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Diffstat (limited to 'kopete/plugins/statistics/sqlite/where.c')
| -rw-r--r-- | kopete/plugins/statistics/sqlite/where.c | 1210 |
1 files changed, 1210 insertions, 0 deletions
diff --git a/kopete/plugins/statistics/sqlite/where.c b/kopete/plugins/statistics/sqlite/where.c new file mode 100644 index 00000000..08c174e9 --- /dev/null +++ b/kopete/plugins/statistics/sqlite/where.c @@ -0,0 +1,1210 @@ +/* +** 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; +} |