Add //third_party/sqlite to dirs_to_snapshot, remove net_sql.patch

third_party/sqlite/sqlite-src-3080704/ext/misc/closure.c

+/*
+** 2013-04-16
+**
+** 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 a virtual table that finds the transitive
+** closure of a parent/child relationship in a real table.  The virtual 
+** table is called "transitive_closure".
+**
+** A transitive_closure virtual table is created like this:
+**
+**     CREATE VIRTUAL TABLE x USING transitive_closure(
+**        tablename=<tablename>,      -- T
+**        idcolumn=<columnname>,      -- X
+**        parentcolumn=<columnname>   -- P
+**     );
+**
+** When it is created, the new transitive_closure table may be supplied 
+** with default values for the name of a table T and columns T.X and T.P.
+** The T.X and T.P columns must contain integers.  The ideal case is for 
+** T.X to be the INTEGER PRIMARY KEY.  The T.P column should reference
+** the T.X column. The row referenced by T.P is the parent of the current row.
+**
+** The tablename, idcolumn, and parentcolumn supplied by the CREATE VIRTUAL
+** TABLE statement may be overridden in individual queries by including
+** terms like tablename='newtable', idcolumn='id2', or 
+** parentcolumn='parent3' in the WHERE clause of the query.
+**
+** For efficiency, it is essential that there be an index on the P column:
+**
+**    CREATE Tidx1 ON T(P)
+**
+** Suppose a specific instance of the closure table is as follows:
+**
+**    CREATE VIRTUAL TABLE ct1 USING transitive_closure(
+**       tablename='group',
+**       idcolumn='groupId',
+**       parentcolumn='parentId'
+**    );
+**
+** Such an instance of the transitive_closure virtual table would be
+** appropriate for walking a tree defined using a table like this, for example:
+**
+**    CREATE TABLE group(
+**      groupId INTEGER PRIMARY KEY,
+**      parentId INTEGER REFERENCES group
+**    );
+**    CREATE INDEX group_idx1 ON group(parentId);
+**
+** The group table above would presumably have other application-specific
+** fields.  The key point here is that rows of the group table form a
+** tree.  The purpose of the ct1 virtual table is to easily extract
+** branches of that tree.
+**
+** Once it has been created, the ct1 virtual table can be queried
+** as follows:
+**
+**    SELECT * FROM element
+**     WHERE element.groupId IN (SELECT id FROM ct1 WHERE root=?1);
+**
+** The above query will return all elements that are part of group ?1
+** or children of group ?1 or grand-children of ?1 and so forth for all
+** descendents of group ?1.  The same query can be formulated as a join:
+**
+**    SELECT element.* FROM element, ct1
+**     WHERE element.groupid=ct1.id
+**       AND ct1.root=?1;
+**
+** The depth of the transitive_closure (the number of generations of
+** parent/child relations to follow) can be limited by setting "depth"
+** column in the WHERE clause.  So, for example, the following query
+** finds only children and grandchildren but no further descendents:
+**
+**    SELECT element.* FROM element, ct1
+**     WHERE element.groupid=ct1.id
+**       AND ct1.root=?1
+**       AND ct1.depth<=2;
+**
+** The "ct1.depth<=2" term could be a strict equality "ct1.depth=2" in
+** order to find only the grandchildren of ?1, not ?1 itself or the
+** children of ?1.
+** 
+** The root=?1 term must be supplied in WHERE clause or else the query
+** of the ct1 virtual table will return an empty set.  The tablename,
+** idcolumn, and parentcolumn attributes can be overridden in the WHERE
+** clause if desired.  So, for example, the ct1 table could be repurposed
+** to find ancestors rather than descendents by inverting the roles of
+** the idcolumn and parentcolumn:
+**
+**    SELECT element.* FROM element, ct1
+**     WHERE element.groupid=ct1.id
+**       AND ct1.root=?1
+**       AND ct1.idcolumn='parentId'
+**       AND ct1.parentcolumn='groupId';
+**
+** Multiple calls to ct1 could be combined.  For example, the following
+** query finds all elements that "cousins" of groupId ?1.  That is to say
+** elements where the groupId is a grandchild of the grandparent of ?1.
+** (This definition of "cousins" also includes siblings and self.)
+**
+**    SELECT element.* FROM element, ct1
+**     WHERE element.groupId=ct1.id
+**       AND ct1.depth=2
+**       AND ct1.root IN (SELECT id FROM ct1
+**                         WHERE root=?1
+**                           AND depth=2
+**                           AND idcolumn='parentId'
+**                           AND parentcolumn='groupId');
+**
+** In our example, the group.groupId column is unique and thus the
+** subquery will return exactly one row.  For that reason, the IN
+** operator could be replaced by "=" to get the same result.  But
+** in the general case where the idcolumn is not unique, an IN operator
+** would be required for this kind of query.
+**
+** Note that because the tablename, idcolumn, and parentcolumn can
+** all be specified in the query, it is possible for an application
+** to define a single transitive_closure virtual table for use on lots
+** of different hierarchy tables.  One might say:
+**
+**     CREATE VIRTUAL TABLE temp.closure USING transitive_closure;
+**
+** As each database connection is being opened.  Then the application
+** would always have a "closure" virtual table handy to use for querying.
+**
+**    SELECT element.* FROM element, closure
+**     WHERE element.groupid=ct1.id
+**       AND closure.root=?1
+**       AND closure.tablename='group'
+**       AND closure.idname='groupId'
+**       AND closure.parentname='parentId';
+**
+** See the documentation at http://www.sqlite.org/loadext.html for information
+** on how to compile and use loadable extensions such as this one.
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <stdio.h>
+#include <ctype.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Forward declaration of objects used by this implementation
+*/
+typedef struct closure_vtab closure_vtab;
+typedef struct closure_cursor closure_cursor;
+typedef struct closure_queue closure_queue;
+typedef struct closure_avl closure_avl;
+
+/*****************************************************************************
+** AVL Tree implementation
+*/
+/*
+** Objects that want to be members of the AVL tree should embedded an
+** instance of this structure.
+*/
+struct closure_avl {
+  sqlite3_int64 id;     /* Id of this entry in the table */
+  int iGeneration;      /* Which generation is this entry part of */
+  closure_avl *pList;   /* A linked list of nodes */
+  closure_avl *pBefore; /* Other elements less than id */
+  closure_avl *pAfter;  /* Other elements greater than id */
+  closure_avl *pUp;     /* Parent element */
+  short int height;     /* Height of this node.  Leaf==1 */
+  short int imbalance;  /* Height difference between pBefore and pAfter */
+};
+
+/* Recompute the closure_avl.height and closure_avl.imbalance fields for p.
+** Assume that the children of p have correct heights.
+*/
+static void closureAvlRecomputeHeight(closure_avl *p){
+  short int hBefore = p->pBefore ? p->pBefore->height : 0;
+  short int hAfter = p->pAfter ? p->pAfter->height : 0;
+  p->imbalance = hBefore - hAfter;  /* -: pAfter higher.  +: pBefore higher */
+  p->height = (hBefore>hAfter ? hBefore : hAfter)+1;
+}
+
+/*
+**     P                B
+**    / \              / \
+**   B   Z    ==>     X   P
+**  / \                  / \
+** X   Y                Y   Z
+**
+*/
+static closure_avl *closureAvlRotateBefore(closure_avl *pP){
+  closure_avl *pB = pP->pBefore;
+  closure_avl *pY = pB->pAfter;
+  pB->pUp = pP->pUp;
+  pB->pAfter = pP;
+  pP->pUp = pB;
+  pP->pBefore = pY;
+  if( pY ) pY->pUp = pP;
+  closureAvlRecomputeHeight(pP);
+  closureAvlRecomputeHeight(pB);
+  return pB;
+}
+
+/*
+**     P                A
+**    / \              / \
+**   X   A    ==>     P   Z
+**      / \          / \
+**     Y   Z        X   Y
+**
+*/
+static closure_avl *closureAvlRotateAfter(closure_avl *pP){
+  closure_avl *pA = pP->pAfter;
+  closure_avl *pY = pA->pBefore;
+  pA->pUp = pP->pUp;
+  pA->pBefore = pP;
+  pP->pUp = pA;
+  pP->pAfter = pY;
+  if( pY ) pY->pUp = pP;
+  closureAvlRecomputeHeight(pP);
+  closureAvlRecomputeHeight(pA);
+  return pA;
+}
+
+/*
+** Return a pointer to the pBefore or pAfter pointer in the parent
+** of p that points to p.  Or if p is the root node, return pp.
+*/
+static closure_avl **closureAvlFromPtr(closure_avl *p, closure_avl **pp){
+  closure_avl *pUp = p->pUp;
+  if( pUp==0 ) return pp;
+  if( pUp->pAfter==p ) return &pUp->pAfter;
+  return &pUp->pBefore;
+}
+
+/*
+** Rebalance all nodes starting with p and working up to the root.
+** Return the new root.
+*/
+static closure_avl *closureAvlBalance(closure_avl *p){
+  closure_avl *pTop = p;
+  closure_avl **pp;
+  while( p ){
+    closureAvlRecomputeHeight(p);
+    if( p->imbalance>=2 ){
+      closure_avl *pB = p->pBefore;
+      if( pB->imbalance<0 ) p->pBefore = closureAvlRotateAfter(pB);
+      pp = closureAvlFromPtr(p,&p);
+      p = *pp = closureAvlRotateBefore(p);
+    }else if( p->imbalance<=(-2) ){
+      closure_avl *pA = p->pAfter;
+      if( pA->imbalance>0 ) p->pAfter = closureAvlRotateBefore(pA);
+      pp = closureAvlFromPtr(p,&p);
+      p = *pp = closureAvlRotateAfter(p);
+    }
+    pTop = p;
+    p = p->pUp;
+  }
+  return pTop;
+}
+
+/* Search the tree rooted at p for an entry with id.  Return a pointer
+** to the entry or return NULL.
+*/
+static closure_avl *closureAvlSearch(closure_avl *p, sqlite3_int64 id){
+  while( p && id!=p->id ){
+    p = (id<p->id) ? p->pBefore : p->pAfter;
+  }
+  return p;
+}
+
+/* Find the first node (the one with the smallest key).
+*/
+static closure_avl *closureAvlFirst(closure_avl *p){
+  if( p ) while( p->pBefore ) p = p->pBefore;
+  return p;
+}
+
+/* Return the node with the next larger key after p.
+*/
+closure_avl *closureAvlNext(closure_avl *p){
+  closure_avl *pPrev = 0;
+  while( p && p->pAfter==pPrev ){
+    pPrev = p;
+    p = p->pUp;
+  }
+  if( p && pPrev==0 ){
+    p = closureAvlFirst(p->pAfter);
+  }
+  return p;
+}
+
+/* Insert a new node pNew.  Return NULL on success.  If the key is not
+** unique, then do not perform the insert but instead leave pNew unchanged
+** and return a pointer to an existing node with the same key.
+*/
+static closure_avl *closureAvlInsert(
+  closure_avl **ppHead,  /* Head of the tree */
+  closure_avl *pNew      /* New node to be inserted */
+){
+  closure_avl *p = *ppHead;
+  if( p==0 ){
+    p = pNew;
+    pNew->pUp = 0;
+  }else{
+    while( p ){
+      if( pNew->id<p->id ){
+        if( p->pBefore ){
+          p = p->pBefore;
+        }else{
+          p->pBefore = pNew;
+          pNew->pUp = p;
+          break;
+        }
+      }else if( pNew->id>p->id ){
+        if( p->pAfter ){
+          p = p->pAfter;
+        }else{
+          p->pAfter = pNew;
+          pNew->pUp = p;
+          break;
+        }
+      }else{
+        return p;
+      }
+    }
+  }
+  pNew->pBefore = 0;
+  pNew->pAfter = 0;
+  pNew->height = 1;
+  pNew->imbalance = 0;
+  *ppHead = closureAvlBalance(p);
+  return 0;
+}
+
+/* Walk the tree can call xDestroy on each node
+*/
+static void closureAvlDestroy(closure_avl *p, void (*xDestroy)(closure_avl*)){
+  if( p ){
+    closureAvlDestroy(p->pBefore, xDestroy);
+    closureAvlDestroy(p->pAfter, xDestroy);
+    xDestroy(p);
+  }
+}
+/*
+** End of the AVL Tree implementation
+******************************************************************************/
+
+/* 
+** A closure virtual-table object 
+*/
+struct closure_vtab {
+  sqlite3_vtab base;         /* Base class - must be first */
+  char *zDb;                 /* Name of database.  (ex: "main") */
+  char *zSelf;               /* Name of this virtual table */
+  char *zTableName;          /* Name of table holding parent/child relation */
+  char *zIdColumn;           /* Name of ID column of zTableName */
+  char *zParentColumn;       /* Name of PARENT column in zTableName */
+  sqlite3 *db;               /* The database connection */
+  int nCursor;               /* Number of pending cursors */
+};
+
+/* A closure cursor object */
+struct closure_cursor {
+  sqlite3_vtab_cursor base;  /* Base class - must be first */
+  closure_vtab *pVtab;       /* The virtual table this cursor belongs to */
+  char *zTableName;          /* Name of table holding parent/child relation */
+  char *zIdColumn;           /* Name of ID column of zTableName */
+  char *zParentColumn;       /* Name of PARENT column in zTableName */
+  closure_avl *pCurrent;     /* Current element of output */
+  closure_avl *pClosure;     /* The complete closure tree */
+};
+
+/* A queue of AVL nodes */
+struct closure_queue {
+  closure_avl *pFirst;       /* Oldest node on the queue */
+  closure_avl *pLast;        /* Youngest node on the queue */
+};
+
+/*
+** Add a node to the end of the queue
+*/
+static void queuePush(closure_queue *pQueue, closure_avl *pNode){
+  pNode->pList = 0;
+  if( pQueue->pLast ){
+    pQueue->pLast->pList = pNode;
+  }else{
+    pQueue->pFirst = pNode;
+  }
+  pQueue->pLast = pNode;
+}
+
+/*
+** Extract the oldest element (the front element) from the queue.
+*/
+static closure_avl *queuePull(closure_queue *pQueue){
+  closure_avl *p = pQueue->pFirst;
+  if( p ){
+    pQueue->pFirst = p->pList;
+    if( pQueue->pFirst==0 ) pQueue->pLast = 0;
+  }
+  return p;
+}
+
+/*
+** This function converts an SQL quoted string into an unquoted string
+** and returns a pointer to a buffer allocated using sqlite3_malloc() 
+** containing the result. The caller should eventually free this buffer
+** using sqlite3_free.
+**
+** Examples:
+**
+**     "abc"   becomes   abc
+**     'xyz'   becomes   xyz
+**     [pqr]   becomes   pqr
+**     `mno`   becomes   mno
+*/
+static char *closureDequote(const char *zIn){
+  int nIn;                        /* Size of input string, in bytes */
+  char *zOut;                     /* Output (dequoted) string */
+
+  nIn = (int)strlen(zIn);
+  zOut = sqlite3_malloc(nIn+1);
+  if( zOut ){
+    char q = zIn[0];              /* Quote character (if any ) */
+
+    if( q!='[' && q!= '\'' && q!='"' && q!='`' ){
+      memcpy(zOut, zIn, nIn+1);
+    }else{
+      int iOut = 0;               /* Index of next byte to write to output */
+      int iIn;                    /* Index of next byte to read from input */
+
+      if( q=='[' ) q = ']';
+      for(iIn=1; iIn<nIn; iIn++){
+        if( zIn[iIn]==q ) iIn++;
+        zOut[iOut++] = zIn[iIn];
+      }
+    }
+    assert( (int)strlen(zOut)<=nIn );
+  }
+  return zOut;
+}
+
+/*
+** Deallocate an closure_vtab object
+*/
+static void closureFree(closure_vtab *p){
+  if( p ){
+    sqlite3_free(p->zDb);
+    sqlite3_free(p->zSelf);
+    sqlite3_free(p->zTableName);
+    sqlite3_free(p->zIdColumn);
+    sqlite3_free(p->zParentColumn);
+    memset(p, 0, sizeof(*p));
+    sqlite3_free(p);
+  }
+}
+
+/*
+** xDisconnect/xDestroy method for the closure module.
+*/
+static int closureDisconnect(sqlite3_vtab *pVtab){
+  closure_vtab *p = (closure_vtab*)pVtab;
+  assert( p->nCursor==0 );
+  closureFree(p);
+  return SQLITE_OK;
+}
+
+/*
+** Check to see if the argument is of the form:
+**
+**       KEY = VALUE
+**
+** If it is, return a pointer to the first character of VALUE.
+** If not, return NULL.  Spaces around the = are ignored.
+*/
+static const char *closureValueOfKey(const char *zKey, const char *zStr){
+  int nKey = (int)strlen(zKey);
+  int nStr = (int)strlen(zStr);
+  int i;
+  if( nStr<nKey+1 ) return 0;
+  if( memcmp(zStr, zKey, nKey)!=0 ) return 0;
+  for(i=nKey; isspace(zStr[i]); i++){}
+  if( zStr[i]!='=' ) return 0;
+  i++;
+  while( isspace(zStr[i]) ){ i++; }
+  return zStr+i;
+}
+
+/*
+** xConnect/xCreate method for the closure module. Arguments are:
+**
+**   argv[0]    -> module name  ("transitive_closure")
+**   argv[1]    -> database name
+**   argv[2]    -> table name
+**   argv[3...] -> arguments
+*/
+static int closureConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc = SQLITE_OK;              /* Return code */
+  closure_vtab *pNew = 0;          /* New virtual table */
+  const char *zDb = argv[1];
+  const char *zVal;
+  int i;
+
+  (void)pAux;
+  *ppVtab = 0;
+  pNew = sqlite3_malloc( sizeof(*pNew) );
+  if( pNew==0 ) return SQLITE_NOMEM;
+  rc = SQLITE_NOMEM;
+  memset(pNew, 0, sizeof(*pNew));
+  pNew->db = db;
+  pNew->zDb = sqlite3_mprintf("%s", zDb);
+  if( pNew->zDb==0 ) goto closureConnectError;
+  pNew->zSelf = sqlite3_mprintf("%s", argv[2]);
+  if( pNew->zSelf==0 ) goto closureConnectError;
+  for(i=3; i<argc; i++){
+    zVal = closureValueOfKey("tablename", argv[i]);
+    if( zVal ){
+      sqlite3_free(pNew->zTableName);
+      pNew->zTableName = closureDequote(zVal);
+      if( pNew->zTableName==0 ) goto closureConnectError;
+      continue;
+    }
+    zVal = closureValueOfKey("idcolumn", argv[i]);
+    if( zVal ){
+      sqlite3_free(pNew->zIdColumn);
+      pNew->zIdColumn = closureDequote(zVal);
+      if( pNew->zIdColumn==0 ) goto closureConnectError;
+      continue;
+    }
+    zVal = closureValueOfKey("parentcolumn", argv[i]);
+    if( zVal ){
+      sqlite3_free(pNew->zParentColumn);
+      pNew->zParentColumn = closureDequote(zVal);
+      if( pNew->zParentColumn==0 ) goto closureConnectError;
+      continue;
+    }
+    *pzErr = sqlite3_mprintf("unrecognized argument: [%s]\n", argv[i]);
+    closureFree(pNew);
+    *ppVtab = 0;
+    return SQLITE_ERROR;
+  }
+  rc = sqlite3_declare_vtab(db,
+         "CREATE TABLE x(id,depth,root HIDDEN,tablename HIDDEN,"
+                        "idcolumn HIDDEN,parentcolumn HIDDEN)"
+       );
+#define CLOSURE_COL_ID              0
+#define CLOSURE_COL_DEPTH           1
+#define CLOSURE_COL_ROOT            2
+#define CLOSURE_COL_TABLENAME       3
+#define CLOSURE_COL_IDCOLUMN        4
+#define CLOSURE_COL_PARENTCOLUMN    5
+  if( rc!=SQLITE_OK ){
+    closureFree(pNew);
+  }
+  *ppVtab = &pNew->base;
+  return rc;
+
+closureConnectError:
+  closureFree(pNew);
+  return rc;
+}
+
+/*
+** Open a new closure cursor.
+*/
+static int closureOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  closure_vtab *p = (closure_vtab*)pVTab;
+  closure_cursor *pCur;
+  pCur = sqlite3_malloc( sizeof(*pCur) );
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(*pCur));
+  pCur->pVtab = p;
+  *ppCursor = &pCur->base;
+  p->nCursor++;
+  return SQLITE_OK;
+}
+
+/*
+** Free up all the memory allocated by a cursor.  Set it rLimit to 0
+** to indicate that it is at EOF.
+*/
+static void closureClearCursor(closure_cursor *pCur){
+  closureAvlDestroy(pCur->pClosure, (void(*)(closure_avl*))sqlite3_free);
+  sqlite3_free(pCur->zTableName);
+  sqlite3_free(pCur->zIdColumn);
+  sqlite3_free(pCur->zParentColumn);
+  pCur->zTableName = 0;
+  pCur->zIdColumn = 0;
+  pCur->zParentColumn = 0;
+  pCur->pCurrent = 0;
+  pCur->pClosure = 0;
+}
+
+/*
+** Close a closure cursor.
+*/
+static int closureClose(sqlite3_vtab_cursor *cur){
+  closure_cursor *pCur = (closure_cursor *)cur;
+  closureClearCursor(pCur);
+  pCur->pVtab->nCursor--;
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Advance a cursor to its next row of output
+*/
+static int closureNext(sqlite3_vtab_cursor *cur){
+  closure_cursor *pCur = (closure_cursor*)cur;
+  pCur->pCurrent = closureAvlNext(pCur->pCurrent);
+  return SQLITE_OK;
+}
+
+/*
+** Allocate and insert a node
+*/
+static int closureInsertNode(
+  closure_queue *pQueue,  /* Add new node to this queue */
+  closure_cursor *pCur,   /* The cursor into which to add the node */
+  sqlite3_int64 id,       /* The node ID */
+  int iGeneration         /* The generation number for this node */
+){
+  closure_avl *pNew = sqlite3_malloc( sizeof(*pNew) );
+  if( pNew==0 ) return SQLITE_NOMEM;
+  memset(pNew, 0, sizeof(*pNew));
+  pNew->id = id;
+  pNew->iGeneration = iGeneration;
+  closureAvlInsert(&pCur->pClosure, pNew);
+  queuePush(pQueue, pNew);
+  return SQLITE_OK;
+}
+
+/*
+** Called to "rewind" a cursor back to the beginning so that
+** it starts its output over again.  Always called at least once
+** prior to any closureColumn, closureRowid, or closureEof call.
+**
+** This routine actually computes the closure.
+**
+** See the comment at the beginning of closureBestIndex() for a 
+** description of the meaning of idxNum.  The idxStr parameter is
+** not used.
+*/
+static int closureFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  closure_cursor *pCur = (closure_cursor *)pVtabCursor;
+  closure_vtab *pVtab = pCur->pVtab;
+  sqlite3_int64 iRoot;
+  int mxGen = 999999999;
+  char *zSql;
+  sqlite3_stmt *pStmt;
+  closure_avl *pAvl;
+  int rc = SQLITE_OK;
+  const char *zTableName = pVtab->zTableName;
+  const char *zIdColumn = pVtab->zIdColumn;
+  const char *zParentColumn = pVtab->zParentColumn;
+  closure_queue sQueue;
+
+  (void)idxStr;  /* Unused parameter */
+  (void)argc;    /* Unused parameter */
+  closureClearCursor(pCur);
+  memset(&sQueue, 0, sizeof(sQueue));
+  if( (idxNum & 1)==0 ){
+    /* No root=$root in the WHERE clause.  Return an empty set */
+    return SQLITE_OK;
+  }
+  iRoot = sqlite3_value_int64(argv[0]);
+  if( (idxNum & 0x000f0)!=0 ){
+    mxGen = sqlite3_value_int(argv[(idxNum>>4)&0x0f]);
+    if( (idxNum & 0x00002)!=0 ) mxGen--;
+  }
+  if( (idxNum & 0x00f00)!=0 ){
+    zTableName = (const char*)sqlite3_value_text(argv[(idxNum>>8)&0x0f]);
+    pCur->zTableName = sqlite3_mprintf("%s", zTableName);
+  }
+  if( (idxNum & 0x0f000)!=0 ){
+    zIdColumn = (const char*)sqlite3_value_text(argv[(idxNum>>12)&0x0f]);
+    pCur->zIdColumn = sqlite3_mprintf("%s", zIdColumn);
+  }
+  if( (idxNum & 0x0f0000)!=0 ){
+    zParentColumn = (const char*)sqlite3_value_text(argv[(idxNum>>16)&0x0f]);
+    pCur->zParentColumn = sqlite3_mprintf("%s", zParentColumn);
+  }
+
+  zSql = sqlite3_mprintf(
+       "SELECT \"%w\".\"%w\" FROM \"%w\" WHERE \"%w\".\"%w\"=?1",
+       zTableName, zIdColumn, zTableName, zTableName, zParentColumn);
+  if( zSql==0 ){
+    return SQLITE_NOMEM;
+  }else{
+    rc = sqlite3_prepare_v2(pVtab->db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+    if( rc ){
+      sqlite3_free(pVtab->base.zErrMsg);
+      pVtab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pVtab->db));
+      return rc;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    rc = closureInsertNode(&sQueue, pCur, iRoot, 0);
+  }
+  while( (pAvl = queuePull(&sQueue))!=0 ){
+    if( pAvl->iGeneration>=mxGen ) continue;
+    sqlite3_bind_int64(pStmt, 1, pAvl->id);
+    while( rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
+      if( sqlite3_column_type(pStmt,0)==SQLITE_INTEGER ){
+        sqlite3_int64 iNew = sqlite3_column_int64(pStmt, 0);
+        if( closureAvlSearch(pCur->pClosure, iNew)==0 ){
+          rc = closureInsertNode(&sQueue, pCur, iNew, pAvl->iGeneration+1);
+        }
+      }
+    }
+    sqlite3_reset(pStmt);
+  }
+  sqlite3_finalize(pStmt);
+  if( rc==SQLITE_OK ){
+    pCur->pCurrent = closureAvlFirst(pCur->pClosure);
+  }
+
+  return rc;
+}
+
+/*
+** Only the word and distance columns have values.  All other columns
+** return NULL
+*/
+static int closureColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  closure_cursor *pCur = (closure_cursor*)cur;
+  switch( i ){
+    case CLOSURE_COL_ID: {
+      sqlite3_result_int64(ctx, pCur->pCurrent->id);
+      break;
+    }
+    case CLOSURE_COL_DEPTH: {
+      sqlite3_result_int(ctx, pCur->pCurrent->iGeneration);
+      break;
+    }
+    case CLOSURE_COL_ROOT: {
+      sqlite3_result_null(ctx);
+      break;
+    }
+    case CLOSURE_COL_TABLENAME: {
+      sqlite3_result_text(ctx,
+         pCur->zTableName ? pCur->zTableName : pCur->pVtab->zTableName,
+         -1, SQLITE_TRANSIENT);
+      break;
+    }
+    case CLOSURE_COL_IDCOLUMN: {
+      sqlite3_result_text(ctx,
+         pCur->zIdColumn ? pCur->zIdColumn : pCur->pVtab->zIdColumn,
+         -1, SQLITE_TRANSIENT);
+      break;
+    }
+    case CLOSURE_COL_PARENTCOLUMN: {
+      sqlite3_result_text(ctx,
+         pCur->zParentColumn ? pCur->zParentColumn : pCur->pVtab->zParentColumn,
+         -1, SQLITE_TRANSIENT);
+      break;
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The rowid.  For the closure table, this is the same as the "id" column.
+*/
+static int closureRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  closure_cursor *pCur = (closure_cursor*)cur;
+  *pRowid = pCur->pCurrent->id;
+  return SQLITE_OK;
+}
+
+/*
+** EOF indicator
+*/
+static int closureEof(sqlite3_vtab_cursor *cur){
+  closure_cursor *pCur = (closure_cursor*)cur;
+  return pCur->pCurrent==0;
+}
+
+/*
+** Search for terms of these forms:
+**
+**   (A)    root = $root
+**   (B1)   depth < $depth
+**   (B2)   depth <= $depth
+**   (B3)   depth = $depth
+**   (C)    tablename = $tablename
+**   (D)    idcolumn = $idcolumn
+**   (E)    parentcolumn = $parentcolumn
+**
+** 
+**
+**   idxNum       meaning
+**   ----------   ------------------------------------------------------
+**   0x00000001   Term of the form (A) found
+**   0x00000002   The term of bit-2 is like (B1)
+**   0x000000f0   Index in filter.argv[] of $depth.  0 if not used.
+**   0x00000f00   Index in filter.argv[] of $tablename.  0 if not used.
+**   0x0000f000   Index in filter.argv[] of $idcolumn.  0 if not used
+**   0x000f0000   Index in filter.argv[] of $parentcolumn.  0 if not used.
+**
+** There must be a term of type (A).  If there is not, then the index type
+** is 0 and the query will return an empty set.
+*/
+static int closureBestIndex(
+  sqlite3_vtab *pTab,             /* The virtual table */
+  sqlite3_index_info *pIdxInfo    /* Information about the query */
+){
+  int iPlan = 0;
+  int i;
+  int idx = 1;
+  int seenMatch = 0;
+  const struct sqlite3_index_constraint *pConstraint;
+  closure_vtab *pVtab = (closure_vtab*)pTab;
+  double rCost = 10000000.0;
+
+  pConstraint = pIdxInfo->aConstraint;
+  for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
+    if( pConstraint->iColumn==CLOSURE_COL_ROOT
+     && pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      seenMatch = 1;
+    }
+    if( pConstraint->usable==0 ) continue;
+    if( (iPlan & 1)==0 
+     && pConstraint->iColumn==CLOSURE_COL_ROOT
+     && pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ
+    ){
+      iPlan |= 1;
+      pIdxInfo->aConstraintUsage[i].argvIndex = 1;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+      rCost /= 100.0;
+    }
+    if( (iPlan & 0x0000f0)==0
+     && pConstraint->iColumn==CLOSURE_COL_DEPTH
+     && (pConstraint->op==SQLITE_INDEX_CONSTRAINT_LT
+           || pConstraint->op==SQLITE_INDEX_CONSTRAINT_LE
+           || pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ)
+    ){
+      iPlan |= idx<<4;
+      pIdxInfo->aConstraintUsage[i].argvIndex = ++idx;
+      if( pConstraint->op==SQLITE_INDEX_CONSTRAINT_LT ) iPlan |= 0x000002;
+      rCost /= 5.0;
+    }
+    if( (iPlan & 0x000f00)==0
+     && pConstraint->iColumn==CLOSURE_COL_TABLENAME
+     && pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ
+    ){
+      iPlan |= idx<<8;
+      pIdxInfo->aConstraintUsage[i].argvIndex = ++idx;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+      rCost /= 5.0;
+    }
+    if( (iPlan & 0x00f000)==0
+     && pConstraint->iColumn==CLOSURE_COL_IDCOLUMN
+     && pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ
+    ){
+      iPlan |= idx<<12;
+      pIdxInfo->aConstraintUsage[i].argvIndex = ++idx;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+    }
+    if( (iPlan & 0x0f0000)==0
+     && pConstraint->iColumn==CLOSURE_COL_PARENTCOLUMN
+     && pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ
+    ){
+      iPlan |= idx<<16;
+      pIdxInfo->aConstraintUsage[i].argvIndex = ++idx;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+    }
+  }
+  if( (pVtab->zTableName==0    && (iPlan & 0x000f00)==0)
+   || (pVtab->zIdColumn==0     && (iPlan & 0x00f000)==0)
+   || (pVtab->zParentColumn==0 && (iPlan & 0x0f0000)==0)
+  ){
+    /* All of tablename, idcolumn, and parentcolumn must be specified
+    ** in either the CREATE VIRTUAL TABLE or in the WHERE clause constraints
+    ** or else the result is an empty set. */
+    iPlan = 0;
+  }
+  pIdxInfo->idxNum = iPlan;
+  if( pIdxInfo->nOrderBy==1
+   && pIdxInfo->aOrderBy[0].iColumn==CLOSURE_COL_ID
+   && pIdxInfo->aOrderBy[0].desc==0
+  ){
+    pIdxInfo->orderByConsumed = 1;
+  }
+  if( seenMatch && (iPlan&1)==0 ) rCost *= 1e30;
+  pIdxInfo->estimatedCost = rCost;
+   
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that implements the "transitive_closure".
+*/
+static sqlite3_module closureModule = {
+  0,                      /* iVersion */
+  closureConnect,         /* xCreate */
+  closureConnect,         /* xConnect */
+  closureBestIndex,       /* xBestIndex */
+  closureDisconnect,      /* xDisconnect */
+  closureDisconnect,      /* xDestroy */
+  closureOpen,            /* xOpen - open a cursor */
+  closureClose,           /* xClose - close a cursor */
+  closureFilter,          /* xFilter - configure scan constraints */
+  closureNext,            /* xNext - advance a cursor */
+  closureEof,             /* xEof - check for end of scan */
+  closureColumn,          /* xColumn - read data */
+  closureRowid,           /* xRowid - read data */
+  0,                      /* xUpdate */
+  0,                      /* xBegin */
+  0,                      /* xSync */
+  0,                      /* xCommit */
+  0,                      /* xRollback */
+  0,                      /* xFindMethod */
+  0,                      /* xRename */
+  0,                      /* xSavepoint */
+  0,                      /* xRelease */
+  0                       /* xRollbackTo */
+};
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** Register the closure virtual table
+*/
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_closure_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  int rc = SQLITE_OK;
+  SQLITE_EXTENSION_INIT2(pApi);
+  (void)pzErrMsg;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  rc = sqlite3_create_module(db, "transitive_closure", &closureModule, 0);
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+  return rc;
+}