/* ** 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 module contains C code that generates VDBE code used to process ** the WHERE clause of SQL statements. ** ** $Id$ */ #include "sqliteInt.h" /* ** The query generator uses an array of instances of this structure to ** help it analyze the subexpressions of the WHERE clause. Each WHERE ** clause subexpression is separated from the others by an AND operator. */ typedef struct ExprInfo ExprInfo; struct ExprInfo { Expr *p; /* Pointer to the subexpression */ u8 indexable; /* True if this subexprssion is usable by an index */ short int idxLeft; /* p->pLeft is a column in this table number. -1 if ** p->pLeft is not the column of any table */ short int idxRight; /* p->pRight is a column in this table number. -1 if ** p->pRight is not the column of any table */ unsigned prereqLeft; /* Bitmask of tables referenced by p->pLeft */ unsigned prereqRight; /* Bitmask of tables referenced by p->pRight */ unsigned prereqAll; /* Bitmask of tables referenced by p */ }; /* ** An instance of the following structure keeps track of a mapping ** between VDBE cursor numbers and bitmasks. The VDBE cursor numbers ** are small integers contained in SrcList_item.iCursor and Expr.iTable ** fields. For any given WHERE clause, we want to track which cursors ** are being used, so we assign a single bit in a 32-bit word to track ** that cursor. Then a 32-bit integer is able to show the set of all ** cursors being used. */ typedef struct ExprMaskSet ExprMaskSet; struct ExprMaskSet { int n; /* Number of assigned cursor values */ int ix[31]; /* Cursor assigned to each bit */ }; /* ** Determine the number of elements in an array. */ #define ARRAYSIZE(X) (sizeof(X)/sizeof(X[0])) /* ** This routine is used to divide the WHERE expression into subexpressions ** separated by the AND operator. ** ** aSlot[] is an array of subexpressions structures. ** There are nSlot spaces left in this array. This routine attempts to ** split pExpr into subexpressions and fills aSlot[] with those subexpressions. ** The return value is the number of slots filled. */ static int exprSplit(int nSlot, ExprInfo *aSlot, Expr *pExpr){ int cnt = 0; if( pExpr==0 || nSlot<1 ) return 0; if( nSlot==1 || pExpr->op!=TK_AND ){ aSlot[0].p = pExpr; return 1; } if( pExpr->pLeft->op!=TK_AND ){ aSlot[0].p = pExpr->pLeft; cnt = 1 + exprSplit(nSlot-1, &aSlot[1], pExpr->pRight); }else{ cnt = exprSplit(nSlot, aSlot, pExpr->pLeft); cnt += exprSplit(nSlot-cnt, &aSlot[cnt], pExpr->pRight); } return cnt; } /* ** Initialize an expression mask set */ #define initMaskSet(P) memset(P, 0, sizeof(*P)) /* ** Return the bitmask for the given cursor. Assign a new bitmask ** if this is the first time the cursor has been seen. */ static int getMask(ExprMaskSet *pMaskSet, int iCursor){ int i; for(i=0; i<pMaskSet->n; i++){ if( pMaskSet->ix[i]==iCursor ) return 1<<i; } if( i==pMaskSet->n && i<ARRAYSIZE(pMaskSet->ix) ){ pMaskSet->n++; pMaskSet->ix[i] = iCursor; return 1<<i; } return 0; } /* ** Destroy an expression mask set */ #define freeMaskSet(P) /* NO-OP */ /* ** This routine walks (recursively) an expression tree and generates ** a bitmask indicating which tables are used in that expression ** tree. ** ** In order for this routine to work, the calling function must have ** previously invoked sqlite3ExprResolveIds() on the expression. See ** the header comment on that routine for additional information. ** The sqlite3ExprResolveIds() routines looks for column names and ** sets their opcodes to TK_COLUMN and their Expr.iTable fields to ** the VDBE cursor number of the table. */ static int exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){ unsigned int mask = 0; if( p==0 ) return 0; if( p->op==TK_COLUMN ){ mask = getMask(pMaskSet, p->iTable); if( mask==0 ) mask = -1; return mask; } if( p->pRight ){ mask = exprTableUsage(pMaskSet, p->pRight); } if( p->pLeft ){ mask |= exprTableUsage(pMaskSet, p->pLeft); } if( p->pList ){ int i; for(i=0; i<p->pList->nExpr; i++){ mask |= exprTableUsage(pMaskSet, p->pList->a[i].pExpr); } } return mask; } /* ** Return TRUE if the given operator is one of the operators that is ** allowed for an indexable WHERE clause. The allowed operators are ** "=", "<", ">", "<=", ">=", and "IN". */ static int allowedOp(int op){ assert( TK_GT==TK_LE-1 && TK_LE==TK_LT-1 && TK_LT==TK_GE-1 && TK_EQ==TK_GT-1); return op==TK_IN || (op>=TK_EQ && op<=TK_GE); } /* ** Swap two integers. */ #define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;} /* ** Return the index in the SrcList that uses cursor iCur. If iCur is ** used by the first entry in SrcList return 0. If iCur is used by ** the second entry return 1. And so forth. ** ** SrcList is the set of tables in the FROM clause in the order that ** they will be processed. The value returned here gives us an index ** of which tables will be processed first. */ static int tableOrder(SrcList *pList, int iCur){ int i; for(i=0; i<pList->nSrc; i++){ if( pList->a[i].iCursor==iCur ) return i; } return -1; } /* ** The input to this routine is an ExprInfo structure with only the ** "p" field filled in. The job of this routine is to analyze the ** subexpression and populate all the other fields of the ExprInfo ** structure. */ static void exprAnalyze(SrcList *pSrc, ExprMaskSet *pMaskSet, ExprInfo *pInfo){ Expr *pExpr = pInfo->p; pInfo->prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft); pInfo->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight); pInfo->prereqAll = exprTableUsage(pMaskSet, pExpr); pInfo->indexable = 0; pInfo->idxLeft = -1; pInfo->idxRight = -1; if( allowedOp(pExpr->op) && (pInfo->prereqRight & pInfo->prereqLeft)==0 ){ if( pExpr->pRight && pExpr->pRight->op==TK_COLUMN ){ pInfo->idxRight = pExpr->pRight->iTable; pInfo->indexable = 1; } if( pExpr->pLeft->op==TK_COLUMN ){ pInfo->idxLeft = pExpr->pLeft->iTable; pInfo->indexable = 1; } } if( pInfo->indexable ){ assert( pInfo->idxLeft!=pInfo->idxRight ); /* We want the expression to be of the form "X = expr", not "expr = X". ** So flip it over if necessary. If the expression is "X = Y", then ** we want Y to come from an earlier table than X. ** ** The collating sequence rule is to always choose the left expression. ** So if we do a flip, we also have to move the collating sequence. */ if( tableOrder(pSrc,pInfo->idxLeft)<tableOrder(pSrc,pInfo->idxRight) ){ assert( pExpr->op!=TK_IN ); SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl); SWAP(Expr*,pExpr->pRight,pExpr->pLeft); if( pExpr->op>=TK_GT ){ assert( TK_LT==TK_GT+2 ); assert( TK_GE==TK_LE+2 ); assert( TK_GT>TK_EQ ); assert( TK_GT<TK_LE ); assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE ); pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT; } SWAP(unsigned, pInfo->prereqLeft, pInfo->prereqRight); SWAP(short int, pInfo->idxLeft, pInfo->idxRight); } } } /* ** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the ** left-most table in the FROM clause of that same SELECT statement and ** the table has a cursor number of "base". ** ** This routine attempts to find an index for pTab that generates the ** correct record sequence for the given ORDER BY clause. The return value ** is a pointer to an index that does the job. NULL is returned if the ** table has no index that will generate the correct sort order. ** ** If there are two or more indices that generate the correct sort order ** and pPreferredIdx is one of those indices, then return pPreferredIdx. ** ** nEqCol is the number of columns of pPreferredIdx that are used as ** equality constraints. Any index returned must have exactly this same ** set of columns. The ORDER BY clause only matches index columns beyond the ** the first nEqCol columns. ** ** All terms of the ORDER BY clause must be either ASC or DESC. The ** *pbRev value is set to 1 if the ORDER BY clause is all DESC and it is ** set to 0 if the ORDER BY clause is all ASC. */ static Index *findSortingIndex( Parse *pParse, Table *pTab, /* The table to be sorted */ int base, /* Cursor number for pTab */ ExprList *pOrderBy, /* The ORDER BY clause */ Index *pPreferredIdx, /* Use this index, if possible and not NULL */ int nEqCol, /* Number of index columns used with == constraints */ int *pbRev /* Set to 1 if ORDER BY is DESC */ ){ int i, j; Index *pMatch; Index *pIdx; int sortOrder; sqlite3 *db = pParse->db; assert( pOrderBy!=0 ); assert( pOrderBy->nExpr>0 ); sortOrder = pOrderBy->a[0].sortOrder; for(i=0; i<pOrderBy->nExpr; i++){ Expr *p; if( pOrderBy->a[i].sortOrder!=sortOrder ){ /* Indices can only be used if all ORDER BY terms are either ** DESC or ASC. Indices cannot be used on a mixture. */ return 0; } p = pOrderBy->a[i].pExpr; if( p->op!=TK_COLUMN || p->iTable!=base ){ /* Can not use an index sort on anything that is not a column in the ** left-most table of the FROM clause */ return 0; } } /* If we get this far, it means the ORDER BY clause consists only of ** ascending columns in the left-most table of the FROM clause. Now ** check for a matching index. */ pMatch = 0; for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){ int nExpr = pOrderBy->nExpr; if( pIdx->nColumn < nEqCol || pIdx->nColumn < nExpr ) continue; for(i=j=0; i<nEqCol; i++){ CollSeq *pColl = sqlite3ExprCollSeq(pParse, pOrderBy->a[j].pExpr); if( !pColl ) pColl = db->pDfltColl; if( pPreferredIdx->aiColumn[i]!=pIdx->aiColumn[i] ) break; if( pPreferredIdx->keyInfo.aColl[i]!=pIdx->keyInfo.aColl[i] ) break; if( j<nExpr && pOrderBy->a[j].pExpr->iColumn==pIdx->aiColumn[i] && pColl==pIdx->keyInfo.aColl[i] ){ j++; } } if( i<nEqCol ) continue; for(i=0; i+j<nExpr; i++){ CollSeq *pColl = sqlite3ExprCollSeq(pParse, pOrderBy->a[i+j].pExpr); if( !pColl ) pColl = db->pDfltColl; if( pOrderBy->a[i+j].pExpr->iColumn!=pIdx->aiColumn[i+nEqCol] || pColl!=pIdx->keyInfo.aColl[i+nEqCol] ) break; } if( i+j>=nExpr ){ pMatch = pIdx; if( pIdx==pPreferredIdx ) break; } } if( pMatch && pbRev ){ *pbRev = sortOrder==SQLITE_SO_DESC; } return pMatch; } /* ** Disable a term in the WHERE clause. Except, do not disable the term ** if it controls a LEFT OUTER JOIN and it did not originate in the ON ** or USING clause of that join. ** ** Consider the term t2.z='ok' in the following queries: ** ** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok' ** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok' ** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok' ** ** The t2.z='ok' is disabled in the in (2) because it did not originate ** in the ON clause. The term is disabled in (3) because it is not part ** of a LEFT OUTER JOIN. In (1), the term is not disabled. ** ** Disabling a term causes that term to not be tested in the inner loop ** of the join. Disabling is an optimization. We would get the correct ** results if nothing were ever disabled, but joins might run a little ** slower. The trick is to disable as much as we can without disabling ** too much. If we disabled in (1), we'd get the wrong answer. ** See ticket #813. */ static void disableTerm(WhereLevel *pLevel, Expr **ppExpr){ Expr *pExpr = *ppExpr; if( pLevel->iLeftJoin==0 || ExprHasProperty(pExpr, EP_FromJoin) ){ *ppExpr = 0; } } /* ** Generate code that builds a probe for an index. Details: ** ** * Check the top nColumn entries on the stack. If any ** of those entries are NULL, jump immediately to brk, ** which is the loop exit, since no index entry will match ** if any part of the key is NULL. ** ** * Construct a probe entry from the top nColumn entries in ** the stack with affinities appropriate for index pIdx. */ static void buildIndexProbe(Vdbe *v, int nColumn, int brk, Index *pIdx){ sqlite3VdbeAddOp(v, OP_NotNull, -nColumn, sqlite3VdbeCurrentAddr(v)+3); sqlite3VdbeAddOp(v, OP_Pop, nColumn, 0); sqlite3VdbeAddOp(v, OP_Goto, 0, brk); sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0); sqlite3IndexAffinityStr(v, pIdx); } /* ** Generate code for an equality term of the WHERE clause. An equality ** term can be either X=expr or X IN (...). pTerm is the X. */ static void codeEqualityTerm( Parse *pParse, /* The parsing context */ ExprInfo *pTerm, /* The term of the WHERE clause to be coded */ int brk, /* Jump here to abandon the loop */ WhereLevel *pLevel /* When level of the FROM clause we are working on */ ){ Expr *pX = pTerm->p; if( pX->op!=TK_IN ){ assert( pX->op==TK_EQ ); sqlite3ExprCode(pParse, pX->pRight); }else{ int iTab = pX->iTable; Vdbe *v = pParse->pVdbe; sqlite3VdbeAddOp(v, OP_Rewind, iTab, brk); sqlite3VdbeAddOp(v, OP_KeyAsData, iTab, 1); pLevel->inP2 = sqlite3VdbeAddOp(v, OP_IdxColumn, iTab, 0); pLevel->inOp = OP_Next; pLevel->inP1 = iTab; } disableTerm(pLevel, &pTerm->p); } /* ** Generate the beginning of the loop used for WHERE clause processing. ** The return value is a pointer to an (opaque) structure that contains ** information needed to terminate the loop. Later, the calling routine ** should invoke sqlite3WhereEnd() with the return value of this function ** in order to complete the WHERE clause processing. ** ** If an error occurs, this routine returns NULL. ** ** The basic idea is to do a nested loop, one loop for each table in ** the FROM clause of a select. (INSERT and UPDATE statements are the ** same as a SELECT with only a single table in the FROM clause.) For ** example, if the SQL is this: ** ** SELECT * FROM t1, t2, t3 WHERE ...; ** ** Then the code generated is conceptually like the following: ** ** foreach row1 in t1 do \ Code generated ** foreach row2 in t2 do |-- by sqlite3WhereBegin() ** foreach row3 in t3 do / ** ... ** end \ Code generated ** end |-- by sqlite3WhereEnd() ** end / ** ** There are Btree cursors associated with each table. t1 uses cursor ** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor. ** And so forth. This routine generates code to open those VDBE cursors ** and sqlite3WhereEnd() generates the code to close them. ** ** If the WHERE clause is empty, the foreach loops must each scan their ** entire tables. Thus a three-way join is an O(N^3) operation. But if ** the tables have indices and there are terms in the WHERE clause that ** refer to those indices, a complete table scan can be avoided and the ** code will run much faster. Most of the work of this routine is checking ** to see if there are indices that can be used to speed up the loop. ** ** Terms of the WHERE clause are also used to limit which rows actually ** make it to the "..." in the middle of the loop. After each "foreach", ** terms of the WHERE clause that use only terms in that loop and outer ** loops are evaluated and if false a jump is made around all subsequent ** inner loops (or around the "..." if the test occurs within the inner- ** most loop) ** ** OUTER JOINS ** ** An outer join of tables t1 and t2 is conceptally coded as follows: ** ** foreach row1 in t1 do ** flag = 0 ** foreach row2 in t2 do ** start: ** ... ** flag = 1 ** end ** if flag==0 then ** move the row2 cursor to a null row ** goto start ** fi ** end ** ** ORDER BY CLAUSE PROCESSING ** ** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement, ** if there is one. If there is no ORDER BY clause or if this routine ** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL. ** ** If an index can be used so that the natural output order of the table ** scan is correct for the ORDER BY clause, then that index is used and ** *ppOrderBy is set to NULL. This is an optimization that prevents an ** unnecessary sort of the result set if an index appropriate for the ** ORDER BY clause already exists. ** ** If the where clause loops cannot be arranged to provide the correct ** output order, then the *ppOrderBy is unchanged. */ WhereInfo *sqlite3WhereBegin( Parse *pParse, /* The parser context */ SrcList *pTabList, /* A list of all tables to be scanned */ Expr *pWhere, /* The WHERE clause */ int pushKey, /* If TRUE, leave the table key on the stack */ ExprList **ppOrderBy /* An ORDER BY clause, or NULL */ ){ int i; /* Loop counter */ WhereInfo *pWInfo; /* Will become the return value of this function */ Vdbe *v = pParse->pVdbe; /* The virtual database engine */ int brk, cont = 0; /* Addresses used during code generation */ int nExpr; /* Number of subexpressions in the WHERE clause */ int loopMask; /* One bit set for each outer loop */ int haveKey = 0; /* True if KEY is on the stack */ ExprInfo *pTerm; /* A single term in the WHERE clause; ptr to aExpr[] */ ExprMaskSet maskSet; /* The expression mask set */ int iDirectEq[32]; /* Term of the form ROWID==X for the N-th table */ int iDirectLt[32]; /* Term of the form ROWID<X or ROWID<=X */ int iDirectGt[32]; /* Term of the form ROWID>X or ROWID>=X */ ExprInfo aExpr[101]; /* The WHERE clause is divided into these terms */ /* pushKey is only allowed if there is a single table (as in an INSERT or ** UPDATE statement) */ assert( pushKey==0 || pTabList->nSrc==1 ); /* Split the WHERE clause into separate subexpressions where each ** subexpression is separated by an AND operator. If the aExpr[] ** array fills up, the last entry might point to an expression which ** contains additional unfactored AND operators. */ initMaskSet(&maskSet); memset(aExpr, 0, sizeof(aExpr)); nExpr = exprSplit(ARRAYSIZE(aExpr), aExpr, pWhere); if( nExpr==ARRAYSIZE(aExpr) ){ sqlite3ErrorMsg(pParse, "WHERE clause too complex - no more " "than %d terms allowed", (int)ARRAYSIZE(aExpr)-1); return 0; } /* Allocate and initialize the WhereInfo structure that will become the ** return value. */ pWInfo = sqliteMalloc( sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel)); if( sqlite3_malloc_failed ){ /* sqliteFree(pWInfo); // Leak memory when malloc fails */ return 0; } pWInfo->pParse = pParse; pWInfo->pTabList = pTabList; pWInfo->iBreak = sqlite3VdbeMakeLabel(v); /* Special case: a WHERE clause that is constant. Evaluate the ** expression and either jump over all of the code or fall thru. */ if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstant(pWhere)) ){ sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1); pWhere = 0; } /* Analyze all of the subexpressions. */ for(pTerm=aExpr, i=0; i<nExpr; i++, pTerm++){ TriggerStack *pStack; exprAnalyze(pTabList, &maskSet, pTerm); /* If we are executing a trigger body, remove all references to ** new.* and old.* tables from the prerequisite masks. */ if( (pStack = pParse->trigStack)!=0 ){ int x; if( (x=pStack->newIdx) >= 0 ){ int mask = ~getMask(&maskSet, x); pTerm->prereqRight &= mask; pTerm->prereqLeft &= mask; pTerm->prereqAll &= mask; } if( (x=pStack->oldIdx) >= 0 ){ int mask = ~getMask(&maskSet, x); pTerm->prereqRight &= mask; pTerm->prereqLeft &= mask; pTerm->prereqAll &= mask; } } } /* Figure out what index to use (if any) for each nested loop. ** Make pWInfo->a[i].pIdx point to the index to use for the i-th nested ** loop where i==0 is the outer loop and i==pTabList->nSrc-1 is the inner ** loop. ** ** If terms exist that use the ROWID of any table, then set the ** iDirectEq[], iDirectLt[], or iDirectGt[] elements for that table ** to the index of the term containing the ROWID. We always prefer ** to use a ROWID which can directly access a table rather than an ** index which requires reading an index first to get the rowid then ** doing a second read of the actual database table. ** ** Actually, if there are more than 32 tables in the join, only the ** first 32 tables are candidates for indices. This is (again) due ** to the limit of 32 bits in an integer bitmask. */ loopMask = 0; for(i=0; i<pTabList->nSrc && i<ARRAYSIZE(iDirectEq); i++){ int j; WhereLevel *pLevel = &pWInfo->a[i]; int iCur = pTabList->a[i].iCursor; /* The cursor for this table */ int mask = getMask(&maskSet, iCur); /* Cursor mask for this table */ Table *pTab = pTabList->a[i].pTab; Index *pIdx; Index *pBestIdx = 0; int bestScore = 0; /* Check to see if there is an expression that uses only the ** ROWID field of this table. For terms of the form ROWID==expr ** set iDirectEq[i] to the index of the term. For terms of the ** form ROWID<expr or ROWID<=expr set iDirectLt[i] to the term index. ** For terms like ROWID>expr or ROWID>=expr set iDirectGt[i]. ** ** (Added:) Treat ROWID IN expr like ROWID=expr. */ pLevel->iCur = -1; iDirectEq[i] = -1; iDirectLt[i] = -1; iDirectGt[i] = -1; for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){ Expr *pX = pTerm->p; if( pTerm->idxLeft==iCur && pX->pLeft->iColumn<0 && (pTerm->prereqRight & loopMask)==pTerm->prereqRight ){ switch( pX->op ){ case TK_IN: case TK_EQ: iDirectEq[i] = j; break; case TK_LE: case TK_LT: iDirectLt[i] = j; break; case TK_GE: case TK_GT: iDirectGt[i] = j; break; } } } if( iDirectEq[i]>=0 ){ loopMask |= mask; pLevel->pIdx = 0; continue; } /* Do a search for usable indices. Leave pBestIdx pointing to ** the "best" index. pBestIdx is left set to NULL if no indices ** are usable. ** ** The best index is determined as follows. For each of the ** left-most terms that is fixed by an equality operator, add ** 8 to the score. The right-most term of the index may be ** constrained by an inequality. Add 1 if for an "x<..." constraint ** and add 2 for an "x>..." constraint. Chose the index that ** gives the best score. ** ** This scoring system is designed so that the score can later be ** used to determine how the index is used. If the score&7 is 0 ** then all constraints are equalities. If score&1 is not 0 then ** there is an inequality used as a termination key. (ex: "x<...") ** If score&2 is not 0 then there is an inequality used as the ** start key. (ex: "x>..."). A score or 4 is the special case ** of an IN operator constraint. (ex: "x IN ..."). ** ** The IN operator (as in "<expr> IN (...)") is treated the same as ** an equality comparison except that it can only be used on the ** left-most column of an index and other terms of the WHERE clause ** cannot be used in conjunction with the IN operator to help satisfy ** other columns of the index. */ for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){ int eqMask = 0; /* Index columns covered by an x=... term */ int ltMask = 0; /* Index columns covered by an x<... term */ int gtMask = 0; /* Index columns covered by an x>... term */ int inMask = 0; /* Index columns covered by an x IN .. term */ int nEq, m, score; if( pIdx->nColumn>32 ) continue; /* Ignore indices too many columns */ for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){ Expr *pX = pTerm->p; CollSeq *pColl = sqlite3ExprCollSeq(pParse, pX->pLeft); if( !pColl && pX->pRight ){ pColl = sqlite3ExprCollSeq(pParse, pX->pRight); } if( !pColl ){ pColl = pParse->db->pDfltColl; } if( pTerm->idxLeft==iCur && (pTerm->prereqRight & loopMask)==pTerm->prereqRight ){ int iColumn = pX->pLeft->iColumn; int k; char idxaff = pIdx->pTable->aCol[iColumn].affinity; for(k=0; k<pIdx->nColumn; k++){ /* If the collating sequences or affinities don't match, ** ignore this index. */ if( pColl!=pIdx->keyInfo.aColl[k] ) continue; if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue; if( pIdx->aiColumn[k]==iColumn ){ switch( pX->op ){ case TK_IN: { if( k==0 ) inMask |= 1; break; } case TK_EQ: { eqMask |= 1<<k; break; } case TK_LE: case TK_LT: { ltMask |= 1<<k; break; } case TK_GE: case TK_GT: { gtMask |= 1<<k; break; } default: { /* CANT_HAPPEN */ assert( 0 ); break; } } break; } } } } /* The following loop ends with nEq set to the number of columns ** on the left of the index with == constraints. */ for(nEq=0; nEq<pIdx->nColumn; nEq++){ m = (1<<(nEq+1))-1; if( (m & eqMask)!=m ) break; } score = nEq*8; /* Base score is 8 times number of == constraints */ m = 1<<nEq; if( m & ltMask ) score++; /* Increase score for a < constraint */ if( m & gtMask ) score+=2; /* Increase score for a > constraint */ if( score==0 && inMask ) score = 4; /* Default score for IN constraint */ if( score>bestScore ){ pBestIdx = pIdx; bestScore = score; } } pLevel->pIdx = pBestIdx; pLevel->score = bestScore; pLevel->bRev = 0; loopMask |= mask; if( pBestIdx ){ pLevel->iCur = pParse->nTab++; } } /* Check to see if the ORDER BY clause is or can be satisfied by the ** use of an index on the first table. */ if( ppOrderBy && *ppOrderBy && pTabList->nSrc>0 ){ Index *pSortIdx; Index *pIdx; Table *pTab; int bRev = 0; pTab = pTabList->a[0].pTab; pIdx = pWInfo->a[0].pIdx; if( pIdx && pWInfo->a[0].score==4 ){ /* If there is already an IN index on the left-most table, ** it will not give the correct sort order. ** So, pretend that no suitable index is found. */ pSortIdx = 0; }else if( iDirectEq[0]>=0 || iDirectLt[0]>=0 || iDirectGt[0]>=0 ){ /* If the left-most column is accessed using its ROWID, then do ** not try to sort by index. */ pSortIdx = 0; }else{ int nEqCol = (pWInfo->a[0].score+4)/8; pSortIdx = findSortingIndex(pParse, pTab, pTabList->a[0].iCursor, *ppOrderBy, pIdx, nEqCol, &bRev); } if( pSortIdx && (pIdx==0 || pIdx==pSortIdx) ){ if( pIdx==0 ){ pWInfo->a[0].pIdx = pSortIdx; pWInfo->a[0].iCur = pParse->nTab++; } pWInfo->a[0].bRev = bRev; *ppOrderBy = 0; } } /* Open all tables in the pTabList and all indices used by those tables. */ sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */ for(i=0; i<pTabList->nSrc; i++){ Table *pTab; Index *pIx; pTab = pTabList->a[i].pTab; if( pTab->isTransient || pTab->pSelect ) continue; sqlite3OpenTableForReading(v, pTabList->a[i].iCursor, pTab); sqlite3CodeVerifySchema(pParse, pTab->iDb); if( (pIx = pWInfo->a[i].pIdx)!=0 ){ sqlite3VdbeAddOp(v, OP_Integer, pIx->iDb, 0); sqlite3VdbeOp3(v, OP_OpenRead, pWInfo->a[i].iCur, pIx->tnum, (char*)&pIx->keyInfo, P3_KEYINFO); } } /* Generate the code to do the search */ loopMask = 0; for(i=0; i<pTabList->nSrc; i++){ int j, k; int iCur = pTabList->a[i].iCursor; Index *pIdx; WhereLevel *pLevel = &pWInfo->a[i]; /* If this is the right table of a LEFT OUTER JOIN, allocate and ** initialize a memory cell that records if this table matches any ** row of the left table of the join. */ if( i>0 && (pTabList->a[i-1].jointype & JT_LEFT)!=0 ){ if( !pParse->nMem ) pParse->nMem++; pLevel->iLeftJoin = pParse->nMem++; sqlite3VdbeAddOp(v, OP_String8, 0, 0); sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1); VdbeComment((v, "# init LEFT JOIN no-match flag")); } pIdx = pLevel->pIdx; pLevel->inOp = OP_Noop; if( i<ARRAYSIZE(iDirectEq) && (k = iDirectEq[i])>=0 ){ /* Case 1: We can directly reference a single row using an ** equality comparison against the ROWID field. Or ** we reference multiple rows using a "rowid IN (...)" ** construct. */ assert( k<nExpr ); pTerm = &aExpr[k]; assert( pTerm->p!=0 ); assert( pTerm->idxLeft==iCur ); brk = pLevel->brk = sqlite3VdbeMakeLabel(v); codeEqualityTerm(pParse, pTerm, brk, pLevel); cont = pLevel->cont = sqlite3VdbeMakeLabel(v); sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk); haveKey = 0; sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk); pLevel->op = OP_Noop; }else if( pIdx!=0 && pLevel->score>0 && pLevel->score%4==0 ){ /* Case 2: There is an index and all terms of the WHERE clause that ** refer to the index use the "==" or "IN" operators. */ int start; int nColumn = (pLevel->score+4)/8; brk = pLevel->brk = sqlite3VdbeMakeLabel(v); /* For each column of the index, find the term of the WHERE clause that ** constraints that column. If the WHERE clause term is X=expr, then ** evaluation expr and leave the result on the stack */ for(j=0; j<nColumn; j++){ for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){ Expr *pX = pTerm->p; if( pX==0 ) continue; if( pTerm->idxLeft==iCur && (pTerm->prereqRight & loopMask)==pTerm->prereqRight && pX->pLeft->iColumn==pIdx->aiColumn[j] ){ char idxaff = pIdx->pTable->aCol[pX->pLeft->iColumn].affinity; if( sqlite3IndexAffinityOk(pX, idxaff) ){ codeEqualityTerm(pParse, pTerm, brk, pLevel); break; } } } } pLevel->iMem = pParse->nMem++; cont = pLevel->cont = sqlite3VdbeMakeLabel(v); buildIndexProbe(v, nColumn, brk, pIdx); sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0); /* Generate code (1) to move to the first matching element of the table. ** Then generate code (2) that jumps to "brk" after the cursor is past ** the last matching element of the table. The code (1) is executed ** once to initialize the search, the code (2) is executed before each ** iteration of the scan to see if the scan has finished. */ if( pLevel->bRev ){ /* Scan in reverse order */ sqlite3VdbeAddOp(v, OP_MoveLe, pLevel->iCur, brk); start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); sqlite3VdbeAddOp(v, OP_IdxLT, pLevel->iCur, brk); pLevel->op = OP_Prev; }else{ /* Scan in the forward order */ sqlite3VdbeAddOp(v, OP_MoveGe, pLevel->iCur, brk); start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); sqlite3VdbeOp3(v, OP_IdxGE, pLevel->iCur, brk, "+", P3_STATIC); pLevel->op = OP_Next; } sqlite3VdbeAddOp(v, OP_RowKey, pLevel->iCur, 0); sqlite3VdbeAddOp(v, OP_IdxIsNull, nColumn, cont); sqlite3VdbeAddOp(v, OP_IdxRecno, pLevel->iCur, 0); if( i==pTabList->nSrc-1 && pushKey ){ haveKey = 1; }else{ sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); haveKey = 0; } pLevel->p1 = pLevel->iCur; pLevel->p2 = start; }else if( i<ARRAYSIZE(iDirectLt) && (iDirectLt[i]>=0 || iDirectGt[i]>=0) ){ /* Case 3: We have an inequality comparison against the ROWID field. */ int testOp = OP_Noop; int start; brk = pLevel->brk = sqlite3VdbeMakeLabel(v); cont = pLevel->cont = sqlite3VdbeMakeLabel(v); if( iDirectGt[i]>=0 ){ Expr *pX; k = iDirectGt[i]; assert( k<nExpr ); pTerm = &aExpr[k]; pX = pTerm->p; assert( pX!=0 ); assert( pTerm->idxLeft==iCur ); sqlite3ExprCode(pParse, pX->pRight); sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LT || pX->op==TK_GT, brk); sqlite3VdbeAddOp(v, OP_MoveGe, iCur, brk); disableTerm(pLevel, &pTerm->p); }else{ sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk); } if( iDirectLt[i]>=0 ){ Expr *pX; k = iDirectLt[i]; assert( k<nExpr ); pTerm = &aExpr[k]; pX = pTerm->p; assert( pX!=0 ); assert( pTerm->idxLeft==iCur ); sqlite3ExprCode(pParse, pX->pRight); pLevel->iMem = pParse->nMem++; sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); if( pX->op==TK_LT || pX->op==TK_GT ){ testOp = OP_Ge; }else{ testOp = OP_Gt; } disableTerm(pLevel, &pTerm->p); } start = sqlite3VdbeCurrentAddr(v); pLevel->op = OP_Next; pLevel->p1 = iCur; pLevel->p2 = start; if( testOp!=OP_Noop ){ sqlite3VdbeAddOp(v, OP_Recno, iCur, 0); sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); sqlite3VdbeAddOp(v, testOp, 0, brk); } haveKey = 0; }else if( pIdx==0 ){ /* Case 4: There is no usable index. We must do a complete ** scan of the entire database table. */ int start; brk = pLevel->brk = sqlite3VdbeMakeLabel(v); cont = pLevel->cont = sqlite3VdbeMakeLabel(v); sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk); start = sqlite3VdbeCurrentAddr(v); pLevel->op = OP_Next; pLevel->p1 = iCur; pLevel->p2 = start; haveKey = 0; }else{ /* Case 5: The WHERE clause term that refers to the right-most ** column of the index is an inequality. For example, if ** the index is on (x,y,z) and the WHERE clause is of the ** form "x=5 AND y<10" then this case is used. Only the ** right-most column can be an inequality - the rest must ** use the "==" operator. ** ** This case is also used when there are no WHERE clause ** constraints but an index is selected anyway, in order ** to force the output order to conform to an ORDER BY. */ int score = pLevel->score; int nEqColumn = score/8; int start; int leFlag=0, geFlag=0; int testOp; /* Evaluate the equality constraints */ for(j=0; j<nEqColumn; j++){ int iIdxCol = pIdx->aiColumn[j]; for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){ Expr *pX = pTerm->p; if( pX==0 ) continue; if( pTerm->idxLeft==iCur && pX->op==TK_EQ && (pTerm->prereqRight & loopMask)==pTerm->prereqRight && pX->pLeft->iColumn==iIdxCol ){ sqlite3ExprCode(pParse, pX->pRight); disableTerm(pLevel, &pTerm->p); break; } } } /* Duplicate the equality term values because they will all be ** used twice: once to make the termination key and once to make the ** start key. */ for(j=0; j<nEqColumn; j++){ sqlite3VdbeAddOp(v, OP_Dup, nEqColumn-1, 0); } /* Labels for the beginning and end of the loop */ cont = pLevel->cont = sqlite3VdbeMakeLabel(v); brk = pLevel->brk = sqlite3VdbeMakeLabel(v); /* Generate the termination key. This is the key value that ** will end the search. There is no termination key if there ** are no equality terms and no "X<..." term. ** ** 2002-Dec-04: On a reverse-order scan, the so-called "termination" ** key computed here really ends up being the start key. */ if( (score & 1)!=0 ){ for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){ Expr *pX = pTerm->p; if( pX==0 ) continue; if( pTerm->idxLeft==iCur && (pX->op==TK_LT || pX->op==TK_LE) && (pTerm->prereqRight & loopMask)==pTerm->prereqRight && pX->pLeft->iColumn==pIdx->aiColumn[j] ){ sqlite3ExprCode(pParse, pX->pRight); leFlag = pX->op==TK_LE; disableTerm(pLevel, &pTerm->p); break; } } testOp = OP_IdxGE; }else{ testOp = nEqColumn>0 ? OP_IdxGE : OP_Noop; leFlag = 1; } if( testOp!=OP_Noop ){ int nCol = nEqColumn + (score & 1); pLevel->iMem = pParse->nMem++; buildIndexProbe(v, nCol, brk, pIdx); if( pLevel->bRev ){ int op = leFlag ? OP_MoveLe : OP_MoveLt; sqlite3VdbeAddOp(v, op, pLevel->iCur, brk); }else{ sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); } }else if( pLevel->bRev ){ sqlite3VdbeAddOp(v, OP_Last, pLevel->iCur, brk); } /* Generate the start key. This is the key that defines the lower ** bound on the search. There is no start key if there are no ** equality terms and if there is no "X>..." term. In ** that case, generate a "Rewind" instruction in place of the ** start key search. ** ** 2002-Dec-04: In the case of a reverse-order search, the so-called ** "start" key really ends up being used as the termination key. */ if( (score & 2)!=0 ){ for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){ Expr *pX = pTerm->p; if( pX==0 ) continue; if( pTerm->idxLeft==iCur && (pX->op==TK_GT || pX->op==TK_GE) && (pTerm->prereqRight & loopMask)==pTerm->prereqRight && pX->pLeft->iColumn==pIdx->aiColumn[j] ){ sqlite3ExprCode(pParse, pX->pRight); geFlag = pX->op==TK_GE; disableTerm(pLevel, &pTerm->p); break; } } }else{ geFlag = 1; } if( nEqColumn>0 || (score&2)!=0 ){ int nCol = nEqColumn + ((score&2)!=0); buildIndexProbe(v, nCol, brk, pIdx); if( pLevel->bRev ){ pLevel->iMem = pParse->nMem++; sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); testOp = OP_IdxLT; }else{ int op = geFlag ? OP_MoveGe : OP_MoveGt; sqlite3VdbeAddOp(v, op, pLevel->iCur, brk); } }else if( pLevel->bRev ){ testOp = OP_Noop; }else{ sqlite3VdbeAddOp(v, OP_Rewind, pLevel->iCur, brk); } /* Generate the the top of the loop. If there is a termination ** key we have to test for that key and abort at the top of the ** loop. */ start = sqlite3VdbeCurrentAddr(v); if( testOp!=OP_Noop ){ sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); sqlite3VdbeAddOp(v, testOp, pLevel->iCur, brk); if( (leFlag && !pLevel->bRev) || (!geFlag && pLevel->bRev) ){ sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC); } } sqlite3VdbeAddOp(v, OP_RowKey, pLevel->iCur, 0); sqlite3VdbeAddOp(v, OP_IdxIsNull, nEqColumn + (score & 1), cont); sqlite3VdbeAddOp(v, OP_IdxRecno, pLevel->iCur, 0); if( i==pTabList->nSrc-1 && pushKey ){ haveKey = 1; }else{ sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); haveKey = 0; } /* Record the instruction used to terminate the loop. */ pLevel->op = pLevel->bRev ? OP_Prev : OP_Next; pLevel->p1 = pLevel->iCur; pLevel->p2 = start; } loopMask |= getMask(&maskSet, iCur); /* Insert code to test every subexpression that can be completely ** computed using the current set of tables. */ for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){ if( pTerm->p==0 ) continue; if( (pTerm->prereqAll & loopMask)!=pTerm->prereqAll ) continue; if( pLevel->iLeftJoin && !ExprHasProperty(pTerm->p,EP_FromJoin) ){ continue; } if( haveKey ){ haveKey = 0; sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); } sqlite3ExprIfFalse(pParse, pTerm->p, cont, 1); pTerm->p = 0; } brk = cont; /* For a LEFT OUTER JOIN, generate code that will record the fact that ** at least one row of the right table has matched the left table. */ if( pLevel->iLeftJoin ){ pLevel->top = sqlite3VdbeCurrentAddr(v); sqlite3VdbeAddOp(v, OP_Integer, 1, 0); sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1); VdbeComment((v, "# record LEFT JOIN hit")); for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){ if( pTerm->p==0 ) continue; if( (pTerm->prereqAll & loopMask)!=pTerm->prereqAll ) continue; if( haveKey ){ /* Cannot happen. "haveKey" can only be true if pushKey is true ** an pushKey can only be true for DELETE and UPDATE and there are ** no outer joins with DELETE and UPDATE. */ haveKey = 0; sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); } sqlite3ExprIfFalse(pParse, pTerm->p, cont, 1); pTerm->p = 0; } } } pWInfo->iContinue = cont; if( pushKey && !haveKey ){ sqlite3VdbeAddOp(v, OP_Recno, pTabList->a[0].iCursor, 0); } freeMaskSet(&maskSet); return pWInfo; } /* ** Generate the end of the WHERE loop. See comments on ** sqlite3WhereBegin() for additional information. */ void sqlite3WhereEnd(WhereInfo *pWInfo){ Vdbe *v = pWInfo->pParse->pVdbe; int i; WhereLevel *pLevel; SrcList *pTabList = pWInfo->pTabList; for(i=pTabList->nSrc-1; i>=0; i--){ pLevel = &pWInfo->a[i]; sqlite3VdbeResolveLabel(v, pLevel->cont); if( pLevel->op!=OP_Noop ){ sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2); } sqlite3VdbeResolveLabel(v, pLevel->brk); if( pLevel->inOp!=OP_Noop ){ sqlite3VdbeAddOp(v, pLevel->inOp, pLevel->inP1, pLevel->inP2); } if( pLevel->iLeftJoin ){ int addr; addr = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iLeftJoin, 0); sqlite3VdbeAddOp(v, OP_NotNull, 1, addr+4 + (pLevel->iCur>=0)); sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0); if( pLevel->iCur>=0 ){ sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iCur, 0); } sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top); } } sqlite3VdbeResolveLabel(v, pWInfo->iBreak); for(i=0; i<pTabList->nSrc; i++){ Table *pTab = pTabList->a[i].pTab; assert( pTab!=0 ); if( pTab->isTransient || pTab->pSelect ) continue; pLevel = &pWInfo->a[i]; sqlite3VdbeAddOp(v, OP_Close, pTabList->a[i].iCursor, 0); if( pLevel->pIdx!=0 ){ sqlite3VdbeAddOp(v, OP_Close, pLevel->iCur, 0); } } sqliteFree(pWInfo); return; }