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Diffstat (limited to 'src/sqlite/where.c')
| -rw-r--r-- | src/sqlite/where.c | 1439 |
1 files changed, 1439 insertions, 0 deletions
diff --git a/src/sqlite/where.c b/src/sqlite/where.c new file mode 100644 index 0000000..a6cf2e7 --- /dev/null +++ b/src/sqlite/where.c @@ -0,0 +1,1439 @@ +/* +** 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. This module is reponsible for +** generating the code that loops through a table looking for applicable +** rows. Indices are selected and used to speed the search when doing +** so is applicable. Because this module is responsible for selecting +** indices, you might also think of this module as the "query optimizer". +** +** $Id: where.c,v 1.1.1.1 2006/02/03 20:35:19 hoganrobert Exp $ +*/ +#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. +** +** The idxLeft and idxRight fields are the VDBE cursor numbers for the +** table that contains the column that appears on the left-hand and +** right-hand side of ExprInfo.p. If either side of ExprInfo.p is +** something other than a simple column reference, then idxLeft or +** idxRight are -1. +** +** It is the VDBE cursor number is the value stored in Expr.iTable +** when Expr.op==TK_COLUMN and the value stored in SrcList.a[].iCursor. +** +** prereqLeft, prereqRight, and prereqAll record sets of cursor numbers, +** but they do so indirectly. A single ExprMaskSet structure translates +** cursor number into bits and the translated bit is stored in the prereq +** fields. The translation is used in order to maximize the number of +** bits that will fit in a Bitmask. The VDBE cursor numbers might be +** spread out over the non-negative integers. For example, the cursor +** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The ExprMaskSet +** translates these sparse cursor numbers into consecutive integers +** beginning with 0 in order to make the best possible use of the available +** bits in the Bitmask. So, in the example above, the cursor numbers +** would be mapped into integers 0 through 7. +** +** prereqLeft tells us every VDBE cursor that is referenced on the +** left-hand side of ExprInfo.p. prereqRight does the same for the +** right-hand side of the expression. The following identity always +** holds: +** +** prereqAll = prereqLeft | prereqRight +** +** The ExprInfo.indexable field is true if the ExprInfo.p expression +** is of a form that might control an index. Indexable expressions +** look like this: +** +** <column> <op> <expr> +** +** Where <column> is a simple column name and <op> is on of the operators +** that allowedOp() recognizes. +*/ +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 */ + Bitmask prereqLeft; /* Bitmask of tables referenced by p->pLeft */ + Bitmask prereqRight; /* Bitmask of tables referenced by p->pRight */ + Bitmask prereqAll; /* Bitmask of tables referenced by p */ +}; + +/* +** An instance of the following structure keeps track of a mapping +** between VDBE cursor numbers and bits of the bitmasks in ExprInfo. +** +** The VDBE cursor numbers are small integers contained in +** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE +** clause, the cursor numbers might not begin with 0 and they might +** contain gaps in the numbering sequence. But we want to make maximum +** use of the bits in our bitmasks. This structure provides a mapping +** from the sparse cursor numbers into consecutive integers beginning +** with 0. +** +** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask +** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A. +** +** For example, if the WHERE clause expression used these VDBE +** cursors: 4, 5, 8, 29, 57, 73. Then the ExprMaskSet structure +** would map those cursor numbers into bits 0 through 5. +** +** Note that the mapping is not necessarily ordered. In the example +** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0, +** 57->5, 73->4. Or one of 719 other combinations might be used. It +** does not really matter. What is important is that sparse cursor +** numbers all get mapped into bit numbers that begin with 0 and contain +** no gaps. +*/ +typedef struct ExprMaskSet ExprMaskSet; +struct ExprMaskSet { + int n; /* Number of assigned cursor values */ + int ix[sizeof(Bitmask)*8]; /* Cursor assigned to each bit */ +}; + +/* +** Determine the number of elements in an array. +*/ +#define ARRAYSIZE(X) (sizeof(X)/sizeof(X[0])) + +/* +** This routine identifies subexpressions in the WHERE clause where +** each subexpression is separate by the AND operator. aSlot is +** filled with pointers to the subexpressions. For example: +** +** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22) +** \________/ \_______________/ \________________/ +** slot[0] slot[1] slot[2] +** +** The original WHERE clause in pExpr is unaltered. All this routine +** does is make aSlot[] entries point to substructure within pExpr. +** +** aSlot[] is an array of subexpressions structures. There are nSlot +** spaces left in this array. This routine finds as many AND-separated +** subexpressions as it can and puts pointers to those subexpressions +** into aSlot[] entries. 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 number. Return 0 if +** iCursor is not in the set. +*/ +static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){ + int i; + for(i=0; i<pMaskSet->n; i++){ + if( pMaskSet->ix[i]==iCursor ){ + return ((Bitmask)1)<<i; + } + } + return 0; +} + +/* +** Create a new mask for cursor iCursor. +*/ +static void createMask(ExprMaskSet *pMaskSet, int iCursor){ + if( pMaskSet->n<ARRAYSIZE(pMaskSet->ix) ){ + pMaskSet->ix[pMaskSet->n++] = iCursor; + } +} + +/* +** 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 sqlite3ExprResolveNames() on the expression. See +** the header comment on that routine for additional information. +** The sqlite3ExprResolveNames() 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 Bitmask exprListTableUsage(ExprMaskSet *, ExprList *); +static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){ + Bitmask mask = 0; + if( p==0 ) return 0; + if( p->op==TK_COLUMN ){ + mask = getMask(pMaskSet, p->iTable); + return mask; + } + mask = exprTableUsage(pMaskSet, p->pRight); + mask |= exprTableUsage(pMaskSet, p->pLeft); + mask |= exprListTableUsage(pMaskSet, p->pList); + if( p->pSelect ){ + Select *pS = p->pSelect; + mask |= exprListTableUsage(pMaskSet, pS->pEList); + mask |= exprListTableUsage(pMaskSet, pS->pGroupBy); + mask |= exprListTableUsage(pMaskSet, pS->pOrderBy); + mask |= exprTableUsage(pMaskSet, pS->pWhere); + mask |= exprTableUsage(pMaskSet, pS->pHaving); + } + return mask; +} +static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){ + int i; + Bitmask mask = 0; + if( pList ){ + for(i=0; i<pList->nExpr; i++){ + mask |= exprTableUsage(pMaskSet, 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 term. 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 objects of type T. +*/ +#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; + struct SrcList_item *pItem; + for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){ + if( pItem->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); + } + } + +} + +/* +** This routine decides if pIdx can be used to satisfy the ORDER BY +** clause. If it can, it returns 1. If pIdx cannot satisfy the +** ORDER BY clause, this routine returns 0. +** +** 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". pIdx is an index on pTab. +** +** nEqCol is the number of columns of pIdx that are used as equality +** constraints. Any of these columns may be missing from the ORDER BY +** clause and the match can still be a success. +** +** If the index is UNIQUE, then the ORDER BY clause is allowed to have +** additional terms past the end of the index and the match will still +** be a success. +** +** All terms of the ORDER BY that match against the index must be either +** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE +** index do not need to satisfy this constraint.) 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 int isSortingIndex( + Parse *pParse, /* Parsing context */ + Index *pIdx, /* The index we are testing */ + Table *pTab, /* The table to be sorted */ + int base, /* Cursor number for pTab */ + ExprList *pOrderBy, /* The ORDER BY clause */ + int nEqCol, /* Number of index columns with == constraints */ + int *pbRev /* Set to 1 if ORDER BY is DESC */ +){ + int i, j; /* Loop counters */ + int sortOrder; /* Which direction we are sorting */ + int nTerm; /* Number of ORDER BY terms */ + struct ExprList_item *pTerm; /* A term of the ORDER BY clause */ + sqlite3 *db = pParse->db; + + assert( pOrderBy!=0 ); + nTerm = pOrderBy->nExpr; + assert( nTerm>0 ); + + /* Match terms of the ORDER BY clause against columns of + ** the index. + */ + for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<pIdx->nColumn; i++){ + Expr *pExpr; /* The expression of the ORDER BY pTerm */ + CollSeq *pColl; /* The collating sequence of pExpr */ + + pExpr = pTerm->pExpr; + if( pExpr->op!=TK_COLUMN || pExpr->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; + } + pColl = sqlite3ExprCollSeq(pParse, pExpr); + if( !pColl ) pColl = db->pDfltColl; + if( pExpr->iColumn!=pIdx->aiColumn[i] || pColl!=pIdx->keyInfo.aColl[i] ){ + /* Term j of the ORDER BY clause does not match column i of the index */ + if( i<nEqCol ){ + /* If an index column that is constrained by == fails to match an + ** ORDER BY term, that is OK. Just ignore that column of the index + */ + continue; + }else{ + /* If an index column fails to match and is not constrained by == + ** then the index cannot satisfy the ORDER BY constraint. + */ + return 0; + } + } + if( i>nEqCol ){ + if( pTerm->sortOrder!=sortOrder ){ + /* Indices can only be used if all ORDER BY terms past the + ** equality constraints are all either DESC or ASC. */ + return 0; + } + }else{ + sortOrder = pTerm->sortOrder; + } + j++; + pTerm++; + } + + /* The index can be used for sorting if all terms of the ORDER BY clause + ** or covered or if we ran out of index columns and the it is a UNIQUE + ** index. + */ + if( j>=nTerm || (i>=pIdx->nColumn && pIdx->onError!=OE_None) ){ + *pbRev = sortOrder==SQLITE_SO_DESC; + return 1; + } + return 0; +} + +/* +** Check table to see if the ORDER BY clause in pOrderBy can be satisfied +** by sorting in order of ROWID. Return true if so and set *pbRev to be +** true for reverse ROWID and false for forward ROWID order. +*/ +static int sortableByRowid( + int base, /* Cursor number for table to be sorted */ + ExprList *pOrderBy, /* The ORDER BY clause */ + int *pbRev /* Set to 1 if ORDER BY is DESC */ +){ + Expr *p; + + assert( pOrderBy!=0 ); + assert( pOrderBy->nExpr>0 ); + p = pOrderBy->a[0].pExpr; + if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1 ){ + *pbRev = pOrderBy->a[0].sortOrder; + return 1; + } + return 0; +} + + +/* +** 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 originates +** 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); +#ifndef SQLITE_OMIT_SUBQUERY + }else{ + int iTab; + Vdbe *v = pParse->pVdbe; + + sqlite3CodeSubselect(pParse, pX); + iTab = pX->iTable; + sqlite3VdbeAddOp(v, OP_Rewind, iTab, brk); + VdbeComment((v, "# %.*s", pX->span.n, pX->span.z)); + pLevel->inP2 = sqlite3VdbeAddOp(v, OP_Column, iTab, 0); + pLevel->inOp = OP_Next; + pLevel->inP1 = iTab; +#endif + } + disableTerm(pLevel, &pTerm->p); +} + +/* +** The number of bits in a Bitmask +*/ +#define BMS (sizeof(Bitmask)*8-1) + + +/* +** 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. +** +** The code that sqlite3WhereBegin() generates leaves the cursors named +** in pTabList pointing at their appropriate entries. The [...] code +** can use OP_Column and OP_Rowid opcodes on these cursors to extract +** data from the various tables of the loop. +** +** 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 */ + 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 */ + Bitmask loopMask; /* One bit set for each outer loop */ + ExprInfo *pTerm; /* A single term in the WHERE clause; ptr to aExpr[] */ + ExprMaskSet maskSet; /* The expression mask set */ + int iDirectEq[BMS]; /* Term of the form ROWID==X for the N-th table */ + int iDirectLt[BMS]; /* Term of the form ROWID<X or ROWID<=X */ + int iDirectGt[BMS]; /* Term of the form ROWID>X or ROWID>=X */ + ExprInfo aExpr[101]; /* The WHERE clause is divided into these terms */ + struct SrcList_item *pTabItem; /* A single entry from pTabList */ + WhereLevel *pLevel; /* A single level in the pWInfo list */ + + /* The number of terms in the FROM clause is limited by the number of + ** bits in a Bitmask + */ + if( pTabList->nSrc>sizeof(Bitmask)*8 ){ + sqlite3ErrorMsg(pParse, "at most %d tables in a join", + sizeof(Bitmask)*8); + return 0; + } + + /* 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); /* Avoid leaking 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(i=0; i<pTabList->nSrc; i++){ + createMask(&maskSet, pTabList->a[i].iCursor); + } + for(pTerm=aExpr, i=0; i<nExpr; i++, pTerm++){ + exprAnalyze(pTabList, &maskSet, pTerm); + } + + /* 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; + pTabItem = pTabList->a; + pLevel = pWInfo->a; + for(i=0; i<pTabList->nSrc && i<ARRAYSIZE(iDirectEq); i++,pTabItem++,pLevel++){ + int j; + int iCur = pTabItem->iCursor; /* The cursor for this table */ + Bitmask mask = getMask(&maskSet, iCur); /* Cursor mask for this table */ + Table *pTab = pTabItem->pTab; + Index *pIdx; + Index *pBestIdx = 0; + int bestScore = 0; + int bestRev = 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->iIdxCur = -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 we found a term that tests ROWID with == or IN, that term + ** will be used to locate the rows in the database table. There + ** is not need to continue into the code below that looks for + ** an index. We will always use the ROWID over an index. + */ + 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 the one with the highest score. The score + ** for the index is determined as follows. For each of the + ** left-most terms that is fixed by an equality operator, add + ** 32 to the score. The right-most term of the index may be + ** constrained by an inequality. Add 4 if for an "x<..." constraint + ** and add 8 for an "x>..." constraint. If both constraints + ** are present, add 12. + ** + ** If the left-most term of the index uses an IN operator + ** (ex: "x IN (...)") then add 16 to the score. + ** + ** If an index can be used for sorting, add 2 to the score. + ** If an index contains all the terms of a table that are ever + ** used by any expression in the SQL statement, then add 1 to + ** the score. + ** + ** This scoring system is designed so that the score can later be + ** used to determine how the index is used. If the score&0x1c is 0 + ** then all constraints are equalities. If score&0x4 is not 0 then + ** there is an inequality used as a termination key. (ex: "x<...") + ** If score&0x8 is not 0 then there is an inequality used as the + ** start key. (ex: "x>..."). A score or 0x10 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){ + Bitmask eqMask = 0; /* Index columns covered by an x=... term */ + Bitmask ltMask = 0; /* Index columns covered by an x<... term */ + Bitmask gtMask = 0; /* Index columns covered by an x>... term */ + Bitmask inMask = 0; /* Index columns covered by an x IN .. term */ + Bitmask m; + int nEq, score, bRev = 0; + + if( pIdx->nColumn>sizeof(eqMask)*8 ){ + continue; /* Ignore indices with too many columns to analyze */ + } + 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 = iColumn>=0 ? pIdx->pTable->aCol[iColumn].affinity : 0; + 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 |= ((Bitmask)1)<<k; + break; + } + case TK_LE: + case TK_LT: { + ltMask |= ((Bitmask)1)<<k; + break; + } + case TK_GE: + case TK_GT: { + gtMask |= ((Bitmask)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 = (((Bitmask)1)<<(nEq+1))-1; + if( (m & eqMask)!=m ) break; + } + + /* Begin assemblying the score + */ + score = nEq*32; /* Base score is 32 times number of == constraints */ + m = ((Bitmask)1)<<nEq; + if( m & ltMask ) score+=4; /* Increase score for a < constraint */ + if( m & gtMask ) score+=8; /* Increase score for a > constraint */ + if( score==0 && inMask ) score = 16; /* Default score for IN constraint */ + + /* Give bonus points if this index can be used for sorting + */ + if( i==0 && score!=16 && ppOrderBy && *ppOrderBy ){ + int base = pTabList->a[0].iCursor; + if( isSortingIndex(pParse, pIdx, pTab, base, *ppOrderBy, nEq, &bRev) ){ + score += 2; + } + } + + /* Check to see if we can get away with using just the index without + ** ever reading the table. If that is the case, then add one bonus + ** point to the score. + */ + if( score && pTabItem->colUsed < (((Bitmask)1)<<(BMS-1)) ){ + for(m=0, j=0; j<pIdx->nColumn; j++){ + int x = pIdx->aiColumn[j]; + if( x<BMS-1 ){ + m |= ((Bitmask)1)<<x; + } + } + if( (pTabItem->colUsed & m)==pTabItem->colUsed ){ + score++; + } + } + + /* If the score for this index is the best we have seen so far, then + ** save it + */ + if( score>bestScore ){ + pBestIdx = pIdx; + bestScore = score; + bestRev = bRev; + } + } + pLevel->pIdx = pBestIdx; + pLevel->score = bestScore; + pLevel->bRev = bestRev; + loopMask |= mask; + if( pBestIdx ){ + pLevel->iIdxCur = 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 *pIdx; /* Index derived from the WHERE clause */ + Table *pTab; /* Left-most table in the FROM clause */ + int bRev = 0; /* True to reverse the output order */ + int iCur; /* Btree-cursor that will be used by pTab */ + WhereLevel *pLevel0 = &pWInfo->a[0]; + + pTab = pTabList->a[0].pTab; + pIdx = pLevel0->pIdx; + iCur = pTabList->a[0].iCursor; + if( pIdx==0 && sortableByRowid(iCur, *ppOrderBy, &bRev) ){ + /* The ORDER BY clause specifies ROWID order, which is what we + ** were going to be doing anyway... + */ + *ppOrderBy = 0; + pLevel0->bRev = bRev; + }else if( pLevel0->score==16 ){ + /* 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. + */ + }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. But do delete the ORDER BY clause + ** if it is redundant. + */ + }else if( (pLevel0->score&2)!=0 ){ + /* The index that was selected for searching will cause rows to + ** appear in sorted order. + */ + *ppOrderBy = 0; + } + } + + /* Open all tables in the pTabList and any indices selected for + ** searching those tables. + */ + sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */ + pLevel = pWInfo->a; + for(i=0, pTabItem=pTabList->a; i<pTabList->nSrc; i++, pTabItem++, pLevel++){ + Table *pTab; + Index *pIx; + int iIdxCur = pLevel->iIdxCur; + + pTab = pTabItem->pTab; + if( pTab->isTransient || pTab->pSelect ) continue; + if( (pLevel->score & 1)==0 ){ + sqlite3OpenTableForReading(v, pTabItem->iCursor, pTab); + } + pLevel->iTabCur = pTabItem->iCursor; + if( (pIx = pLevel->pIdx)!=0 ){ + sqlite3VdbeAddOp(v, OP_Integer, pIx->iDb, 0); + sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum, + (char*)&pIx->keyInfo, P3_KEYINFO); + } + if( (pLevel->score & 1)!=0 ){ + sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1); + } + sqlite3CodeVerifySchema(pParse, pTab->iDb); + } + pWInfo->iTop = sqlite3VdbeCurrentAddr(v); + + /* Generate the code to do the search + */ + loopMask = 0; + pLevel = pWInfo->a; + pTabItem = pTabList->a; + for(i=0; i<pTabList->nSrc; i++, pTabItem++, pLevel++){ + int j, k; + int iCur = pTabItem->iCursor; /* The VDBE cursor for the table */ + Index *pIdx; /* The index we will be using */ + int iIdxCur; /* The VDBE cursor for the index */ + int omitTable; /* True if we use the index only */ + + pIdx = pLevel->pIdx; + iIdxCur = pLevel->iIdxCur; + pLevel->inOp = OP_Noop; + + /* Check to see if it is appropriate to omit the use of the table + ** here and use its index instead. + */ + omitTable = (pLevel->score&1)!=0; + + /* 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_Null, 0, 0); + sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1); + VdbeComment((v, "# init LEFT JOIN no-match flag")); + } + + 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 ); + assert( omitTable==0 ); + brk = pLevel->brk = sqlite3VdbeMakeLabel(v); + codeEqualityTerm(pParse, pTerm, brk, pLevel); + cont = pLevel->cont = sqlite3VdbeMakeLabel(v); + sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk); + sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk); + VdbeComment((v, "pk")); + pLevel->op = OP_Noop; + }else if( pIdx!=0 && pLevel->score>3 && (pLevel->score&0x0c)==0 ){ + /* Case 2: There is an index and all terms of the WHERE clause that + ** refer to the index using the "==" or "IN" operators. + */ + int start; + int nColumn = (pLevel->score+16)/32; + 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] + && (pX->op==TK_EQ || pX->op==TK_IN) + ){ + 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, iIdxCur, brk); + start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); + sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, brk); + pLevel->op = OP_Prev; + }else{ + /* Scan in the forward order */ + sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, brk); + start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); + sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, brk, "+", P3_STATIC); + pLevel->op = OP_Next; + } + sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0); + sqlite3VdbeAddOp(v, OP_IdxIsNull, nColumn, cont); + if( !omitTable ){ + sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0); + sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); + } + pLevel->p1 = iIdxCur; + 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; + int bRev = pLevel->bRev; + + assert( omitTable==0 ); + brk = pLevel->brk = sqlite3VdbeMakeLabel(v); + cont = pLevel->cont = sqlite3VdbeMakeLabel(v); + if( bRev ){ + int t = iDirectGt[i]; + iDirectGt[i] = iDirectLt[i]; + iDirectLt[i] = t; + } + 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_LE || pX->op==TK_GT, brk); + sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk); + VdbeComment((v, "pk")); + disableTerm(pLevel, &pTerm->p); + }else{ + sqlite3VdbeAddOp(v, bRev ? OP_Last : 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 = bRev ? OP_Le : OP_Ge; + }else{ + testOp = bRev ? OP_Lt : OP_Gt; + } + disableTerm(pLevel, &pTerm->p); + } + start = sqlite3VdbeCurrentAddr(v); + pLevel->op = bRev ? OP_Prev : OP_Next; + pLevel->p1 = iCur; + pLevel->p2 = start; + if( testOp!=OP_Noop ){ + sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0); + sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); + sqlite3VdbeAddOp(v, testOp, 'n', brk); + } + }else if( pIdx==0 ){ + /* Case 4: There is no usable index. We must do a complete + ** scan of the entire database table. + */ + int start; + int opRewind; + + assert( omitTable==0 ); + brk = pLevel->brk = sqlite3VdbeMakeLabel(v); + cont = pLevel->cont = sqlite3VdbeMakeLabel(v); + if( pLevel->bRev ){ + opRewind = OP_Last; + pLevel->op = OP_Prev; + }else{ + opRewind = OP_Rewind; + pLevel->op = OP_Next; + } + sqlite3VdbeAddOp(v, opRewind, iCur, brk); + start = sqlite3VdbeCurrentAddr(v); + pLevel->p1 = iCur; + pLevel->p2 = start; + }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/32; + 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 & 4)!=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 & 4)!=0); + pLevel->iMem = pParse->nMem++; + buildIndexProbe(v, nCol, brk, pIdx); + if( pLevel->bRev ){ + int op = leFlag ? OP_MoveLe : OP_MoveLt; + sqlite3VdbeAddOp(v, op, iIdxCur, brk); + }else{ + sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); + } + }else if( pLevel->bRev ){ + sqlite3VdbeAddOp(v, OP_Last, iIdxCur, 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 & 8)!=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&8)!=0 ){ + int nCol = nEqColumn + ((score&8)!=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, iIdxCur, brk); + } + }else if( pLevel->bRev ){ + testOp = OP_Noop; + }else{ + sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, 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, iIdxCur, brk); + if( (leFlag && !pLevel->bRev) || (!geFlag && pLevel->bRev) ){ + sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC); + } + } + sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0); + sqlite3VdbeAddOp(v, OP_IdxIsNull, nEqColumn + ((score&4)!=0), cont); + if( !omitTable ){ + sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0); + sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); + } + + /* Record the instruction used to terminate the loop. + */ + pLevel->op = pLevel->bRev ? OP_Prev : OP_Next; + pLevel->p1 = iIdxCur; + 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; + } + 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; + sqlite3ExprIfFalse(pParse, pTerm->p, cont, 1); + pTerm->p = 0; + } + } + } + pWInfo->iContinue = cont; + 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; + struct SrcList_item *pTabItem; + + /* Generate loop termination code. + */ + 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->iIdxCur>=0)); + sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0); + if( pLevel->iIdxCur>=0 ){ + sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0); + } + sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top); + } + } + + /* The "break" point is here, just past the end of the outer loop. + ** Set it. + */ + sqlite3VdbeResolveLabel(v, pWInfo->iBreak); + + /* Close all of the cursors that were opend by sqlite3WhereBegin. + */ + pLevel = pWInfo->a; + pTabItem = pTabList->a; + for(i=0; i<pTabList->nSrc; i++, pTabItem++, pLevel++){ + Table *pTab = pTabItem->pTab; + assert( pTab!=0 ); + if( pTab->isTransient || pTab->pSelect ) continue; + if( (pLevel->score & 1)==0 ){ + sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0); + } + if( pLevel->pIdx!=0 ){ + sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0); + } + + /* Make cursor substitutions for cases where we want to use + ** just the index and never reference the table. + ** + ** Calls to the code generator in between sqlite3WhereBegin and + ** sqlite3WhereEnd will have created code that references the table + ** directly. This loop scans all that code looking for opcodes + ** that reference the table and converts them into opcodes that + ** reference the index. + */ + if( pLevel->score & 1 ){ + int i, j, last; + VdbeOp *pOp; + Index *pIdx = pLevel->pIdx; + + assert( pIdx!=0 ); + pOp = sqlite3VdbeGetOp(v, pWInfo->iTop); + last = sqlite3VdbeCurrentAddr(v); + for(i=pWInfo->iTop; i<last; i++, pOp++){ + if( pOp->p1!=pLevel->iTabCur ) continue; + if( pOp->opcode==OP_Column ){ + pOp->p1 = pLevel->iIdxCur; + for(j=0; j<pIdx->nColumn; j++){ + if( pOp->p2==pIdx->aiColumn[j] ){ + pOp->p2 = j; + break; + } + } + }else if( pOp->opcode==OP_Rowid ){ + pOp->p1 = pLevel->iIdxCur; + pOp->opcode = OP_IdxRowid; + }else if( pOp->opcode==OP_NullRow ){ + pOp->opcode = OP_Noop; + } + } + } + } + + /* Final cleanup + */ + sqliteFree(pWInfo); + return; +} |