4
** The author disclaims copyright to this source code. In place of
5
** a legal notice, here is a blessing:
7
** May you do good and not evil.
8
** May you find forgiveness for yourself and forgive others.
9
** May you share freely, never taking more than you give.
11
*************************************************************************
12
** This module contains C code that generates VDBE code used to process
13
** the WHERE clause of SQL statements. This module is reponsible for
14
** generating the code that loops through a table looking for applicable
15
** rows. Indices are selected and used to speed the search when doing
16
** so is applicable. Because this module is responsible for selecting
17
** indices, you might also think of this module as the "query optimizer".
19
** $Id: where.c,v 1.136 2005/03/16 12:15:21 danielk1977 Exp $
21
#include "sqliteInt.h"
24
** The query generator uses an array of instances of this structure to
25
** help it analyze the subexpressions of the WHERE clause. Each WHERE
26
** clause subexpression is separated from the others by an AND operator.
28
** The idxLeft and idxRight fields are the VDBE cursor numbers for the
29
** table that contains the column that appears on the left-hand and
30
** right-hand side of ExprInfo.p. If either side of ExprInfo.p is
31
** something other than a simple column reference, then idxLeft or
34
** It is the VDBE cursor number is the value stored in Expr.iTable
35
** when Expr.op==TK_COLUMN and the value stored in SrcList.a[].iCursor.
37
** prereqLeft, prereqRight, and prereqAll record sets of cursor numbers,
38
** but they do so indirectly. A single ExprMaskSet structure translates
39
** cursor number into bits and the translated bit is stored in the prereq
40
** fields. The translation is used in order to maximize the number of
41
** bits that will fit in a Bitmask. The VDBE cursor numbers might be
42
** spread out over the non-negative integers. For example, the cursor
43
** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The ExprMaskSet
44
** translates these sparse cursor numbers into consecutive integers
45
** beginning with 0 in order to make the best possible use of the available
46
** bits in the Bitmask. So, in the example above, the cursor numbers
47
** would be mapped into integers 0 through 7.
49
** prereqLeft tells us every VDBE cursor that is referenced on the
50
** left-hand side of ExprInfo.p. prereqRight does the same for the
51
** right-hand side of the expression. The following identity always
54
** prereqAll = prereqLeft | prereqRight
56
** The ExprInfo.indexable field is true if the ExprInfo.p expression
57
** is of a form that might control an index. Indexable expressions
60
** <column> <op> <expr>
62
** Where <column> is a simple column name and <op> is on of the operators
63
** that allowedOp() recognizes.
65
typedef struct ExprInfo ExprInfo;
67
Expr *p; /* Pointer to the subexpression */
68
u8 indexable; /* True if this subexprssion is usable by an index */
69
short int idxLeft; /* p->pLeft is a column in this table number. -1 if
70
** p->pLeft is not the column of any table */
71
short int idxRight; /* p->pRight is a column in this table number. -1 if
72
** p->pRight is not the column of any table */
73
Bitmask prereqLeft; /* Bitmask of tables referenced by p->pLeft */
74
Bitmask prereqRight; /* Bitmask of tables referenced by p->pRight */
75
Bitmask prereqAll; /* Bitmask of tables referenced by p */
79
** An instance of the following structure keeps track of a mapping
80
** between VDBE cursor numbers and bits of the bitmasks in ExprInfo.
82
** The VDBE cursor numbers are small integers contained in
83
** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
84
** clause, the cursor numbers might not begin with 0 and they might
85
** contain gaps in the numbering sequence. But we want to make maximum
86
** use of the bits in our bitmasks. This structure provides a mapping
87
** from the sparse cursor numbers into consecutive integers beginning
90
** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
91
** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
93
** For example, if the WHERE clause expression used these VDBE
94
** cursors: 4, 5, 8, 29, 57, 73. Then the ExprMaskSet structure
95
** would map those cursor numbers into bits 0 through 5.
97
** Note that the mapping is not necessarily ordered. In the example
98
** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
99
** 57->5, 73->4. Or one of 719 other combinations might be used. It
100
** does not really matter. What is important is that sparse cursor
101
** numbers all get mapped into bit numbers that begin with 0 and contain
104
typedef struct ExprMaskSet ExprMaskSet;
106
int n; /* Number of assigned cursor values */
107
int ix[sizeof(Bitmask)*8]; /* Cursor assigned to each bit */
111
** Determine the number of elements in an array.
113
#define ARRAYSIZE(X) (sizeof(X)/sizeof(X[0]))
116
** This routine identifies subexpressions in the WHERE clause where
117
** each subexpression is separate by the AND operator. aSlot is
118
** filled with pointers to the subexpressions. For example:
120
** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
121
** \________/ \_______________/ \________________/
122
** slot[0] slot[1] slot[2]
124
** The original WHERE clause in pExpr is unaltered. All this routine
125
** does is make aSlot[] entries point to substructure within pExpr.
127
** aSlot[] is an array of subexpressions structures. There are nSlot
128
** spaces left in this array. This routine finds as many AND-separated
129
** subexpressions as it can and puts pointers to those subexpressions
130
** into aSlot[] entries. The return value is the number of slots filled.
132
static int exprSplit(int nSlot, ExprInfo *aSlot, Expr *pExpr){
134
if( pExpr==0 || nSlot<1 ) return 0;
135
if( nSlot==1 || pExpr->op!=TK_AND ){
139
if( pExpr->pLeft->op!=TK_AND ){
140
aSlot[0].p = pExpr->pLeft;
141
cnt = 1 + exprSplit(nSlot-1, &aSlot[1], pExpr->pRight);
143
cnt = exprSplit(nSlot, aSlot, pExpr->pLeft);
144
cnt += exprSplit(nSlot-cnt, &aSlot[cnt], pExpr->pRight);
150
** Initialize an expression mask set
152
#define initMaskSet(P) memset(P, 0, sizeof(*P))
155
** Return the bitmask for the given cursor number. Return 0 if
156
** iCursor is not in the set.
158
static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){
160
for(i=0; i<pMaskSet->n; i++){
161
if( pMaskSet->ix[i]==iCursor ){
162
return ((Bitmask)1)<<i;
169
** Create a new mask for cursor iCursor.
171
static void createMask(ExprMaskSet *pMaskSet, int iCursor){
172
if( pMaskSet->n<ARRAYSIZE(pMaskSet->ix) ){
173
pMaskSet->ix[pMaskSet->n++] = iCursor;
178
** Destroy an expression mask set
180
#define freeMaskSet(P) /* NO-OP */
183
** This routine walks (recursively) an expression tree and generates
184
** a bitmask indicating which tables are used in that expression
187
** In order for this routine to work, the calling function must have
188
** previously invoked sqlite3ExprResolveNames() on the expression. See
189
** the header comment on that routine for additional information.
190
** The sqlite3ExprResolveNames() routines looks for column names and
191
** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
192
** the VDBE cursor number of the table.
194
static Bitmask exprListTableUsage(ExprMaskSet *, ExprList *);
195
static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
198
if( p->op==TK_COLUMN ){
199
mask = getMask(pMaskSet, p->iTable);
202
mask = exprTableUsage(pMaskSet, p->pRight);
203
mask |= exprTableUsage(pMaskSet, p->pLeft);
204
mask |= exprListTableUsage(pMaskSet, p->pList);
206
Select *pS = p->pSelect;
207
mask |= exprListTableUsage(pMaskSet, pS->pEList);
208
mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
209
mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
210
mask |= exprTableUsage(pMaskSet, pS->pWhere);
211
mask |= exprTableUsage(pMaskSet, pS->pHaving);
215
static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){
219
for(i=0; i<pList->nExpr; i++){
220
mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
227
** Return TRUE if the given operator is one of the operators that is
228
** allowed for an indexable WHERE clause term. The allowed operators are
229
** "=", "<", ">", "<=", ">=", and "IN".
231
static int allowedOp(int op){
232
assert( TK_GT==TK_LE-1 && TK_LE==TK_LT-1 && TK_LT==TK_GE-1 && TK_EQ==TK_GT-1);
233
return op==TK_IN || (op>=TK_EQ && op<=TK_GE);
237
** Swap two objects of type T.
239
#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
242
** Return the index in the SrcList that uses cursor iCur. If iCur is
243
** used by the first entry in SrcList return 0. If iCur is used by
244
** the second entry return 1. And so forth.
246
** SrcList is the set of tables in the FROM clause in the order that
247
** they will be processed. The value returned here gives us an index
248
** of which tables will be processed first.
250
static int tableOrder(SrcList *pList, int iCur){
252
struct SrcList_item *pItem;
253
for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){
254
if( pItem->iCursor==iCur ) return i;
260
** The input to this routine is an ExprInfo structure with only the
261
** "p" field filled in. The job of this routine is to analyze the
262
** subexpression and populate all the other fields of the ExprInfo
265
static void exprAnalyze(SrcList *pSrc, ExprMaskSet *pMaskSet, ExprInfo *pInfo){
266
Expr *pExpr = pInfo->p;
267
pInfo->prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
268
pInfo->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
269
pInfo->prereqAll = exprTableUsage(pMaskSet, pExpr);
270
pInfo->indexable = 0;
272
pInfo->idxRight = -1;
273
if( allowedOp(pExpr->op) && (pInfo->prereqRight & pInfo->prereqLeft)==0 ){
274
if( pExpr->pRight && pExpr->pRight->op==TK_COLUMN ){
275
pInfo->idxRight = pExpr->pRight->iTable;
276
pInfo->indexable = 1;
278
if( pExpr->pLeft->op==TK_COLUMN ){
279
pInfo->idxLeft = pExpr->pLeft->iTable;
280
pInfo->indexable = 1;
283
if( pInfo->indexable ){
284
assert( pInfo->idxLeft!=pInfo->idxRight );
286
/* We want the expression to be of the form "X = expr", not "expr = X".
287
** So flip it over if necessary. If the expression is "X = Y", then
288
** we want Y to come from an earlier table than X.
290
** The collating sequence rule is to always choose the left expression.
291
** So if we do a flip, we also have to move the collating sequence.
293
if( tableOrder(pSrc,pInfo->idxLeft)<tableOrder(pSrc,pInfo->idxRight) ){
294
assert( pExpr->op!=TK_IN );
295
SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
296
SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
297
if( pExpr->op>=TK_GT ){
298
assert( TK_LT==TK_GT+2 );
299
assert( TK_GE==TK_LE+2 );
300
assert( TK_GT>TK_EQ );
301
assert( TK_GT<TK_LE );
302
assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
303
pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
305
SWAP(unsigned, pInfo->prereqLeft, pInfo->prereqRight);
306
SWAP(short int, pInfo->idxLeft, pInfo->idxRight);
313
** This routine decides if pIdx can be used to satisfy the ORDER BY
314
** clause. If it can, it returns 1. If pIdx cannot satisfy the
315
** ORDER BY clause, this routine returns 0.
317
** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
318
** left-most table in the FROM clause of that same SELECT statement and
319
** the table has a cursor number of "base". pIdx is an index on pTab.
321
** nEqCol is the number of columns of pIdx that are used as equality
322
** constraints. Any of these columns may be missing from the ORDER BY
323
** clause and the match can still be a success.
325
** If the index is UNIQUE, then the ORDER BY clause is allowed to have
326
** additional terms past the end of the index and the match will still
329
** All terms of the ORDER BY that match against the index must be either
330
** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
331
** index do not need to satisfy this constraint.) The *pbRev value is
332
** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
333
** the ORDER BY clause is all ASC.
335
static int isSortingIndex(
336
Parse *pParse, /* Parsing context */
337
Index *pIdx, /* The index we are testing */
338
Table *pTab, /* The table to be sorted */
339
int base, /* Cursor number for pTab */
340
ExprList *pOrderBy, /* The ORDER BY clause */
341
int nEqCol, /* Number of index columns with == constraints */
342
int *pbRev /* Set to 1 if ORDER BY is DESC */
344
int i, j; /* Loop counters */
345
int sortOrder; /* Which direction we are sorting */
346
int nTerm; /* Number of ORDER BY terms */
347
struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
348
sqlite3 *db = pParse->db;
350
assert( pOrderBy!=0 );
351
nTerm = pOrderBy->nExpr;
354
/* Match terms of the ORDER BY clause against columns of
357
for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<pIdx->nColumn; i++){
358
Expr *pExpr; /* The expression of the ORDER BY pTerm */
359
CollSeq *pColl; /* The collating sequence of pExpr */
361
pExpr = pTerm->pExpr;
362
if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
363
/* Can not use an index sort on anything that is not a column in the
364
** left-most table of the FROM clause */
367
pColl = sqlite3ExprCollSeq(pParse, pExpr);
368
if( !pColl ) pColl = db->pDfltColl;
369
if( pExpr->iColumn!=pIdx->aiColumn[i] || pColl!=pIdx->keyInfo.aColl[i] ){
370
/* Term j of the ORDER BY clause does not match column i of the index */
372
/* If an index column that is constrained by == fails to match an
373
** ORDER BY term, that is OK. Just ignore that column of the index
377
/* If an index column fails to match and is not constrained by ==
378
** then the index cannot satisfy the ORDER BY constraint.
384
if( pTerm->sortOrder!=sortOrder ){
385
/* Indices can only be used if all ORDER BY terms past the
386
** equality constraints are all either DESC or ASC. */
390
sortOrder = pTerm->sortOrder;
396
/* The index can be used for sorting if all terms of the ORDER BY clause
397
** or covered or if we ran out of index columns and the it is a UNIQUE
400
if( j>=nTerm || (i>=pIdx->nColumn && pIdx->onError!=OE_None) ){
401
*pbRev = sortOrder==SQLITE_SO_DESC;
408
** Check table to see if the ORDER BY clause in pOrderBy can be satisfied
409
** by sorting in order of ROWID. Return true if so and set *pbRev to be
410
** true for reverse ROWID and false for forward ROWID order.
412
static int sortableByRowid(
413
int base, /* Cursor number for table to be sorted */
414
ExprList *pOrderBy, /* The ORDER BY clause */
415
int *pbRev /* Set to 1 if ORDER BY is DESC */
419
assert( pOrderBy!=0 );
420
assert( pOrderBy->nExpr>0 );
421
p = pOrderBy->a[0].pExpr;
422
if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1 ){
423
*pbRev = pOrderBy->a[0].sortOrder;
431
** Disable a term in the WHERE clause. Except, do not disable the term
432
** if it controls a LEFT OUTER JOIN and it did not originate in the ON
433
** or USING clause of that join.
435
** Consider the term t2.z='ok' in the following queries:
437
** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
438
** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
439
** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
441
** The t2.z='ok' is disabled in the in (2) because it originates
442
** in the ON clause. The term is disabled in (3) because it is not part
443
** of a LEFT OUTER JOIN. In (1), the term is not disabled.
445
** Disabling a term causes that term to not be tested in the inner loop
446
** of the join. Disabling is an optimization. We would get the correct
447
** results if nothing were ever disabled, but joins might run a little
448
** slower. The trick is to disable as much as we can without disabling
449
** too much. If we disabled in (1), we'd get the wrong answer.
452
static void disableTerm(WhereLevel *pLevel, Expr **ppExpr){
453
Expr *pExpr = *ppExpr;
454
if( pLevel->iLeftJoin==0 || ExprHasProperty(pExpr, EP_FromJoin) ){
460
** Generate code that builds a probe for an index. Details:
462
** * Check the top nColumn entries on the stack. If any
463
** of those entries are NULL, jump immediately to brk,
464
** which is the loop exit, since no index entry will match
465
** if any part of the key is NULL.
467
** * Construct a probe entry from the top nColumn entries in
468
** the stack with affinities appropriate for index pIdx.
470
static void buildIndexProbe(Vdbe *v, int nColumn, int brk, Index *pIdx){
471
sqlite3VdbeAddOp(v, OP_NotNull, -nColumn, sqlite3VdbeCurrentAddr(v)+3);
472
sqlite3VdbeAddOp(v, OP_Pop, nColumn, 0);
473
sqlite3VdbeAddOp(v, OP_Goto, 0, brk);
474
sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
475
sqlite3IndexAffinityStr(v, pIdx);
479
** Generate code for an equality term of the WHERE clause. An equality
480
** term can be either X=expr or X IN (...). pTerm is the X.
482
static void codeEqualityTerm(
483
Parse *pParse, /* The parsing context */
484
ExprInfo *pTerm, /* The term of the WHERE clause to be coded */
485
int brk, /* Jump here to abandon the loop */
486
WhereLevel *pLevel /* When level of the FROM clause we are working on */
490
assert( pX->op==TK_EQ );
491
sqlite3ExprCode(pParse, pX->pRight);
492
#ifndef SQLITE_OMIT_SUBQUERY
495
Vdbe *v = pParse->pVdbe;
497
sqlite3CodeSubselect(pParse, pX);
499
sqlite3VdbeAddOp(v, OP_Rewind, iTab, brk);
500
sqlite3VdbeAddOp(v, OP_KeyAsData, iTab, 1);
501
VdbeComment((v, "# %.*s", pX->span.n, pX->span.z));
502
pLevel->inP2 = sqlite3VdbeAddOp(v, OP_Column, iTab, 0);
503
pLevel->inOp = OP_Next;
507
disableTerm(pLevel, &pTerm->p);
511
** The number of bits in a Bitmask
513
#define BMS (sizeof(Bitmask)*8-1)
517
** Generate the beginning of the loop used for WHERE clause processing.
518
** The return value is a pointer to an opaque structure that contains
519
** information needed to terminate the loop. Later, the calling routine
520
** should invoke sqlite3WhereEnd() with the return value of this function
521
** in order to complete the WHERE clause processing.
523
** If an error occurs, this routine returns NULL.
525
** The basic idea is to do a nested loop, one loop for each table in
526
** the FROM clause of a select. (INSERT and UPDATE statements are the
527
** same as a SELECT with only a single table in the FROM clause.) For
528
** example, if the SQL is this:
530
** SELECT * FROM t1, t2, t3 WHERE ...;
532
** Then the code generated is conceptually like the following:
534
** foreach row1 in t1 do \ Code generated
535
** foreach row2 in t2 do |-- by sqlite3WhereBegin()
536
** foreach row3 in t3 do /
538
** end \ Code generated
539
** end |-- by sqlite3WhereEnd()
542
** There are Btree cursors associated with each table. t1 uses cursor
543
** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
544
** And so forth. This routine generates code to open those VDBE cursors
545
** and sqlite3WhereEnd() generates the code to close them.
547
** The code that sqlite3WhereBegin() generates leaves the cursors named
548
** in pTabList pointing at their appropriate entries. The [...] code
549
** can use OP_Column and OP_Recno opcodes on these cursors to extract
550
** data from the various tables of the loop.
552
** If the WHERE clause is empty, the foreach loops must each scan their
553
** entire tables. Thus a three-way join is an O(N^3) operation. But if
554
** the tables have indices and there are terms in the WHERE clause that
555
** refer to those indices, a complete table scan can be avoided and the
556
** code will run much faster. Most of the work of this routine is checking
557
** to see if there are indices that can be used to speed up the loop.
559
** Terms of the WHERE clause are also used to limit which rows actually
560
** make it to the "..." in the middle of the loop. After each "foreach",
561
** terms of the WHERE clause that use only terms in that loop and outer
562
** loops are evaluated and if false a jump is made around all subsequent
563
** inner loops (or around the "..." if the test occurs within the inner-
568
** An outer join of tables t1 and t2 is conceptally coded as follows:
570
** foreach row1 in t1 do
572
** foreach row2 in t2 do
578
** move the row2 cursor to a null row
583
** ORDER BY CLAUSE PROCESSING
585
** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
586
** if there is one. If there is no ORDER BY clause or if this routine
587
** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
589
** If an index can be used so that the natural output order of the table
590
** scan is correct for the ORDER BY clause, then that index is used and
591
** *ppOrderBy is set to NULL. This is an optimization that prevents an
592
** unnecessary sort of the result set if an index appropriate for the
593
** ORDER BY clause already exists.
595
** If the where clause loops cannot be arranged to provide the correct
596
** output order, then the *ppOrderBy is unchanged.
598
WhereInfo *sqlite3WhereBegin(
599
Parse *pParse, /* The parser context */
600
SrcList *pTabList, /* A list of all tables to be scanned */
601
Expr *pWhere, /* The WHERE clause */
602
ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
603
Fetch *pFetch /* Initial location of cursors. NULL otherwise */
605
int i; /* Loop counter */
606
WhereInfo *pWInfo; /* Will become the return value of this function */
607
Vdbe *v = pParse->pVdbe; /* The virtual database engine */
608
int brk, cont = 0; /* Addresses used during code generation */
609
int nExpr; /* Number of subexpressions in the WHERE clause */
610
Bitmask loopMask; /* One bit set for each outer loop */
611
ExprInfo *pTerm; /* A single term in the WHERE clause; ptr to aExpr[] */
612
ExprMaskSet maskSet; /* The expression mask set */
613
int iDirectEq[BMS]; /* Term of the form ROWID==X for the N-th table */
614
int iDirectLt[BMS]; /* Term of the form ROWID<X or ROWID<=X */
615
int iDirectGt[BMS]; /* Term of the form ROWID>X or ROWID>=X */
616
ExprInfo aExpr[101]; /* The WHERE clause is divided into these terms */
617
struct SrcList_item *pTabItem; /* A single entry from pTabList */
618
WhereLevel *pLevel; /* A single level in the pWInfo list */
620
/* The number of terms in the FROM clause is limited by the number of
623
if( pTabList->nSrc>sizeof(Bitmask)*8 ){
624
sqlite3ErrorMsg(pParse, "at most %d tables in a join",
629
/* Split the WHERE clause into separate subexpressions where each
630
** subexpression is separated by an AND operator. If the aExpr[]
631
** array fills up, the last entry might point to an expression which
632
** contains additional unfactored AND operators.
634
initMaskSet(&maskSet);
635
memset(aExpr, 0, sizeof(aExpr));
636
nExpr = exprSplit(ARRAYSIZE(aExpr), aExpr, pWhere);
637
if( nExpr==ARRAYSIZE(aExpr) ){
638
sqlite3ErrorMsg(pParse, "WHERE clause too complex - no more "
639
"than %d terms allowed", (int)ARRAYSIZE(aExpr)-1);
643
/* Allocate and initialize the WhereInfo structure that will become the
646
pWInfo = sqliteMalloc( sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
647
if( sqlite3_malloc_failed ){
648
sqliteFree(pWInfo); /* Avoid leaking memory when malloc fails */
651
pWInfo->pParse = pParse;
652
pWInfo->pTabList = pTabList;
653
pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
655
/* Special case: a WHERE clause that is constant. Evaluate the
656
** expression and either jump over all of the code or fall thru.
658
if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstant(pWhere)) ){
659
sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
663
/* Analyze all of the subexpressions.
665
for(i=0; i<pTabList->nSrc; i++){
666
createMask(&maskSet, pTabList->a[i].iCursor);
668
for(pTerm=aExpr, i=0; i<nExpr; i++, pTerm++){
669
exprAnalyze(pTabList, &maskSet, pTerm);
672
/* Figure out what index to use (if any) for each nested loop.
673
** Make pWInfo->a[i].pIdx point to the index to use for the i-th nested
674
** loop where i==0 is the outer loop and i==pTabList->nSrc-1 is the inner
677
** If terms exist that use the ROWID of any table, then set the
678
** iDirectEq[], iDirectLt[], or iDirectGt[] elements for that table
679
** to the index of the term containing the ROWID. We always prefer
680
** to use a ROWID which can directly access a table rather than an
681
** index which requires reading an index first to get the rowid then
682
** doing a second read of the actual database table.
684
** Actually, if there are more than 32 tables in the join, only the
685
** first 32 tables are candidates for indices. This is (again) due
686
** to the limit of 32 bits in an integer bitmask.
689
pTabItem = pTabList->a;
691
for(i=0; i<pTabList->nSrc && i<ARRAYSIZE(iDirectEq); i++,pTabItem++,pLevel++){
693
int iCur = pTabItem->iCursor; /* The cursor for this table */
694
Bitmask mask = getMask(&maskSet, iCur); /* Cursor mask for this table */
695
Table *pTab = pTabItem->pTab;
701
/* Check to see if there is an expression that uses only the
702
** ROWID field of this table. For terms of the form ROWID==expr
703
** set iDirectEq[i] to the index of the term. For terms of the
704
** form ROWID<expr or ROWID<=expr set iDirectLt[i] to the term index.
705
** For terms like ROWID>expr or ROWID>=expr set iDirectGt[i].
707
** (Added:) Treat ROWID IN expr like ROWID=expr.
709
pLevel->iIdxCur = -1;
713
for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){
715
if( pTerm->idxLeft==iCur && pX->pLeft->iColumn<0
716
&& (pTerm->prereqRight & loopMask)==pTerm->prereqRight ){
719
case TK_EQ: iDirectEq[i] = j; break;
721
case TK_LT: iDirectLt[i] = j; break;
723
case TK_GT: iDirectGt[i] = j; break;
728
/* If we found a term that tests ROWID with == or IN, that term
729
** will be used to locate the rows in the database table. There
730
** is not need to continue into the code below that looks for
731
** an index. We will always use the ROWID over an index.
733
if( iDirectEq[i]>=0 ){
739
/* Do a search for usable indices. Leave pBestIdx pointing to
740
** the "best" index. pBestIdx is left set to NULL if no indices
743
** The best index is the one with the highest score. The score
744
** for the index is determined as follows. For each of the
745
** left-most terms that is fixed by an equality operator, add
746
** 32 to the score. The right-most term of the index may be
747
** constrained by an inequality. Add 4 if for an "x<..." constraint
748
** and add 8 for an "x>..." constraint. If both constraints
749
** are present, add 12.
751
** If the left-most term of the index uses an IN operator
752
** (ex: "x IN (...)") then add 16 to the score.
754
** If an index can be used for sorting, add 2 to the score.
755
** If an index contains all the terms of a table that are ever
756
** used by any expression in the SQL statement, then add 1 to
759
** This scoring system is designed so that the score can later be
760
** used to determine how the index is used. If the score&0x1c is 0
761
** then all constraints are equalities. If score&0x4 is not 0 then
762
** there is an inequality used as a termination key. (ex: "x<...")
763
** If score&0x8 is not 0 then there is an inequality used as the
764
** start key. (ex: "x>..."). A score or 0x10 is the special case
765
** of an IN operator constraint. (ex: "x IN ...").
767
** The IN operator (as in "<expr> IN (...)") is treated the same as
768
** an equality comparison except that it can only be used on the
769
** left-most column of an index and other terms of the WHERE clause
770
** cannot be used in conjunction with the IN operator to help satisfy
771
** other columns of the index.
773
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
774
Bitmask eqMask = 0; /* Index columns covered by an x=... term */
775
Bitmask ltMask = 0; /* Index columns covered by an x<... term */
776
Bitmask gtMask = 0; /* Index columns covered by an x>... term */
777
Bitmask inMask = 0; /* Index columns covered by an x IN .. term */
779
int nEq, score, bRev = 0;
781
if( pIdx->nColumn>sizeof(eqMask)*8 ){
782
continue; /* Ignore indices with too many columns to analyze */
784
for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){
786
CollSeq *pColl = sqlite3ExprCollSeq(pParse, pX->pLeft);
787
if( !pColl && pX->pRight ){
788
pColl = sqlite3ExprCollSeq(pParse, pX->pRight);
791
pColl = pParse->db->pDfltColl;
793
if( pTerm->idxLeft==iCur
794
&& (pTerm->prereqRight & loopMask)==pTerm->prereqRight ){
795
int iColumn = pX->pLeft->iColumn;
797
char idxaff = pIdx->pTable->aCol[iColumn].affinity;
798
for(k=0; k<pIdx->nColumn; k++){
799
/* If the collating sequences or affinities don't match,
800
** ignore this index. */
801
if( pColl!=pIdx->keyInfo.aColl[k] ) continue;
802
if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
803
if( pIdx->aiColumn[k]==iColumn ){
806
if( k==0 ) inMask |= 1;
810
eqMask |= ((Bitmask)1)<<k;
815
ltMask |= ((Bitmask)1)<<k;
820
gtMask |= ((Bitmask)1)<<k;
835
/* The following loop ends with nEq set to the number of columns
836
** on the left of the index with == constraints.
838
for(nEq=0; nEq<pIdx->nColumn; nEq++){
839
m = (((Bitmask)1)<<(nEq+1))-1;
840
if( (m & eqMask)!=m ) break;
843
/* Begin assemblying the score
845
score = nEq*32; /* Base score is 32 times number of == constraints */
846
m = ((Bitmask)1)<<nEq;
847
if( m & ltMask ) score+=4; /* Increase score for a < constraint */
848
if( m & gtMask ) score+=8; /* Increase score for a > constraint */
849
if( score==0 && inMask ) score = 16; /* Default score for IN constraint */
851
/* Give bonus points if this index can be used for sorting
853
if( i==0 && score!=16 && ppOrderBy && *ppOrderBy ){
854
int base = pTabList->a[0].iCursor;
855
if( isSortingIndex(pParse, pIdx, pTab, base, *ppOrderBy, nEq, &bRev) ){
860
/* Check to see if we can get away with using just the index without
861
** ever reading the table. If that is the case, then add one bonus
862
** point to the score.
864
if( score && pTabItem->colUsed < (((Bitmask)1)<<(BMS-1)) ){
865
for(m=0, j=0; j<pIdx->nColumn; j++){
866
int x = pIdx->aiColumn[j];
868
m |= ((Bitmask)1)<<x;
871
if( (pTabItem->colUsed & m)==pTabItem->colUsed ){
876
/* If the score for this index is the best we have seen so far, then
879
if( score>bestScore ){
885
pLevel->pIdx = pBestIdx;
886
pLevel->score = bestScore;
887
pLevel->bRev = bestRev;
890
pLevel->iIdxCur = pParse->nTab++;
894
/* Check to see if the ORDER BY clause is or can be satisfied by the
895
** use of an index on the first table.
897
if( ppOrderBy && *ppOrderBy && pTabList->nSrc>0 ){
898
Index *pIdx; /* Index derived from the WHERE clause */
899
Table *pTab; /* Left-most table in the FROM clause */
900
int bRev = 0; /* True to reverse the output order */
901
int iCur; /* Btree-cursor that will be used by pTab */
902
WhereLevel *pLevel0 = &pWInfo->a[0];
904
pTab = pTabList->a[0].pTab;
905
pIdx = pLevel0->pIdx;
906
iCur = pTabList->a[0].iCursor;
907
if( pIdx==0 && sortableByRowid(iCur, *ppOrderBy, &bRev) ){
908
/* The ORDER BY clause specifies ROWID order, which is what we
909
** were going to be doing anyway...
912
pLevel0->bRev = bRev;
913
}else if( pLevel0->score==16 ){
914
/* If there is already an IN index on the left-most table,
915
** it will not give the correct sort order.
916
** So, pretend that no suitable index is found.
918
}else if( iDirectEq[0]>=0 || iDirectLt[0]>=0 || iDirectGt[0]>=0 ){
919
/* If the left-most column is accessed using its ROWID, then do
920
** not try to sort by index. But do delete the ORDER BY clause
921
** if it is redundant.
923
}else if( (pLevel0->score&2)!=0 ){
924
/* The index that was selected for searching will cause rows to
925
** appear in sorted order.
931
/* Open all tables in the pTabList and any indices selected for
932
** searching those tables.
934
sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
936
for(i=0, pTabItem=pTabList->a; i<pTabList->nSrc; i++, pTabItem++, pLevel++){
939
int iIdxCur = pLevel->iIdxCur;
941
pTab = pTabItem->pTab;
942
if( pTab->isTransient || pTab->pSelect ) continue;
943
if( (pLevel->score & 1)==0 ){
944
sqlite3OpenTableForReading(v, pTabItem->iCursor, pTab);
946
pLevel->iTabCur = pTabItem->iCursor;
947
if( (pIx = pLevel->pIdx)!=0 ){
948
sqlite3VdbeAddOp(v, OP_Integer, pIx->iDb, 0);
949
sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
950
(char*)&pIx->keyInfo, P3_KEYINFO);
952
if( (pLevel->score & 1)!=0 ){
953
sqlite3VdbeAddOp(v, OP_KeyAsData, iIdxCur, 1);
954
sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
956
sqlite3CodeVerifySchema(pParse, pTab->iDb);
958
pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
960
/* Generate the code to do the search
964
pTabItem = pTabList->a;
965
for(i=0; i<pTabList->nSrc; i++, pTabItem++, pLevel++){
967
int iCur = pTabItem->iCursor; /* The VDBE cursor for the table */
968
Index *pIdx; /* The index we will be using */
969
int iIdxCur; /* The VDBE cursor for the index */
970
int omitTable; /* True if we use the index only */
973
iIdxCur = pLevel->iIdxCur;
974
pLevel->inOp = OP_Noop;
976
/* Check to see if it is appropriate to omit the use of the table
977
** here and use its index instead.
979
omitTable = (pLevel->score&1)!=0;
981
/* If this is the right table of a LEFT OUTER JOIN, allocate and
982
** initialize a memory cell that records if this table matches any
983
** row of the left table of the join.
985
if( i>0 && (pTabList->a[i-1].jointype & JT_LEFT)!=0 ){
986
if( !pParse->nMem ) pParse->nMem++;
987
pLevel->iLeftJoin = pParse->nMem++;
988
sqlite3VdbeAddOp(v, OP_String8, 0, 0);
989
sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
990
VdbeComment((v, "# init LEFT JOIN no-match flag"));
993
if( i<ARRAYSIZE(iDirectEq) && (k = iDirectEq[i])>=0 ){
994
/* Case 1: We can directly reference a single row using an
995
** equality comparison against the ROWID field. Or
996
** we reference multiple rows using a "rowid IN (...)"
1001
assert( pTerm->p!=0 );
1002
assert( pTerm->idxLeft==iCur );
1003
assert( omitTable==0 );
1004
brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
1005
codeEqualityTerm(pParse, pTerm, brk, pLevel);
1006
cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
1007
sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk);
1008
sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk);
1009
VdbeComment((v, "pk"));
1010
pLevel->op = OP_Noop;
1011
}else if( pIdx!=0 && pLevel->score>3 && (pLevel->score&0x0c)==0 ){
1012
/* Case 2: There is an index and all terms of the WHERE clause that
1013
** refer to the index using the "==" or "IN" operators.
1016
int nColumn = (pLevel->score+16)/32;
1017
brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
1019
/* For each column of the index, find the term of the WHERE clause that
1020
** constraints that column. If the WHERE clause term is X=expr, then
1021
** evaluation expr and leave the result on the stack */
1022
for(j=0; j<nColumn; j++){
1023
for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){
1024
Expr *pX = pTerm->p;
1025
if( pX==0 ) continue;
1026
if( pTerm->idxLeft==iCur
1027
&& (pTerm->prereqRight & loopMask)==pTerm->prereqRight
1028
&& pX->pLeft->iColumn==pIdx->aiColumn[j]
1029
&& (pX->op==TK_EQ || pX->op==TK_IN)
1031
char idxaff = pIdx->pTable->aCol[pX->pLeft->iColumn].affinity;
1032
if( sqlite3IndexAffinityOk(pX, idxaff) ){
1033
codeEqualityTerm(pParse, pTerm, brk, pLevel);
1039
pLevel->iMem = pParse->nMem++;
1040
cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
1041
buildIndexProbe(v, nColumn, brk, pIdx);
1042
sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);
1044
/* Generate code (1) to move to the first matching element of the table.
1045
** Then generate code (2) that jumps to "brk" after the cursor is past
1046
** the last matching element of the table. The code (1) is executed
1047
** once to initialize the search, the code (2) is executed before each
1048
** iteration of the scan to see if the scan has finished. */
1050
/* Scan in reverse order */
1051
sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, brk);
1052
start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1053
sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, brk);
1054
pLevel->op = OP_Prev;
1056
/* Scan in the forward order */
1057
sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, brk);
1058
start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1059
sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, brk, "+", P3_STATIC);
1060
pLevel->op = OP_Next;
1062
sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0);
1063
sqlite3VdbeAddOp(v, OP_IdxIsNull, nColumn, cont);
1065
sqlite3VdbeAddOp(v, OP_IdxRecno, iIdxCur, 0);
1066
sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
1068
pLevel->p1 = iIdxCur;
1070
}else if( i<ARRAYSIZE(iDirectLt) && (iDirectLt[i]>=0 || iDirectGt[i]>=0) ){
1071
/* Case 3: We have an inequality comparison against the ROWID field.
1073
int testOp = OP_Noop;
1075
int bRev = pLevel->bRev;
1077
assert( omitTable==0 );
1078
brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
1079
cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
1081
int t = iDirectGt[i];
1082
iDirectGt[i] = iDirectLt[i];
1085
if( iDirectGt[i]>=0 ){
1092
assert( pTerm->idxLeft==iCur );
1093
sqlite3ExprCode(pParse, pX->pRight);
1094
sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk);
1095
sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk);
1096
VdbeComment((v, "pk"));
1097
disableTerm(pLevel, &pTerm->p);
1099
sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
1101
if( iDirectLt[i]>=0 ){
1108
assert( pTerm->idxLeft==iCur );
1109
sqlite3ExprCode(pParse, pX->pRight);
1110
pLevel->iMem = pParse->nMem++;
1111
sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1112
if( pX->op==TK_LT || pX->op==TK_GT ){
1113
testOp = bRev ? OP_Le : OP_Ge;
1115
testOp = bRev ? OP_Lt : OP_Gt;
1117
disableTerm(pLevel, &pTerm->p);
1119
start = sqlite3VdbeCurrentAddr(v);
1120
pLevel->op = bRev ? OP_Prev : OP_Next;
1123
if( testOp!=OP_Noop ){
1124
sqlite3VdbeAddOp(v, OP_Recno, iCur, 0);
1125
sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1126
sqlite3VdbeAddOp(v, testOp, (int)(('n'<<8)&0x0000FF00), brk);
1128
}else if( pIdx==0 ){
1129
/* Case 4: There is no usable index. We must do a complete
1130
** scan of the entire database table.
1135
assert( omitTable==0 );
1136
brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
1137
cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
1140
pLevel->op = OP_Prev;
1142
opRewind = OP_Rewind;
1143
pLevel->op = OP_Next;
1145
sqlite3VdbeAddOp(v, opRewind, iCur, brk);
1146
start = sqlite3VdbeCurrentAddr(v);
1150
/* Case 5: The WHERE clause term that refers to the right-most
1151
** column of the index is an inequality. For example, if
1152
** the index is on (x,y,z) and the WHERE clause is of the
1153
** form "x=5 AND y<10" then this case is used. Only the
1154
** right-most column can be an inequality - the rest must
1155
** use the "==" operator.
1157
** This case is also used when there are no WHERE clause
1158
** constraints but an index is selected anyway, in order
1159
** to force the output order to conform to an ORDER BY.
1161
int score = pLevel->score;
1162
int nEqColumn = score/32;
1164
int leFlag=0, geFlag=0;
1167
/* Evaluate the equality constraints
1169
for(j=0; j<nEqColumn; j++){
1170
int iIdxCol = pIdx->aiColumn[j];
1171
for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){
1172
Expr *pX = pTerm->p;
1173
if( pX==0 ) continue;
1174
if( pTerm->idxLeft==iCur
1176
&& (pTerm->prereqRight & loopMask)==pTerm->prereqRight
1177
&& pX->pLeft->iColumn==iIdxCol
1179
sqlite3ExprCode(pParse, pX->pRight);
1180
disableTerm(pLevel, &pTerm->p);
1186
/* Duplicate the equality term values because they will all be
1187
** used twice: once to make the termination key and once to make the
1190
for(j=0; j<nEqColumn; j++){
1191
sqlite3VdbeAddOp(v, OP_Dup, nEqColumn-1, 0);
1194
/* Labels for the beginning and end of the loop
1196
cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
1197
brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
1199
/* Generate the termination key. This is the key value that
1200
** will end the search. There is no termination key if there
1201
** are no equality terms and no "X<..." term.
1203
** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
1204
** key computed here really ends up being the start key.
1206
if( (score & 4)!=0 ){
1207
for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){
1208
Expr *pX = pTerm->p;
1209
if( pX==0 ) continue;
1210
if( pTerm->idxLeft==iCur
1211
&& (pX->op==TK_LT || pX->op==TK_LE)
1212
&& (pTerm->prereqRight & loopMask)==pTerm->prereqRight
1213
&& pX->pLeft->iColumn==pIdx->aiColumn[j]
1215
sqlite3ExprCode(pParse, pX->pRight);
1216
leFlag = pX->op==TK_LE;
1217
disableTerm(pLevel, &pTerm->p);
1223
testOp = nEqColumn>0 ? OP_IdxGE : OP_Noop;
1226
if( testOp!=OP_Noop ){
1227
int nCol = nEqColumn + ((score & 4)!=0);
1228
pLevel->iMem = pParse->nMem++;
1229
buildIndexProbe(v, nCol, brk, pIdx);
1231
int op = leFlag ? OP_MoveLe : OP_MoveLt;
1232
sqlite3VdbeAddOp(v, op, iIdxCur, brk);
1234
sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1236
}else if( pLevel->bRev ){
1237
sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk);
1240
/* Generate the start key. This is the key that defines the lower
1241
** bound on the search. There is no start key if there are no
1242
** equality terms and if there is no "X>..." term. In
1243
** that case, generate a "Rewind" instruction in place of the
1244
** start key search.
1246
** 2002-Dec-04: In the case of a reverse-order search, the so-called
1247
** "start" key really ends up being used as the termination key.
1249
if( (score & 8)!=0 ){
1250
for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){
1251
Expr *pX = pTerm->p;
1252
if( pX==0 ) continue;
1253
if( pTerm->idxLeft==iCur
1254
&& (pX->op==TK_GT || pX->op==TK_GE)
1255
&& (pTerm->prereqRight & loopMask)==pTerm->prereqRight
1256
&& pX->pLeft->iColumn==pIdx->aiColumn[j]
1258
sqlite3ExprCode(pParse, pX->pRight);
1259
geFlag = pX->op==TK_GE;
1260
disableTerm(pLevel, &pTerm->p);
1267
if( nEqColumn>0 || (score&8)!=0 ){
1268
int nCol = nEqColumn + ((score&8)!=0);
1269
buildIndexProbe(v, nCol, brk, pIdx);
1271
pLevel->iMem = pParse->nMem++;
1272
sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1275
int op = geFlag ? OP_MoveGe : OP_MoveGt;
1276
sqlite3VdbeAddOp(v, op, iIdxCur, brk);
1278
}else if( pLevel->bRev ){
1281
sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk);
1284
/* Generate the the top of the loop. If there is a termination
1285
** key we have to test for that key and abort at the top of the
1288
start = sqlite3VdbeCurrentAddr(v);
1289
if( testOp!=OP_Noop ){
1290
sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1291
sqlite3VdbeAddOp(v, testOp, iIdxCur, brk);
1292
if( (leFlag && !pLevel->bRev) || (!geFlag && pLevel->bRev) ){
1293
sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
1296
sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0);
1297
sqlite3VdbeAddOp(v, OP_IdxIsNull, nEqColumn + ((score&4)!=0), cont);
1299
sqlite3VdbeAddOp(v, OP_IdxRecno, iIdxCur, 0);
1300
sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
1303
/* Record the instruction used to terminate the loop.
1305
pLevel->op = pLevel->bRev ? OP_Prev : OP_Next;
1306
pLevel->p1 = iIdxCur;
1309
loopMask |= getMask(&maskSet, iCur);
1311
/* Insert code to test every subexpression that can be completely
1312
** computed using the current set of tables.
1314
for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){
1315
if( pTerm->p==0 ) continue;
1316
if( (pTerm->prereqAll & loopMask)!=pTerm->prereqAll ) continue;
1317
if( pLevel->iLeftJoin && !ExprHasProperty(pTerm->p,EP_FromJoin) ){
1320
sqlite3ExprIfFalse(pParse, pTerm->p, cont, 1);
1325
/* For a LEFT OUTER JOIN, generate code that will record the fact that
1326
** at least one row of the right table has matched the left table.
1328
if( pLevel->iLeftJoin ){
1329
pLevel->top = sqlite3VdbeCurrentAddr(v);
1330
sqlite3VdbeAddOp(v, OP_Integer, 1, 0);
1331
sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
1332
VdbeComment((v, "# record LEFT JOIN hit"));
1333
for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){
1334
if( pTerm->p==0 ) continue;
1335
if( (pTerm->prereqAll & loopMask)!=pTerm->prereqAll ) continue;
1336
sqlite3ExprIfFalse(pParse, pTerm->p, cont, 1);
1341
pWInfo->iContinue = cont;
1342
freeMaskSet(&maskSet);
1347
** Generate the end of the WHERE loop. See comments on
1348
** sqlite3WhereBegin() for additional information.
1350
void sqlite3WhereEnd(WhereInfo *pWInfo){
1351
Vdbe *v = pWInfo->pParse->pVdbe;
1354
SrcList *pTabList = pWInfo->pTabList;
1355
struct SrcList_item *pTabItem;
1357
/* Generate loop termination code.
1359
for(i=pTabList->nSrc-1; i>=0; i--){
1360
pLevel = &pWInfo->a[i];
1361
sqlite3VdbeResolveLabel(v, pLevel->cont);
1362
if( pLevel->op!=OP_Noop ){
1363
sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
1365
sqlite3VdbeResolveLabel(v, pLevel->brk);
1366
if( pLevel->inOp!=OP_Noop ){
1367
sqlite3VdbeAddOp(v, pLevel->inOp, pLevel->inP1, pLevel->inP2);
1369
if( pLevel->iLeftJoin ){
1371
addr = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iLeftJoin, 0);
1372
sqlite3VdbeAddOp(v, OP_NotNull, 1, addr+4 + (pLevel->iIdxCur>=0));
1373
sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
1374
if( pLevel->iIdxCur>=0 ){
1375
sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0);
1377
sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top);
1381
/* The "break" point is here, just past the end of the outer loop.
1384
sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
1386
/* Close all of the cursors that were opend by sqlite3WhereBegin.
1389
pTabItem = pTabList->a;
1390
for(i=0; i<pTabList->nSrc; i++, pTabItem++, pLevel++){
1391
Table *pTab = pTabItem->pTab;
1393
if( pTab->isTransient || pTab->pSelect ) continue;
1394
if( (pLevel->score & 1)==0 ){
1395
sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
1397
if( pLevel->pIdx!=0 ){
1398
sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
1401
/* Make cursor substitutions for cases where we want to use
1402
** just the index and never reference the table.
1404
** Calls to the code generator in between sqlite3WhereBegin and
1405
** sqlite3WhereEnd will have created code that references the table
1406
** directly. This loop scans all that code looking for opcodes
1407
** that reference the table and converts them into opcodes that
1408
** reference the index.
1410
if( pLevel->score & 1 ){
1413
Index *pIdx = pLevel->pIdx;
1416
pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
1417
last = sqlite3VdbeCurrentAddr(v);
1418
for(i=pWInfo->iTop; i<last; i++, pOp++){
1419
if( pOp->p1!=pLevel->iTabCur ) continue;
1420
if( pOp->opcode==OP_Column ){
1421
pOp->p1 = pLevel->iIdxCur;
1422
for(j=0; j<pIdx->nColumn; j++){
1423
if( pOp->p2==pIdx->aiColumn[j] ){
1428
}else if( pOp->opcode==OP_Recno ){
1429
pOp->p1 = pLevel->iIdxCur;
1430
pOp->opcode = OP_IdxRecno;
1431
}else if( pOp->opcode==OP_NullRow ){
1432
pOp->opcode = OP_Noop;
added
removed
src/3rdparty/sqlite/where.c
