.
+*/
+SQLITE_PRIVATE int sqlite3IcuInit(sqlite3 *db){
+  static const struct IcuScalar {
+    const char *zName;                        /* Function name */
+    unsigned char nArg;                       /* Number of arguments */
+    unsigned short enc;                       /* Optimal text encoding */
+    unsigned char iContext;                   /* sqlite3_user_data() context */
+    void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
+  } scalars[] = {
+    {"icu_load_collation",  2, SQLITE_UTF8,                1, icuLoadCollation},
+    {"regexp", 2, SQLITE_ANY|SQLITE_DETERMINISTIC,         0, icuRegexpFunc},
+    {"lower",  1, SQLITE_UTF16|SQLITE_DETERMINISTIC,       0, icuCaseFunc16},
+    {"lower",  2, SQLITE_UTF16|SQLITE_DETERMINISTIC,       0, icuCaseFunc16},
+    {"upper",  1, SQLITE_UTF16|SQLITE_DETERMINISTIC,       1, icuCaseFunc16},
+    {"upper",  2, SQLITE_UTF16|SQLITE_DETERMINISTIC,       1, icuCaseFunc16},
+    {"lower",  1, SQLITE_UTF8|SQLITE_DETERMINISTIC,        0, icuCaseFunc16},
+    {"lower",  2, SQLITE_UTF8|SQLITE_DETERMINISTIC,        0, icuCaseFunc16},
+    {"upper",  1, SQLITE_UTF8|SQLITE_DETERMINISTIC,        1, icuCaseFunc16},
+    {"upper",  2, SQLITE_UTF8|SQLITE_DETERMINISTIC,        1, icuCaseFunc16},
+    {"like",   2, SQLITE_UTF8|SQLITE_DETERMINISTIC,        0, icuLikeFunc},
+    {"like",   3, SQLITE_UTF8|SQLITE_DETERMINISTIC,        0, icuLikeFunc},
+  };
+  int rc = SQLITE_OK;
+  int i;
+
+  
+  for(i=0; rc==SQLITE_OK && i<(int)(sizeof(scalars)/sizeof(scalars[0])); i++){
+    const struct IcuScalar *p = &scalars[i];
+    rc = sqlite3_create_function(
+        db, p->zName, p->nArg, p->enc, 
+        p->iContext ? (void*)db : (void*)0,
+        p->xFunc, 0, 0
+    );
+  }
+
+  return rc;
+}
+
+#if !SQLITE_CORE
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+SQLITE_API int sqlite3_icu_init(
+  sqlite3 *db, 
+  char **pzErrMsg,
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi)
+  return sqlite3IcuInit(db);
+}
+#endif
+
+#endif
+
+/************** End of icu.c *************************************************/
+/************** Begin file fts3_icu.c ****************************************/
+/*
+** 2007 June 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements a tokenizer for fts3 based on the ICU library.
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+#ifdef SQLITE_ENABLE_ICU
+
+/* #include <assert.h> */
+/* #include <string.h> */
+/* #include "fts3_tokenizer.h" */
+
+#include <unicode/ubrk.h>
+/* #include <unicode/ucol.h> */
+/* #include <unicode/ustring.h> */
+#include <unicode/utf16.h>
+
+typedef struct IcuTokenizer IcuTokenizer;
+typedef struct IcuCursor IcuCursor;
+
+struct IcuTokenizer {
+  sqlite3_tokenizer base;
+  char *zLocale;
+};
+
+struct IcuCursor {
+  sqlite3_tokenizer_cursor base;
+
+  UBreakIterator *pIter;      /* ICU break-iterator object */
+  int nChar;                  /* Number of UChar elements in pInput */
+  UChar *aChar;               /* Copy of input using utf-16 encoding */
+  int *aOffset;               /* Offsets of each character in utf-8 input */
+
+  int nBuffer;
+  char *zBuffer;
+
+  int iToken;
+};
+
+/*
+** Create a new tokenizer instance.
+*/
+static int icuCreate(
+  int argc,                            /* Number of entries in argv[] */
+  const char * const *argv,            /* Tokenizer creation arguments */
+  sqlite3_tokenizer **ppTokenizer      /* OUT: Created tokenizer */
+){
+  IcuTokenizer *p;
+  int n = 0;
+
+  if( argc>0 ){
+    n = strlen(argv[0])+1;
+  }
+  p = (IcuTokenizer *)sqlite3_malloc(sizeof(IcuTokenizer)+n);
+  if( !p ){
+    return SQLITE_NOMEM;
+  }
+  memset(p, 0, sizeof(IcuTokenizer));
+
+  if( n ){
+    p->zLocale = (char *)&p[1];
+    memcpy(p->zLocale, argv[0], n);
+  }
+
+  *ppTokenizer = (sqlite3_tokenizer *)p;
+
+  return SQLITE_OK;
+}
+
+/*
+** Destroy a tokenizer
+*/
+static int icuDestroy(sqlite3_tokenizer *pTokenizer){
+  IcuTokenizer *p = (IcuTokenizer *)pTokenizer;
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Prepare to begin tokenizing a particular string.  The input
+** string to be tokenized is pInput[0..nBytes-1].  A cursor
+** used to incrementally tokenize this string is returned in 
+** *ppCursor.
+*/
+static int icuOpen(
+  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
+  const char *zInput,                    /* Input string */
+  int nInput,                            /* Length of zInput in bytes */
+  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
+){
+  IcuTokenizer *p = (IcuTokenizer *)pTokenizer;
+  IcuCursor *pCsr;
+
+  const int32_t opt = U_FOLD_CASE_DEFAULT;
+  UErrorCode status = U_ZERO_ERROR;
+  int nChar;
+
+  UChar32 c;
+  int iInput = 0;
+  int iOut = 0;
+
+  *ppCursor = 0;
+
+  if( zInput==0 ){
+    nInput = 0;
+    zInput = "";
+  }else if( nInput<0 ){
+    nInput = strlen(zInput);
+  }
+  nChar = nInput+1;
+  pCsr = (IcuCursor *)sqlite3_malloc(
+      sizeof(IcuCursor) +                /* IcuCursor */
+      ((nChar+3)&~3) * sizeof(UChar) +   /* IcuCursor.aChar[] */
+      (nChar+1) * sizeof(int)            /* IcuCursor.aOffset[] */
+  );
+  if( !pCsr ){
+    return SQLITE_NOMEM;
+  }
+  memset(pCsr, 0, sizeof(IcuCursor));
+  pCsr->aChar = (UChar *)&pCsr[1];
+  pCsr->aOffset = (int *)&pCsr->aChar[(nChar+3)&~3];
+
+  pCsr->aOffset[iOut] = iInput;
+  U8_NEXT(zInput, iInput, nInput, c); 
+  while( c>0 ){
+    int isError = 0;
+    c = u_foldCase(c, opt);
+    U16_APPEND(pCsr->aChar, iOut, nChar, c, isError);
+    if( isError ){
+      sqlite3_free(pCsr);
+      return SQLITE_ERROR;
+    }
+    pCsr->aOffset[iOut] = iInput;
+
+    if( iInput<nInput ){
+      U8_NEXT(zInput, iInput, nInput, c);
+    }else{
+      c = 0;
+    }
+  }
+
+  pCsr->pIter = ubrk_open(UBRK_WORD, p->zLocale, pCsr->aChar, iOut, &status);
+  if( !U_SUCCESS(status) ){
+    sqlite3_free(pCsr);
+    return SQLITE_ERROR;
+  }
+  pCsr->nChar = iOut;
+
+  ubrk_first(pCsr->pIter);
+  *ppCursor = (sqlite3_tokenizer_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+/*
+** Close a tokenization cursor previously opened by a call to icuOpen().
+*/
+static int icuClose(sqlite3_tokenizer_cursor *pCursor){
+  IcuCursor *pCsr = (IcuCursor *)pCursor;
+  ubrk_close(pCsr->pIter);
+  sqlite3_free(pCsr->zBuffer);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/*
+** Extract the next token from a tokenization cursor.
+*/
+static int icuNext(
+  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
+  const char **ppToken,               /* OUT: *ppToken is the token text */
+  int *pnBytes,                       /* OUT: Number of bytes in token */
+  int *piStartOffset,                 /* OUT: Starting offset of token */
+  int *piEndOffset,                   /* OUT: Ending offset of token */
+  int *piPosition                     /* OUT: Position integer of token */
+){
+  IcuCursor *pCsr = (IcuCursor *)pCursor;
+
+  int iStart = 0;
+  int iEnd = 0;
+  int nByte = 0;
+
+  while( iStart==iEnd ){
+    UChar32 c;
+
+    iStart = ubrk_current(pCsr->pIter);
+    iEnd = ubrk_next(pCsr->pIter);
+    if( iEnd==UBRK_DONE ){
+      return SQLITE_DONE;
+    }
+
+    while( iStart<iEnd ){
+      int iWhite = iStart;
+      U16_NEXT(pCsr->aChar, iWhite, pCsr->nChar, c);
+      if( u_isspace(c) ){
+        iStart = iWhite;
+      }else{
+        break;
+      }
+    }
+    assert(iStart<=iEnd);
+  }
+
+  do {
+    UErrorCode status = U_ZERO_ERROR;
+    if( nByte ){
+      char *zNew = sqlite3_realloc(pCsr->zBuffer, nByte);
+      if( !zNew ){
+        return SQLITE_NOMEM;
+      }
+      pCsr->zBuffer = zNew;
+      pCsr->nBuffer = nByte;
+    }
+
+    u_strToUTF8(
+        pCsr->zBuffer, pCsr->nBuffer, &nByte,    /* Output vars */
+        &pCsr->aChar[iStart], iEnd-iStart,       /* Input vars */
+        &status                                  /* Output success/failure */
+    );
+  } while( nByte>pCsr->nBuffer );
+
+  *ppToken = pCsr->zBuffer;
+  *pnBytes = nByte;
+  *piStartOffset = pCsr->aOffset[iStart];
+  *piEndOffset = pCsr->aOffset[iEnd];
+  *piPosition = pCsr->iToken++;
+
+  return SQLITE_OK;
+}
+
+/*
+** The set of routines that implement the simple tokenizer
+*/
+static const sqlite3_tokenizer_module icuTokenizerModule = {
+  0,                           /* iVersion    */
+  icuCreate,                   /* xCreate     */
+  icuDestroy,                  /* xCreate     */
+  icuOpen,                     /* xOpen       */
+  icuClose,                    /* xClose      */
+  icuNext,                     /* xNext       */
+  0,                           /* xLanguageid */
+};
+
+/*
+** Set *ppModule to point at the implementation of the ICU tokenizer.
+*/
+SQLITE_PRIVATE void sqlite3Fts3IcuTokenizerModule(
+  sqlite3_tokenizer_module const**ppModule
+){
+  *ppModule = &icuTokenizerModule;
+}
+
+#endif /* defined(SQLITE_ENABLE_ICU) */
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_icu.c ********************************************/
+
+/* Chain include. */ 
+#include "sqlite3.08.c"