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1/*
2** 2001 September 15
3**
4** The author disclaims copyright to this source code. In place of
5** a legal notice, here is a blessing:
6**
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.
10**
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".
18**
19** $Id: where.c,v 1.253 2007/06/11 12:56:15 drh Exp $
20*/
21#include "sqliteInt.h"
22
23/*
24** The number of bits in a Bitmask. "BMS" means "BitMask Size".
25*/
26#define BMS (sizeof(Bitmask)*8)
27
28/*
29** Trace output macros
30*/
31#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
32int sqlite3_where_trace = 0;
33# define WHERETRACE(X) if(sqlite3_where_trace) sqlite3DebugPrintf X
34#else
35# define WHERETRACE(X)
36#endif
37
38/* Forward reference
39*/
40typedef struct WhereClause WhereClause;
41typedef struct ExprMaskSet ExprMaskSet;
42
43/*
44** The query generator uses an array of instances of this structure to
45** help it analyze the subexpressions of the WHERE clause. Each WHERE
46** clause subexpression is separated from the others by an AND operator.
47**
48** All WhereTerms are collected into a single WhereClause structure.
49** The following identity holds:
50**
51** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
52**
53** When a term is of the form:
54**
55** X <op> <expr>
56**
57** where X is a column name and <op> is one of certain operators,
58** then WhereTerm.leftCursor and WhereTerm.leftColumn record the
59** cursor number and column number for X. WhereTerm.operator records
60** the <op> using a bitmask encoding defined by WO_xxx below. The
61** use of a bitmask encoding for the operator allows us to search
62** quickly for terms that match any of several different operators.
63**
64** prereqRight and prereqAll record sets of cursor numbers,
65** but they do so indirectly. A single ExprMaskSet structure translates
66** cursor number into bits and the translated bit is stored in the prereq
67** fields. The translation is used in order to maximize the number of
68** bits that will fit in a Bitmask. The VDBE cursor numbers might be
69** spread out over the non-negative integers. For example, the cursor
70** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The ExprMaskSet
71** translates these sparse cursor numbers into consecutive integers
72** beginning with 0 in order to make the best possible use of the available
73** bits in the Bitmask. So, in the example above, the cursor numbers
74** would be mapped into integers 0 through 7.
75*/
76typedef struct WhereTerm WhereTerm;
77struct WhereTerm {
78 Expr *pExpr; /* Pointer to the subexpression */
79 i16 iParent; /* Disable pWC->a[iParent] when this term disabled */
80 i16 leftCursor; /* Cursor number of X in "X <op> <expr>" */
81 i16 leftColumn; /* Column number of X in "X <op> <expr>" */
82 u16 eOperator; /* A WO_xx value describing <op> */
83 u8 flags; /* Bit flags. See below */
84 u8 nChild; /* Number of children that must disable us */
85 WhereClause *pWC; /* The clause this term is part of */
86 Bitmask prereqRight; /* Bitmask of tables used by pRight */
87 Bitmask prereqAll; /* Bitmask of tables referenced by p */
88};
89
90/*
91** Allowed values of WhereTerm.flags
92*/
93#define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(pExpr) */
94#define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */
95#define TERM_CODED 0x04 /* This term is already coded */
96#define TERM_COPIED 0x08 /* Has a child */
97#define TERM_OR_OK 0x10 /* Used during OR-clause processing */
98
99/*
100** An instance of the following structure holds all information about a
101** WHERE clause. Mostly this is a container for one or more WhereTerms.
102*/
103struct WhereClause {
104 Parse *pParse; /* The parser context */
105 ExprMaskSet *pMaskSet; /* Mapping of table indices to bitmasks */
106 int nTerm; /* Number of terms */
107 int nSlot; /* Number of entries in a[] */
108 WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
109 WhereTerm aStatic[10]; /* Initial static space for a[] */
110};
111
112/*
113** An instance of the following structure keeps track of a mapping
114** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
115**
116** The VDBE cursor numbers are small integers contained in
117** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
118** clause, the cursor numbers might not begin with 0 and they might
119** contain gaps in the numbering sequence. But we want to make maximum
120** use of the bits in our bitmasks. This structure provides a mapping
121** from the sparse cursor numbers into consecutive integers beginning
122** with 0.
123**
124** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
125** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
126**
127** For example, if the WHERE clause expression used these VDBE
128** cursors: 4, 5, 8, 29, 57, 73. Then the ExprMaskSet structure
129** would map those cursor numbers into bits 0 through 5.
130**
131** Note that the mapping is not necessarily ordered. In the example
132** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
133** 57->5, 73->4. Or one of 719 other combinations might be used. It
134** does not really matter. What is important is that sparse cursor
135** numbers all get mapped into bit numbers that begin with 0 and contain
136** no gaps.
137*/
138struct ExprMaskSet {
139 int n; /* Number of assigned cursor values */
140 int ix[sizeof(Bitmask)*8]; /* Cursor assigned to each bit */
141};
142
143
144/*
145** Bitmasks for the operators that indices are able to exploit. An
146** OR-ed combination of these values can be used when searching for
147** terms in the where clause.
148*/
149#define WO_IN 1
150#define WO_EQ 2
151#define WO_LT (WO_EQ<<(TK_LT-TK_EQ))
152#define WO_LE (WO_EQ<<(TK_LE-TK_EQ))
153#define WO_GT (WO_EQ<<(TK_GT-TK_EQ))
154#define WO_GE (WO_EQ<<(TK_GE-TK_EQ))
155#define WO_MATCH 64
156#define WO_ISNULL 128
157
158/*
159** Value for flags returned by bestIndex().
160**
161** The least significant byte is reserved as a mask for WO_ values above.
162** The WhereLevel.flags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
163** But if the table is the right table of a left join, WhereLevel.flags
164** is set to WO_IN|WO_EQ. The WhereLevel.flags field can then be used as
165** the "op" parameter to findTerm when we are resolving equality constraints.
166** ISNULL constraints will then not be used on the right table of a left
167** join. Tickets #2177 and #2189.
168*/
169#define WHERE_ROWID_EQ 0x000100 /* rowid=EXPR or rowid IN (...) */
170#define WHERE_ROWID_RANGE 0x000200 /* rowid<EXPR and/or rowid>EXPR */
171#define WHERE_COLUMN_EQ 0x001000 /* x=EXPR or x IN (...) */
172#define WHERE_COLUMN_RANGE 0x002000 /* x<EXPR and/or x>EXPR */
173#define WHERE_COLUMN_IN 0x004000 /* x IN (...) */
174#define WHERE_TOP_LIMIT 0x010000 /* x<EXPR or x<=EXPR constraint */
175#define WHERE_BTM_LIMIT 0x020000 /* x>EXPR or x>=EXPR constraint */
176#define WHERE_IDX_ONLY 0x080000 /* Use index only - omit table */
177#define WHERE_ORDERBY 0x100000 /* Output will appear in correct order */
178#define WHERE_REVERSE 0x200000 /* Scan in reverse order */
179#define WHERE_UNIQUE 0x400000 /* Selects no more than one row */
180#define WHERE_VIRTUALTABLE 0x800000 /* Use virtual-table processing */
181
182/*
183** Initialize a preallocated WhereClause structure.
184*/
185static void whereClauseInit(
186 WhereClause *pWC, /* The WhereClause to be initialized */
187 Parse *pParse, /* The parsing context */
188 ExprMaskSet *pMaskSet /* Mapping from table indices to bitmasks */
189){
190 pWC->pParse = pParse;
191 pWC->pMaskSet = pMaskSet;
192 pWC->nTerm = 0;
193 pWC->nSlot = ArraySize(pWC->aStatic);
194 pWC->a = pWC->aStatic;
195}
196
197/*
198** Deallocate a WhereClause structure. The WhereClause structure
199** itself is not freed. This routine is the inverse of whereClauseInit().
200*/
201static void whereClauseClear(WhereClause *pWC){
202 int i;
203 WhereTerm *a;
204 for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
205 if( a->flags & TERM_DYNAMIC ){
206 sqlite3ExprDelete(a->pExpr);
207 }
208 }
209 if( pWC->a!=pWC->aStatic ){
210 sqliteFree(pWC->a);
211 }
212}
213
214/*
215** Add a new entries to the WhereClause structure. Increase the allocated
216** space as necessary.
217**
218** If the flags argument includes TERM_DYNAMIC, then responsibility
219** for freeing the expression p is assumed by the WhereClause object.
220**
221** WARNING: This routine might reallocate the space used to store
222** WhereTerms. All pointers to WhereTerms should be invalided after
223** calling this routine. Such pointers may be reinitialized by referencing
224** the pWC->a[] array.
225*/
226static int whereClauseInsert(WhereClause *pWC, Expr *p, int flags){
227 WhereTerm *pTerm;
228 int idx;
229 if( pWC->nTerm>=pWC->nSlot ){
230 WhereTerm *pOld = pWC->a;
231 pWC->a = sqliteMalloc( sizeof(pWC->a[0])*pWC->nSlot*2 );
232 if( pWC->a==0 ){
233 if( flags & TERM_DYNAMIC ){
234 sqlite3ExprDelete(p);
235 }
236 return 0;
237 }
238 memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
239 if( pOld!=pWC->aStatic ){
240 sqliteFree(pOld);
241 }
242 pWC->nSlot *= 2;
243 }
244 pTerm = &pWC->a[idx = pWC->nTerm];
245 pWC->nTerm++;
246 pTerm->pExpr = p;
247 pTerm->flags = flags;
248 pTerm->pWC = pWC;
249 pTerm->iParent = -1;
250 return idx;
251}
252
253/*
254** This routine identifies subexpressions in the WHERE clause where
255** each subexpression is separated by the AND operator or some other
256** operator specified in the op parameter. The WhereClause structure
257** is filled with pointers to subexpressions. For example:
258**
259** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
260** \________/ \_______________/ \________________/
261** slot[0] slot[1] slot[2]
262**
263** The original WHERE clause in pExpr is unaltered. All this routine
264** does is make slot[] entries point to substructure within pExpr.
265**
266** In the previous sentence and in the diagram, "slot[]" refers to
267** the WhereClause.a[] array. This array grows as needed to contain
268** all terms of the WHERE clause.
269*/
270static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
271 if( pExpr==0 ) return;
272 if( pExpr->op!=op ){
273 whereClauseInsert(pWC, pExpr, 0);
274 }else{
275 whereSplit(pWC, pExpr->pLeft, op);
276 whereSplit(pWC, pExpr->pRight, op);
277 }
278}
279
280/*
281** Initialize an expression mask set
282*/
283#define initMaskSet(P) memset(P, 0, sizeof(*P))
284
285/*
286** Return the bitmask for the given cursor number. Return 0 if
287** iCursor is not in the set.
288*/
289static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){
290 int i;
291 for(i=0; i<pMaskSet->n; i++){
292 if( pMaskSet->ix[i]==iCursor ){
293 return ((Bitmask)1)<<i;
294 }
295 }
296 return 0;
297}
298
299/*
300** Create a new mask for cursor iCursor.
301**
302** There is one cursor per table in the FROM clause. The number of
303** tables in the FROM clause is limited by a test early in the
304** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
305** array will never overflow.
306*/
307static void createMask(ExprMaskSet *pMaskSet, int iCursor){
308 assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
309 pMaskSet->ix[pMaskSet->n++] = iCursor;
310}
311
312/*
313** This routine walks (recursively) an expression tree and generates
314** a bitmask indicating which tables are used in that expression
315** tree.
316**
317** In order for this routine to work, the calling function must have
318** previously invoked sqlite3ExprResolveNames() on the expression. See
319** the header comment on that routine for additional information.
320** The sqlite3ExprResolveNames() routines looks for column names and
321** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
322** the VDBE cursor number of the table. This routine just has to
323** translate the cursor numbers into bitmask values and OR all
324** the bitmasks together.
325*/
326static Bitmask exprListTableUsage(ExprMaskSet*, ExprList*);
327static Bitmask exprSelectTableUsage(ExprMaskSet*, Select*);
328static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
329 Bitmask mask = 0;
330 if( p==0 ) return 0;
331 if( p->op==TK_COLUMN ){
332 mask = getMask(pMaskSet, p->iTable);
333 return mask;
334 }
335 mask = exprTableUsage(pMaskSet, p->pRight);
336 mask |= exprTableUsage(pMaskSet, p->pLeft);
337 mask |= exprListTableUsage(pMaskSet, p->pList);
338 mask |= exprSelectTableUsage(pMaskSet, p->pSelect);
339 return mask;
340}
341static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){
342 int i;
343 Bitmask mask = 0;
344 if( pList ){
345 for(i=0; i<pList->nExpr; i++){
346 mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
347 }
348 }
349 return mask;
350}
351static Bitmask exprSelectTableUsage(ExprMaskSet *pMaskSet, Select *pS){
352 Bitmask mask;
353 if( pS==0 ){
354 mask = 0;
355 }else{
356 mask = exprListTableUsage(pMaskSet, pS->pEList);
357 mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
358 mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
359 mask |= exprTableUsage(pMaskSet, pS->pWhere);
360 mask |= exprTableUsage(pMaskSet, pS->pHaving);
361 }
362 return mask;
363}
364
365/*
366** Return TRUE if the given operator is one of the operators that is
367** allowed for an indexable WHERE clause term. The allowed operators are
368** "=", "<", ">", "<=", ">=", and "IN".
369*/
370static int allowedOp(int op){
371 assert( TK_GT>TK_EQ && TK_GT<TK_GE );
372 assert( TK_LT>TK_EQ && TK_LT<TK_GE );
373 assert( TK_LE>TK_EQ && TK_LE<TK_GE );
374 assert( TK_GE==TK_EQ+4 );
375 return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
376}
377
378/*
379** Swap two objects of type T.
380*/
381#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
382
383/*
384** Commute a comparision operator. Expressions of the form "X op Y"
385** are converted into "Y op X".
386*/
387static void exprCommute(Expr *pExpr){
388 assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
389 SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
390 SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
391 if( pExpr->op>=TK_GT ){
392 assert( TK_LT==TK_GT+2 );
393 assert( TK_GE==TK_LE+2 );
394 assert( TK_GT>TK_EQ );
395 assert( TK_GT<TK_LE );
396 assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
397 pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
398 }
399}
400
401/*
402** Translate from TK_xx operator to WO_xx bitmask.
403*/
404static int operatorMask(int op){
405 int c;
406 assert( allowedOp(op) );
407 if( op==TK_IN ){
408 c = WO_IN;
409 }else if( op==TK_ISNULL ){
410 c = WO_ISNULL;
411 }else{
412 c = WO_EQ<<(op-TK_EQ);
413 }
414 assert( op!=TK_ISNULL || c==WO_ISNULL );
415 assert( op!=TK_IN || c==WO_IN );
416 assert( op!=TK_EQ || c==WO_EQ );
417 assert( op!=TK_LT || c==WO_LT );
418 assert( op!=TK_LE || c==WO_LE );
419 assert( op!=TK_GT || c==WO_GT );
420 assert( op!=TK_GE || c==WO_GE );
421 return c;
422}
423
424/*
425** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
426** where X is a reference to the iColumn of table iCur and <op> is one of
427** the WO_xx operator codes specified by the op parameter.
428** Return a pointer to the term. Return 0 if not found.
429*/
430static WhereTerm *findTerm(
431 WhereClause *pWC, /* The WHERE clause to be searched */
432 int iCur, /* Cursor number of LHS */
433 int iColumn, /* Column number of LHS */
434 Bitmask notReady, /* RHS must not overlap with this mask */
435 u16 op, /* Mask of WO_xx values describing operator */
436 Index *pIdx /* Must be compatible with this index, if not NULL */
437){
438 WhereTerm *pTerm;
439 int k;
440 for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
441 if( pTerm->leftCursor==iCur
442 && (pTerm->prereqRight & notReady)==0
443 && pTerm->leftColumn==iColumn
444 && (pTerm->eOperator & op)!=0
445 ){
446 if( iCur>=0 && pIdx && pTerm->eOperator!=WO_ISNULL ){
447 Expr *pX = pTerm->pExpr;
448 CollSeq *pColl;
449 char idxaff;
450 int j;
451 Parse *pParse = pWC->pParse;
452
453 idxaff = pIdx->pTable->aCol[iColumn].affinity;
454 if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
455
456 /* Figure out the collation sequence required from an index for
457 ** it to be useful for optimising expression pX. Store this
458 ** value in variable pColl.
459 */
460 assert(pX->pLeft);
461 pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
462 if( !pColl ){
463 pColl = pParse->db->pDfltColl;
464 }
465
466 for(j=0; j<pIdx->nColumn && pIdx->aiColumn[j]!=iColumn; j++){}
467 assert( j<pIdx->nColumn );
468 if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
469 }
470 return pTerm;
471 }
472 }
473 return 0;
474}
475
476/* Forward reference */
477static void exprAnalyze(SrcList*, WhereClause*, int);
478
479/*
480** Call exprAnalyze on all terms in a WHERE clause.
481**
482**
483*/
484static void exprAnalyzeAll(
485 SrcList *pTabList, /* the FROM clause */
486 WhereClause *pWC /* the WHERE clause to be analyzed */
487){
488 int i;
489 for(i=pWC->nTerm-1; i>=0; i--){
490 exprAnalyze(pTabList, pWC, i);
491 }
492}
493
494#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
495/*
496** Check to see if the given expression is a LIKE or GLOB operator that
497** can be optimized using inequality constraints. Return TRUE if it is
498** so and false if not.
499**
500** In order for the operator to be optimizible, the RHS must be a string
501** literal that does not begin with a wildcard.
502*/
503static int isLikeOrGlob(
504 sqlite3 *db, /* The database */
505 Expr *pExpr, /* Test this expression */
506 int *pnPattern, /* Number of non-wildcard prefix characters */
507 int *pisComplete /* True if the only wildcard is % in the last character */
508){
509 const char *z;
510 Expr *pRight, *pLeft;
511 ExprList *pList;
512 int c, cnt;
513 int noCase;
514 char wc[3];
515 CollSeq *pColl;
516
517 if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){
518 return 0;
519 }
520 pList = pExpr->pList;
521 pRight = pList->a[0].pExpr;
522 if( pRight->op!=TK_STRING ){
523 return 0;
524 }
525 pLeft = pList->a[1].pExpr;
526 if( pLeft->op!=TK_COLUMN ){
527 return 0;
528 }
529 pColl = pLeft->pColl;
530 if( pColl==0 ){
531 /* TODO: Coverage testing doesn't get this case. Is it actually possible
532 ** for an expression of type TK_COLUMN to not have an assigned collation
533 ** sequence at this point?
534 */
535 pColl = db->pDfltColl;
536 }
537 if( (pColl->type!=SQLITE_COLL_BINARY || noCase) &&
538 (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){
539 return 0;
540 }
541 sqlite3DequoteExpr(pRight);
542 z = (char *)pRight->token.z;
543 for(cnt=0; (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2]; cnt++){}
544 if( cnt==0 || 255==(u8)z[cnt] ){
545 return 0;
546 }
547 *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0;
548 *pnPattern = cnt;
549 return 1;
550}
551#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
552
553
554#ifndef SQLITE_OMIT_VIRTUALTABLE
555/*
556** Check to see if the given expression is of the form
557**
558** column MATCH expr
559**
560** If it is then return TRUE. If not, return FALSE.
561*/
562static int isMatchOfColumn(
563 Expr *pExpr /* Test this expression */
564){
565 ExprList *pList;
566
567 if( pExpr->op!=TK_FUNCTION ){
568 return 0;
569 }
570 if( pExpr->token.n!=5 ||
571 sqlite3StrNICmp((const char*)pExpr->token.z,"match",5)!=0 ){
572 return 0;
573 }
574 pList = pExpr->pList;
575 if( pList->nExpr!=2 ){
576 return 0;
577 }
578 if( pList->a[1].pExpr->op != TK_COLUMN ){
579 return 0;
580 }
581 return 1;
582}
583#endif /* SQLITE_OMIT_VIRTUALTABLE */
584
585/*
586** If the pBase expression originated in the ON or USING clause of
587** a join, then transfer the appropriate markings over to derived.
588*/
589static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
590 pDerived->flags |= pBase->flags & EP_FromJoin;
591 pDerived->iRightJoinTable = pBase->iRightJoinTable;
592}
593
594#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
595/*
596** Return TRUE if the given term of an OR clause can be converted
597** into an IN clause. The iCursor and iColumn define the left-hand
598** side of the IN clause.
599**
600** The context is that we have multiple OR-connected equality terms
601** like this:
602**
603** a=<expr1> OR a=<expr2> OR b=<expr3> OR ...
604**
605** The pOrTerm input to this routine corresponds to a single term of
606** this OR clause. In order for the term to be a condidate for
607** conversion to an IN operator, the following must be true:
608**
609** * The left-hand side of the term must be the column which
610** is identified by iCursor and iColumn.
611**
612** * If the right-hand side is also a column, then the affinities
613** of both right and left sides must be such that no type
614** conversions are required on the right. (Ticket #2249)
615**
616** If both of these conditions are true, then return true. Otherwise
617** return false.
618*/
619static int orTermIsOptCandidate(WhereTerm *pOrTerm, int iCursor, int iColumn){
620 int affLeft, affRight;
621 assert( pOrTerm->eOperator==WO_EQ );
622 if( pOrTerm->leftCursor!=iCursor ){
623 return 0;
624 }
625 if( pOrTerm->leftColumn!=iColumn ){
626 return 0;
627 }
628 affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
629 if( affRight==0 ){
630 return 1;
631 }
632 affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
633 if( affRight!=affLeft ){
634 return 0;
635 }
636 return 1;
637}
638
639/*
640** Return true if the given term of an OR clause can be ignored during
641** a check to make sure all OR terms are candidates for optimization.
642** In other words, return true if a call to the orTermIsOptCandidate()
643** above returned false but it is not necessary to disqualify the
644** optimization.
645**
646** Suppose the original OR phrase was this:
647**
648** a=4 OR a=11 OR a=b
649**
650** During analysis, the third term gets flipped around and duplicate
651** so that we are left with this:
652**
653** a=4 OR a=11 OR a=b OR b=a
654**
655** Since the last two terms are duplicates, only one of them
656** has to qualify in order for the whole phrase to qualify. When
657** this routine is called, we know that pOrTerm did not qualify.
658** This routine merely checks to see if pOrTerm has a duplicate that
659** might qualify. If there is a duplicate that has not yet been
660** disqualified, then return true. If there are no duplicates, or
661** the duplicate has also been disqualifed, return false.
662*/
663static int orTermHasOkDuplicate(WhereClause *pOr, WhereTerm *pOrTerm){
664 if( pOrTerm->flags & TERM_COPIED ){
665 /* This is the original term. The duplicate is to the left had
666 ** has not yet been analyzed and thus has not yet been disqualified. */
667 return 1;
668 }
669 if( (pOrTerm->flags & TERM_VIRTUAL)!=0
670 && (pOr->a[pOrTerm->iParent].flags & TERM_OR_OK)!=0 ){
671 /* This is a duplicate term. The original qualified so this one
672 ** does not have to. */
673 return 1;
674 }
675 /* This is either a singleton term or else it is a duplicate for
676 ** which the original did not qualify. Either way we are done for. */
677 return 0;
678}
679#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
680
681/*
682** The input to this routine is an WhereTerm structure with only the
683** "pExpr" field filled in. The job of this routine is to analyze the
684** subexpression and populate all the other fields of the WhereTerm
685** structure.
686**
687** If the expression is of the form "<expr> <op> X" it gets commuted
688** to the standard form of "X <op> <expr>". If the expression is of
689** the form "X <op> Y" where both X and Y are columns, then the original
690** expression is unchanged and a new virtual expression of the form
691** "Y <op> X" is added to the WHERE clause and analyzed separately.
692*/
693static void exprAnalyze(
694 SrcList *pSrc, /* the FROM clause */
695 WhereClause *pWC, /* the WHERE clause */
696 int idxTerm /* Index of the term to be analyzed */
697){
698 WhereTerm *pTerm = &pWC->a[idxTerm];
699 ExprMaskSet *pMaskSet = pWC->pMaskSet;
700 Expr *pExpr = pTerm->pExpr;
701 Bitmask prereqLeft;
702 Bitmask prereqAll;
703 int nPattern;
704 int isComplete;
705 int op;
706
707 if( sqlite3MallocFailed() ) return;
708 prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
709 op = pExpr->op;
710 if( op==TK_IN ){
711 assert( pExpr->pRight==0 );
712 pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList)
713 | exprSelectTableUsage(pMaskSet, pExpr->pSelect);
714 }else if( op==TK_ISNULL ){
715 pTerm->prereqRight = 0;
716 }else{
717 pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
718 }
719 prereqAll = exprTableUsage(pMaskSet, pExpr);
720 if( ExprHasProperty(pExpr, EP_FromJoin) ){
721 prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable);
722 }
723 pTerm->prereqAll = prereqAll;
724 pTerm->leftCursor = -1;
725 pTerm->iParent = -1;
726 pTerm->eOperator = 0;
727 if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
728 Expr *pLeft = pExpr->pLeft;
729 Expr *pRight = pExpr->pRight;
730 if( pLeft->op==TK_COLUMN ){
731 pTerm->leftCursor = pLeft->iTable;
732 pTerm->leftColumn = pLeft->iColumn;
733 pTerm->eOperator = operatorMask(op);
734 }
735 if( pRight && pRight->op==TK_COLUMN ){
736 WhereTerm *pNew;
737 Expr *pDup;
738 if( pTerm->leftCursor>=0 ){
739 int idxNew;
740 pDup = sqlite3ExprDup(pExpr);
741 if( sqlite3MallocFailed() ){
742 sqlite3ExprDelete(pDup);
743 return;
744 }
745 idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
746 if( idxNew==0 ) return;
747 pNew = &pWC->a[idxNew];
748 pNew->iParent = idxTerm;
749 pTerm = &pWC->a[idxTerm];
750 pTerm->nChild = 1;
751 pTerm->flags |= TERM_COPIED;
752 }else{
753 pDup = pExpr;
754 pNew = pTerm;
755 }
756 exprCommute(pDup);
757 pLeft = pDup->pLeft;
758 pNew->leftCursor = pLeft->iTable;
759 pNew->leftColumn = pLeft->iColumn;
760 pNew->prereqRight = prereqLeft;
761 pNew->prereqAll = prereqAll;
762 pNew->eOperator = operatorMask(pDup->op);
763 }
764 }
765
766#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
767 /* If a term is the BETWEEN operator, create two new virtual terms
768 ** that define the range that the BETWEEN implements.
769 */
770 else if( pExpr->op==TK_BETWEEN ){
771 ExprList *pList = pExpr->pList;
772 int i;
773 static const u8 ops[] = {TK_GE, TK_LE};
774 assert( pList!=0 );
775 assert( pList->nExpr==2 );
776 for(i=0; i<2; i++){
777 Expr *pNewExpr;
778 int idxNew;
779 pNewExpr = sqlite3Expr(ops[i], sqlite3ExprDup(pExpr->pLeft),
780 sqlite3ExprDup(pList->a[i].pExpr), 0);
781 idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
782 exprAnalyze(pSrc, pWC, idxNew);
783 pTerm = &pWC->a[idxTerm];
784 pWC->a[idxNew].iParent = idxTerm;
785 }
786 pTerm->nChild = 2;
787 }
788#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
789
790#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
791 /* Attempt to convert OR-connected terms into an IN operator so that
792 ** they can make use of indices. Example:
793 **
794 ** x = expr1 OR expr2 = x OR x = expr3
795 **
796 ** is converted into
797 **
798 ** x IN (expr1,expr2,expr3)
799 **
800 ** This optimization must be omitted if OMIT_SUBQUERY is defined because
801 ** the compiler for the the IN operator is part of sub-queries.
802 */
803 else if( pExpr->op==TK_OR ){
804 int ok;
805 int i, j;
806 int iColumn, iCursor;
807 WhereClause sOr;
808 WhereTerm *pOrTerm;
809
810 assert( (pTerm->flags & TERM_DYNAMIC)==0 );
811 whereClauseInit(&sOr, pWC->pParse, pMaskSet);
812 whereSplit(&sOr, pExpr, TK_OR);
813 exprAnalyzeAll(pSrc, &sOr);
814 assert( sOr.nTerm>=2 );
815 j = 0;
816 do{
817 assert( j<sOr.nTerm );
818 iColumn = sOr.a[j].leftColumn;
819 iCursor = sOr.a[j].leftCursor;
820 ok = iCursor>=0;
821 for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
822 if( pOrTerm->eOperator!=WO_EQ ){
823 goto or_not_possible;
824 }
825 if( orTermIsOptCandidate(pOrTerm, iCursor, iColumn) ){
826 pOrTerm->flags |= TERM_OR_OK;
827 }else if( orTermHasOkDuplicate(&sOr, pOrTerm) ){
828 pOrTerm->flags &= ~TERM_OR_OK;
829 }else{
830 ok = 0;
831 }
832 }
833 }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<2 );
834 if( ok ){
835 ExprList *pList = 0;
836 Expr *pNew, *pDup;
837 Expr *pLeft = 0;
838 for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
839 if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue;
840 pDup = sqlite3ExprDup(pOrTerm->pExpr->pRight);
841 pList = sqlite3ExprListAppend(pList, pDup, 0);
842 pLeft = pOrTerm->pExpr->pLeft;
843 }
844 assert( pLeft!=0 );
845 pDup = sqlite3ExprDup(pLeft);
846 pNew = sqlite3Expr(TK_IN, pDup, 0, 0);
847 if( pNew ){
848 int idxNew;
849 transferJoinMarkings(pNew, pExpr);
850 pNew->pList = pList;
851 idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
852 exprAnalyze(pSrc, pWC, idxNew);
853 pTerm = &pWC->a[idxTerm];
854 pWC->a[idxNew].iParent = idxTerm;
855 pTerm->nChild = 1;
856 }else{
857 sqlite3ExprListDelete(pList);
858 }
859 }
860or_not_possible:
861 whereClauseClear(&sOr);
862 }
863#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
864
865#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
866 /* Add constraints to reduce the search space on a LIKE or GLOB
867 ** operator.
868 */
869 if( isLikeOrGlob(pWC->pParse->db, pExpr, &nPattern, &isComplete) ){
870 Expr *pLeft, *pRight;
871 Expr *pStr1, *pStr2;
872 Expr *pNewExpr1, *pNewExpr2;
873 int idxNew1, idxNew2;
874
875 pLeft = pExpr->pList->a[1].pExpr;
876 pRight = pExpr->pList->a[0].pExpr;
877 pStr1 = sqlite3Expr(TK_STRING, 0, 0, 0);
878 if( pStr1 ){
879 sqlite3TokenCopy(&pStr1->token, &pRight->token);
880 pStr1->token.n = nPattern;
881 pStr1->flags = EP_Dequoted;
882 }
883 pStr2 = sqlite3ExprDup(pStr1);
884 if( pStr2 ){
885 assert( pStr2->token.dyn );
886 ++*(u8*)&pStr2->token.z[nPattern-1];
887 }
888 pNewExpr1 = sqlite3Expr(TK_GE, sqlite3ExprDup(pLeft), pStr1, 0);
889 idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
890 exprAnalyze(pSrc, pWC, idxNew1);
891 pNewExpr2 = sqlite3Expr(TK_LT, sqlite3ExprDup(pLeft), pStr2, 0);
892 idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
893 exprAnalyze(pSrc, pWC, idxNew2);
894 pTerm = &pWC->a[idxTerm];
895 if( isComplete ){
896 pWC->a[idxNew1].iParent = idxTerm;
897 pWC->a[idxNew2].iParent = idxTerm;
898 pTerm->nChild = 2;
899 }
900 }
901#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
902
903#ifndef SQLITE_OMIT_VIRTUALTABLE
904 /* Add a WO_MATCH auxiliary term to the constraint set if the
905 ** current expression is of the form: column MATCH expr.
906 ** This information is used by the xBestIndex methods of
907 ** virtual tables. The native query optimizer does not attempt
908 ** to do anything with MATCH functions.
909 */
910 if( isMatchOfColumn(pExpr) ){
911 int idxNew;
912 Expr *pRight, *pLeft;
913 WhereTerm *pNewTerm;
914 Bitmask prereqColumn, prereqExpr;
915
916 pRight = pExpr->pList->a[0].pExpr;
917 pLeft = pExpr->pList->a[1].pExpr;
918 prereqExpr = exprTableUsage(pMaskSet, pRight);
919 prereqColumn = exprTableUsage(pMaskSet, pLeft);
920 if( (prereqExpr & prereqColumn)==0 ){
921 Expr *pNewExpr;
922 pNewExpr = sqlite3Expr(TK_MATCH, 0, sqlite3ExprDup(pRight), 0);
923 idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
924 pNewTerm = &pWC->a[idxNew];
925 pNewTerm->prereqRight = prereqExpr;
926 pNewTerm->leftCursor = pLeft->iTable;
927 pNewTerm->leftColumn = pLeft->iColumn;
928 pNewTerm->eOperator = WO_MATCH;
929 pNewTerm->iParent = idxTerm;
930 pTerm = &pWC->a[idxTerm];
931 pTerm->nChild = 1;
932 pTerm->flags |= TERM_COPIED;
933 pNewTerm->prereqAll = pTerm->prereqAll;
934 }
935 }
936#endif /* SQLITE_OMIT_VIRTUALTABLE */
937}
938
939/*
940** Return TRUE if any of the expressions in pList->a[iFirst...] contain
941** a reference to any table other than the iBase table.
942*/
943static int referencesOtherTables(
944 ExprList *pList, /* Search expressions in ths list */
945 ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
946 int iFirst, /* Be searching with the iFirst-th expression */
947 int iBase /* Ignore references to this table */
948){
949 Bitmask allowed = ~getMask(pMaskSet, iBase);
950 while( iFirst<pList->nExpr ){
951 if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
952 return 1;
953 }
954 }
955 return 0;
956}
957
958
959/*
960** This routine decides if pIdx can be used to satisfy the ORDER BY
961** clause. If it can, it returns 1. If pIdx cannot satisfy the
962** ORDER BY clause, this routine returns 0.
963**
964** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
965** left-most table in the FROM clause of that same SELECT statement and
966** the table has a cursor number of "base". pIdx is an index on pTab.
967**
968** nEqCol is the number of columns of pIdx that are used as equality
969** constraints. Any of these columns may be missing from the ORDER BY
970** clause and the match can still be a success.
971**
972** All terms of the ORDER BY that match against the index must be either
973** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
974** index do not need to satisfy this constraint.) The *pbRev value is
975** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
976** the ORDER BY clause is all ASC.
977*/
978static int isSortingIndex(
979 Parse *pParse, /* Parsing context */
980 ExprMaskSet *pMaskSet, /* Mapping from table indices to bitmaps */
981 Index *pIdx, /* The index we are testing */
982 int base, /* Cursor number for the table to be sorted */
983 ExprList *pOrderBy, /* The ORDER BY clause */
984 int nEqCol, /* Number of index columns with == constraints */
985 int *pbRev /* Set to 1 if ORDER BY is DESC */
986){
987 int i, j; /* Loop counters */
988 int sortOrder = 0; /* XOR of index and ORDER BY sort direction */
989 int nTerm; /* Number of ORDER BY terms */
990 struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
991 sqlite3 *db = pParse->db;
992
993 assert( pOrderBy!=0 );
994 nTerm = pOrderBy->nExpr;
995 assert( nTerm>0 );
996
997 /* Match terms of the ORDER BY clause against columns of
998 ** the index.
999 **
1000 ** Note that indices have pIdx->nColumn regular columns plus
1001 ** one additional column containing the rowid. The rowid column
1002 ** of the index is also allowed to match against the ORDER BY
1003 ** clause.
1004 */
1005 for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
1006 Expr *pExpr; /* The expression of the ORDER BY pTerm */
1007 CollSeq *pColl; /* The collating sequence of pExpr */
1008 int termSortOrder; /* Sort order for this term */
1009 int iColumn; /* The i-th column of the index. -1 for rowid */
1010 int iSortOrder; /* 1 for DESC, 0 for ASC on the i-th index term */
1011 const char *zColl; /* Name of the collating sequence for i-th index term */
1012
1013 pExpr = pTerm->pExpr;
1014 if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
1015 /* Can not use an index sort on anything that is not a column in the
1016 ** left-most table of the FROM clause */
1017 break;
1018 }
1019 pColl = sqlite3ExprCollSeq(pParse, pExpr);
1020 if( !pColl ){
1021 pColl = db->pDfltColl;
1022 }
1023 if( i<pIdx->nColumn ){
1024 iColumn = pIdx->aiColumn[i];
1025 if( iColumn==pIdx->pTable->iPKey ){
1026 iColumn = -1;
1027 }
1028 iSortOrder = pIdx->aSortOrder[i];
1029 zColl = pIdx->azColl[i];
1030 }else{
1031 iColumn = -1;
1032 iSortOrder = 0;
1033 zColl = pColl->zName;
1034 }
1035 if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
1036 /* Term j of the ORDER BY clause does not match column i of the index */
1037 if( i<nEqCol ){
1038 /* If an index column that is constrained by == fails to match an
1039 ** ORDER BY term, that is OK. Just ignore that column of the index
1040 */
1041 continue;
1042 }else{
1043 /* If an index column fails to match and is not constrained by ==
1044 ** then the index cannot satisfy the ORDER BY constraint.
1045 */
1046 return 0;
1047 }
1048 }
1049 assert( pIdx->aSortOrder!=0 );
1050 assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
1051 assert( iSortOrder==0 || iSortOrder==1 );
1052 termSortOrder = iSortOrder ^ pTerm->sortOrder;
1053 if( i>nEqCol ){
1054 if( termSortOrder!=sortOrder ){
1055 /* Indices can only be used if all ORDER BY terms past the
1056 ** equality constraints are all either DESC or ASC. */
1057 return 0;
1058 }
1059 }else{
1060 sortOrder = termSortOrder;
1061 }
1062 j++;
1063 pTerm++;
1064 if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1065 /* If the indexed column is the primary key and everything matches
1066 ** so far and none of the ORDER BY terms to the right reference other
1067 ** tables in the join, then we are assured that the index can be used
1068 ** to sort because the primary key is unique and so none of the other
1069 ** columns will make any difference
1070 */
1071 j = nTerm;
1072 }
1073 }
1074
1075 *pbRev = sortOrder!=0;
1076 if( j>=nTerm ){
1077 /* All terms of the ORDER BY clause are covered by this index so
1078 ** this index can be used for sorting. */
1079 return 1;
1080 }
1081 if( pIdx->onError!=OE_None && i==pIdx->nColumn
1082 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1083 /* All terms of this index match some prefix of the ORDER BY clause
1084 ** and the index is UNIQUE and no terms on the tail of the ORDER BY
1085 ** clause reference other tables in a join. If this is all true then
1086 ** the order by clause is superfluous. */
1087 return 1;
1088 }
1089 return 0;
1090}
1091
1092/*
1093** Check table to see if the ORDER BY clause in pOrderBy can be satisfied
1094** by sorting in order of ROWID. Return true if so and set *pbRev to be
1095** true for reverse ROWID and false for forward ROWID order.
1096*/
1097static int sortableByRowid(
1098 int base, /* Cursor number for table to be sorted */
1099 ExprList *pOrderBy, /* The ORDER BY clause */
1100 ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
1101 int *pbRev /* Set to 1 if ORDER BY is DESC */
1102){
1103 Expr *p;
1104
1105 assert( pOrderBy!=0 );
1106 assert( pOrderBy->nExpr>0 );
1107 p = pOrderBy->a[0].pExpr;
1108 if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1
1109 && !referencesOtherTables(pOrderBy, pMaskSet, 1, base) ){
1110 *pbRev = pOrderBy->a[0].sortOrder;
1111 return 1;
1112 }
1113 return 0;
1114}
1115
1116/*
1117** Prepare a crude estimate of the logarithm of the input value.
1118** The results need not be exact. This is only used for estimating
1119** the total cost of performing operatings with O(logN) or O(NlogN)
1120** complexity. Because N is just a guess, it is no great tragedy if
1121** logN is a little off.
1122*/
1123static double estLog(double N){
1124 double logN = 1;
1125 double x = 10;
1126 while( N>x ){
1127 logN += 1;
1128 x *= 10;
1129 }
1130 return logN;
1131}
1132
1133/*
1134** Two routines for printing the content of an sqlite3_index_info
1135** structure. Used for testing and debugging only. If neither
1136** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
1137** are no-ops.
1138*/
1139#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
1140static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
1141 int i;
1142 if( !sqlite3_where_trace ) return;
1143 for(i=0; i<p->nConstraint; i++){
1144 sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
1145 i,
1146 p->aConstraint[i].iColumn,
1147 p->aConstraint[i].iTermOffset,
1148 p->aConstraint[i].op,
1149 p->aConstraint[i].usable);
1150 }
1151 for(i=0; i<p->nOrderBy; i++){
1152 sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
1153 i,
1154 p->aOrderBy[i].iColumn,
1155 p->aOrderBy[i].desc);
1156 }
1157}
1158static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
1159 int i;
1160 if( !sqlite3_where_trace ) return;
1161 for(i=0; i<p->nConstraint; i++){
1162 sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
1163 i,
1164 p->aConstraintUsage[i].argvIndex,
1165 p->aConstraintUsage[i].omit);
1166 }
1167 sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
1168 sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
1169 sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
1170 sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
1171}
1172#else
1173#define TRACE_IDX_INPUTS(A)
1174#define TRACE_IDX_OUTPUTS(A)
1175#endif
1176
1177#ifndef SQLITE_OMIT_VIRTUALTABLE
1178/*
1179** Compute the best index for a virtual table.
1180**
1181** The best index is computed by the xBestIndex method of the virtual
1182** table module. This routine is really just a wrapper that sets up
1183** the sqlite3_index_info structure that is used to communicate with
1184** xBestIndex.
1185**
1186** In a join, this routine might be called multiple times for the
1187** same virtual table. The sqlite3_index_info structure is created
1188** and initialized on the first invocation and reused on all subsequent
1189** invocations. The sqlite3_index_info structure is also used when
1190** code is generated to access the virtual table. The whereInfoDelete()
1191** routine takes care of freeing the sqlite3_index_info structure after
1192** everybody has finished with it.
1193*/
1194static double bestVirtualIndex(
1195 Parse *pParse, /* The parsing context */
1196 WhereClause *pWC, /* The WHERE clause */
1197 struct SrcList_item *pSrc, /* The FROM clause term to search */
1198 Bitmask notReady, /* Mask of cursors that are not available */
1199 ExprList *pOrderBy, /* The order by clause */
1200 int orderByUsable, /* True if we can potential sort */
1201 sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
1202){
1203 Table *pTab = pSrc->pTab;
1204 sqlite3_index_info *pIdxInfo;
1205 struct sqlite3_index_constraint *pIdxCons;
1206 struct sqlite3_index_orderby *pIdxOrderBy;
1207 struct sqlite3_index_constraint_usage *pUsage;
1208 WhereTerm *pTerm;
1209 int i, j;
1210 int nOrderBy;
1211 int rc;
1212
1213 /* If the sqlite3_index_info structure has not been previously
1214 ** allocated and initialized for this virtual table, then allocate
1215 ** and initialize it now
1216 */
1217 pIdxInfo = *ppIdxInfo;
1218 if( pIdxInfo==0 ){
1219 WhereTerm *pTerm;
1220 int nTerm;
1221 WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));
1222
1223 /* Count the number of possible WHERE clause constraints referring
1224 ** to this virtual table */
1225 for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
1226 if( pTerm->leftCursor != pSrc->iCursor ) continue;
1227 if( pTerm->eOperator==WO_IN ) continue;
1228 nTerm++;
1229 }
1230
1231 /* If the ORDER BY clause contains only columns in the current
1232 ** virtual table then allocate space for the aOrderBy part of
1233 ** the sqlite3_index_info structure.
1234 */
1235 nOrderBy = 0;
1236 if( pOrderBy ){
1237 for(i=0; i<pOrderBy->nExpr; i++){
1238 Expr *pExpr = pOrderBy->a[i].pExpr;
1239 if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
1240 }
1241 if( i==pOrderBy->nExpr ){
1242 nOrderBy = pOrderBy->nExpr;
1243 }
1244 }
1245
1246 /* Allocate the sqlite3_index_info structure
1247 */
1248 pIdxInfo = sqliteMalloc( sizeof(*pIdxInfo)
1249 + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
1250 + sizeof(*pIdxOrderBy)*nOrderBy );
1251 if( pIdxInfo==0 ){
1252 sqlite3ErrorMsg(pParse, "out of memory");
1253 return 0.0;
1254 }
1255 *ppIdxInfo = pIdxInfo;
1256
1257 /* Initialize the structure. The sqlite3_index_info structure contains
1258 ** many fields that are declared "const" to prevent xBestIndex from
1259 ** changing them. We have to do some funky casting in order to
1260 ** initialize those fields.
1261 */
1262 pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
1263 pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
1264 pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
1265 *(int*)&pIdxInfo->nConstraint = nTerm;
1266 *(int*)&pIdxInfo->nOrderBy = nOrderBy;
1267 *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
1268 *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
1269 *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
1270 pUsage;
1271
1272 for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
1273 if( pTerm->leftCursor != pSrc->iCursor ) continue;
1274 if( pTerm->eOperator==WO_IN ) continue;
1275 pIdxCons[j].iColumn = pTerm->leftColumn;
1276 pIdxCons[j].iTermOffset = i;
1277 pIdxCons[j].op = pTerm->eOperator;
1278 /* The direct assignment in the previous line is possible only because
1279 ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
1280 ** following asserts verify this fact. */
1281 assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
1282 assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
1283 assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
1284 assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
1285 assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
1286 assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
1287 assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
1288 j++;
1289 }
1290 for(i=0; i<nOrderBy; i++){
1291 Expr *pExpr = pOrderBy->a[i].pExpr;
1292 pIdxOrderBy[i].iColumn = pExpr->iColumn;
1293 pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
1294 }
1295 }
1296
1297 /* At this point, the sqlite3_index_info structure that pIdxInfo points
1298 ** to will have been initialized, either during the current invocation or
1299 ** during some prior invocation. Now we just have to customize the
1300 ** details of pIdxInfo for the current invocation and pass it to
1301 ** xBestIndex.
1302 */
1303
1304 /* The module name must be defined. Also, by this point there must
1305 ** be a pointer to an sqlite3_vtab structure. Otherwise
1306 ** sqlite3ViewGetColumnNames() would have picked up the error.
1307 */
1308 assert( pTab->azModuleArg && pTab->azModuleArg[0] );
1309 assert( pTab->pVtab );
1310#if 0
1311 if( pTab->pVtab==0 ){
1312 sqlite3ErrorMsg(pParse, "undefined module %s for table %s",
1313 pTab->azModuleArg[0], pTab->zName);
1314 return 0.0;
1315 }
1316#endif
1317
1318 /* Set the aConstraint[].usable fields and initialize all
1319 ** output variables to zero.
1320 **
1321 ** aConstraint[].usable is true for constraints where the right-hand
1322 ** side contains only references to tables to the left of the current
1323 ** table. In other words, if the constraint is of the form:
1324 **
1325 ** column = expr
1326 **
1327 ** and we are evaluating a join, then the constraint on column is
1328 ** only valid if all tables referenced in expr occur to the left
1329 ** of the table containing column.
1330 **
1331 ** The aConstraints[] array contains entries for all constraints
1332 ** on the current table. That way we only have to compute it once
1333 ** even though we might try to pick the best index multiple times.
1334 ** For each attempt at picking an index, the order of tables in the
1335 ** join might be different so we have to recompute the usable flag
1336 ** each time.
1337 */
1338 pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
1339 pUsage = pIdxInfo->aConstraintUsage;
1340 for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
1341 j = pIdxCons->iTermOffset;
1342 pTerm = &pWC->a[j];
1343 pIdxCons->usable = (pTerm->prereqRight & notReady)==0;
1344 }
1345 memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
1346 if( pIdxInfo->needToFreeIdxStr ){
1347 sqlite3_free(pIdxInfo->idxStr);
1348 }
1349 pIdxInfo->idxStr = 0;
1350 pIdxInfo->idxNum = 0;
1351 pIdxInfo->needToFreeIdxStr = 0;
1352 pIdxInfo->orderByConsumed = 0;
1353 pIdxInfo->estimatedCost = SQLITE_BIG_DBL / 2.0;
1354 nOrderBy = pIdxInfo->nOrderBy;
1355 if( pIdxInfo->nOrderBy && !orderByUsable ){
1356 *(int*)&pIdxInfo->nOrderBy = 0;
1357 }
1358
1359 sqlite3SafetyOff(pParse->db);
1360 WHERETRACE(("xBestIndex for %s\n", pTab->zName));
1361 TRACE_IDX_INPUTS(pIdxInfo);
1362 rc = pTab->pVtab->pModule->xBestIndex(pTab->pVtab, pIdxInfo);
1363 TRACE_IDX_OUTPUTS(pIdxInfo);
1364 if( rc!=SQLITE_OK ){
1365 if( rc==SQLITE_NOMEM ){
1366 sqlite3FailedMalloc();
1367 }else {
1368 sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
1369 }
1370 sqlite3SafetyOn(pParse->db);
1371 }else{
1372 rc = sqlite3SafetyOn(pParse->db);
1373 }
1374 *(int*)&pIdxInfo->nOrderBy = nOrderBy;
1375
1376 return pIdxInfo->estimatedCost;
1377}
1378#endif /* SQLITE_OMIT_VIRTUALTABLE */
1379
1380/*
1381** Find the best index for accessing a particular table. Return a pointer
1382** to the index, flags that describe how the index should be used, the
1383** number of equality constraints, and the "cost" for this index.
1384**
1385** The lowest cost index wins. The cost is an estimate of the amount of
1386** CPU and disk I/O need to process the request using the selected index.
1387** Factors that influence cost include:
1388**
1389** * The estimated number of rows that will be retrieved. (The
1390** fewer the better.)
1391**
1392** * Whether or not sorting must occur.
1393**
1394** * Whether or not there must be separate lookups in the
1395** index and in the main table.
1396**
1397*/
1398static double bestIndex(
1399 Parse *pParse, /* The parsing context */
1400 WhereClause *pWC, /* The WHERE clause */
1401 struct SrcList_item *pSrc, /* The FROM clause term to search */
1402 Bitmask notReady, /* Mask of cursors that are not available */
1403 ExprList *pOrderBy, /* The order by clause */
1404 Index **ppIndex, /* Make *ppIndex point to the best index */
1405 int *pFlags, /* Put flags describing this choice in *pFlags */
1406 int *pnEq /* Put the number of == or IN constraints here */
1407){
1408 WhereTerm *pTerm;
1409 Index *bestIdx = 0; /* Index that gives the lowest cost */
1410 double lowestCost; /* The cost of using bestIdx */
1411 int bestFlags = 0; /* Flags associated with bestIdx */
1412 int bestNEq = 0; /* Best value for nEq */
1413 int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
1414 Index *pProbe; /* An index we are evaluating */
1415 int rev; /* True to scan in reverse order */
1416 int flags; /* Flags associated with pProbe */
1417 int nEq; /* Number of == or IN constraints */
1418 int eqTermMask; /* Mask of valid equality operators */
1419 double cost; /* Cost of using pProbe */
1420
1421 WHERETRACE(("bestIndex: tbl=%s notReady=%x\n", pSrc->pTab->zName, notReady));
1422 lowestCost = SQLITE_BIG_DBL;
1423 pProbe = pSrc->pTab->pIndex;
1424
1425 /* If the table has no indices and there are no terms in the where
1426 ** clause that refer to the ROWID, then we will never be able to do
1427 ** anything other than a full table scan on this table. We might as
1428 ** well put it first in the join order. That way, perhaps it can be
1429 ** referenced by other tables in the join.
1430 */
1431 if( pProbe==0 &&
1432 findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 &&
1433 (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev)) ){
1434 *pFlags = 0;
1435 *ppIndex = 0;
1436 *pnEq = 0;
1437 return 0.0;
1438 }
1439
1440 /* Check for a rowid=EXPR or rowid IN (...) constraints
1441 */
1442 pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
1443 if( pTerm ){
1444 Expr *pExpr;
1445 *ppIndex = 0;
1446 bestFlags = WHERE_ROWID_EQ;
1447 if( pTerm->eOperator & WO_EQ ){
1448 /* Rowid== is always the best pick. Look no further. Because only
1449 ** a single row is generated, output is always in sorted order */
1450 *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE;
1451 *pnEq = 1;
1452 WHERETRACE(("... best is rowid\n"));
1453 return 0.0;
1454 }else if( (pExpr = pTerm->pExpr)->pList!=0 ){
1455 /* Rowid IN (LIST): cost is NlogN where N is the number of list
1456 ** elements. */
1457 lowestCost = pExpr->pList->nExpr;
1458 lowestCost *= estLog(lowestCost);
1459 }else{
1460 /* Rowid IN (SELECT): cost is NlogN where N is the number of rows
1461 ** in the result of the inner select. We have no way to estimate
1462 ** that value so make a wild guess. */
1463 lowestCost = 200;
1464 }
1465 WHERETRACE(("... rowid IN cost: %.9g\n", lowestCost));
1466 }
1467
1468 /* Estimate the cost of a table scan. If we do not know how many
1469 ** entries are in the table, use 1 million as a guess.
1470 */
1471 cost = pProbe ? pProbe->aiRowEst[0] : 1000000;
1472 WHERETRACE(("... table scan base cost: %.9g\n", cost));
1473 flags = WHERE_ROWID_RANGE;
1474
1475 /* Check for constraints on a range of rowids in a table scan.
1476 */
1477 pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0);
1478 if( pTerm ){
1479 if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){
1480 flags |= WHERE_TOP_LIMIT;
1481 cost /= 3; /* Guess that rowid<EXPR eliminates two-thirds or rows */
1482 }
1483 if( findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0) ){
1484 flags |= WHERE_BTM_LIMIT;
1485 cost /= 3; /* Guess that rowid>EXPR eliminates two-thirds of rows */
1486 }
1487 WHERETRACE(("... rowid range reduces cost to %.9g\n", cost));
1488 }else{
1489 flags = 0;
1490 }
1491
1492 /* If the table scan does not satisfy the ORDER BY clause, increase
1493 ** the cost by NlogN to cover the expense of sorting. */
1494 if( pOrderBy ){
1495 if( sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev) ){
1496 flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE;
1497 if( rev ){
1498 flags |= WHERE_REVERSE;
1499 }
1500 }else{
1501 cost += cost*estLog(cost);
1502 WHERETRACE(("... sorting increases cost to %.9g\n", cost));
1503 }
1504 }
1505 if( cost<lowestCost ){
1506 lowestCost = cost;
1507 bestFlags = flags;
1508 }
1509
1510 /* If the pSrc table is the right table of a LEFT JOIN then we may not
1511 ** use an index to satisfy IS NULL constraints on that table. This is
1512 ** because columns might end up being NULL if the table does not match -
1513 ** a circumstance which the index cannot help us discover. Ticket #2177.
1514 */
1515 if( (pSrc->jointype & JT_LEFT)!=0 ){
1516 eqTermMask = WO_EQ|WO_IN;
1517 }else{
1518 eqTermMask = WO_EQ|WO_IN|WO_ISNULL;
1519 }
1520
1521 /* Look at each index.
1522 */
1523 for(; pProbe; pProbe=pProbe->pNext){
1524 int i; /* Loop counter */
1525 double inMultiplier = 1;
1526
1527 WHERETRACE(("... index %s:\n", pProbe->zName));
1528
1529 /* Count the number of columns in the index that are satisfied
1530 ** by x=EXPR constraints or x IN (...) constraints.
1531 */
1532 flags = 0;
1533 for(i=0; i<pProbe->nColumn; i++){
1534 int j = pProbe->aiColumn[i];
1535 pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pProbe);
1536 if( pTerm==0 ) break;
1537 flags |= WHERE_COLUMN_EQ;
1538 if( pTerm->eOperator & WO_IN ){
1539 Expr *pExpr = pTerm->pExpr;
1540 flags |= WHERE_COLUMN_IN;
1541 if( pExpr->pSelect!=0 ){
1542 inMultiplier *= 25;
1543 }else if( pExpr->pList!=0 ){
1544 inMultiplier *= pExpr->pList->nExpr + 1;
1545 }
1546 }
1547 }
1548 cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier);
1549 nEq = i;
1550 if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0
1551 && nEq==pProbe->nColumn ){
1552 flags |= WHERE_UNIQUE;
1553 }
1554 WHERETRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n", nEq, inMultiplier, cost));
1555
1556 /* Look for range constraints
1557 */
1558 if( nEq<pProbe->nColumn ){
1559 int j = pProbe->aiColumn[nEq];
1560 pTerm = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pProbe);
1561 if( pTerm ){
1562 flags |= WHERE_COLUMN_RANGE;
1563 if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pProbe) ){
1564 flags |= WHERE_TOP_LIMIT;
1565 cost /= 3;
1566 }
1567 if( findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pProbe) ){
1568 flags |= WHERE_BTM_LIMIT;
1569 cost /= 3;
1570 }
1571 WHERETRACE(("...... range reduces cost to %.9g\n", cost));
1572 }
1573 }
1574
1575 /* Add the additional cost of sorting if that is a factor.
1576 */
1577 if( pOrderBy ){
1578 if( (flags & WHERE_COLUMN_IN)==0 &&
1579 isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev) ){
1580 if( flags==0 ){
1581 flags = WHERE_COLUMN_RANGE;
1582 }
1583 flags |= WHERE_ORDERBY;
1584 if( rev ){
1585 flags |= WHERE_REVERSE;
1586 }
1587 }else{
1588 cost += cost*estLog(cost);
1589 WHERETRACE(("...... orderby increases cost to %.9g\n", cost));
1590 }
1591 }
1592
1593 /* Check to see if we can get away with using just the index without
1594 ** ever reading the table. If that is the case, then halve the
1595 ** cost of this index.
1596 */
1597 if( flags && pSrc->colUsed < (((Bitmask)1)<<(BMS-1)) ){
1598 Bitmask m = pSrc->colUsed;
1599 int j;
1600 for(j=0; j<pProbe->nColumn; j++){
1601 int x = pProbe->aiColumn[j];
1602 if( x<BMS-1 ){
1603 m &= ~(((Bitmask)1)<<x);
1604 }
1605 }
1606 if( m==0 ){
1607 flags |= WHERE_IDX_ONLY;
1608 cost /= 2;
1609 WHERETRACE(("...... idx-only reduces cost to %.9g\n", cost));
1610 }
1611 }
1612
1613 /* If this index has achieved the lowest cost so far, then use it.
1614 */
1615 if( cost < lowestCost ){
1616 bestIdx = pProbe;
1617 lowestCost = cost;
1618 assert( flags!=0 );
1619 bestFlags = flags;
1620 bestNEq = nEq;
1621 }
1622 }
1623
1624 /* Report the best result
1625 */
1626 *ppIndex = bestIdx;
1627 WHERETRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n",
1628 bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq));
1629 *pFlags = bestFlags | eqTermMask;
1630 *pnEq = bestNEq;
1631 return lowestCost;
1632}
1633
1634
1635/*
1636** Disable a term in the WHERE clause. Except, do not disable the term
1637** if it controls a LEFT OUTER JOIN and it did not originate in the ON
1638** or USING clause of that join.
1639**
1640** Consider the term t2.z='ok' in the following queries:
1641**
1642** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
1643** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
1644** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
1645**
1646** The t2.z='ok' is disabled in the in (2) because it originates
1647** in the ON clause. The term is disabled in (3) because it is not part
1648** of a LEFT OUTER JOIN. In (1), the term is not disabled.
1649**
1650** Disabling a term causes that term to not be tested in the inner loop
1651** of the join. Disabling is an optimization. When terms are satisfied
1652** by indices, we disable them to prevent redundant tests in the inner
1653** loop. We would get the correct results if nothing were ever disabled,
1654** but joins might run a little slower. The trick is to disable as much
1655** as we can without disabling too much. If we disabled in (1), we'd get
1656** the wrong answer. See ticket #813.
1657*/
1658static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
1659 if( pTerm
1660 && (pTerm->flags & TERM_CODED)==0
1661 && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
1662 ){
1663 pTerm->flags |= TERM_CODED;
1664 if( pTerm->iParent>=0 ){
1665 WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
1666 if( (--pOther->nChild)==0 ){
1667 disableTerm(pLevel, pOther);
1668 }
1669 }
1670 }
1671}
1672
1673/*
1674** Generate code that builds a probe for an index.
1675**
1676** There should be nColumn values on the stack. The index
1677** to be probed is pIdx. Pop the values from the stack and
1678** replace them all with a single record that is the index
1679** problem.
1680*/
1681static void buildIndexProbe(
1682 Vdbe *v, /* Generate code into this VM */
1683 int nColumn, /* The number of columns to check for NULL */
1684 Index *pIdx /* Index that we will be searching */
1685){
1686 sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
1687 sqlite3IndexAffinityStr(v, pIdx);
1688}
1689
1690
1691/*
1692** Generate code for a single equality term of the WHERE clause. An equality
1693** term can be either X=expr or X IN (...). pTerm is the term to be
1694** coded.
1695**
1696** The current value for the constraint is left on the top of the stack.
1697**
1698** For a constraint of the form X=expr, the expression is evaluated and its
1699** result is left on the stack. For constraints of the form X IN (...)
1700** this routine sets up a loop that will iterate over all values of X.
1701*/
1702static void codeEqualityTerm(
1703 Parse *pParse, /* The parsing context */
1704 WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
1705 WhereLevel *pLevel /* When level of the FROM clause we are working on */
1706){
1707 Expr *pX = pTerm->pExpr;
1708 Vdbe *v = pParse->pVdbe;
1709 if( pX->op==TK_EQ ){
1710 sqlite3ExprCode(pParse, pX->pRight);
1711 }else if( pX->op==TK_ISNULL ){
1712 sqlite3VdbeAddOp(v, OP_Null, 0, 0);
1713#ifndef SQLITE_OMIT_SUBQUERY
1714 }else{
1715 int iTab;
1716 struct InLoop *pIn;
1717
1718 assert( pX->op==TK_IN );
1719 sqlite3CodeSubselect(pParse, pX);
1720 iTab = pX->iTable;
1721 sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0);
1722 VdbeComment((v, "# %.*s", pX->span.n, pX->span.z));
1723 if( pLevel->nIn==0 ){
1724 pLevel->nxt = sqlite3VdbeMakeLabel(v);
1725 }
1726 pLevel->nIn++;
1727 pLevel->aInLoop = sqliteReallocOrFree(pLevel->aInLoop,
1728 sizeof(pLevel->aInLoop[0])*pLevel->nIn);
1729 pIn = pLevel->aInLoop;
1730 if( pIn ){
1731 pIn += pLevel->nIn - 1;
1732 pIn->iCur = iTab;
1733 pIn->topAddr = sqlite3VdbeAddOp(v, OP_Column, iTab, 0);
1734 sqlite3VdbeAddOp(v, OP_IsNull, -1, 0);
1735 }else{
1736 pLevel->nIn = 0;
1737 }
1738#endif
1739 }
1740 disableTerm(pLevel, pTerm);
1741}
1742
1743/*
1744** Generate code that will evaluate all == and IN constraints for an
1745** index. The values for all constraints are left on the stack.
1746**
1747** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
1748** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
1749** The index has as many as three equality constraints, but in this
1750** example, the third "c" value is an inequality. So only two
1751** constraints are coded. This routine will generate code to evaluate
1752** a==5 and b IN (1,2,3). The current values for a and b will be left
1753** on the stack - a is the deepest and b the shallowest.
1754**
1755** In the example above nEq==2. But this subroutine works for any value
1756** of nEq including 0. If nEq==0, this routine is nearly a no-op.
1757** The only thing it does is allocate the pLevel->iMem memory cell.
1758**
1759** This routine always allocates at least one memory cell and puts
1760** the address of that memory cell in pLevel->iMem. The code that
1761** calls this routine will use pLevel->iMem to store the termination
1762** key value of the loop. If one or more IN operators appear, then
1763** this routine allocates an additional nEq memory cells for internal
1764** use.
1765*/
1766static void codeAllEqualityTerms(
1767 Parse *pParse, /* Parsing context */
1768 WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
1769 WhereClause *pWC, /* The WHERE clause */
1770 Bitmask notReady /* Which parts of FROM have not yet been coded */
1771){
1772 int nEq = pLevel->nEq; /* The number of == or IN constraints to code */
1773 int termsInMem = 0; /* If true, store value in mem[] cells */
1774 Vdbe *v = pParse->pVdbe; /* The virtual machine under construction */
1775 Index *pIdx = pLevel->pIdx; /* The index being used for this loop */
1776 int iCur = pLevel->iTabCur; /* The cursor of the table */
1777 WhereTerm *pTerm; /* A single constraint term */
1778 int j; /* Loop counter */
1779
1780 /* Figure out how many memory cells we will need then allocate them.
1781 ** We always need at least one used to store the loop terminator
1782 ** value. If there are IN operators we'll need one for each == or
1783 ** IN constraint.
1784 */
1785 pLevel->iMem = pParse->nMem++;
1786 if( pLevel->flags & WHERE_COLUMN_IN ){
1787 pParse->nMem += pLevel->nEq;
1788 termsInMem = 1;
1789 }
1790
1791 /* Evaluate the equality constraints
1792 */
1793 assert( pIdx->nColumn>=nEq );
1794 for(j=0; j<nEq; j++){
1795 int k = pIdx->aiColumn[j];
1796 pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
1797 if( pTerm==0 ) break;
1798 assert( (pTerm->flags & TERM_CODED)==0 );
1799 codeEqualityTerm(pParse, pTerm, pLevel);
1800 if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
1801 sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), pLevel->brk);
1802 }
1803 if( termsInMem ){
1804 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1);
1805 }
1806 }
1807
1808 /* Make sure all the constraint values are on the top of the stack
1809 */
1810 if( termsInMem ){
1811 for(j=0; j<nEq; j++){
1812 sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem+j+1, 0);
1813 }
1814 }
1815}
1816
1817#if defined(SQLITE_TEST)
1818/*
1819** The following variable holds a text description of query plan generated
1820** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin
1821** overwrites the previous. This information is used for testing and
1822** analysis only.
1823*/
1824char sqlite3_query_plan[BMS*2*40]; /* Text of the join */
1825static int nQPlan = 0; /* Next free slow in _query_plan[] */
1826
1827#endif /* SQLITE_TEST */
1828
1829
1830/*
1831** Free a WhereInfo structure
1832*/
1833static void whereInfoFree(WhereInfo *pWInfo){
1834 if( pWInfo ){
1835 int i;
1836 for(i=0; i<pWInfo->nLevel; i++){
1837 sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
1838 if( pInfo ){
1839 if( pInfo->needToFreeIdxStr ){
1840 /* Coverage: Don't think this can be reached. By the time this
1841 ** function is called, the index-strings have been passed
1842 ** to the vdbe layer for deletion.
1843 */
1844 sqlite3_free(pInfo->idxStr);
1845 }
1846 sqliteFree(pInfo);
1847 }
1848 }
1849 sqliteFree(pWInfo);
1850 }
1851}
1852
1853
1854/*
1855** Generate the beginning of the loop used for WHERE clause processing.
1856** The return value is a pointer to an opaque structure that contains
1857** information needed to terminate the loop. Later, the calling routine
1858** should invoke sqlite3WhereEnd() with the return value of this function
1859** in order to complete the WHERE clause processing.
1860**
1861** If an error occurs, this routine returns NULL.
1862**
1863** The basic idea is to do a nested loop, one loop for each table in
1864** the FROM clause of a select. (INSERT and UPDATE statements are the
1865** same as a SELECT with only a single table in the FROM clause.) For
1866** example, if the SQL is this:
1867**
1868** SELECT * FROM t1, t2, t3 WHERE ...;
1869**
1870** Then the code generated is conceptually like the following:
1871**
1872** foreach row1 in t1 do \ Code generated
1873** foreach row2 in t2 do |-- by sqlite3WhereBegin()
1874** foreach row3 in t3 do /
1875** ...
1876** end \ Code generated
1877** end |-- by sqlite3WhereEnd()
1878** end /
1879**
1880** Note that the loops might not be nested in the order in which they
1881** appear in the FROM clause if a different order is better able to make
1882** use of indices. Note also that when the IN operator appears in
1883** the WHERE clause, it might result in additional nested loops for
1884** scanning through all values on the right-hand side of the IN.
1885**
1886** There are Btree cursors associated with each table. t1 uses cursor
1887** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
1888** And so forth. This routine generates code to open those VDBE cursors
1889** and sqlite3WhereEnd() generates the code to close them.
1890**
1891** The code that sqlite3WhereBegin() generates leaves the cursors named
1892** in pTabList pointing at their appropriate entries. The [...] code
1893** can use OP_Column and OP_Rowid opcodes on these cursors to extract
1894** data from the various tables of the loop.
1895**
1896** If the WHERE clause is empty, the foreach loops must each scan their
1897** entire tables. Thus a three-way join is an O(N^3) operation. But if
1898** the tables have indices and there are terms in the WHERE clause that
1899** refer to those indices, a complete table scan can be avoided and the
1900** code will run much faster. Most of the work of this routine is checking
1901** to see if there are indices that can be used to speed up the loop.
1902**
1903** Terms of the WHERE clause are also used to limit which rows actually
1904** make it to the "..." in the middle of the loop. After each "foreach",
1905** terms of the WHERE clause that use only terms in that loop and outer
1906** loops are evaluated and if false a jump is made around all subsequent
1907** inner loops (or around the "..." if the test occurs within the inner-
1908** most loop)
1909**
1910** OUTER JOINS
1911**
1912** An outer join of tables t1 and t2 is conceptally coded as follows:
1913**
1914** foreach row1 in t1 do
1915** flag = 0
1916** foreach row2 in t2 do
1917** start:
1918** ...
1919** flag = 1
1920** end
1921** if flag==0 then
1922** move the row2 cursor to a null row
1923** goto start
1924** fi
1925** end
1926**
1927** ORDER BY CLAUSE PROCESSING
1928**
1929** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
1930** if there is one. If there is no ORDER BY clause or if this routine
1931** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
1932**
1933** If an index can be used so that the natural output order of the table
1934** scan is correct for the ORDER BY clause, then that index is used and
1935** *ppOrderBy is set to NULL. This is an optimization that prevents an
1936** unnecessary sort of the result set if an index appropriate for the
1937** ORDER BY clause already exists.
1938**
1939** If the where clause loops cannot be arranged to provide the correct
1940** output order, then the *ppOrderBy is unchanged.
1941*/
1942WhereInfo *sqlite3WhereBegin(
1943 Parse *pParse, /* The parser context */
1944 SrcList *pTabList, /* A list of all tables to be scanned */
1945 Expr *pWhere, /* The WHERE clause */
1946 ExprList **ppOrderBy /* An ORDER BY clause, or NULL */
1947){
1948 int i; /* Loop counter */
1949 WhereInfo *pWInfo; /* Will become the return value of this function */
1950 Vdbe *v = pParse->pVdbe; /* The virtual database engine */
1951 int brk, cont = 0; /* Addresses used during code generation */
1952 Bitmask notReady; /* Cursors that are not yet positioned */
1953 WhereTerm *pTerm; /* A single term in the WHERE clause */
1954 ExprMaskSet maskSet; /* The expression mask set */
1955 WhereClause wc; /* The WHERE clause is divided into these terms */
1956 struct SrcList_item *pTabItem; /* A single entry from pTabList */
1957 WhereLevel *pLevel; /* A single level in the pWInfo list */
1958 int iFrom; /* First unused FROM clause element */
1959 int andFlags; /* AND-ed combination of all wc.a[].flags */
1960
1961 /* The number of tables in the FROM clause is limited by the number of
1962 ** bits in a Bitmask
1963 */
1964 if( pTabList->nSrc>BMS ){
1965 sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
1966 return 0;
1967 }
1968
1969 /* Split the WHERE clause into separate subexpressions where each
1970 ** subexpression is separated by an AND operator.
1971 */
1972 initMaskSet(&maskSet);
1973 whereClauseInit(&wc, pParse, &maskSet);
1974 whereSplit(&wc, pWhere, TK_AND);
1975
1976 /* Allocate and initialize the WhereInfo structure that will become the
1977 ** return value.
1978 */
1979 pWInfo = sqliteMalloc( sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
1980 if( sqlite3MallocFailed() ){
1981 goto whereBeginNoMem;
1982 }
1983 pWInfo->nLevel = pTabList->nSrc;
1984 pWInfo->pParse = pParse;
1985 pWInfo->pTabList = pTabList;
1986 pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
1987
1988 /* Special case: a WHERE clause that is constant. Evaluate the
1989 ** expression and either jump over all of the code or fall thru.
1990 */
1991 if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
1992 sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
1993 pWhere = 0;
1994 }
1995
1996 /* Analyze all of the subexpressions. Note that exprAnalyze() might
1997 ** add new virtual terms onto the end of the WHERE clause. We do not
1998 ** want to analyze these virtual terms, so start analyzing at the end
1999 ** and work forward so that the added virtual terms are never processed.
2000 */
2001 for(i=0; i<pTabList->nSrc; i++){
2002 createMask(&maskSet, pTabList->a[i].iCursor);
2003 }
2004 exprAnalyzeAll(pTabList, &wc);
2005 if( sqlite3MallocFailed() ){
2006 goto whereBeginNoMem;
2007 }
2008
2009 /* Chose the best index to use for each table in the FROM clause.
2010 **
2011 ** This loop fills in the following fields:
2012 **
2013 ** pWInfo->a[].pIdx The index to use for this level of the loop.
2014 ** pWInfo->a[].flags WHERE_xxx flags associated with pIdx
2015 ** pWInfo->a[].nEq The number of == and IN constraints
2016 ** pWInfo->a[].iFrom When term of the FROM clause is being coded
2017 ** pWInfo->a[].iTabCur The VDBE cursor for the database table
2018 ** pWInfo->a[].iIdxCur The VDBE cursor for the index
2019 **
2020 ** This loop also figures out the nesting order of tables in the FROM
2021 ** clause.
2022 */
2023 notReady = ~(Bitmask)0;
2024 pTabItem = pTabList->a;
2025 pLevel = pWInfo->a;
2026 andFlags = ~0;
2027 WHERETRACE(("*** Optimizer Start ***\n"));
2028 for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2029 Index *pIdx; /* Index for FROM table at pTabItem */
2030 int flags; /* Flags asssociated with pIdx */
2031 int nEq; /* Number of == or IN constraints */
2032 double cost; /* The cost for pIdx */
2033 int j; /* For looping over FROM tables */
2034 Index *pBest = 0; /* The best index seen so far */
2035 int bestFlags = 0; /* Flags associated with pBest */
2036 int bestNEq = 0; /* nEq associated with pBest */
2037 double lowestCost; /* Cost of the pBest */
2038 int bestJ = 0; /* The value of j */
2039 Bitmask m; /* Bitmask value for j or bestJ */
2040 int once = 0; /* True when first table is seen */
2041 sqlite3_index_info *pIndex; /* Current virtual index */
2042
2043 lowestCost = SQLITE_BIG_DBL;
2044 for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
2045 int doNotReorder; /* True if this table should not be reordered */
2046
2047 doNotReorder = (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
2048 if( once && doNotReorder ) break;
2049 m = getMask(&maskSet, pTabItem->iCursor);
2050 if( (m & notReady)==0 ){
2051 if( j==iFrom ) iFrom++;
2052 continue;
2053 }
2054 assert( pTabItem->pTab );
2055#ifndef SQLITE_OMIT_VIRTUALTABLE
2056 if( IsVirtual(pTabItem->pTab) ){
2057 sqlite3_index_info **ppIdxInfo = &pWInfo->a[j].pIdxInfo;
2058 cost = bestVirtualIndex(pParse, &wc, pTabItem, notReady,
2059 ppOrderBy ? *ppOrderBy : 0, i==0,
2060 ppIdxInfo);
2061 flags = WHERE_VIRTUALTABLE;
2062 pIndex = *ppIdxInfo;
2063 if( pIndex && pIndex->orderByConsumed ){
2064 flags = WHERE_VIRTUALTABLE | WHERE_ORDERBY;
2065 }
2066 pIdx = 0;
2067 nEq = 0;
2068 if( (SQLITE_BIG_DBL/2.0)<cost ){
2069 /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
2070 ** inital value of lowestCost in this loop. If it is, then
2071 ** the (cost<lowestCost) test below will never be true and
2072 ** pLevel->pBestIdx never set.
2073 */
2074 cost = (SQLITE_BIG_DBL/2.0);
2075 }
2076 }else
2077#endif
2078 {
2079 cost = bestIndex(pParse, &wc, pTabItem, notReady,
2080 (i==0 && ppOrderBy) ? *ppOrderBy : 0,
2081 &pIdx, &flags, &nEq);
2082 pIndex = 0;
2083 }
2084 if( cost<lowestCost ){
2085 once = 1;
2086 lowestCost = cost;
2087 pBest = pIdx;
2088 bestFlags = flags;
2089 bestNEq = nEq;
2090 bestJ = j;
2091 pLevel->pBestIdx = pIndex;
2092 }
2093 if( doNotReorder ) break;
2094 }
2095 WHERETRACE(("*** Optimizer choose table %d for loop %d\n", bestJ,
2096 pLevel-pWInfo->a));
2097 if( (bestFlags & WHERE_ORDERBY)!=0 ){
2098 *ppOrderBy = 0;
2099 }
2100 andFlags &= bestFlags;
2101 pLevel->flags = bestFlags;
2102 pLevel->pIdx = pBest;
2103 pLevel->nEq = bestNEq;
2104 pLevel->aInLoop = 0;
2105 pLevel->nIn = 0;
2106 if( pBest ){
2107 pLevel->iIdxCur = pParse->nTab++;
2108 }else{
2109 pLevel->iIdxCur = -1;
2110 }
2111 notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor);
2112 pLevel->iFrom = bestJ;
2113 }
2114 WHERETRACE(("*** Optimizer Finished ***\n"));
2115
2116 /* If the total query only selects a single row, then the ORDER BY
2117 ** clause is irrelevant.
2118 */
2119 if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
2120 *ppOrderBy = 0;
2121 }
2122
2123 /* Open all tables in the pTabList and any indices selected for
2124 ** searching those tables.
2125 */
2126 sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
2127 for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2128 Table *pTab; /* Table to open */
2129 Index *pIx; /* Index used to access pTab (if any) */
2130 int iDb; /* Index of database containing table/index */
2131 int iIdxCur = pLevel->iIdxCur;
2132
2133#ifndef SQLITE_OMIT_EXPLAIN
2134 if( pParse->explain==2 ){
2135 char *zMsg;
2136 struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
2137 zMsg = sqlite3MPrintf("TABLE %s", pItem->zName);
2138 if( pItem->zAlias ){
2139 zMsg = sqlite3MPrintf("%z AS %s", zMsg, pItem->zAlias);
2140 }
2141 if( (pIx = pLevel->pIdx)!=0 ){
2142 zMsg = sqlite3MPrintf("%z WITH INDEX %s", zMsg, pIx->zName);
2143 }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
2144 zMsg = sqlite3MPrintf("%z USING PRIMARY KEY", zMsg);
2145 }
2146#ifndef SQLITE_OMIT_VIRTUALTABLE
2147 else if( pLevel->pBestIdx ){
2148 sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
2149 zMsg = sqlite3MPrintf("%z VIRTUAL TABLE INDEX %d:%s", zMsg,
2150 pBestIdx->idxNum, pBestIdx->idxStr);
2151 }
2152#endif
2153 if( pLevel->flags & WHERE_ORDERBY ){
2154 zMsg = sqlite3MPrintf("%z ORDER BY", zMsg);
2155 }
2156 sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_DYNAMIC);
2157 }
2158#endif /* SQLITE_OMIT_EXPLAIN */
2159 pTabItem = &pTabList->a[pLevel->iFrom];
2160 pTab = pTabItem->pTab;
2161 iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
2162 if( pTab->isEphem || pTab->pSelect ) continue;
2163#ifndef SQLITE_OMIT_VIRTUALTABLE
2164 if( pLevel->pBestIdx ){
2165 int iCur = pTabItem->iCursor;
2166 sqlite3VdbeOp3(v, OP_VOpen, iCur, 0, (const char*)pTab->pVtab, P3_VTAB);
2167 }else
2168#endif
2169 if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
2170 sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead);
2171 if( pTab->nCol<(sizeof(Bitmask)*8) ){
2172 Bitmask b = pTabItem->colUsed;
2173 int n = 0;
2174 for(; b; b=b>>1, n++){}
2175 sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, n);
2176 assert( n<=pTab->nCol );
2177 }
2178 }else{
2179 sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
2180 }
2181 pLevel->iTabCur = pTabItem->iCursor;
2182 if( (pIx = pLevel->pIdx)!=0 ){
2183 KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
2184 assert( pIx->pSchema==pTab->pSchema );
2185 sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
2186 VdbeComment((v, "# %s", pIx->zName));
2187 sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
2188 (char*)pKey, P3_KEYINFO_HANDOFF);
2189 }
2190 if( (pLevel->flags & (WHERE_IDX_ONLY|WHERE_COLUMN_RANGE))!=0 ){
2191 /* Only call OP_SetNumColumns on the index if we might later use
2192 ** OP_Column on the index. */
2193 sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
2194 }
2195 sqlite3CodeVerifySchema(pParse, iDb);
2196 }
2197 pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
2198
2199 /* Generate the code to do the search. Each iteration of the for
2200 ** loop below generates code for a single nested loop of the VM
2201 ** program.
2202 */
2203 notReady = ~(Bitmask)0;
2204 for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2205 int j;
2206 int iCur = pTabItem->iCursor; /* The VDBE cursor for the table */
2207 Index *pIdx; /* The index we will be using */
2208 int nxt; /* Where to jump to continue with the next IN case */
2209 int iIdxCur; /* The VDBE cursor for the index */
2210 int omitTable; /* True if we use the index only */
2211 int bRev; /* True if we need to scan in reverse order */
2212
2213 pTabItem = &pTabList->a[pLevel->iFrom];
2214 iCur = pTabItem->iCursor;
2215 pIdx = pLevel->pIdx;
2216 iIdxCur = pLevel->iIdxCur;
2217 bRev = (pLevel->flags & WHERE_REVERSE)!=0;
2218 omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;
2219
2220 /* Create labels for the "break" and "continue" instructions
2221 ** for the current loop. Jump to brk to break out of a loop.
2222 ** Jump to cont to go immediately to the next iteration of the
2223 ** loop.
2224 **
2225 ** When there is an IN operator, we also have a "nxt" label that
2226 ** means to continue with the next IN value combination. When
2227 ** there are no IN operators in the constraints, the "nxt" label
2228 ** is the same as "brk".
2229 */
2230 brk = pLevel->brk = pLevel->nxt = sqlite3VdbeMakeLabel(v);
2231 cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
2232
2233 /* If this is the right table of a LEFT OUTER JOIN, allocate and
2234 ** initialize a memory cell that records if this table matches any
2235 ** row of the left table of the join.
2236 */
2237 if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
2238 if( !pParse->nMem ) pParse->nMem++;
2239 pLevel->iLeftJoin = pParse->nMem++;
2240 sqlite3VdbeAddOp(v, OP_MemInt, 0, pLevel->iLeftJoin);
2241 VdbeComment((v, "# init LEFT JOIN no-match flag"));
2242 }
2243
2244#ifndef SQLITE_OMIT_VIRTUALTABLE
2245 if( pLevel->pBestIdx ){
2246 /* Case 0: The table is a virtual-table. Use the VFilter and VNext
2247 ** to access the data.
2248 */
2249 int j;
2250 sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
2251 int nConstraint = pBestIdx->nConstraint;
2252 struct sqlite3_index_constraint_usage *aUsage =
2253 pBestIdx->aConstraintUsage;
2254 const struct sqlite3_index_constraint *aConstraint =
2255 pBestIdx->aConstraint;
2256
2257 for(j=1; j<=nConstraint; j++){
2258 int k;
2259 for(k=0; k<nConstraint; k++){
2260 if( aUsage[k].argvIndex==j ){
2261 int iTerm = aConstraint[k].iTermOffset;
2262 sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight);
2263 break;
2264 }
2265 }
2266 if( k==nConstraint ) break;
2267 }
2268 sqlite3VdbeAddOp(v, OP_Integer, j-1, 0);
2269 sqlite3VdbeAddOp(v, OP_Integer, pBestIdx->idxNum, 0);
2270 sqlite3VdbeOp3(v, OP_VFilter, iCur, brk, pBestIdx->idxStr,
2271 pBestIdx->needToFreeIdxStr ? P3_MPRINTF : P3_STATIC);
2272 pBestIdx->needToFreeIdxStr = 0;
2273 for(j=0; j<pBestIdx->nConstraint; j++){
2274 if( aUsage[j].omit ){
2275 int iTerm = aConstraint[j].iTermOffset;
2276 disableTerm(pLevel, &wc.a[iTerm]);
2277 }
2278 }
2279 pLevel->op = OP_VNext;
2280 pLevel->p1 = iCur;
2281 pLevel->p2 = sqlite3VdbeCurrentAddr(v);
2282 }else
2283#endif /* SQLITE_OMIT_VIRTUALTABLE */
2284
2285 if( pLevel->flags & WHERE_ROWID_EQ ){
2286 /* Case 1: We can directly reference a single row using an
2287 ** equality comparison against the ROWID field. Or
2288 ** we reference multiple rows using a "rowid IN (...)"
2289 ** construct.
2290 */
2291 pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
2292 assert( pTerm!=0 );
2293 assert( pTerm->pExpr!=0 );
2294 assert( pTerm->leftCursor==iCur );
2295 assert( omitTable==0 );
2296 codeEqualityTerm(pParse, pTerm, pLevel);
2297 nxt = pLevel->nxt;
2298 sqlite3VdbeAddOp(v, OP_MustBeInt, 1, nxt);
2299 sqlite3VdbeAddOp(v, OP_NotExists, iCur, nxt);
2300 VdbeComment((v, "pk"));
2301 pLevel->op = OP_Noop;
2302 }else if( pLevel->flags & WHERE_ROWID_RANGE ){
2303 /* Case 2: We have an inequality comparison against the ROWID field.
2304 */
2305 int testOp = OP_Noop;
2306 int start;
2307 WhereTerm *pStart, *pEnd;
2308
2309 assert( omitTable==0 );
2310 pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
2311 pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0);
2312 if( bRev ){
2313 pTerm = pStart;
2314 pStart = pEnd;
2315 pEnd = pTerm;
2316 }
2317 if( pStart ){
2318 Expr *pX;
2319 pX = pStart->pExpr;
2320 assert( pX!=0 );
2321 assert( pStart->leftCursor==iCur );
2322 sqlite3ExprCode(pParse, pX->pRight);
2323 sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk);
2324 sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk);
2325 VdbeComment((v, "pk"));
2326 disableTerm(pLevel, pStart);
2327 }else{
2328 sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
2329 }
2330 if( pEnd ){
2331 Expr *pX;
2332 pX = pEnd->pExpr;
2333 assert( pX!=0 );
2334 assert( pEnd->leftCursor==iCur );
2335 sqlite3ExprCode(pParse, pX->pRight);
2336 pLevel->iMem = pParse->nMem++;
2337 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
2338 if( pX->op==TK_LT || pX->op==TK_GT ){
2339 testOp = bRev ? OP_Le : OP_Ge;
2340 }else{
2341 testOp = bRev ? OP_Lt : OP_Gt;
2342 }
2343 disableTerm(pLevel, pEnd);
2344 }
2345 start = sqlite3VdbeCurrentAddr(v);
2346 pLevel->op = bRev ? OP_Prev : OP_Next;
2347 pLevel->p1 = iCur;
2348 pLevel->p2 = start;
2349 if( testOp!=OP_Noop ){
2350 sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
2351 sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2352 sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC|0x100, brk);
2353 }
2354 }else if( pLevel->flags & WHERE_COLUMN_RANGE ){
2355 /* Case 3: The WHERE clause term that refers to the right-most
2356 ** column of the index is an inequality. For example, if
2357 ** the index is on (x,y,z) and the WHERE clause is of the
2358 ** form "x=5 AND y<10" then this case is used. Only the
2359 ** right-most column can be an inequality - the rest must
2360 ** use the "==" and "IN" operators.
2361 **
2362 ** This case is also used when there are no WHERE clause
2363 ** constraints but an index is selected anyway, in order
2364 ** to force the output order to conform to an ORDER BY.
2365 */
2366 int start;
2367 int nEq = pLevel->nEq;
2368 int topEq=0; /* True if top limit uses ==. False is strictly < */
2369 int btmEq=0; /* True if btm limit uses ==. False if strictly > */
2370 int topOp, btmOp; /* Operators for the top and bottom search bounds */
2371 int testOp;
2372 int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
2373 int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;
2374
2375 /* Generate code to evaluate all constraint terms using == or IN
2376 ** and level the values of those terms on the stack.
2377 */
2378 codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
2379
2380 /* Duplicate the equality term values because they will all be
2381 ** used twice: once to make the termination key and once to make the
2382 ** start key.
2383 */
2384 for(j=0; j<nEq; j++){
2385 sqlite3VdbeAddOp(v, OP_Dup, nEq-1, 0);
2386 }
2387
2388 /* Figure out what comparison operators to use for top and bottom
2389 ** search bounds. For an ascending index, the bottom bound is a > or >=
2390 ** operator and the top bound is a < or <= operator. For a descending
2391 ** index the operators are reversed.
2392 */
2393 if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){
2394 topOp = WO_LT|WO_LE;
2395 btmOp = WO_GT|WO_GE;
2396 }else{
2397 topOp = WO_GT|WO_GE;
2398 btmOp = WO_LT|WO_LE;
2399 SWAP(int, topLimit, btmLimit);
2400 }
2401
2402 /* Generate the termination key. This is the key value that
2403 ** will end the search. There is no termination key if there
2404 ** are no equality terms and no "X<..." term.
2405 **
2406 ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
2407 ** key computed here really ends up being the start key.
2408 */
2409 nxt = pLevel->nxt;
2410 if( topLimit ){
2411 Expr *pX;
2412 int k = pIdx->aiColumn[j];
2413 pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx);
2414 assert( pTerm!=0 );
2415 pX = pTerm->pExpr;
2416 assert( (pTerm->flags & TERM_CODED)==0 );
2417 sqlite3ExprCode(pParse, pX->pRight);
2418 sqlite3VdbeAddOp(v, OP_IsNull, -(nEq*2+1), nxt);
2419 topEq = pTerm->eOperator & (WO_LE|WO_GE);
2420 disableTerm(pLevel, pTerm);
2421 testOp = OP_IdxGE;
2422 }else{
2423 testOp = nEq>0 ? OP_IdxGE : OP_Noop;
2424 topEq = 1;
2425 }
2426 if( testOp!=OP_Noop ){
2427 int nCol = nEq + topLimit;
2428 pLevel->iMem = pParse->nMem++;
2429 buildIndexProbe(v, nCol, pIdx);
2430 if( bRev ){
2431 int op = topEq ? OP_MoveLe : OP_MoveLt;
2432 sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
2433 }else{
2434 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
2435 }
2436 }else if( bRev ){
2437 sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk);
2438 }
2439
2440 /* Generate the start key. This is the key that defines the lower
2441 ** bound on the search. There is no start key if there are no
2442 ** equality terms and if there is no "X>..." term. In
2443 ** that case, generate a "Rewind" instruction in place of the
2444 ** start key search.
2445 **
2446 ** 2002-Dec-04: In the case of a reverse-order search, the so-called
2447 ** "start" key really ends up being used as the termination key.
2448 */
2449 if( btmLimit ){
2450 Expr *pX;
2451 int k = pIdx->aiColumn[j];
2452 pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx);
2453 assert( pTerm!=0 );
2454 pX = pTerm->pExpr;
2455 assert( (pTerm->flags & TERM_CODED)==0 );
2456 sqlite3ExprCode(pParse, pX->pRight);
2457 sqlite3VdbeAddOp(v, OP_IsNull, -(nEq+1), nxt);
2458 btmEq = pTerm->eOperator & (WO_LE|WO_GE);
2459 disableTerm(pLevel, pTerm);
2460 }else{
2461 btmEq = 1;
2462 }
2463 if( nEq>0 || btmLimit ){
2464 int nCol = nEq + btmLimit;
2465 buildIndexProbe(v, nCol, pIdx);
2466 if( bRev ){
2467 pLevel->iMem = pParse->nMem++;
2468 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
2469 testOp = OP_IdxLT;
2470 }else{
2471 int op = btmEq ? OP_MoveGe : OP_MoveGt;
2472 sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
2473 }
2474 }else if( bRev ){
2475 testOp = OP_Noop;
2476 }else{
2477 sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk);
2478 }
2479
2480 /* Generate the the top of the loop. If there is a termination
2481 ** key we have to test for that key and abort at the top of the
2482 ** loop.
2483 */
2484 start = sqlite3VdbeCurrentAddr(v);
2485 if( testOp!=OP_Noop ){
2486 sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2487 sqlite3VdbeAddOp(v, testOp, iIdxCur, nxt);
2488 if( (topEq && !bRev) || (!btmEq && bRev) ){
2489 sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
2490 }
2491 }
2492 if( topLimit | btmLimit ){
2493 sqlite3VdbeAddOp(v, OP_Column, iIdxCur, nEq);
2494 sqlite3VdbeAddOp(v, OP_IsNull, 1, cont);
2495 }
2496 if( !omitTable ){
2497 sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
2498 sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
2499 }
2500
2501 /* Record the instruction used to terminate the loop.
2502 */
2503 pLevel->op = bRev ? OP_Prev : OP_Next;
2504 pLevel->p1 = iIdxCur;
2505 pLevel->p2 = start;
2506 }else if( pLevel->flags & WHERE_COLUMN_EQ ){
2507 /* Case 4: There is an index and all terms of the WHERE clause that
2508 ** refer to the index using the "==" or "IN" operators.
2509 */
2510 int start;
2511 int nEq = pLevel->nEq;
2512
2513 /* Generate code to evaluate all constraint terms using == or IN
2514 ** and leave the values of those terms on the stack.
2515 */
2516 codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
2517 nxt = pLevel->nxt;
2518
2519 /* Generate a single key that will be used to both start and terminate
2520 ** the search
2521 */
2522 buildIndexProbe(v, nEq, pIdx);
2523 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);
2524
2525 /* Generate code (1) to move to the first matching element of the table.
2526 ** Then generate code (2) that jumps to "nxt" after the cursor is past
2527 ** the last matching element of the table. The code (1) is executed
2528 ** once to initialize the search, the code (2) is executed before each
2529 ** iteration of the scan to see if the scan has finished. */
2530 if( bRev ){
2531 /* Scan in reverse order */
2532 sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, nxt);
2533 start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2534 sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, nxt);
2535 pLevel->op = OP_Prev;
2536 }else{
2537 /* Scan in the forward order */
2538 sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, nxt);
2539 start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2540 sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, nxt, "+", P3_STATIC);
2541 pLevel->op = OP_Next;
2542 }
2543 if( !omitTable ){
2544 sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
2545 sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
2546 }
2547 pLevel->p1 = iIdxCur;
2548 pLevel->p2 = start;
2549 }else{
2550 /* Case 5: There is no usable index. We must do a complete
2551 ** scan of the entire table.
2552 */
2553 assert( omitTable==0 );
2554 assert( bRev==0 );
2555 pLevel->op = OP_Next;
2556 pLevel->p1 = iCur;
2557 pLevel->p2 = 1 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk);
2558 }
2559 notReady &= ~getMask(&maskSet, iCur);
2560
2561 /* Insert code to test every subexpression that can be completely
2562 ** computed using the current set of tables.
2563 */
2564 for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
2565 Expr *pE;
2566 if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
2567 if( (pTerm->prereqAll & notReady)!=0 ) continue;
2568 pE = pTerm->pExpr;
2569 assert( pE!=0 );
2570 if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
2571 continue;
2572 }
2573 sqlite3ExprIfFalse(pParse, pE, cont, 1);
2574 pTerm->flags |= TERM_CODED;
2575 }
2576
2577 /* For a LEFT OUTER JOIN, generate code that will record the fact that
2578 ** at least one row of the right table has matched the left table.
2579 */
2580 if( pLevel->iLeftJoin ){
2581 pLevel->top = sqlite3VdbeCurrentAddr(v);
2582 sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin);
2583 VdbeComment((v, "# record LEFT JOIN hit"));
2584 for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
2585 if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
2586 if( (pTerm->prereqAll & notReady)!=0 ) continue;
2587 assert( pTerm->pExpr );
2588 sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1);
2589 pTerm->flags |= TERM_CODED;
2590 }
2591 }
2592 }
2593
2594#ifdef SQLITE_TEST /* For testing and debugging use only */
2595 /* Record in the query plan information about the current table
2596 ** and the index used to access it (if any). If the table itself
2597 ** is not used, its name is just '{}'. If no index is used
2598 ** the index is listed as "{}". If the primary key is used the
2599 ** index name is '*'.
2600 */
2601 for(i=0; i<pTabList->nSrc; i++){
2602 char *z;
2603 int n;
2604 pLevel = &pWInfo->a[i];
2605 pTabItem = &pTabList->a[pLevel->iFrom];
2606 z = pTabItem->zAlias;
2607 if( z==0 ) z = pTabItem->pTab->zName;
2608 n = strlen(z);
2609 if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
2610 if( pLevel->flags & WHERE_IDX_ONLY ){
2611 memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
2612 nQPlan += 2;
2613 }else{
2614 memcpy(&sqlite3_query_plan[nQPlan], z, n);
2615 nQPlan += n;
2616 }
2617 sqlite3_query_plan[nQPlan++] = ' ';
2618 }
2619 if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
2620 memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
2621 nQPlan += 2;
2622 }else if( pLevel->pIdx==0 ){
2623 memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
2624 nQPlan += 3;
2625 }else{
2626 n = strlen(pLevel->pIdx->zName);
2627 if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
2628 memcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName, n);
2629 nQPlan += n;
2630 sqlite3_query_plan[nQPlan++] = ' ';
2631 }
2632 }
2633 }
2634 while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
2635 sqlite3_query_plan[--nQPlan] = 0;
2636 }
2637 sqlite3_query_plan[nQPlan] = 0;
2638 nQPlan = 0;
2639#endif /* SQLITE_TEST // Testing and debugging use only */
2640
2641 /* Record the continuation address in the WhereInfo structure. Then
2642 ** clean up and return.
2643 */
2644 pWInfo->iContinue = cont;
2645 whereClauseClear(&wc);
2646 return pWInfo;
2647
2648 /* Jump here if malloc fails */
2649whereBeginNoMem:
2650 whereClauseClear(&wc);
2651 whereInfoFree(pWInfo);
2652 return 0;
2653}
2654
2655/*
2656** Generate the end of the WHERE loop. See comments on
2657** sqlite3WhereBegin() for additional information.
2658*/
2659void sqlite3WhereEnd(WhereInfo *pWInfo){
2660 Vdbe *v = pWInfo->pParse->pVdbe;
2661 int i;
2662 WhereLevel *pLevel;
2663 SrcList *pTabList = pWInfo->pTabList;
2664
2665 /* Generate loop termination code.
2666 */
2667 for(i=pTabList->nSrc-1; i>=0; i--){
2668 pLevel = &pWInfo->a[i];
2669 sqlite3VdbeResolveLabel(v, pLevel->cont);
2670 if( pLevel->op!=OP_Noop ){
2671 sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
2672 }
2673 if( pLevel->nIn ){
2674 struct InLoop *pIn;
2675 int j;
2676 sqlite3VdbeResolveLabel(v, pLevel->nxt);
2677 for(j=pLevel->nIn, pIn=&pLevel->aInLoop[j-1]; j>0; j--, pIn--){
2678 sqlite3VdbeJumpHere(v, pIn->topAddr+1);
2679 sqlite3VdbeAddOp(v, OP_Next, pIn->iCur, pIn->topAddr);
2680 sqlite3VdbeJumpHere(v, pIn->topAddr-1);
2681 }
2682 sqliteFree(pLevel->aInLoop);
2683 }
2684 sqlite3VdbeResolveLabel(v, pLevel->brk);
2685 if( pLevel->iLeftJoin ){
2686 int addr;
2687 addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0);
2688 sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
2689 if( pLevel->iIdxCur>=0 ){
2690 sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0);
2691 }
2692 sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top);
2693 sqlite3VdbeJumpHere(v, addr);
2694 }
2695 }
2696
2697 /* The "break" point is here, just past the end of the outer loop.
2698 ** Set it.
2699 */
2700 sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
2701
2702 /* Close all of the cursors that were opened by sqlite3WhereBegin.
2703 */
2704 for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2705 struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
2706 Table *pTab = pTabItem->pTab;
2707 assert( pTab!=0 );
2708 if( pTab->isEphem || pTab->pSelect ) continue;
2709 if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
2710 sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
2711 }
2712 if( pLevel->pIdx!=0 ){
2713 sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
2714 }
2715
2716 /* Make cursor substitutions for cases where we want to use
2717 ** just the index and never reference the table.
2718 **
2719 ** Calls to the code generator in between sqlite3WhereBegin and
2720 ** sqlite3WhereEnd will have created code that references the table
2721 ** directly. This loop scans all that code looking for opcodes
2722 ** that reference the table and converts them into opcodes that
2723 ** reference the index.
2724 */
2725 if( pLevel->flags & WHERE_IDX_ONLY ){
2726 int k, j, last;
2727 VdbeOp *pOp;
2728 Index *pIdx = pLevel->pIdx;
2729
2730 assert( pIdx!=0 );
2731 pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
2732 last = sqlite3VdbeCurrentAddr(v);
2733 for(k=pWInfo->iTop; k<last; k++, pOp++){
2734 if( pOp->p1!=pLevel->iTabCur ) continue;
2735 if( pOp->opcode==OP_Column ){
2736 pOp->p1 = pLevel->iIdxCur;
2737 for(j=0; j<pIdx->nColumn; j++){
2738 if( pOp->p2==pIdx->aiColumn[j] ){
2739 pOp->p2 = j;
2740 break;
2741 }
2742 }
2743 }else if( pOp->opcode==OP_Rowid ){
2744 pOp->p1 = pLevel->iIdxCur;
2745 pOp->opcode = OP_IdxRowid;
2746 }else if( pOp->opcode==OP_NullRow ){
2747 pOp->opcode = OP_Noop;
2748 }
2749 }
2750 }
2751 }
2752
2753 /* Final cleanup
2754 */
2755 whereInfoFree(pWInfo);
2756 return;
2757}

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