/* ** 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. (Sometime 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). ** ** There is an added cost of O(N) when switching between TEST and ** SMALLEST primitives. */ #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 */ u8 rsFlags; /* Various flags */ u8 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 ){ struct RowSetChunk *pNew; pNew = sqlite3DbMallocRaw(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( (p->rsFlags & ROWSET_SORTED)!=0 && rowid<=pLast->v ){ 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; while( pA && pB ){ assert( pA->pRight==0 || pA->v<=pA->pRight->v ); assert( pB->pRight==0 || pB->v<=pB->pRight->v ); if( pA->v<pB->v ){ pTail->pRight = pA; pA = pA->pRight; pTail = pTail->pRight; }else if( pB->v<pA->v ){ pTail->pRight = pB; pB = pB->pRight; pTail = pTail->pRight; }else{ pA = pA->pRight; } } if( pA ){ assert( pA->pRight==0 || pA->v<=pA->pRight->v ); pTail->pRight = pA; }else{ assert( pB==0 || pB->pRight==0 || pB->v<=pB->pRight->v ); pTail->pRight = pB; } 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 = 0; for(i=0; i<sizeof(aBucket)/sizeof(aBucket[0]); i++){ pIn = rowSetEntryMerge(pIn, 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 ){ return 0; } if( iDepth==1 ){ p = *ppList; *ppList = p->pRight; p->pLeft = p->pRight = 0; return p; } pLeft = rowSetNDeepTree(ppList, iDepth-1); p = *ppList; if( p==0 ){ return pLeft; } p->pLeft = pLeft; *ppList = p->pRight; p->pRight = rowSetNDeepTree(ppList, iDepth-1); 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; } /* ** Take all the entries on p->pEntry and on the trees in p->pForest and ** sort them all together into one big ordered list on p->pEntry. ** ** This routine should only be called once in the life of a RowSet. */ static void rowSetToList(RowSet *p){ /* This routine is called only once */ assert( p!=0 && (p->rsFlags & ROWSET_NEXT)==0 ); if( (p->rsFlags & ROWSET_SORTED)==0 ){ p->pEntry = rowSetEntrySort(p->pEntry); } /* While this module could theoretically support it, sqlite3RowSetNext() ** is never called after sqlite3RowSetText() for the same RowSet. So ** there is never a forest to deal with. Should this change, simply ** remove the assert() and the #if 0. */ assert( p->pForest==0 ); #if 0 while( p->pForest ){ struct RowSetEntry *pTree = p->pForest->pLeft; if( pTree ){ struct RowSetEntry *pHead, *pTail; rowSetTreeToList(pTree, &pHead, &pTail); p->pEntry = rowSetEntryMerge(p->pEntry, pHead); } p->pForest = p->pForest->pRight; } #endif p->rsFlags |= ROWSET_NEXT; /* Verify this routine is never called again */ } /* ** 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. */ int sqlite3RowSetNext(RowSet *p, i64 *pRowid){ assert( p!=0 ); /* Merge the forest into a single sorted list on first call */ if( (p->rsFlags & ROWSET_NEXT)==0 ) rowSetToList(p); /* Return the next entry on the list */ if( p->pEntry ){ *pRowid = p->pEntry->v; p->pEntry = p->pEntry->pRight; if( p->pEntry==0 ){ 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 entires ** on pRowSet->pEntry, then sort those entires into the forest at ** pRowSet->pForest so that they can be tested. */ int sqlite3RowSetTest(RowSet *pRowSet, u8 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 */ if( iBatch!=pRowSet->iBatch ){ p = pRowSet->pEntry; if( p ){ struct RowSetEntry **ppPrevTree = &pRowSet->pForest; if( (pRowSet->rsFlags & ROWSET_SORTED)==0 ){ 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; }