[sql] Import reference version of SQLite 3.17..

third_party/sqlite/sqlite-src-3170000/src/rowset.c

+/*
+** 2008 December 3
+**
+** 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 implements an object we call a "RowSet".
+**
+** The RowSet object is a collection of rowids.  Rowids
+** are inserted into the RowSet in an arbitrary order.  Inserts
+** can be intermixed with tests to see if a given rowid has been
+** previously inserted into the RowSet.
+**
+** After all inserts are finished, it is possible to extract the
+** elements of the RowSet in sorted order.  Once this extraction
+** process has started, no new elements may be inserted.
+**
+** Hence, the primitive operations for a RowSet are:
+**
+**    CREATE
+**    INSERT
+**    TEST
+**    SMALLEST
+**    DESTROY
+**
+** The CREATE and DESTROY primitives are the constructor and destructor,
+** obviously.  The INSERT primitive adds a new element to the RowSet.
+** TEST checks to see if an element is already in the RowSet.  SMALLEST
+** extracts the least value from the RowSet.
+**
+** The INSERT primitive might allocate additional memory.  Memory is
+** allocated in chunks so most INSERTs do no allocation.  There is an 
+** upper bound on the size of allocated memory.  No memory is freed
+** until DESTROY.
+**
+** The TEST primitive includes a "batch" number.  The TEST primitive
+** will only see elements that were inserted before the last change
+** in the batch number.  In other words, if an INSERT occurs between
+** two TESTs where the TESTs have the same batch nubmer, then the
+** value added by the INSERT will not be visible to the second TEST.
+** The initial batch number is zero, so if the very first TEST contains
+** a non-zero batch number, it will see all prior INSERTs.
+**
+** No INSERTs may occurs after a SMALLEST.  An assertion will fail if
+** that is attempted.
+**
+** The cost of an INSERT is roughly constant.  (Sometimes new memory
+** has to be allocated on an INSERT.)  The cost of a TEST with a new
+** batch number is O(NlogN) where N is the number of elements in the RowSet.
+** The cost of a TEST using the same batch number is O(logN).  The cost
+** of the first SMALLEST is O(NlogN).  Second and subsequent SMALLEST
+** primitives are constant time.  The cost of DESTROY is O(N).
+**
+** TEST and SMALLEST may not be used by the same RowSet.  This used to
+** be possible, but the feature was not used, so it was removed in order
+** to simplify the code.
+*/
+#include "sqliteInt.h"
+
+
+/*
+** Target size for allocation chunks.
+*/
+#define ROWSET_ALLOCATION_SIZE 1024
+
+/*
+** The number of rowset entries per allocation chunk.
+*/
+#define ROWSET_ENTRY_PER_CHUNK  \
+                       ((ROWSET_ALLOCATION_SIZE-8)/sizeof(struct RowSetEntry))
+
+/*
+** Each entry in a RowSet is an instance of the following object.
+**
+** This same object is reused to store a linked list of trees of RowSetEntry
+** objects.  In that alternative use, pRight points to the next entry
+** in the list, pLeft points to the tree, and v is unused.  The
+** RowSet.pForest value points to the head of this forest list.
+*/
+struct RowSetEntry {            
+  i64 v;                        /* ROWID value for this entry */
+  struct RowSetEntry *pRight;   /* Right subtree (larger entries) or list */
+  struct RowSetEntry *pLeft;    /* Left subtree (smaller entries) */
+};
+
+/*
+** RowSetEntry objects are allocated in large chunks (instances of the
+** following structure) to reduce memory allocation overhead.  The
+** chunks are kept on a linked list so that they can be deallocated
+** when the RowSet is destroyed.
+*/
+struct RowSetChunk {
+  struct RowSetChunk *pNextChunk;        /* Next chunk on list of them all */
+  struct RowSetEntry aEntry[ROWSET_ENTRY_PER_CHUNK]; /* Allocated entries */
+};
+
+/*
+** A RowSet in an instance of the following structure.
+**
+** A typedef of this structure if found in sqliteInt.h.
+*/
+struct RowSet {
+  struct RowSetChunk *pChunk;    /* List of all chunk allocations */
+  sqlite3 *db;                   /* The database connection */
+  struct RowSetEntry *pEntry;    /* List of entries using pRight */
+  struct RowSetEntry *pLast;     /* Last entry on the pEntry list */
+  struct RowSetEntry *pFresh;    /* Source of new entry objects */
+  struct RowSetEntry *pForest;   /* List of binary trees of entries */
+  u16 nFresh;                    /* Number of objects on pFresh */
+  u16 rsFlags;                   /* Various flags */
+  int iBatch;                    /* Current insert batch */
+};
+
+/*
+** Allowed values for RowSet.rsFlags
+*/
+#define ROWSET_SORTED  0x01   /* True if RowSet.pEntry is sorted */
+#define ROWSET_NEXT    0x02   /* True if sqlite3RowSetNext() has been called */
+
+/*
+** Turn bulk memory into a RowSet object.  N bytes of memory
+** are available at pSpace.  The db pointer is used as a memory context
+** for any subsequent allocations that need to occur.
+** Return a pointer to the new RowSet object.
+**
+** It must be the case that N is sufficient to make a Rowset.  If not
+** an assertion fault occurs.
+** 
+** If N is larger than the minimum, use the surplus as an initial
+** allocation of entries available to be filled.
+*/
+RowSet *sqlite3RowSetInit(sqlite3 *db, void *pSpace, unsigned int N){
+  RowSet *p;
+  assert( N >= ROUND8(sizeof(*p)) );
+  p = pSpace;
+  p->pChunk = 0;
+  p->db = db;
+  p->pEntry = 0;
+  p->pLast = 0;
+  p->pForest = 0;
+  p->pFresh = (struct RowSetEntry*)(ROUND8(sizeof(*p)) + (char*)p);
+  p->nFresh = (u16)((N - ROUND8(sizeof(*p)))/sizeof(struct RowSetEntry));
+  p->rsFlags = ROWSET_SORTED;
+  p->iBatch = 0;
+  return p;
+}
+
+/*
+** Deallocate all chunks from a RowSet.  This frees all memory that
+** the RowSet has allocated over its lifetime.  This routine is
+** the destructor for the RowSet.
+*/
+void sqlite3RowSetClear(RowSet *p){
+  struct RowSetChunk *pChunk, *pNextChunk;
+  for(pChunk=p->pChunk; pChunk; pChunk = pNextChunk){
+    pNextChunk = pChunk->pNextChunk;
+    sqlite3DbFree(p->db, pChunk);
+  }
+  p->pChunk = 0;
+  p->nFresh = 0;
+  p->pEntry = 0;
+  p->pLast = 0;
+  p->pForest = 0;
+  p->rsFlags = ROWSET_SORTED;
+}
+
+/*
+** Allocate a new RowSetEntry object that is associated with the
+** given RowSet.  Return a pointer to the new and completely uninitialized
+** objected.
+**
+** In an OOM situation, the RowSet.db->mallocFailed flag is set and this
+** routine returns NULL.
+*/
+static struct RowSetEntry *rowSetEntryAlloc(RowSet *p){
+  assert( p!=0 );
+  if( p->nFresh==0 ){  /*OPTIMIZATION-IF-FALSE*/
+    /* We could allocate a fresh RowSetEntry each time one is needed, but it
+    ** is more efficient to pull a preallocated entry from the pool */
+    struct RowSetChunk *pNew;
+    pNew = sqlite3DbMallocRawNN(p->db, sizeof(*pNew));
+    if( pNew==0 ){
+      return 0;
+    }
+    pNew->pNextChunk = p->pChunk;
+    p->pChunk = pNew;
+    p->pFresh = pNew->aEntry;
+    p->nFresh = ROWSET_ENTRY_PER_CHUNK;
+  }
+  p->nFresh--;
+  return p->pFresh++;
+}
+
+/*
+** Insert a new value into a RowSet.
+**
+** The mallocFailed flag of the database connection is set if a
+** memory allocation fails.
+*/
+void sqlite3RowSetInsert(RowSet *p, i64 rowid){
+  struct RowSetEntry *pEntry;  /* The new entry */
+  struct RowSetEntry *pLast;   /* The last prior entry */
+
+  /* This routine is never called after sqlite3RowSetNext() */
+  assert( p!=0 && (p->rsFlags & ROWSET_NEXT)==0 );
+
+  pEntry = rowSetEntryAlloc(p);
+  if( pEntry==0 ) return;
+  pEntry->v = rowid;
+  pEntry->pRight = 0;
+  pLast = p->pLast;
+  if( pLast ){
+    if( rowid<=pLast->v ){  /*OPTIMIZATION-IF-FALSE*/
+      /* Avoid unnecessary sorts by preserving the ROWSET_SORTED flags
+      ** where possible */
+      p->rsFlags &= ~ROWSET_SORTED;
+    }
+    pLast->pRight = pEntry;
+  }else{
+    p->pEntry = pEntry;
+  }
+  p->pLast = pEntry;
+}
+
+/*
+** Merge two lists of RowSetEntry objects.  Remove duplicates.
+**
+** The input lists are connected via pRight pointers and are 
+** assumed to each already be in sorted order.
+*/
+static struct RowSetEntry *rowSetEntryMerge(
+  struct RowSetEntry *pA,    /* First sorted list to be merged */
+  struct RowSetEntry *pB     /* Second sorted list to be merged */
+){
+  struct RowSetEntry head;
+  struct RowSetEntry *pTail;
+
+  pTail = &head;
+  assert( pA!=0 && pB!=0 );
+  for(;;){
+    assert( pA->pRight==0 || pA->v<=pA->pRight->v );
+    assert( pB->pRight==0 || pB->v<=pB->pRight->v );
+    if( pA->v<=pB->v ){
+      if( pA->v<pB->v ) pTail = pTail->pRight = pA;
+      pA = pA->pRight;
+      if( pA==0 ){
+        pTail->pRight = pB;
+        break;
+      }
+    }else{
+      pTail = pTail->pRight = pB;
+      pB = pB->pRight;
+      if( pB==0 ){
+        pTail->pRight = pA;
+        break;
+      }
+    }
+  }
+  return head.pRight;
+}
+
+/*
+** Sort all elements on the list of RowSetEntry objects into order of
+** increasing v.
+*/ 
+static struct RowSetEntry *rowSetEntrySort(struct RowSetEntry *pIn){
+  unsigned int i;
+  struct RowSetEntry *pNext, *aBucket[40];
+
+  memset(aBucket, 0, sizeof(aBucket));
+  while( pIn ){
+    pNext = pIn->pRight;
+    pIn->pRight = 0;
+    for(i=0; aBucket[i]; i++){
+      pIn = rowSetEntryMerge(aBucket[i], pIn);
+      aBucket[i] = 0;
+    }
+    aBucket[i] = pIn;
+    pIn = pNext;
+  }
+  pIn = aBucket[0];
+  for(i=1; i<sizeof(aBucket)/sizeof(aBucket[0]); i++){
+    if( aBucket[i]==0 ) continue;
+    pIn = pIn ? rowSetEntryMerge(pIn, aBucket[i]) : aBucket[i];
+  }
+  return pIn;
+}
+
+
+/*
+** The input, pIn, is a binary tree (or subtree) of RowSetEntry objects.
+** Convert this tree into a linked list connected by the pRight pointers
+** and return pointers to the first and last elements of the new list.
+*/
+static void rowSetTreeToList(
+  struct RowSetEntry *pIn,         /* Root of the input tree */
+  struct RowSetEntry **ppFirst,    /* Write head of the output list here */
+  struct RowSetEntry **ppLast      /* Write tail of the output list here */
+){
+  assert( pIn!=0 );
+  if( pIn->pLeft ){
+    struct RowSetEntry *p;
+    rowSetTreeToList(pIn->pLeft, ppFirst, &p);
+    p->pRight = pIn;
+  }else{
+    *ppFirst = pIn;
+  }
+  if( pIn->pRight ){
+    rowSetTreeToList(pIn->pRight, &pIn->pRight, ppLast);
+  }else{
+    *ppLast = pIn;
+  }
+  assert( (*ppLast)->pRight==0 );
+}
+
+
+/*
+** Convert a sorted list of elements (connected by pRight) into a binary
+** tree with depth of iDepth.  A depth of 1 means the tree contains a single
+** node taken from the head of *ppList.  A depth of 2 means a tree with
+** three nodes.  And so forth.
+**
+** Use as many entries from the input list as required and update the
+** *ppList to point to the unused elements of the list.  If the input
+** list contains too few elements, then construct an incomplete tree
+** and leave *ppList set to NULL.
+**
+** Return a pointer to the root of the constructed binary tree.
+*/
+static struct RowSetEntry *rowSetNDeepTree(
+  struct RowSetEntry **ppList,
+  int iDepth
+){
+  struct RowSetEntry *p;         /* Root of the new tree */
+  struct RowSetEntry *pLeft;     /* Left subtree */
+  if( *ppList==0 ){ /*OPTIMIZATION-IF-TRUE*/
+    /* Prevent unnecessary deep recursion when we run out of entries */
+    return 0; 
+  }
+  if( iDepth>1 ){   /*OPTIMIZATION-IF-TRUE*/
+    /* This branch causes a *balanced* tree to be generated.  A valid tree
+    ** is still generated without this branch, but the tree is wildly
+    ** unbalanced and inefficient. */
+    pLeft = rowSetNDeepTree(ppList, iDepth-1);
+    p = *ppList;
+    if( p==0 ){     /*OPTIMIZATION-IF-FALSE*/
+      /* It is safe to always return here, but the resulting tree
+      ** would be unbalanced */
+      return pLeft;
+    }
+    p->pLeft = pLeft;
+    *ppList = p->pRight;
+    p->pRight = rowSetNDeepTree(ppList, iDepth-1);
+  }else{
+    p = *ppList;
+    *ppList = p->pRight;
+    p->pLeft = p->pRight = 0;
+  }
+  return p;
+}
+
+/*
+** Convert a sorted list of elements into a binary tree. Make the tree
+** as deep as it needs to be in order to contain the entire list.
+*/
+static struct RowSetEntry *rowSetListToTree(struct RowSetEntry *pList){
+  int iDepth;           /* Depth of the tree so far */
+  struct RowSetEntry *p;       /* Current tree root */
+  struct RowSetEntry *pLeft;   /* Left subtree */
+
+  assert( pList!=0 );
+  p = pList;
+  pList = p->pRight;
+  p->pLeft = p->pRight = 0;
+  for(iDepth=1; pList; iDepth++){
+    pLeft = p;
+    p = pList;
+    pList = p->pRight;
+    p->pLeft = pLeft;
+    p->pRight = rowSetNDeepTree(&pList, iDepth);
+  }
+  return p;
+}
+
+/*
+** Extract the smallest element from the RowSet.
+** Write the element into *pRowid.  Return 1 on success.  Return
+** 0 if the RowSet is already empty.
+**
+** After this routine has been called, the sqlite3RowSetInsert()
+** routine may not be called again.
+**
+** This routine may not be called after sqlite3RowSetTest() has
+** been used.  Older versions of RowSet allowed that, but as the
+** capability was not used by the code generator, it was removed
+** for code economy.
+*/
+int sqlite3RowSetNext(RowSet *p, i64 *pRowid){
+  assert( p!=0 );
+  assert( p->pForest==0 );  /* Cannot be used with sqlite3RowSetText() */
+
+  /* Merge the forest into a single sorted list on first call */
+  if( (p->rsFlags & ROWSET_NEXT)==0 ){  /*OPTIMIZATION-IF-FALSE*/
+    if( (p->rsFlags & ROWSET_SORTED)==0 ){  /*OPTIMIZATION-IF-FALSE*/
+      p->pEntry = rowSetEntrySort(p->pEntry);
+    }
+    p->rsFlags |= ROWSET_SORTED|ROWSET_NEXT;
+  }
+
+  /* Return the next entry on the list */
+  if( p->pEntry ){
+    *pRowid = p->pEntry->v;
+    p->pEntry = p->pEntry->pRight;
+    if( p->pEntry==0 ){ /*OPTIMIZATION-IF-TRUE*/
+      /* Free memory immediately, rather than waiting on sqlite3_finalize() */
+      sqlite3RowSetClear(p);
+    }
+    return 1;
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Check to see if element iRowid was inserted into the rowset as
+** part of any insert batch prior to iBatch.  Return 1 or 0.
+**
+** If this is the first test of a new batch and if there exist entries
+** on pRowSet->pEntry, then sort those entries into the forest at
+** pRowSet->pForest so that they can be tested.
+*/
+int sqlite3RowSetTest(RowSet *pRowSet, int iBatch, sqlite3_int64 iRowid){
+  struct RowSetEntry *p, *pTree;
+
+  /* This routine is never called after sqlite3RowSetNext() */
+  assert( pRowSet!=0 && (pRowSet->rsFlags & ROWSET_NEXT)==0 );
+
+  /* Sort entries into the forest on the first test of a new batch.
+  ** To save unnecessary work, only do this when the batch number changes.
+  */
+  if( iBatch!=pRowSet->iBatch ){  /*OPTIMIZATION-IF-FALSE*/
+    p = pRowSet->pEntry;
+    if( p ){
+      struct RowSetEntry **ppPrevTree = &pRowSet->pForest;
+      if( (pRowSet->rsFlags & ROWSET_SORTED)==0 ){ /*OPTIMIZATION-IF-FALSE*/
+        /* Only sort the current set of entiries if they need it */
+        p = rowSetEntrySort(p);
+      }
+      for(pTree = pRowSet->pForest; pTree; pTree=pTree->pRight){
+        ppPrevTree = &pTree->pRight;
+        if( pTree->pLeft==0 ){
+          pTree->pLeft = rowSetListToTree(p);
+          break;
+        }else{
+          struct RowSetEntry *pAux, *pTail;
+          rowSetTreeToList(pTree->pLeft, &pAux, &pTail);
+          pTree->pLeft = 0;
+          p = rowSetEntryMerge(pAux, p);
+        }
+      }
+      if( pTree==0 ){
+        *ppPrevTree = pTree = rowSetEntryAlloc(pRowSet);
+        if( pTree ){
+          pTree->v = 0;
+          pTree->pRight = 0;
+          pTree->pLeft = rowSetListToTree(p);
+        }
+      }
+      pRowSet->pEntry = 0;
+      pRowSet->pLast = 0;
+      pRowSet->rsFlags |= ROWSET_SORTED;
+    }
+    pRowSet->iBatch = iBatch;
+  }
+
+  /* Test to see if the iRowid value appears anywhere in the forest.
+  ** Return 1 if it does and 0 if not.
+  */
+  for(pTree = pRowSet->pForest; pTree; pTree=pTree->pRight){
+    p = pTree->pLeft;
+    while( p ){
+      if( p->v<iRowid ){
+        p = p->pRight;
+      }else if( p->v>iRowid ){
+        p = p->pLeft;
+      }else{
+        return 1;
+      }
+    }
+  }
+  return 0;
+}