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+/*
+** 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 number, 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 */
+
+/*
+** Allocate a RowSet object. Return NULL if a memory allocation
+** error occurs.
+*/
+RowSet *sqlite3RowSetInit(sqlite3 *db){
+ RowSet *p = sqlite3DbMallocRawNN(db, sizeof(*p));
+ if( p ){
+ int N = sqlite3DbMallocSize(db, p);
+ 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(void *pArg){
+ RowSet *p = (RowSet*)pArg;
+ 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;
+}
+
+/*
+** 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 sqlite3RowSetDelete(void *pArg){
+ sqlite3RowSetClear(pArg);
+ sqlite3DbFree(((RowSet*)pArg)->db, pArg);
+}
+
+/*
+** Allocate a new RowSetEntry object that is associated with the
+** given RowSet. Return a pointer to the new and completely uninitialized
+** object.
+**
+** 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 entries 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-08-21 14:14:25 +0000