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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 1.261 2007/09/13 17:54:40 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 sqlite3_free(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 = sqlite3_malloc( sizeof(pWC->a[0])*pWC->nSlot*2 );
232 if( pWC->a==0 ){
233 pWC->pParse->db->mallocFailed = 1;
234 if( flags & TERM_DYNAMIC ){
235 sqlite3ExprDelete(p);
236 }
237 return 0;
238 }
239 memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
240 if( pOld!=pWC->aStatic ){
241 sqlite3_free(pOld);
242 }
243 pWC->nSlot *= 2;
244 }
245 pTerm = &pWC->a[idx = pWC->nTerm];
246 pWC->nTerm++;
247 pTerm->pExpr = p;
248 pTerm->flags = flags;
249 pTerm->pWC = pWC;
250 pTerm->iParent = -1;
251 return idx;
252}
253
254/*
255** This routine identifies subexpressions in the WHERE clause where
256** each subexpression is separated by the AND operator or some other
257** operator specified in the op parameter. The WhereClause structure
258** is filled with pointers to subexpressions. For example:
259**
260** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
261** \________/ \_______________/ \________________/
262** slot[0] slot[1] slot[2]
263**
264** The original WHERE clause in pExpr is unaltered. All this routine
265** does is make slot[] entries point to substructure within pExpr.
266**
267** In the previous sentence and in the diagram, "slot[]" refers to
268** the WhereClause.a[] array. This array grows as needed to contain
269** all terms of the WHERE clause.
270*/
271static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
272 if( pExpr==0 ) return;
273 if( pExpr->op!=op ){
274 whereClauseInsert(pWC, pExpr, 0);
275 }else{
276 whereSplit(pWC, pExpr->pLeft, op);
277 whereSplit(pWC, pExpr->pRight, op);
278 }
279}
280
281/*
282** Initialize an expression mask set
283*/
284#define initMaskSet(P) memset(P, 0, sizeof(*P))
285
286/*
287** Return the bitmask for the given cursor number. Return 0 if
288** iCursor is not in the set.
289*/
290static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){
291 int i;
292 for(i=0; i<pMaskSet->n; i++){
293 if( pMaskSet->ix[i]==iCursor ){
294 return ((Bitmask)1)<<i;
295 }
296 }
297 return 0;
298}
299
300/*
301** Create a new mask for cursor iCursor.
302**
303** There is one cursor per table in the FROM clause. The number of
304** tables in the FROM clause is limited by a test early in the
305** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
306** array will never overflow.
307*/
308static void createMask(ExprMaskSet *pMaskSet, int iCursor){
309 assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
310 pMaskSet->ix[pMaskSet->n++] = iCursor;
311}
312
313/*
314** This routine walks (recursively) an expression tree and generates
315** a bitmask indicating which tables are used in that expression
316** tree.
317**
318** In order for this routine to work, the calling function must have
319** previously invoked sqlite3ExprResolveNames() on the expression. See
320** the header comment on that routine for additional information.
321** The sqlite3ExprResolveNames() routines looks for column names and
322** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
323** the VDBE cursor number of the table. This routine just has to
324** translate the cursor numbers into bitmask values and OR all
325** the bitmasks together.
326*/
327static Bitmask exprListTableUsage(ExprMaskSet*, ExprList*);
328static Bitmask exprSelectTableUsage(ExprMaskSet*, Select*);
329static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
330 Bitmask mask = 0;
331 if( p==0 ) return 0;
332 if( p->op==TK_COLUMN ){
333 mask = getMask(pMaskSet, p->iTable);
334 return mask;
335 }
336 mask = exprTableUsage(pMaskSet, p->pRight);
337 mask |= exprTableUsage(pMaskSet, p->pLeft);
338 mask |= exprListTableUsage(pMaskSet, p->pList);
339 mask |= exprSelectTableUsage(pMaskSet, p->pSelect);
340 return mask;
341}
342static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){
343 int i;
344 Bitmask mask = 0;
345 if( pList ){
346 for(i=0; i<pList->nExpr; i++){
347 mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
348 }
349 }
350 return mask;
351}
352static Bitmask exprSelectTableUsage(ExprMaskSet *pMaskSet, Select *pS){
353 Bitmask mask = 0;
354 while( pS ){
355 mask |= exprListTableUsage(pMaskSet, pS->pEList);
356 mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
357 mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
358 mask |= exprTableUsage(pMaskSet, pS->pWhere);
359 mask |= exprTableUsage(pMaskSet, pS->pHaving);
360 pS = pS->pPrior;
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**
387** If a collation sequence is associated with either the left or right
388** side of the comparison, it remains associated with the same side after
389** the commutation. So "Y collate NOCASE op X" becomes
390** "X collate NOCASE op Y". This is because any collation sequence on
391** the left hand side of a comparison overrides any collation sequence
392** attached to the right. For the same reason the EP_ExpCollate flag
393** is not commuted.
394*/
395static void exprCommute(Expr *pExpr){
396 u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
397 u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
398 assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
399 SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
400 pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
401 pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
402 SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
403 if( pExpr->op>=TK_GT ){
404 assert( TK_LT==TK_GT+2 );
405 assert( TK_GE==TK_LE+2 );
406 assert( TK_GT>TK_EQ );
407 assert( TK_GT<TK_LE );
408 assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
409 pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
410 }
411}
412
413/*
414** Translate from TK_xx operator to WO_xx bitmask.
415*/
416static int operatorMask(int op){
417 int c;
418 assert( allowedOp(op) );
419 if( op==TK_IN ){
420 c = WO_IN;
421 }else if( op==TK_ISNULL ){
422 c = WO_ISNULL;
423 }else{
424 c = WO_EQ<<(op-TK_EQ);
425 }
426 assert( op!=TK_ISNULL || c==WO_ISNULL );
427 assert( op!=TK_IN || c==WO_IN );
428 assert( op!=TK_EQ || c==WO_EQ );
429 assert( op!=TK_LT || c==WO_LT );
430 assert( op!=TK_LE || c==WO_LE );
431 assert( op!=TK_GT || c==WO_GT );
432 assert( op!=TK_GE || c==WO_GE );
433 return c;
434}
435
436/*
437** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
438** where X is a reference to the iColumn of table iCur and <op> is one of
439** the WO_xx operator codes specified by the op parameter.
440** Return a pointer to the term. Return 0 if not found.
441*/
442static WhereTerm *findTerm(
443 WhereClause *pWC, /* The WHERE clause to be searched */
444 int iCur, /* Cursor number of LHS */
445 int iColumn, /* Column number of LHS */
446 Bitmask notReady, /* RHS must not overlap with this mask */
447 u16 op, /* Mask of WO_xx values describing operator */
448 Index *pIdx /* Must be compatible with this index, if not NULL */
449){
450 WhereTerm *pTerm;
451 int k;
452 for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
453 if( pTerm->leftCursor==iCur
454 && (pTerm->prereqRight & notReady)==0
455 && pTerm->leftColumn==iColumn
456 && (pTerm->eOperator & op)!=0
457 ){
458 if( iCur>=0 && pIdx && pTerm->eOperator!=WO_ISNULL ){
459 Expr *pX = pTerm->pExpr;
460 CollSeq *pColl;
461 char idxaff;
462 int j;
463 Parse *pParse = pWC->pParse;
464
465 idxaff = pIdx->pTable->aCol[iColumn].affinity;
466 if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
467
468 /* Figure out the collation sequence required from an index for
469 ** it to be useful for optimising expression pX. Store this
470 ** value in variable pColl.
471 */
472 assert(pX->pLeft);
473 pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
474 if( !pColl ){
475 pColl = pParse->db->pDfltColl;
476 }
477
478 for(j=0; j<pIdx->nColumn && pIdx->aiColumn[j]!=iColumn; j++){}
479 assert( j<pIdx->nColumn );
480 if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
481 }
482 return pTerm;
483 }
484 }
485 return 0;
486}
487
488/* Forward reference */
489static void exprAnalyze(SrcList*, WhereClause*, int);
490
491/*
492** Call exprAnalyze on all terms in a WHERE clause.
493**
494**
495*/
496static void exprAnalyzeAll(
497 SrcList *pTabList, /* the FROM clause */
498 WhereClause *pWC /* the WHERE clause to be analyzed */
499){
500 int i;
501 for(i=pWC->nTerm-1; i>=0; i--){
502 exprAnalyze(pTabList, pWC, i);
503 }
504}
505
506#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
507/*
508** Check to see if the given expression is a LIKE or GLOB operator that
509** can be optimized using inequality constraints. Return TRUE if it is
510** so and false if not.
511**
512** In order for the operator to be optimizible, the RHS must be a string
513** literal that does not begin with a wildcard.
514*/
515static int isLikeOrGlob(
516 sqlite3 *db, /* The database */
517 Expr *pExpr, /* Test this expression */
518 int *pnPattern, /* Number of non-wildcard prefix characters */
519 int *pisComplete /* True if the only wildcard is % in the last character */
520){
521 const char *z;
522 Expr *pRight, *pLeft;
523 ExprList *pList;
524 int c, cnt;
525 int noCase;
526 char wc[3];
527 CollSeq *pColl;
528
529 if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){
530 return 0;
531 }
532 pList = pExpr->pList;
533 pRight = pList->a[0].pExpr;
534 if( pRight->op!=TK_STRING ){
535 return 0;
536 }
537 pLeft = pList->a[1].pExpr;
538 if( pLeft->op!=TK_COLUMN ){
539 return 0;
540 }
541 pColl = pLeft->pColl;
542 if( pColl==0 ){
543 /* TODO: Coverage testing doesn't get this case. Is it actually possible
544 ** for an expression of type TK_COLUMN to not have an assigned collation
545 ** sequence at this point?
546 */
547 pColl = db->pDfltColl;
548 }
549 if( (pColl->type!=SQLITE_COLL_BINARY || noCase) &&
550 (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){
551 return 0;
552 }
553 sqlite3DequoteExpr(db, pRight);
554 z = (char *)pRight->token.z;
555 for(cnt=0; (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2]; cnt++){}
556 if( cnt==0 || 255==(u8)z[cnt] ){
557 return 0;
558 }
559 *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0;
560 *pnPattern = cnt;
561 return 1;
562}
563#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
564
565
566#ifndef SQLITE_OMIT_VIRTUALTABLE
567/*
568** Check to see if the given expression is of the form
569**
570** column MATCH expr
571**
572** If it is then return TRUE. If not, return FALSE.
573*/
574static int isMatchOfColumn(
575 Expr *pExpr /* Test this expression */
576){
577 ExprList *pList;
578
579 if( pExpr->op!=TK_FUNCTION ){
580 return 0;
581 }
582 if( pExpr->token.n!=5 ||
583 sqlite3StrNICmp((const char*)pExpr->token.z,"match",5)!=0 ){
584 return 0;
585 }
586 pList = pExpr->pList;
587 if( pList->nExpr!=2 ){
588 return 0;
589 }
590 if( pList->a[1].pExpr->op != TK_COLUMN ){
591 return 0;
592 }
593 return 1;
594}
595#endif /* SQLITE_OMIT_VIRTUALTABLE */
596
597/*
598** If the pBase expression originated in the ON or USING clause of
599** a join, then transfer the appropriate markings over to derived.
600*/
601static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
602 pDerived->flags |= pBase->flags & EP_FromJoin;
603 pDerived->iRightJoinTable = pBase->iRightJoinTable;
604}
605
606#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
607/*
608** Return TRUE if the given term of an OR clause can be converted
609** into an IN clause. The iCursor and iColumn define the left-hand
610** side of the IN clause.
611**
612** The context is that we have multiple OR-connected equality terms
613** like this:
614**
615** a=<expr1> OR a=<expr2> OR b=<expr3> OR ...
616**
617** The pOrTerm input to this routine corresponds to a single term of
618** this OR clause. In order for the term to be a condidate for
619** conversion to an IN operator, the following must be true:
620**
621** * The left-hand side of the term must be the column which
622** is identified by iCursor and iColumn.
623**
624** * If the right-hand side is also a column, then the affinities
625** of both right and left sides must be such that no type
626** conversions are required on the right. (Ticket #2249)
627**
628** If both of these conditions are true, then return true. Otherwise
629** return false.
630*/
631static int orTermIsOptCandidate(WhereTerm *pOrTerm, int iCursor, int iColumn){
632 int affLeft, affRight;
633 assert( pOrTerm->eOperator==WO_EQ );
634 if( pOrTerm->leftCursor!=iCursor ){
635 return 0;
636 }
637 if( pOrTerm->leftColumn!=iColumn ){
638 return 0;
639 }
640 affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
641 if( affRight==0 ){
642 return 1;
643 }
644 affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
645 if( affRight!=affLeft ){
646 return 0;
647 }
648 return 1;
649}
650
651/*
652** Return true if the given term of an OR clause can be ignored during
653** a check to make sure all OR terms are candidates for optimization.
654** In other words, return true if a call to the orTermIsOptCandidate()
655** above returned false but it is not necessary to disqualify the
656** optimization.
657**
658** Suppose the original OR phrase was this:
659**
660** a=4 OR a=11 OR a=b
661**
662** During analysis, the third term gets flipped around and duplicate
663** so that we are left with this:
664**
665** a=4 OR a=11 OR a=b OR b=a
666**
667** Since the last two terms are duplicates, only one of them
668** has to qualify in order for the whole phrase to qualify. When
669** this routine is called, we know that pOrTerm did not qualify.
670** This routine merely checks to see if pOrTerm has a duplicate that
671** might qualify. If there is a duplicate that has not yet been
672** disqualified, then return true. If there are no duplicates, or
673** the duplicate has also been disqualifed, return false.
674*/
675static int orTermHasOkDuplicate(WhereClause *pOr, WhereTerm *pOrTerm){
676 if( pOrTerm->flags & TERM_COPIED ){
677 /* This is the original term. The duplicate is to the left had
678 ** has not yet been analyzed and thus has not yet been disqualified. */
679 return 1;
680 }
681 if( (pOrTerm->flags & TERM_VIRTUAL)!=0
682 && (pOr->a[pOrTerm->iParent].flags & TERM_OR_OK)!=0 ){
683 /* This is a duplicate term. The original qualified so this one
684 ** does not have to. */
685 return 1;
686 }
687 /* This is either a singleton term or else it is a duplicate for
688 ** which the original did not qualify. Either way we are done for. */
689 return 0;
690}
691#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
692
693/*
694** The input to this routine is an WhereTerm structure with only the
695** "pExpr" field filled in. The job of this routine is to analyze the
696** subexpression and populate all the other fields of the WhereTerm
697** structure.
698**
699** If the expression is of the form "<expr> <op> X" it gets commuted
700** to the standard form of "X <op> <expr>". If the expression is of
701** the form "X <op> Y" where both X and Y are columns, then the original
702** expression is unchanged and a new virtual expression of the form
703** "Y <op> X" is added to the WHERE clause and analyzed separately.
704*/
705static void exprAnalyze(
706 SrcList *pSrc, /* the FROM clause */
707 WhereClause *pWC, /* the WHERE clause */
708 int idxTerm /* Index of the term to be analyzed */
709){
710 WhereTerm *pTerm = &pWC->a[idxTerm];
711 ExprMaskSet *pMaskSet = pWC->pMaskSet;
712 Expr *pExpr = pTerm->pExpr;
713 Bitmask prereqLeft;
714 Bitmask prereqAll;
715 int nPattern;
716 int isComplete;
717 int op;
718 Parse *pParse = pWC->pParse;
719 sqlite3 *db = pParse->db;
720
721 if( db->mallocFailed ) return;
722 prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
723 op = pExpr->op;
724 if( op==TK_IN ){
725 assert( pExpr->pRight==0 );
726 pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList)
727 | exprSelectTableUsage(pMaskSet, pExpr->pSelect);
728 }else if( op==TK_ISNULL ){
729 pTerm->prereqRight = 0;
730 }else{
731 pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
732 }
733 prereqAll = exprTableUsage(pMaskSet, pExpr);
734 if( ExprHasProperty(pExpr, EP_FromJoin) ){
735 prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable);
736 }
737 pTerm->prereqAll = prereqAll;
738 pTerm->leftCursor = -1;
739 pTerm->iParent = -1;
740 pTerm->eOperator = 0;
741 if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
742 Expr *pLeft = pExpr->pLeft;
743 Expr *pRight = pExpr->pRight;
744 if( pLeft->op==TK_COLUMN ){
745 pTerm->leftCursor = pLeft->iTable;
746 pTerm->leftColumn = pLeft->iColumn;
747 pTerm->eOperator = operatorMask(op);
748 }
749 if( pRight && pRight->op==TK_COLUMN ){
750 WhereTerm *pNew;
751 Expr *pDup;
752 if( pTerm->leftCursor>=0 ){
753 int idxNew;
754 pDup = sqlite3ExprDup(db, pExpr);
755 if( db->mallocFailed ){
756 sqlite3ExprDelete(pDup);
757 return;
758 }
759 idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
760 if( idxNew==0 ) return;
761 pNew = &pWC->a[idxNew];
762 pNew->iParent = idxTerm;
763 pTerm = &pWC->a[idxTerm];
764 pTerm->nChild = 1;
765 pTerm->flags |= TERM_COPIED;
766 }else{
767 pDup = pExpr;
768 pNew = pTerm;
769 }
770 exprCommute(pDup);
771 pLeft = pDup->pLeft;
772 pNew->leftCursor = pLeft->iTable;
773 pNew->leftColumn = pLeft->iColumn;
774 pNew->prereqRight = prereqLeft;
775 pNew->prereqAll = prereqAll;
776 pNew->eOperator = operatorMask(pDup->op);
777 }
778 }
779
780#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
781 /* If a term is the BETWEEN operator, create two new virtual terms
782 ** that define the range that the BETWEEN implements.
783 */
784 else if( pExpr->op==TK_BETWEEN ){
785 ExprList *pList = pExpr->pList;
786 int i;
787 static const u8 ops[] = {TK_GE, TK_LE};
788 assert( pList!=0 );
789 assert( pList->nExpr==2 );
790 for(i=0; i<2; i++){
791 Expr *pNewExpr;
792 int idxNew;
793 pNewExpr = sqlite3Expr(db, ops[i], sqlite3ExprDup(db, pExpr->pLeft),
794 sqlite3ExprDup(db, pList->a[i].pExpr), 0);
795 idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
796 exprAnalyze(pSrc, pWC, idxNew);
797 pTerm = &pWC->a[idxTerm];
798 pWC->a[idxNew].iParent = idxTerm;
799 }
800 pTerm->nChild = 2;
801 }
802#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
803
804#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
805 /* Attempt to convert OR-connected terms into an IN operator so that
806 ** they can make use of indices. Example:
807 **
808 ** x = expr1 OR expr2 = x OR x = expr3
809 **
810 ** is converted into
811 **
812 ** x IN (expr1,expr2,expr3)
813 **
814 ** This optimization must be omitted if OMIT_SUBQUERY is defined because
815 ** the compiler for the the IN operator is part of sub-queries.
816 */
817 else if( pExpr->op==TK_OR ){
818 int ok;
819 int i, j;
820 int iColumn, iCursor;
821 WhereClause sOr;
822 WhereTerm *pOrTerm;
823
824 assert( (pTerm->flags & TERM_DYNAMIC)==0 );
825 whereClauseInit(&sOr, pWC->pParse, pMaskSet);
826 whereSplit(&sOr, pExpr, TK_OR);
827 exprAnalyzeAll(pSrc, &sOr);
828 assert( sOr.nTerm>=2 );
829 j = 0;
830 do{
831 assert( j<sOr.nTerm );
832 iColumn = sOr.a[j].leftColumn;
833 iCursor = sOr.a[j].leftCursor;
834 ok = iCursor>=0;
835 for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
836 if( pOrTerm->eOperator!=WO_EQ ){
837 goto or_not_possible;
838 }
839 if( orTermIsOptCandidate(pOrTerm, iCursor, iColumn) ){
840 pOrTerm->flags |= TERM_OR_OK;
841 }else if( orTermHasOkDuplicate(&sOr, pOrTerm) ){
842 pOrTerm->flags &= ~TERM_OR_OK;
843 }else{
844 ok = 0;
845 }
846 }
847 }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<2 );
848 if( ok ){
849 ExprList *pList = 0;
850 Expr *pNew, *pDup;
851 Expr *pLeft = 0;
852 for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
853 if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue;
854 pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight);
855 pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup, 0);
856 pLeft = pOrTerm->pExpr->pLeft;
857 }
858 assert( pLeft!=0 );
859 pDup = sqlite3ExprDup(db, pLeft);
860 pNew = sqlite3Expr(db, TK_IN, pDup, 0, 0);
861 if( pNew ){
862 int idxNew;
863 transferJoinMarkings(pNew, pExpr);
864 pNew->pList = pList;
865 idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
866 exprAnalyze(pSrc, pWC, idxNew);
867 pTerm = &pWC->a[idxTerm];
868 pWC->a[idxNew].iParent = idxTerm;
869 pTerm->nChild = 1;
870 }else{
871 sqlite3ExprListDelete(pList);
872 }
873 }
874or_not_possible:
875 whereClauseClear(&sOr);
876 }
877#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
878
879#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
880 /* Add constraints to reduce the search space on a LIKE or GLOB
881 ** operator.
882 */
883 if( isLikeOrGlob(db, pExpr, &nPattern, &isComplete) ){
884 Expr *pLeft, *pRight;
885 Expr *pStr1, *pStr2;
886 Expr *pNewExpr1, *pNewExpr2;
887 int idxNew1, idxNew2;
888
889 pLeft = pExpr->pList->a[1].pExpr;
890 pRight = pExpr->pList->a[0].pExpr;
891 pStr1 = sqlite3PExpr(pParse, TK_STRING, 0, 0, 0);
892 if( pStr1 ){
893 sqlite3TokenCopy(db, &pStr1->token, &pRight->token);
894 pStr1->token.n = nPattern;
895 pStr1->flags = EP_Dequoted;
896 }
897 pStr2 = sqlite3ExprDup(db, pStr1);
898 if( pStr2 ){
899 assert( pStr2->token.dyn );
900 ++*(u8*)&pStr2->token.z[nPattern-1];
901 }
902 pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft), pStr1, 0);
903 idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
904 exprAnalyze(pSrc, pWC, idxNew1);
905 pNewExpr2 = sqlite3PExpr(pParse, TK_LT, sqlite3ExprDup(db,pLeft), pStr2, 0);
906 idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
907 exprAnalyze(pSrc, pWC, idxNew2);
908 pTerm = &pWC->a[idxTerm];
909 if( isComplete ){
910 pWC->a[idxNew1].iParent = idxTerm;
911 pWC->a[idxNew2].iParent = idxTerm;
912 pTerm->nChild = 2;
913 }
914 }
915#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
916
917#ifndef SQLITE_OMIT_VIRTUALTABLE
918 /* Add a WO_MATCH auxiliary term to the constraint set if the
919 ** current expression is of the form: column MATCH expr.
920 ** This information is used by the xBestIndex methods of
921 ** virtual tables. The native query optimizer does not attempt
922 ** to do anything with MATCH functions.
923 */
924 if( isMatchOfColumn(pExpr) ){
925 int idxNew;
926 Expr *pRight, *pLeft;
927 WhereTerm *pNewTerm;
928 Bitmask prereqColumn, prereqExpr;
929
930 pRight = pExpr->pList->a[0].pExpr;
931 pLeft = pExpr->pList->a[1].pExpr;
932 prereqExpr = exprTableUsage(pMaskSet, pRight);
933 prereqColumn = exprTableUsage(pMaskSet, pLeft);
934 if( (prereqExpr & prereqColumn)==0 ){
935 Expr *pNewExpr;
936 pNewExpr = sqlite3Expr(db, TK_MATCH, 0, sqlite3ExprDup(db, pRight), 0);
937 idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
938 pNewTerm = &pWC->a[idxNew];
939 pNewTerm->prereqRight = prereqExpr;
940 pNewTerm->leftCursor = pLeft->iTable;
941 pNewTerm->leftColumn = pLeft->iColumn;
942 pNewTerm->eOperator = WO_MATCH;
943 pNewTerm->iParent = idxTerm;
944 pTerm = &pWC->a[idxTerm];
945 pTerm->nChild = 1;
946 pTerm->flags |= TERM_COPIED;
947 pNewTerm->prereqAll = pTerm->prereqAll;
948 }
949 }
950#endif /* SQLITE_OMIT_VIRTUALTABLE */
951}
952
953/*
954** Return TRUE if any of the expressions in pList->a[iFirst...] contain
955** a reference to any table other than the iBase table.
956*/
957static int referencesOtherTables(
958 ExprList *pList, /* Search expressions in ths list */
959 ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
960 int iFirst, /* Be searching with the iFirst-th expression */
961 int iBase /* Ignore references to this table */
962){
963 Bitmask allowed = ~getMask(pMaskSet, iBase);
964 while( iFirst<pList->nExpr ){
965 if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
966 return 1;
967 }
968 }
969 return 0;
970}
971
972
973/*
974** This routine decides if pIdx can be used to satisfy the ORDER BY
975** clause. If it can, it returns 1. If pIdx cannot satisfy the
976** ORDER BY clause, this routine returns 0.
977**
978** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
979** left-most table in the FROM clause of that same SELECT statement and
980** the table has a cursor number of "base". pIdx is an index on pTab.
981**
982** nEqCol is the number of columns of pIdx that are used as equality
983** constraints. Any of these columns may be missing from the ORDER BY
984** clause and the match can still be a success.
985**
986** All terms of the ORDER BY that match against the index must be either
987** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
988** index do not need to satisfy this constraint.) The *pbRev value is
989** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
990** the ORDER BY clause is all ASC.
991*/
992static int isSortingIndex(
993 Parse *pParse, /* Parsing context */
994 ExprMaskSet *pMaskSet, /* Mapping from table indices to bitmaps */
995 Index *pIdx, /* The index we are testing */
996 int base, /* Cursor number for the table to be sorted */
997 ExprList *pOrderBy, /* The ORDER BY clause */
998 int nEqCol, /* Number of index columns with == constraints */
999 int *pbRev /* Set to 1 if ORDER BY is DESC */
1000){
1001 int i, j; /* Loop counters */
1002 int sortOrder = 0; /* XOR of index and ORDER BY sort direction */
1003 int nTerm; /* Number of ORDER BY terms */
1004 struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
1005 sqlite3 *db = pParse->db;
1006
1007 assert( pOrderBy!=0 );
1008 nTerm = pOrderBy->nExpr;
1009 assert( nTerm>0 );
1010
1011 /* Match terms of the ORDER BY clause against columns of
1012 ** the index.
1013 **
1014 ** Note that indices have pIdx->nColumn regular columns plus
1015 ** one additional column containing the rowid. The rowid column
1016 ** of the index is also allowed to match against the ORDER BY
1017 ** clause.
1018 */
1019 for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
1020 Expr *pExpr; /* The expression of the ORDER BY pTerm */
1021 CollSeq *pColl; /* The collating sequence of pExpr */
1022 int termSortOrder; /* Sort order for this term */
1023 int iColumn; /* The i-th column of the index. -1 for rowid */
1024 int iSortOrder; /* 1 for DESC, 0 for ASC on the i-th index term */
1025 const char *zColl; /* Name of the collating sequence for i-th index term */
1026
1027 pExpr = pTerm->pExpr;
1028 if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
1029 /* Can not use an index sort on anything that is not a column in the
1030 ** left-most table of the FROM clause */
1031 break;
1032 }
1033 pColl = sqlite3ExprCollSeq(pParse, pExpr);
1034 if( !pColl ){
1035 pColl = db->pDfltColl;
1036 }
1037 if( i<pIdx->nColumn ){
1038 iColumn = pIdx->aiColumn[i];
1039 if( iColumn==pIdx->pTable->iPKey ){
1040 iColumn = -1;
1041 }
1042 iSortOrder = pIdx->aSortOrder[i];
1043 zColl = pIdx->azColl[i];
1044 }else{
1045 iColumn = -1;
1046 iSortOrder = 0;
1047 zColl = pColl->zName;
1048 }
1049 if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
1050 /* Term j of the ORDER BY clause does not match column i of the index */
1051 if( i<nEqCol ){
1052 /* If an index column that is constrained by == fails to match an
1053 ** ORDER BY term, that is OK. Just ignore that column of the index
1054 */
1055 continue;
1056 }else{
1057 /* If an index column fails to match and is not constrained by ==
1058 ** then the index cannot satisfy the ORDER BY constraint.
1059 */
1060 return 0;
1061 }
1062 }
1063 assert( pIdx->aSortOrder!=0 );
1064 assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
1065 assert( iSortOrder==0 || iSortOrder==1 );
1066 termSortOrder = iSortOrder ^ pTerm->sortOrder;
1067 if( i>nEqCol ){
1068 if( termSortOrder!=sortOrder ){
1069 /* Indices can only be used if all ORDER BY terms past the
1070 ** equality constraints are all either DESC or ASC. */
1071 return 0;
1072 }
1073 }else{
1074 sortOrder = termSortOrder;
1075 }
1076 j++;
1077 pTerm++;
1078 if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1079 /* If the indexed column is the primary key and everything matches
1080 ** so far and none of the ORDER BY terms to the right reference other
1081 ** tables in the join, then we are assured that the index can be used
1082 ** to sort because the primary key is unique and so none of the other
1083 ** columns will make any difference
1084 */
1085 j = nTerm;
1086 }
1087 }
1088
1089 *pbRev = sortOrder!=0;
1090 if( j>=nTerm ){
1091 /* All terms of the ORDER BY clause are covered by this index so
1092 ** this index can be used for sorting. */
1093 return 1;
1094 }
1095 if( pIdx->onError!=OE_None && i==pIdx->nColumn
1096 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1097 /* All terms of this index match some prefix of the ORDER BY clause
1098 ** and the index is UNIQUE and no terms on the tail of the ORDER BY
1099 ** clause reference other tables in a join. If this is all true then
1100 ** the order by clause is superfluous. */
1101 return 1;
1102 }
1103 return 0;
1104}
1105
1106/*
1107** Check table to see if the ORDER BY clause in pOrderBy can be satisfied
1108** by sorting in order of ROWID. Return true if so and set *pbRev to be
1109** true for reverse ROWID and false for forward ROWID order.
1110*/
1111static int sortableByRowid(
1112 int base, /* Cursor number for table to be sorted */
1113 ExprList *pOrderBy, /* The ORDER BY clause */
1114 ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
1115 int *pbRev /* Set to 1 if ORDER BY is DESC */
1116){
1117 Expr *p;
1118
1119 assert( pOrderBy!=0 );
1120 assert( pOrderBy->nExpr>0 );
1121 p = pOrderBy->a[0].pExpr;
1122 if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1
1123 && !referencesOtherTables(pOrderBy, pMaskSet, 1, base) ){
1124 *pbRev = pOrderBy->a[0].sortOrder;
1125 return 1;
1126 }
1127 return 0;
1128}
1129
1130/*
1131** Prepare a crude estimate of the logarithm of the input value.
1132** The results need not be exact. This is only used for estimating
1133** the total cost of performing operatings with O(logN) or O(NlogN)
1134** complexity. Because N is just a guess, it is no great tragedy if
1135** logN is a little off.
1136*/
1137static double estLog(double N){
1138 double logN = 1;
1139 double x = 10;
1140 while( N>x ){
1141 logN += 1;
1142 x *= 10;
1143 }
1144 return logN;
1145}
1146
1147/*
1148** Two routines for printing the content of an sqlite3_index_info
1149** structure. Used for testing and debugging only. If neither
1150** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
1151** are no-ops.
1152*/
1153#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
1154static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
1155 int i;
1156 if( !sqlite3_where_trace ) return;
1157 for(i=0; i<p->nConstraint; i++){
1158 sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
1159 i,
1160 p->aConstraint[i].iColumn,
1161 p->aConstraint[i].iTermOffset,
1162 p->aConstraint[i].op,
1163 p->aConstraint[i].usable);
1164 }
1165 for(i=0; i<p->nOrderBy; i++){
1166 sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
1167 i,
1168 p->aOrderBy[i].iColumn,
1169 p->aOrderBy[i].desc);
1170 }
1171}
1172static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
1173 int i;
1174 if( !sqlite3_where_trace ) return;
1175 for(i=0; i<p->nConstraint; i++){
1176 sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
1177 i,
1178 p->aConstraintUsage[i].argvIndex,
1179 p->aConstraintUsage[i].omit);
1180 }
1181 sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
1182 sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
1183 sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
1184 sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
1185}
1186#else
1187#define TRACE_IDX_INPUTS(A)
1188#define TRACE_IDX_OUTPUTS(A)
1189#endif
1190
1191#ifndef SQLITE_OMIT_VIRTUALTABLE
1192/*
1193** Compute the best index for a virtual table.
1194**
1195** The best index is computed by the xBestIndex method of the virtual
1196** table module. This routine is really just a wrapper that sets up
1197** the sqlite3_index_info structure that is used to communicate with
1198** xBestIndex.
1199**
1200** In a join, this routine might be called multiple times for the
1201** same virtual table. The sqlite3_index_info structure is created
1202** and initialized on the first invocation and reused on all subsequent
1203** invocations. The sqlite3_index_info structure is also used when
1204** code is generated to access the virtual table. The whereInfoDelete()
1205** routine takes care of freeing the sqlite3_index_info structure after
1206** everybody has finished with it.
1207*/
1208static double bestVirtualIndex(
1209 Parse *pParse, /* The parsing context */
1210 WhereClause *pWC, /* The WHERE clause */
1211 struct SrcList_item *pSrc, /* The FROM clause term to search */
1212 Bitmask notReady, /* Mask of cursors that are not available */
1213 ExprList *pOrderBy, /* The order by clause */
1214 int orderByUsable, /* True if we can potential sort */
1215 sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
1216){
1217 Table *pTab = pSrc->pTab;
1218 sqlite3_index_info *pIdxInfo;
1219 struct sqlite3_index_constraint *pIdxCons;
1220 struct sqlite3_index_orderby *pIdxOrderBy;
1221 struct sqlite3_index_constraint_usage *pUsage;
1222 WhereTerm *pTerm;
1223 int i, j;
1224 int nOrderBy;
1225 int rc;
1226
1227 /* If the sqlite3_index_info structure has not been previously
1228 ** allocated and initialized for this virtual table, then allocate
1229 ** and initialize it now
1230 */
1231 pIdxInfo = *ppIdxInfo;
1232 if( pIdxInfo==0 ){
1233 WhereTerm *pTerm;
1234 int nTerm;
1235 WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));
1236
1237 /* Count the number of possible WHERE clause constraints referring
1238 ** to this virtual table */
1239 for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
1240 if( pTerm->leftCursor != pSrc->iCursor ) continue;
1241 if( pTerm->eOperator==WO_IN ) continue;
1242 nTerm++;
1243 }
1244
1245 /* If the ORDER BY clause contains only columns in the current
1246 ** virtual table then allocate space for the aOrderBy part of
1247 ** the sqlite3_index_info structure.
1248 */
1249 nOrderBy = 0;
1250 if( pOrderBy ){
1251 for(i=0; i<pOrderBy->nExpr; i++){
1252 Expr *pExpr = pOrderBy->a[i].pExpr;
1253 if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
1254 }
1255 if( i==pOrderBy->nExpr ){
1256 nOrderBy = pOrderBy->nExpr;
1257 }
1258 }
1259
1260 /* Allocate the sqlite3_index_info structure
1261 */
1262 pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
1263 + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
1264 + sizeof(*pIdxOrderBy)*nOrderBy );
1265 if( pIdxInfo==0 ){
1266 sqlite3ErrorMsg(pParse, "out of memory");
1267 return 0.0;
1268 }
1269 *ppIdxInfo = pIdxInfo;
1270
1271 /* Initialize the structure. The sqlite3_index_info structure contains
1272 ** many fields that are declared "const" to prevent xBestIndex from
1273 ** changing them. We have to do some funky casting in order to
1274 ** initialize those fields.
1275 */
1276 pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
1277 pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
1278 pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
1279 *(int*)&pIdxInfo->nConstraint = nTerm;
1280 *(int*)&pIdxInfo->nOrderBy = nOrderBy;
1281 *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
1282 *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
1283 *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
1284 pUsage;
1285
1286 for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
1287 if( pTerm->leftCursor != pSrc->iCursor ) continue;
1288 if( pTerm->eOperator==WO_IN ) continue;
1289 pIdxCons[j].iColumn = pTerm->leftColumn;
1290 pIdxCons[j].iTermOffset = i;
1291 pIdxCons[j].op = pTerm->eOperator;
1292 /* The direct assignment in the previous line is possible only because
1293 ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
1294 ** following asserts verify this fact. */
1295 assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
1296 assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
1297 assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
1298 assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
1299 assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
1300 assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
1301 assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
1302 j++;
1303 }
1304 for(i=0; i<nOrderBy; i++){
1305 Expr *pExpr = pOrderBy->a[i].pExpr;
1306 pIdxOrderBy[i].iColumn = pExpr->iColumn;
1307 pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
1308 }
1309 }
1310
1311 /* At this point, the sqlite3_index_info structure that pIdxInfo points
1312 ** to will have been initialized, either during the current invocation or
1313 ** during some prior invocation. Now we just have to customize the
1314 ** details of pIdxInfo for the current invocation and pass it to
1315 ** xBestIndex.
1316 */
1317
1318 /* The module name must be defined. Also, by this point there must
1319 ** be a pointer to an sqlite3_vtab structure. Otherwise
1320 ** sqlite3ViewGetColumnNames() would have picked up the error.
1321 */
1322 assert( pTab->azModuleArg && pTab->azModuleArg[0] );
1323 assert( pTab->pVtab );
1324#if 0
1325 if( pTab->pVtab==0 ){
1326 sqlite3ErrorMsg(pParse, "undefined module %s for table %s",
1327 pTab->azModuleArg[0], pTab->zName);
1328 return 0.0;
1329 }
1330#endif
1331
1332 /* Set the aConstraint[].usable fields and initialize all
1333 ** output variables to zero.
1334 **
1335 ** aConstraint[].usable is true for constraints where the right-hand
1336 ** side contains only references to tables to the left of the current
1337 ** table. In other words, if the constraint is of the form:
1338 **
1339 ** column = expr
1340 **
1341 ** and we are evaluating a join, then the constraint on column is
1342 ** only valid if all tables referenced in expr occur to the left
1343 ** of the table containing column.
1344 **
1345 ** The aConstraints[] array contains entries for all constraints
1346 ** on the current table. That way we only have to compute it once
1347 ** even though we might try to pick the best index multiple times.
1348 ** For each attempt at picking an index, the order of tables in the
1349 ** join might be different so we have to recompute the usable flag
1350 ** each time.
1351 */
1352 pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
1353 pUsage = pIdxInfo->aConstraintUsage;
1354 for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
1355 j = pIdxCons->iTermOffset;
1356 pTerm = &pWC->a[j];
1357 pIdxCons->usable = (pTerm->prereqRight & notReady)==0;
1358 }
1359 memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
1360 if( pIdxInfo->needToFreeIdxStr ){
1361 sqlite3_free(pIdxInfo->idxStr);
1362 }
1363 pIdxInfo->idxStr = 0;
1364 pIdxInfo->idxNum = 0;
1365 pIdxInfo->needToFreeIdxStr = 0;
1366 pIdxInfo->orderByConsumed = 0;
1367 pIdxInfo->estimatedCost = SQLITE_BIG_DBL / 2.0;
1368 nOrderBy = pIdxInfo->nOrderBy;
1369 if( pIdxInfo->nOrderBy && !orderByUsable ){
1370 *(int*)&pIdxInfo->nOrderBy = 0;
1371 }
1372
1373 sqlite3SafetyOff(pParse->db);
1374 WHERETRACE(("xBestIndex for %s\n", pTab->zName));
1375 TRACE_IDX_INPUTS(pIdxInfo);
1376 rc = pTab->pVtab->pModule->xBestIndex(pTab->pVtab, pIdxInfo);
1377 TRACE_IDX_OUTPUTS(pIdxInfo);
1378 if( rc!=SQLITE_OK ){
1379 if( rc==SQLITE_NOMEM ){
1380 pParse->db->mallocFailed = 1;
1381 }else {
1382 sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
1383 }
1384 sqlite3SafetyOn(pParse->db);
1385 }else{
1386 rc = sqlite3SafetyOn(pParse->db);
1387 }
1388 *(int*)&pIdxInfo->nOrderBy = nOrderBy;
1389
1390 return pIdxInfo->estimatedCost;
1391}
1392#endif /* SQLITE_OMIT_VIRTUALTABLE */
1393
1394/*
1395** Find the best index for accessing a particular table. Return a pointer
1396** to the index, flags that describe how the index should be used, the
1397** number of equality constraints, and the "cost" for this index.
1398**
1399** The lowest cost index wins. The cost is an estimate of the amount of
1400** CPU and disk I/O need to process the request using the selected index.
1401** Factors that influence cost include:
1402**
1403** * The estimated number of rows that will be retrieved. (The
1404** fewer the better.)
1405**
1406** * Whether or not sorting must occur.
1407**
1408** * Whether or not there must be separate lookups in the
1409** index and in the main table.
1410**
1411*/
1412static double bestIndex(
1413 Parse *pParse, /* The parsing context */
1414 WhereClause *pWC, /* The WHERE clause */
1415 struct SrcList_item *pSrc, /* The FROM clause term to search */
1416 Bitmask notReady, /* Mask of cursors that are not available */
1417 ExprList *pOrderBy, /* The order by clause */
1418 Index **ppIndex, /* Make *ppIndex point to the best index */
1419 int *pFlags, /* Put flags describing this choice in *pFlags */
1420 int *pnEq /* Put the number of == or IN constraints here */
1421){
1422 WhereTerm *pTerm;
1423 Index *bestIdx = 0; /* Index that gives the lowest cost */
1424 double lowestCost; /* The cost of using bestIdx */
1425 int bestFlags = 0; /* Flags associated with bestIdx */
1426 int bestNEq = 0; /* Best value for nEq */
1427 int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
1428 Index *pProbe; /* An index we are evaluating */
1429 int rev; /* True to scan in reverse order */
1430 int flags; /* Flags associated with pProbe */
1431 int nEq; /* Number of == or IN constraints */
1432 int eqTermMask; /* Mask of valid equality operators */
1433 double cost; /* Cost of using pProbe */
1434
1435 WHERETRACE(("bestIndex: tbl=%s notReady=%x\n", pSrc->pTab->zName, notReady));
1436 lowestCost = SQLITE_BIG_DBL;
1437 pProbe = pSrc->pTab->pIndex;
1438
1439 /* If the table has no indices and there are no terms in the where
1440 ** clause that refer to the ROWID, then we will never be able to do
1441 ** anything other than a full table scan on this table. We might as
1442 ** well put it first in the join order. That way, perhaps it can be
1443 ** referenced by other tables in the join.
1444 */
1445 if( pProbe==0 &&
1446 findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 &&
1447 (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev)) ){
1448 *pFlags = 0;
1449 *ppIndex = 0;
1450 *pnEq = 0;
1451 return 0.0;
1452 }
1453
1454 /* Check for a rowid=EXPR or rowid IN (...) constraints
1455 */
1456 pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
1457 if( pTerm ){
1458 Expr *pExpr;
1459 *ppIndex = 0;
1460 bestFlags = WHERE_ROWID_EQ;
1461 if( pTerm->eOperator & WO_EQ ){
1462 /* Rowid== is always the best pick. Look no further. Because only
1463 ** a single row is generated, output is always in sorted order */
1464 *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE;
1465 *pnEq = 1;
1466 WHERETRACE(("... best is rowid\n"));
1467 return 0.0;
1468 }else if( (pExpr = pTerm->pExpr)->pList!=0 ){
1469 /* Rowid IN (LIST): cost is NlogN where N is the number of list
1470 ** elements. */
1471 lowestCost = pExpr->pList->nExpr;
1472 lowestCost *= estLog(lowestCost);
1473 }else{
1474 /* Rowid IN (SELECT): cost is NlogN where N is the number of rows
1475 ** in the result of the inner select. We have no way to estimate
1476 ** that value so make a wild guess. */
1477 lowestCost = 200;
1478 }
1479 WHERETRACE(("... rowid IN cost: %.9g\n", lowestCost));
1480 }
1481
1482 /* Estimate the cost of a table scan. If we do not know how many
1483 ** entries are in the table, use 1 million as a guess.
1484 */
1485 cost = pProbe ? pProbe->aiRowEst[0] : 1000000;
1486 WHERETRACE(("... table scan base cost: %.9g\n", cost));
1487 flags = WHERE_ROWID_RANGE;
1488
1489 /* Check for constraints on a range of rowids in a table scan.
1490 */
1491 pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0);
1492 if( pTerm ){
1493 if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){
1494 flags |= WHERE_TOP_LIMIT;
1495 cost /= 3; /* Guess that rowid<EXPR eliminates two-thirds or rows */
1496 }
1497 if( findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0) ){
1498 flags |= WHERE_BTM_LIMIT;
1499 cost /= 3; /* Guess that rowid>EXPR eliminates two-thirds of rows */
1500 }
1501 WHERETRACE(("... rowid range reduces cost to %.9g\n", cost));
1502 }else{
1503 flags = 0;
1504 }
1505
1506 /* If the table scan does not satisfy the ORDER BY clause, increase
1507 ** the cost by NlogN to cover the expense of sorting. */
1508 if( pOrderBy ){
1509 if( sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev) ){
1510 flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE;
1511 if( rev ){
1512 flags |= WHERE_REVERSE;
1513 }
1514 }else{
1515 cost += cost*estLog(cost);
1516 WHERETRACE(("... sorting increases cost to %.9g\n", cost));
1517 }
1518 }
1519 if( cost<lowestCost ){
1520 lowestCost = cost;
1521 bestFlags = flags;
1522 }
1523
1524 /* If the pSrc table is the right table of a LEFT JOIN then we may not
1525 ** use an index to satisfy IS NULL constraints on that table. This is
1526 ** because columns might end up being NULL if the table does not match -
1527 ** a circumstance which the index cannot help us discover. Ticket #2177.
1528 */
1529 if( (pSrc->jointype & JT_LEFT)!=0 ){
1530 eqTermMask = WO_EQ|WO_IN;
1531 }else{
1532 eqTermMask = WO_EQ|WO_IN|WO_ISNULL;
1533 }
1534
1535 /* Look at each index.
1536 */
1537 for(; pProbe; pProbe=pProbe->pNext){
1538 int i; /* Loop counter */
1539 double inMultiplier = 1;
1540
1541 WHERETRACE(("... index %s:\n", pProbe->zName));
1542
1543 /* Count the number of columns in the index that are satisfied
1544 ** by x=EXPR constraints or x IN (...) constraints.
1545 */
1546 flags = 0;
1547 for(i=0; i<pProbe->nColumn; i++){
1548 int j = pProbe->aiColumn[i];
1549 pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pProbe);
1550 if( pTerm==0 ) break;
1551 flags |= WHERE_COLUMN_EQ;
1552 if( pTerm->eOperator & WO_IN ){
1553 Expr *pExpr = pTerm->pExpr;
1554 flags |= WHERE_COLUMN_IN;
1555 if( pExpr->pSelect!=0 ){
1556 inMultiplier *= 25;
1557 }else if( pExpr->pList!=0 ){
1558 inMultiplier *= pExpr->pList->nExpr + 1;
1559 }
1560 }
1561 }
1562 cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier);
1563 nEq = i;
1564 if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0
1565 && nEq==pProbe->nColumn ){
1566 flags |= WHERE_UNIQUE;
1567 }
1568 WHERETRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n",nEq,inMultiplier,cost));
1569
1570 /* Look for range constraints
1571 */
1572 if( nEq<pProbe->nColumn ){
1573 int j = pProbe->aiColumn[nEq];
1574 pTerm = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pProbe);
1575 if( pTerm ){
1576 flags |= WHERE_COLUMN_RANGE;
1577 if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pProbe) ){
1578 flags |= WHERE_TOP_LIMIT;
1579 cost /= 3;
1580 }
1581 if( findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pProbe) ){
1582 flags |= WHERE_BTM_LIMIT;
1583 cost /= 3;
1584 }
1585 WHERETRACE(("...... range reduces cost to %.9g\n", cost));
1586 }
1587 }
1588
1589 /* Add the additional cost of sorting if that is a factor.
1590 */
1591 if( pOrderBy ){
1592 if( (flags & WHERE_COLUMN_IN)==0 &&
1593 isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev) ){
1594 if( flags==0 ){
1595 flags = WHERE_COLUMN_RANGE;
1596 }
1597 flags |= WHERE_ORDERBY;
1598 if( rev ){
1599 flags |= WHERE_REVERSE;
1600 }
1601 }else{
1602 cost += cost*estLog(cost);
1603 WHERETRACE(("...... orderby increases cost to %.9g\n", cost));
1604 }
1605 }
1606
1607 /* Check to see if we can get away with using just the index without
1608 ** ever reading the table. If that is the case, then halve the
1609 ** cost of this index.
1610 */
1611 if( flags && pSrc->colUsed < (((Bitmask)1)<<(BMS-1)) ){
1612 Bitmask m = pSrc->colUsed;
1613 int j;
1614 for(j=0; j<pProbe->nColumn; j++){
1615 int x = pProbe->aiColumn[j];
1616 if( x<BMS-1 ){
1617 m &= ~(((Bitmask)1)<<x);
1618 }
1619 }
1620 if( m==0 ){
1621 flags |= WHERE_IDX_ONLY;
1622 cost /= 2;
1623 WHERETRACE(("...... idx-only reduces cost to %.9g\n", cost));
1624 }
1625 }
1626
1627 /* If this index has achieved the lowest cost so far, then use it.
1628 */
1629 if( flags && cost < lowestCost ){
1630 bestIdx = pProbe;
1631 lowestCost = cost;
1632 bestFlags = flags;
1633 bestNEq = nEq;
1634 }
1635 }
1636
1637 /* Report the best result
1638 */
1639 *ppIndex = bestIdx;
1640 WHERETRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n",
1641 bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq));
1642 *pFlags = bestFlags | eqTermMask;
1643 *pnEq = bestNEq;
1644 return lowestCost;
1645}
1646
1647
1648/*
1649** Disable a term in the WHERE clause. Except, do not disable the term
1650** if it controls a LEFT OUTER JOIN and it did not originate in the ON
1651** or USING clause of that join.
1652**
1653** Consider the term t2.z='ok' in the following queries:
1654**
1655** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
1656** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
1657** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
1658**
1659** The t2.z='ok' is disabled in the in (2) because it originates
1660** in the ON clause. The term is disabled in (3) because it is not part
1661** of a LEFT OUTER JOIN. In (1), the term is not disabled.
1662**
1663** Disabling a term causes that term to not be tested in the inner loop
1664** of the join. Disabling is an optimization. When terms are satisfied
1665** by indices, we disable them to prevent redundant tests in the inner
1666** loop. We would get the correct results if nothing were ever disabled,
1667** but joins might run a little slower. The trick is to disable as much
1668** as we can without disabling too much. If we disabled in (1), we'd get
1669** the wrong answer. See ticket #813.
1670*/
1671static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
1672 if( pTerm
1673 && (pTerm->flags & TERM_CODED)==0
1674 && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
1675 ){
1676 pTerm->flags |= TERM_CODED;
1677 if( pTerm->iParent>=0 ){
1678 WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
1679 if( (--pOther->nChild)==0 ){
1680 disableTerm(pLevel, pOther);
1681 }
1682 }
1683 }
1684}
1685
1686/*
1687** Generate code that builds a probe for an index.
1688**
1689** There should be nColumn values on the stack. The index
1690** to be probed is pIdx. Pop the values from the stack and
1691** replace them all with a single record that is the index
1692** problem.
1693*/
1694static void buildIndexProbe(
1695 Vdbe *v, /* Generate code into this VM */
1696 int nColumn, /* The number of columns to check for NULL */
1697 Index *pIdx /* Index that we will be searching */
1698){
1699 sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
1700 sqlite3IndexAffinityStr(v, pIdx);
1701}
1702
1703
1704/*
1705** Generate code for a single equality term of the WHERE clause. An equality
1706** term can be either X=expr or X IN (...). pTerm is the term to be
1707** coded.
1708**
1709** The current value for the constraint is left on the top of the stack.
1710**
1711** For a constraint of the form X=expr, the expression is evaluated and its
1712** result is left on the stack. For constraints of the form X IN (...)
1713** this routine sets up a loop that will iterate over all values of X.
1714*/
1715static void codeEqualityTerm(
1716 Parse *pParse, /* The parsing context */
1717 WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
1718 WhereLevel *pLevel /* When level of the FROM clause we are working on */
1719){
1720 Expr *pX = pTerm->pExpr;
1721 Vdbe *v = pParse->pVdbe;
1722 if( pX->op==TK_EQ ){
1723 sqlite3ExprCode(pParse, pX->pRight);
1724 }else if( pX->op==TK_ISNULL ){
1725 sqlite3VdbeAddOp(v, OP_Null, 0, 0);
1726#ifndef SQLITE_OMIT_SUBQUERY
1727 }else{
1728 int iTab;
1729 struct InLoop *pIn;
1730
1731 assert( pX->op==TK_IN );
1732 sqlite3CodeSubselect(pParse, pX);
1733 iTab = pX->iTable;
1734 sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0);
1735 VdbeComment((v, "# %.*s", pX->span.n, pX->span.z));
1736 if( pLevel->nIn==0 ){
1737 pLevel->nxt = sqlite3VdbeMakeLabel(v);
1738 }
1739 pLevel->nIn++;
1740 pLevel->aInLoop = sqlite3DbReallocOrFree(pParse->db, pLevel->aInLoop,
1741 sizeof(pLevel->aInLoop[0])*pLevel->nIn);
1742 pIn = pLevel->aInLoop;
1743 if( pIn ){
1744 pIn += pLevel->nIn - 1;
1745 pIn->iCur = iTab;
1746 pIn->topAddr = sqlite3VdbeAddOp(v, OP_Column, iTab, 0);
1747 sqlite3VdbeAddOp(v, OP_IsNull, -1, 0);
1748 }else{
1749 pLevel->nIn = 0;
1750 }
1751#endif
1752 }
1753 disableTerm(pLevel, pTerm);
1754}
1755
1756/*
1757** Generate code that will evaluate all == and IN constraints for an
1758** index. The values for all constraints are left on the stack.
1759**
1760** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
1761** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
1762** The index has as many as three equality constraints, but in this
1763** example, the third "c" value is an inequality. So only two
1764** constraints are coded. This routine will generate code to evaluate
1765** a==5 and b IN (1,2,3). The current values for a and b will be left
1766** on the stack - a is the deepest and b the shallowest.
1767**
1768** In the example above nEq==2. But this subroutine works for any value
1769** of nEq including 0. If nEq==0, this routine is nearly a no-op.
1770** The only thing it does is allocate the pLevel->iMem memory cell.
1771**
1772** This routine always allocates at least one memory cell and puts
1773** the address of that memory cell in pLevel->iMem. The code that
1774** calls this routine will use pLevel->iMem to store the termination
1775** key value of the loop. If one or more IN operators appear, then
1776** this routine allocates an additional nEq memory cells for internal
1777** use.
1778*/
1779static void codeAllEqualityTerms(
1780 Parse *pParse, /* Parsing context */
1781 WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
1782 WhereClause *pWC, /* The WHERE clause */
1783 Bitmask notReady /* Which parts of FROM have not yet been coded */
1784){
1785 int nEq = pLevel->nEq; /* The number of == or IN constraints to code */
1786 int termsInMem = 0; /* If true, store value in mem[] cells */
1787 Vdbe *v = pParse->pVdbe; /* The virtual machine under construction */
1788 Index *pIdx = pLevel->pIdx; /* The index being used for this loop */
1789 int iCur = pLevel->iTabCur; /* The cursor of the table */
1790 WhereTerm *pTerm; /* A single constraint term */
1791 int j; /* Loop counter */
1792
1793 /* Figure out how many memory cells we will need then allocate them.
1794 ** We always need at least one used to store the loop terminator
1795 ** value. If there are IN operators we'll need one for each == or
1796 ** IN constraint.
1797 */
1798 pLevel->iMem = pParse->nMem++;
1799 if( pLevel->flags & WHERE_COLUMN_IN ){
1800 pParse->nMem += pLevel->nEq;
1801 termsInMem = 1;
1802 }
1803
1804 /* Evaluate the equality constraints
1805 */
1806 assert( pIdx->nColumn>=nEq );
1807 for(j=0; j<nEq; j++){
1808 int k = pIdx->aiColumn[j];
1809 pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
1810 if( pTerm==0 ) break;
1811 assert( (pTerm->flags & TERM_CODED)==0 );
1812 codeEqualityTerm(pParse, pTerm, pLevel);
1813 if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
1814 sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), pLevel->brk);
1815 }
1816 if( termsInMem ){
1817 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1);
1818 }
1819 }
1820
1821 /* Make sure all the constraint values are on the top of the stack
1822 */
1823 if( termsInMem ){
1824 for(j=0; j<nEq; j++){
1825 sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem+j+1, 0);
1826 }
1827 }
1828}
1829
1830#if defined(SQLITE_TEST)
1831/*
1832** The following variable holds a text description of query plan generated
1833** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin
1834** overwrites the previous. This information is used for testing and
1835** analysis only.
1836*/
1837char sqlite3_query_plan[BMS*2*40]; /* Text of the join */
1838static int nQPlan = 0; /* Next free slow in _query_plan[] */
1839
1840#endif /* SQLITE_TEST */
1841
1842
1843/*
1844** Free a WhereInfo structure
1845*/
1846static void whereInfoFree(WhereInfo *pWInfo){
1847 if( pWInfo ){
1848 int i;
1849 for(i=0; i<pWInfo->nLevel; i++){
1850 sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
1851 if( pInfo ){
1852 if( pInfo->needToFreeIdxStr ){
1853 /* Coverage: Don't think this can be reached. By the time this
1854 ** function is called, the index-strings have been passed
1855 ** to the vdbe layer for deletion.
1856 */
1857 sqlite3_free(pInfo->idxStr);
1858 }
1859 sqlite3_free(pInfo);
1860 }
1861 }
1862 sqlite3_free(pWInfo);
1863 }
1864}
1865
1866
1867/*
1868** Generate the beginning of the loop used for WHERE clause processing.
1869** The return value is a pointer to an opaque structure that contains
1870** information needed to terminate the loop. Later, the calling routine
1871** should invoke sqlite3WhereEnd() with the return value of this function
1872** in order to complete the WHERE clause processing.
1873**
1874** If an error occurs, this routine returns NULL.
1875**
1876** The basic idea is to do a nested loop, one loop for each table in
1877** the FROM clause of a select. (INSERT and UPDATE statements are the
1878** same as a SELECT with only a single table in the FROM clause.) For
1879** example, if the SQL is this:
1880**
1881** SELECT * FROM t1, t2, t3 WHERE ...;
1882**
1883** Then the code generated is conceptually like the following:
1884**
1885** foreach row1 in t1 do \ Code generated
1886** foreach row2 in t2 do |-- by sqlite3WhereBegin()
1887** foreach row3 in t3 do /
1888** ...
1889** end \ Code generated
1890** end |-- by sqlite3WhereEnd()
1891** end /
1892**
1893** Note that the loops might not be nested in the order in which they
1894** appear in the FROM clause if a different order is better able to make
1895** use of indices. Note also that when the IN operator appears in
1896** the WHERE clause, it might result in additional nested loops for
1897** scanning through all values on the right-hand side of the IN.
1898**
1899** There are Btree cursors associated with each table. t1 uses cursor
1900** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
1901** And so forth. This routine generates code to open those VDBE cursors
1902** and sqlite3WhereEnd() generates the code to close them.
1903**
1904** The code that sqlite3WhereBegin() generates leaves the cursors named
1905** in pTabList pointing at their appropriate entries. The [...] code
1906** can use OP_Column and OP_Rowid opcodes on these cursors to extract
1907** data from the various tables of the loop.
1908**
1909** If the WHERE clause is empty, the foreach loops must each scan their
1910** entire tables. Thus a three-way join is an O(N^3) operation. But if
1911** the tables have indices and there are terms in the WHERE clause that
1912** refer to those indices, a complete table scan can be avoided and the
1913** code will run much faster. Most of the work of this routine is checking
1914** to see if there are indices that can be used to speed up the loop.
1915**
1916** Terms of the WHERE clause are also used to limit which rows actually
1917** make it to the "..." in the middle of the loop. After each "foreach",
1918** terms of the WHERE clause that use only terms in that loop and outer
1919** loops are evaluated and if false a jump is made around all subsequent
1920** inner loops (or around the "..." if the test occurs within the inner-
1921** most loop)
1922**
1923** OUTER JOINS
1924**
1925** An outer join of tables t1 and t2 is conceptally coded as follows:
1926**
1927** foreach row1 in t1 do
1928** flag = 0
1929** foreach row2 in t2 do
1930** start:
1931** ...
1932** flag = 1
1933** end
1934** if flag==0 then
1935** move the row2 cursor to a null row
1936** goto start
1937** fi
1938** end
1939**
1940** ORDER BY CLAUSE PROCESSING
1941**
1942** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
1943** if there is one. If there is no ORDER BY clause or if this routine
1944** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
1945**
1946** If an index can be used so that the natural output order of the table
1947** scan is correct for the ORDER BY clause, then that index is used and
1948** *ppOrderBy is set to NULL. This is an optimization that prevents an
1949** unnecessary sort of the result set if an index appropriate for the
1950** ORDER BY clause already exists.
1951**
1952** If the where clause loops cannot be arranged to provide the correct
1953** output order, then the *ppOrderBy is unchanged.
1954*/
1955WhereInfo *sqlite3WhereBegin(
1956 Parse *pParse, /* The parser context */
1957 SrcList *pTabList, /* A list of all tables to be scanned */
1958 Expr *pWhere, /* The WHERE clause */
1959 ExprList **ppOrderBy /* An ORDER BY clause, or NULL */
1960){
1961 int i; /* Loop counter */
1962 WhereInfo *pWInfo; /* Will become the return value of this function */
1963 Vdbe *v = pParse->pVdbe; /* The virtual database engine */
1964 int brk, cont = 0; /* Addresses used during code generation */
1965 Bitmask notReady; /* Cursors that are not yet positioned */
1966 WhereTerm *pTerm; /* A single term in the WHERE clause */
1967 ExprMaskSet maskSet; /* The expression mask set */
1968 WhereClause wc; /* The WHERE clause is divided into these terms */
1969 struct SrcList_item *pTabItem; /* A single entry from pTabList */
1970 WhereLevel *pLevel; /* A single level in the pWInfo list */
1971 int iFrom; /* First unused FROM clause element */
1972 int andFlags; /* AND-ed combination of all wc.a[].flags */
1973 sqlite3 *db; /* Database connection */
1974
1975 /* The number of tables in the FROM clause is limited by the number of
1976 ** bits in a Bitmask
1977 */
1978 if( pTabList->nSrc>BMS ){
1979 sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
1980 return 0;
1981 }
1982
1983 /* Split the WHERE clause into separate subexpressions where each
1984 ** subexpression is separated by an AND operator.
1985 */
1986 initMaskSet(&maskSet);
1987 whereClauseInit(&wc, pParse, &maskSet);
1988 whereSplit(&wc, pWhere, TK_AND);
1989
1990 /* Allocate and initialize the WhereInfo structure that will become the
1991 ** return value.
1992 */
1993 db = pParse->db;
1994 pWInfo = sqlite3DbMallocZero(db,
1995 sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
1996 if( db->mallocFailed ){
1997 goto whereBeginNoMem;
1998 }
1999 pWInfo->nLevel = pTabList->nSrc;
2000 pWInfo->pParse = pParse;
2001 pWInfo->pTabList = pTabList;
2002 pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
2003
2004 /* Special case: a WHERE clause that is constant. Evaluate the
2005 ** expression and either jump over all of the code or fall thru.
2006 */
2007 if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
2008 sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
2009 pWhere = 0;
2010 }
2011
2012 /* Analyze all of the subexpressions. Note that exprAnalyze() might
2013 ** add new virtual terms onto the end of the WHERE clause. We do not
2014 ** want to analyze these virtual terms, so start analyzing at the end
2015 ** and work forward so that the added virtual terms are never processed.
2016 */
2017 for(i=0; i<pTabList->nSrc; i++){
2018 createMask(&maskSet, pTabList->a[i].iCursor);
2019 }
2020 exprAnalyzeAll(pTabList, &wc);
2021 if( db->mallocFailed ){
2022 goto whereBeginNoMem;
2023 }
2024
2025 /* Chose the best index to use for each table in the FROM clause.
2026 **
2027 ** This loop fills in the following fields:
2028 **
2029 ** pWInfo->a[].pIdx The index to use for this level of the loop.
2030 ** pWInfo->a[].flags WHERE_xxx flags associated with pIdx
2031 ** pWInfo->a[].nEq The number of == and IN constraints
2032 ** pWInfo->a[].iFrom When term of the FROM clause is being coded
2033 ** pWInfo->a[].iTabCur The VDBE cursor for the database table
2034 ** pWInfo->a[].iIdxCur The VDBE cursor for the index
2035 **
2036 ** This loop also figures out the nesting order of tables in the FROM
2037 ** clause.
2038 */
2039 notReady = ~(Bitmask)0;
2040 pTabItem = pTabList->a;
2041 pLevel = pWInfo->a;
2042 andFlags = ~0;
2043 WHERETRACE(("*** Optimizer Start ***\n"));
2044 for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2045 Index *pIdx; /* Index for FROM table at pTabItem */
2046 int flags; /* Flags asssociated with pIdx */
2047 int nEq; /* Number of == or IN constraints */
2048 double cost; /* The cost for pIdx */
2049 int j; /* For looping over FROM tables */
2050 Index *pBest = 0; /* The best index seen so far */
2051 int bestFlags = 0; /* Flags associated with pBest */
2052 int bestNEq = 0; /* nEq associated with pBest */
2053 double lowestCost; /* Cost of the pBest */
2054 int bestJ = 0; /* The value of j */
2055 Bitmask m; /* Bitmask value for j or bestJ */
2056 int once = 0; /* True when first table is seen */
2057 sqlite3_index_info *pIndex; /* Current virtual index */
2058
2059 lowestCost = SQLITE_BIG_DBL;
2060 for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
2061 int doNotReorder; /* True if this table should not be reordered */
2062
2063 doNotReorder = (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
2064 if( once && doNotReorder ) break;
2065 m = getMask(&maskSet, pTabItem->iCursor);
2066 if( (m & notReady)==0 ){
2067 if( j==iFrom ) iFrom++;
2068 continue;
2069 }
2070 assert( pTabItem->pTab );
2071#ifndef SQLITE_OMIT_VIRTUALTABLE
2072 if( IsVirtual(pTabItem->pTab) ){
2073 sqlite3_index_info **ppIdxInfo = &pWInfo->a[j].pIdxInfo;
2074 cost = bestVirtualIndex(pParse, &wc, pTabItem, notReady,
2075 ppOrderBy ? *ppOrderBy : 0, i==0,
2076 ppIdxInfo);
2077 flags = WHERE_VIRTUALTABLE;
2078 pIndex = *ppIdxInfo;
2079 if( pIndex && pIndex->orderByConsumed ){
2080 flags = WHERE_VIRTUALTABLE | WHERE_ORDERBY;
2081 }
2082 pIdx = 0;
2083 nEq = 0;
2084 if( (SQLITE_BIG_DBL/2.0)<cost ){
2085 /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
2086 ** inital value of lowestCost in this loop. If it is, then
2087 ** the (cost<lowestCost) test below will never be true and
2088 ** pLevel->pBestIdx never set.
2089 */
2090 cost = (SQLITE_BIG_DBL/2.0);
2091 }
2092 }else
2093#endif
2094 {
2095 cost = bestIndex(pParse, &wc, pTabItem, notReady,
2096 (i==0 && ppOrderBy) ? *ppOrderBy : 0,
2097 &pIdx, &flags, &nEq);
2098 pIndex = 0;
2099 }
2100 if( cost<lowestCost ){
2101 once = 1;
2102 lowestCost = cost;
2103 pBest = pIdx;
2104 bestFlags = flags;
2105 bestNEq = nEq;
2106 bestJ = j;
2107 pLevel->pBestIdx = pIndex;
2108 }
2109 if( doNotReorder ) break;
2110 }
2111 WHERETRACE(("*** Optimizer choose table %d for loop %d\n", bestJ,
2112 pLevel-pWInfo->a));
2113 if( (bestFlags & WHERE_ORDERBY)!=0 ){
2114 *ppOrderBy = 0;
2115 }
2116 andFlags &= bestFlags;
2117 pLevel->flags = bestFlags;
2118 pLevel->pIdx = pBest;
2119 pLevel->nEq = bestNEq;
2120 pLevel->aInLoop = 0;
2121 pLevel->nIn = 0;
2122 if( pBest ){
2123 pLevel->iIdxCur = pParse->nTab++;
2124 }else{
2125 pLevel->iIdxCur = -1;
2126 }
2127 notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor);
2128 pLevel->iFrom = bestJ;
2129 }
2130 WHERETRACE(("*** Optimizer Finished ***\n"));
2131
2132 /* If the total query only selects a single row, then the ORDER BY
2133 ** clause is irrelevant.
2134 */
2135 if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
2136 *ppOrderBy = 0;
2137 }
2138
2139 /* Open all tables in the pTabList and any indices selected for
2140 ** searching those tables.
2141 */
2142 sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
2143 for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2144 Table *pTab; /* Table to open */
2145 Index *pIx; /* Index used to access pTab (if any) */
2146 int iDb; /* Index of database containing table/index */
2147 int iIdxCur = pLevel->iIdxCur;
2148
2149#ifndef SQLITE_OMIT_EXPLAIN
2150 if( pParse->explain==2 ){
2151 char *zMsg;
2152 struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
2153 zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName);
2154 if( pItem->zAlias ){
2155 zMsg = sqlite3MPrintf(db, "%z AS %s", zMsg, pItem->zAlias);
2156 }
2157 if( (pIx = pLevel->pIdx)!=0 ){
2158 zMsg = sqlite3MPrintf(db, "%z WITH INDEX %s", zMsg, pIx->zName);
2159 }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
2160 zMsg = sqlite3MPrintf(db, "%z USING PRIMARY KEY", zMsg);
2161 }
2162#ifndef SQLITE_OMIT_VIRTUALTABLE
2163 else if( pLevel->pBestIdx ){
2164 sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
2165 zMsg = sqlite3MPrintf(db, "%z VIRTUAL TABLE INDEX %d:%s", zMsg,
2166 pBestIdx->idxNum, pBestIdx->idxStr);
2167 }
2168#endif
2169 if( pLevel->flags & WHERE_ORDERBY ){
2170 zMsg = sqlite3MPrintf(db, "%z ORDER BY", zMsg);
2171 }
2172 sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_DYNAMIC);
2173 }
2174#endif /* SQLITE_OMIT_EXPLAIN */
2175 pTabItem = &pTabList->a[pLevel->iFrom];
2176 pTab = pTabItem->pTab;
2177 iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
2178 if( pTab->isEphem || pTab->pSelect ) continue;
2179#ifndef SQLITE_OMIT_VIRTUALTABLE
2180 if( pLevel->pBestIdx ){
2181 int iCur = pTabItem->iCursor;
2182 sqlite3VdbeOp3(v, OP_VOpen, iCur, 0, (const char*)pTab->pVtab, P3_VTAB);
2183 }else
2184#endif
2185 if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
2186 sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead);
2187 if( pTab->nCol<(sizeof(Bitmask)*8) ){
2188 Bitmask b = pTabItem->colUsed;
2189 int n = 0;
2190 for(; b; b=b>>1, n++){}
2191 sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, n);
2192 assert( n<=pTab->nCol );
2193 }
2194 }else{
2195 sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
2196 }
2197 pLevel->iTabCur = pTabItem->iCursor;
2198 if( (pIx = pLevel->pIdx)!=0 ){
2199 KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
2200 assert( pIx->pSchema==pTab->pSchema );
2201 sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
2202 VdbeComment((v, "# %s", pIx->zName));
2203 sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
2204 (char*)pKey, P3_KEYINFO_HANDOFF);
2205 }
2206 if( (pLevel->flags & (WHERE_IDX_ONLY|WHERE_COLUMN_RANGE))!=0 ){
2207 /* Only call OP_SetNumColumns on the index if we might later use
2208 ** OP_Column on the index. */
2209 sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
2210 }
2211 sqlite3CodeVerifySchema(pParse, iDb);
2212 }
2213 pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
2214
2215 /* Generate the code to do the search. Each iteration of the for
2216 ** loop below generates code for a single nested loop of the VM
2217 ** program.
2218 */
2219 notReady = ~(Bitmask)0;
2220 for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2221 int j;
2222 int iCur = pTabItem->iCursor; /* The VDBE cursor for the table */
2223 Index *pIdx; /* The index we will be using */
2224 int nxt; /* Where to jump to continue with the next IN case */
2225 int iIdxCur; /* The VDBE cursor for the index */
2226 int omitTable; /* True if we use the index only */
2227 int bRev; /* True if we need to scan in reverse order */
2228
2229 pTabItem = &pTabList->a[pLevel->iFrom];
2230 iCur = pTabItem->iCursor;
2231 pIdx = pLevel->pIdx;
2232 iIdxCur = pLevel->iIdxCur;
2233 bRev = (pLevel->flags & WHERE_REVERSE)!=0;
2234 omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;
2235
2236 /* Create labels for the "break" and "continue" instructions
2237 ** for the current loop. Jump to brk to break out of a loop.
2238 ** Jump to cont to go immediately to the next iteration of the
2239 ** loop.
2240 **
2241 ** When there is an IN operator, we also have a "nxt" label that
2242 ** means to continue with the next IN value combination. When
2243 ** there are no IN operators in the constraints, the "nxt" label
2244 ** is the same as "brk".
2245 */
2246 brk = pLevel->brk = pLevel->nxt = sqlite3VdbeMakeLabel(v);
2247 cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
2248
2249 /* If this is the right table of a LEFT OUTER JOIN, allocate and
2250 ** initialize a memory cell that records if this table matches any
2251 ** row of the left table of the join.
2252 */
2253 if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
2254 if( !pParse->nMem ) pParse->nMem++;
2255 pLevel->iLeftJoin = pParse->nMem++;
2256 sqlite3VdbeAddOp(v, OP_MemInt, 0, pLevel->iLeftJoin);
2257 VdbeComment((v, "# init LEFT JOIN no-match flag"));
2258 }
2259
2260#ifndef SQLITE_OMIT_VIRTUALTABLE
2261 if( pLevel->pBestIdx ){
2262 /* Case 0: The table is a virtual-table. Use the VFilter and VNext
2263 ** to access the data.
2264 */
2265 int j;
2266 sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
2267 int nConstraint = pBestIdx->nConstraint;
2268 struct sqlite3_index_constraint_usage *aUsage =
2269 pBestIdx->aConstraintUsage;
2270 const struct sqlite3_index_constraint *aConstraint =
2271 pBestIdx->aConstraint;
2272
2273 for(j=1; j<=nConstraint; j++){
2274 int k;
2275 for(k=0; k<nConstraint; k++){
2276 if( aUsage[k].argvIndex==j ){
2277 int iTerm = aConstraint[k].iTermOffset;
2278 sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight);
2279 break;
2280 }
2281 }
2282 if( k==nConstraint ) break;
2283 }
2284 sqlite3VdbeAddOp(v, OP_Integer, j-1, 0);
2285 sqlite3VdbeAddOp(v, OP_Integer, pBestIdx->idxNum, 0);
2286 sqlite3VdbeOp3(v, OP_VFilter, iCur, brk, pBestIdx->idxStr,
2287 pBestIdx->needToFreeIdxStr ? P3_MPRINTF : P3_STATIC);
2288 pBestIdx->needToFreeIdxStr = 0;
2289 for(j=0; j<pBestIdx->nConstraint; j++){
2290 if( aUsage[j].omit ){
2291 int iTerm = aConstraint[j].iTermOffset;
2292 disableTerm(pLevel, &wc.a[iTerm]);
2293 }
2294 }
2295 pLevel->op = OP_VNext;
2296 pLevel->p1 = iCur;
2297 pLevel->p2 = sqlite3VdbeCurrentAddr(v);
2298 }else
2299#endif /* SQLITE_OMIT_VIRTUALTABLE */
2300
2301 if( pLevel->flags & WHERE_ROWID_EQ ){
2302 /* Case 1: We can directly reference a single row using an
2303 ** equality comparison against the ROWID field. Or
2304 ** we reference multiple rows using a "rowid IN (...)"
2305 ** construct.
2306 */
2307 pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
2308 assert( pTerm!=0 );
2309 assert( pTerm->pExpr!=0 );
2310 assert( pTerm->leftCursor==iCur );
2311 assert( omitTable==0 );
2312 codeEqualityTerm(pParse, pTerm, pLevel);
2313 nxt = pLevel->nxt;
2314 sqlite3VdbeAddOp(v, OP_MustBeInt, 1, nxt);
2315 sqlite3VdbeAddOp(v, OP_NotExists, iCur, nxt);
2316 VdbeComment((v, "pk"));
2317 pLevel->op = OP_Noop;
2318 }else if( pLevel->flags & WHERE_ROWID_RANGE ){
2319 /* Case 2: We have an inequality comparison against the ROWID field.
2320 */
2321 int testOp = OP_Noop;
2322 int start;
2323 WhereTerm *pStart, *pEnd;
2324
2325 assert( omitTable==0 );
2326 pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
2327 pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0);
2328 if( bRev ){
2329 pTerm = pStart;
2330 pStart = pEnd;
2331 pEnd = pTerm;
2332 }
2333 if( pStart ){
2334 Expr *pX;
2335 pX = pStart->pExpr;
2336 assert( pX!=0 );
2337 assert( pStart->leftCursor==iCur );
2338 sqlite3ExprCode(pParse, pX->pRight);
2339 sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk);
2340 sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk);
2341 VdbeComment((v, "pk"));
2342 disableTerm(pLevel, pStart);
2343 }else{
2344 sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
2345 }
2346 if( pEnd ){
2347 Expr *pX;
2348 pX = pEnd->pExpr;
2349 assert( pX!=0 );
2350 assert( pEnd->leftCursor==iCur );
2351 sqlite3ExprCode(pParse, pX->pRight);
2352 pLevel->iMem = pParse->nMem++;
2353 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
2354 if( pX->op==TK_LT || pX->op==TK_GT ){
2355 testOp = bRev ? OP_Le : OP_Ge;
2356 }else{
2357 testOp = bRev ? OP_Lt : OP_Gt;
2358 }
2359 disableTerm(pLevel, pEnd);
2360 }
2361 start = sqlite3VdbeCurrentAddr(v);
2362 pLevel->op = bRev ? OP_Prev : OP_Next;
2363 pLevel->p1 = iCur;
2364 pLevel->p2 = start;
2365 if( testOp!=OP_Noop ){
2366 sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
2367 sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2368 sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC|0x100, brk);
2369 }
2370 }else if( pLevel->flags & WHERE_COLUMN_RANGE ){
2371 /* Case 3: The WHERE clause term that refers to the right-most
2372 ** column of the index is an inequality. For example, if
2373 ** the index is on (x,y,z) and the WHERE clause is of the
2374 ** form "x=5 AND y<10" then this case is used. Only the
2375 ** right-most column can be an inequality - the rest must
2376 ** use the "==" and "IN" operators.
2377 **
2378 ** This case is also used when there are no WHERE clause
2379 ** constraints but an index is selected anyway, in order
2380 ** to force the output order to conform to an ORDER BY.
2381 */
2382 int start;
2383 int nEq = pLevel->nEq;
2384 int topEq=0; /* True if top limit uses ==. False is strictly < */
2385 int btmEq=0; /* True if btm limit uses ==. False if strictly > */
2386 int topOp, btmOp; /* Operators for the top and bottom search bounds */
2387 int testOp;
2388 int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
2389 int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;
2390
2391 /* Generate code to evaluate all constraint terms using == or IN
2392 ** and level the values of those terms on the stack.
2393 */
2394 codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
2395
2396 /* Duplicate the equality term values because they will all be
2397 ** used twice: once to make the termination key and once to make the
2398 ** start key.
2399 */
2400 for(j=0; j<nEq; j++){
2401 sqlite3VdbeAddOp(v, OP_Dup, nEq-1, 0);
2402 }
2403
2404 /* Figure out what comparison operators to use for top and bottom
2405 ** search bounds. For an ascending index, the bottom bound is a > or >=
2406 ** operator and the top bound is a < or <= operator. For a descending
2407 ** index the operators are reversed.
2408 */
2409 if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){
2410 topOp = WO_LT|WO_LE;
2411 btmOp = WO_GT|WO_GE;
2412 }else{
2413 topOp = WO_GT|WO_GE;
2414 btmOp = WO_LT|WO_LE;
2415 SWAP(int, topLimit, btmLimit);
2416 }
2417
2418 /* Generate the termination key. This is the key value that
2419 ** will end the search. There is no termination key if there
2420 ** are no equality terms and no "X<..." term.
2421 **
2422 ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
2423 ** key computed here really ends up being the start key.
2424 */
2425 nxt = pLevel->nxt;
2426 if( topLimit ){
2427 Expr *pX;
2428 int k = pIdx->aiColumn[j];
2429 pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx);
2430 assert( pTerm!=0 );
2431 pX = pTerm->pExpr;
2432 assert( (pTerm->flags & TERM_CODED)==0 );
2433 sqlite3ExprCode(pParse, pX->pRight);
2434 sqlite3VdbeAddOp(v, OP_IsNull, -(nEq*2+1), nxt);
2435 topEq = pTerm->eOperator & (WO_LE|WO_GE);
2436 disableTerm(pLevel, pTerm);
2437 testOp = OP_IdxGE;
2438 }else{
2439 testOp = nEq>0 ? OP_IdxGE : OP_Noop;
2440 topEq = 1;
2441 }
2442 if( testOp!=OP_Noop ){
2443 int nCol = nEq + topLimit;
2444 pLevel->iMem = pParse->nMem++;
2445 buildIndexProbe(v, nCol, pIdx);
2446 if( bRev ){
2447 int op = topEq ? OP_MoveLe : OP_MoveLt;
2448 sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
2449 }else{
2450 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
2451 }
2452 }else if( bRev ){
2453 sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk);
2454 }
2455
2456 /* Generate the start key. This is the key that defines the lower
2457 ** bound on the search. There is no start key if there are no
2458 ** equality terms and if there is no "X>..." term. In
2459 ** that case, generate a "Rewind" instruction in place of the
2460 ** start key search.
2461 **
2462 ** 2002-Dec-04: In the case of a reverse-order search, the so-called
2463 ** "start" key really ends up being used as the termination key.
2464 */
2465 if( btmLimit ){
2466 Expr *pX;
2467 int k = pIdx->aiColumn[j];
2468 pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx);
2469 assert( pTerm!=0 );
2470 pX = pTerm->pExpr;
2471 assert( (pTerm->flags & TERM_CODED)==0 );
2472 sqlite3ExprCode(pParse, pX->pRight);
2473 sqlite3VdbeAddOp(v, OP_IsNull, -(nEq+1), nxt);
2474 btmEq = pTerm->eOperator & (WO_LE|WO_GE);
2475 disableTerm(pLevel, pTerm);
2476 }else{
2477 btmEq = 1;
2478 }
2479 if( nEq>0 || btmLimit ){
2480 int nCol = nEq + btmLimit;
2481 buildIndexProbe(v, nCol, pIdx);
2482 if( bRev ){
2483 pLevel->iMem = pParse->nMem++;
2484 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
2485 testOp = OP_IdxLT;
2486 }else{
2487 int op = btmEq ? OP_MoveGe : OP_MoveGt;
2488 sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
2489 }
2490 }else if( bRev ){
2491 testOp = OP_Noop;
2492 }else{
2493 sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk);
2494 }
2495
2496 /* Generate the the top of the loop. If there is a termination
2497 ** key we have to test for that key and abort at the top of the
2498 ** loop.
2499 */
2500 start = sqlite3VdbeCurrentAddr(v);
2501 if( testOp!=OP_Noop ){
2502 sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2503 sqlite3VdbeAddOp(v, testOp, iIdxCur, nxt);
2504 if( (topEq && !bRev) || (!btmEq && bRev) ){
2505 sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
2506 }
2507 }
2508 if( topLimit | btmLimit ){
2509 sqlite3VdbeAddOp(v, OP_Column, iIdxCur, nEq);
2510 sqlite3VdbeAddOp(v, OP_IsNull, 1, cont);
2511 }
2512 if( !omitTable ){
2513 sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
2514 sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
2515 }
2516
2517 /* Record the instruction used to terminate the loop.
2518 */
2519 pLevel->op = bRev ? OP_Prev : OP_Next;
2520 pLevel->p1 = iIdxCur;
2521 pLevel->p2 = start;
2522 }else if( pLevel->flags & WHERE_COLUMN_EQ ){
2523 /* Case 4: There is an index and all terms of the WHERE clause that
2524 ** refer to the index using the "==" or "IN" operators.
2525 */
2526 int start;
2527 int nEq = pLevel->nEq;
2528
2529 /* Generate code to evaluate all constraint terms using == or IN
2530 ** and leave the values of those terms on the stack.
2531 */
2532 codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
2533 nxt = pLevel->nxt;
2534
2535 /* Generate a single key that will be used to both start and terminate
2536 ** the search
2537 */
2538 buildIndexProbe(v, nEq, pIdx);
2539 sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);
2540
2541 /* Generate code (1) to move to the first matching element of the table.
2542 ** Then generate code (2) that jumps to "nxt" after the cursor is past
2543 ** the last matching element of the table. The code (1) is executed
2544 ** once to initialize the search, the code (2) is executed before each
2545 ** iteration of the scan to see if the scan has finished. */
2546 if( bRev ){
2547 /* Scan in reverse order */
2548 sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, nxt);
2549 start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2550 sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, nxt);
2551 pLevel->op = OP_Prev;
2552 }else{
2553 /* Scan in the forward order */
2554 sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, nxt);
2555 start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
2556 sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, nxt, "+", P3_STATIC);
2557 pLevel->op = OP_Next;
2558 }
2559 if( !omitTable ){
2560 sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
2561 sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
2562 }
2563 pLevel->p1 = iIdxCur;
2564 pLevel->p2 = start;
2565 }else{
2566 /* Case 5: There is no usable index. We must do a complete
2567 ** scan of the entire table.
2568 */
2569 assert( omitTable==0 );
2570 assert( bRev==0 );
2571 pLevel->op = OP_Next;
2572 pLevel->p1 = iCur;
2573 pLevel->p2 = 1 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk);
2574 }
2575 notReady &= ~getMask(&maskSet, iCur);
2576
2577 /* Insert code to test every subexpression that can be completely
2578 ** computed using the current set of tables.
2579 */
2580 for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
2581 Expr *pE;
2582 if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
2583 if( (pTerm->prereqAll & notReady)!=0 ) continue;
2584 pE = pTerm->pExpr;
2585 assert( pE!=0 );
2586 if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
2587 continue;
2588 }
2589 sqlite3ExprIfFalse(pParse, pE, cont, 1);
2590 pTerm->flags |= TERM_CODED;
2591 }
2592
2593 /* For a LEFT OUTER JOIN, generate code that will record the fact that
2594 ** at least one row of the right table has matched the left table.
2595 */
2596 if( pLevel->iLeftJoin ){
2597 pLevel->top = sqlite3VdbeCurrentAddr(v);
2598 sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin);
2599 VdbeComment((v, "# record LEFT JOIN hit"));
2600 for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
2601 if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
2602 if( (pTerm->prereqAll & notReady)!=0 ) continue;
2603 assert( pTerm->pExpr );
2604 sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1);
2605 pTerm->flags |= TERM_CODED;
2606 }
2607 }
2608 }
2609
2610#ifdef SQLITE_TEST /* For testing and debugging use only */
2611 /* Record in the query plan information about the current table
2612 ** and the index used to access it (if any). If the table itself
2613 ** is not used, its name is just '{}'. If no index is used
2614 ** the index is listed as "{}". If the primary key is used the
2615 ** index name is '*'.
2616 */
2617 for(i=0; i<pTabList->nSrc; i++){
2618 char *z;
2619 int n;
2620 pLevel = &pWInfo->a[i];
2621 pTabItem = &pTabList->a[pLevel->iFrom];
2622 z = pTabItem->zAlias;
2623 if( z==0 ) z = pTabItem->pTab->zName;
2624 n = strlen(z);
2625 if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
2626 if( pLevel->flags & WHERE_IDX_ONLY ){
2627 memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
2628 nQPlan += 2;
2629 }else{
2630 memcpy(&sqlite3_query_plan[nQPlan], z, n);
2631 nQPlan += n;
2632 }
2633 sqlite3_query_plan[nQPlan++] = ' ';
2634 }
2635 if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
2636 memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
2637 nQPlan += 2;
2638 }else if( pLevel->pIdx==0 ){
2639 memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
2640 nQPlan += 3;
2641 }else{
2642 n = strlen(pLevel->pIdx->zName);
2643 if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
2644 memcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName, n);
2645 nQPlan += n;
2646 sqlite3_query_plan[nQPlan++] = ' ';
2647 }
2648 }
2649 }
2650 while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
2651 sqlite3_query_plan[--nQPlan] = 0;
2652 }
2653 sqlite3_query_plan[nQPlan] = 0;
2654 nQPlan = 0;
2655#endif /* SQLITE_TEST // Testing and debugging use only */
2656
2657 /* Record the continuation address in the WhereInfo structure. Then
2658 ** clean up and return.
2659 */
2660 pWInfo->iContinue = cont;
2661 whereClauseClear(&wc);
2662 return pWInfo;
2663
2664 /* Jump here if malloc fails */
2665whereBeginNoMem:
2666 whereClauseClear(&wc);
2667 whereInfoFree(pWInfo);
2668 return 0;
2669}
2670
2671/*
2672** Generate the end of the WHERE loop. See comments on
2673** sqlite3WhereBegin() for additional information.
2674*/
2675void sqlite3WhereEnd(WhereInfo *pWInfo){
2676 Vdbe *v = pWInfo->pParse->pVdbe;
2677 int i;
2678 WhereLevel *pLevel;
2679 SrcList *pTabList = pWInfo->pTabList;
2680
2681 /* Generate loop termination code.
2682 */
2683 for(i=pTabList->nSrc-1; i>=0; i--){
2684 pLevel = &pWInfo->a[i];
2685 sqlite3VdbeResolveLabel(v, pLevel->cont);
2686 if( pLevel->op!=OP_Noop ){
2687 sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
2688 }
2689 if( pLevel->nIn ){
2690 struct InLoop *pIn;
2691 int j;
2692 sqlite3VdbeResolveLabel(v, pLevel->nxt);
2693 for(j=pLevel->nIn, pIn=&pLevel->aInLoop[j-1]; j>0; j--, pIn--){
2694 sqlite3VdbeJumpHere(v, pIn->topAddr+1);
2695 sqlite3VdbeAddOp(v, OP_Next, pIn->iCur, pIn->topAddr);
2696 sqlite3VdbeJumpHere(v, pIn->topAddr-1);
2697 }
2698 sqlite3_free(pLevel->aInLoop);
2699 }
2700 sqlite3VdbeResolveLabel(v, pLevel->brk);
2701 if( pLevel->iLeftJoin ){
2702 int addr;
2703 addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0);
2704 sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
2705 if( pLevel->iIdxCur>=0 ){
2706 sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0);
2707 }
2708 sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top);
2709 sqlite3VdbeJumpHere(v, addr);
2710 }
2711 }
2712
2713 /* The "break" point is here, just past the end of the outer loop.
2714 ** Set it.
2715 */
2716 sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
2717
2718 /* Close all of the cursors that were opened by sqlite3WhereBegin.
2719 */
2720 for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
2721 struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
2722 Table *pTab = pTabItem->pTab;
2723 assert( pTab!=0 );
2724 if( pTab->isEphem || pTab->pSelect ) continue;
2725 if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
2726 sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
2727 }
2728 if( pLevel->pIdx!=0 ){
2729 sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
2730 }
2731
2732 /* Make cursor substitutions for cases where we want to use
2733 ** just the index and never reference the table.
2734 **
2735 ** Calls to the code generator in between sqlite3WhereBegin and
2736 ** sqlite3WhereEnd will have created code that references the table
2737 ** directly. This loop scans all that code looking for opcodes
2738 ** that reference the table and converts them into opcodes that
2739 ** reference the index.
2740 */
2741 if( pLevel->flags & WHERE_IDX_ONLY ){
2742 int k, j, last;
2743 VdbeOp *pOp;
2744 Index *pIdx = pLevel->pIdx;
2745
2746 assert( pIdx!=0 );
2747 pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
2748 last = sqlite3VdbeCurrentAddr(v);
2749 for(k=pWInfo->iTop; k<last; k++, pOp++){
2750 if( pOp->p1!=pLevel->iTabCur ) continue;
2751 if( pOp->opcode==OP_Column ){
2752 pOp->p1 = pLevel->iIdxCur;
2753 for(j=0; j<pIdx->nColumn; j++){
2754 if( pOp->p2==pIdx->aiColumn[j] ){
2755 pOp->p2 = j;
2756 break;
2757 }
2758 }
2759 }else if( pOp->opcode==OP_Rowid ){
2760 pOp->p1 = pLevel->iIdxCur;
2761 pOp->opcode = OP_IdxRowid;
2762 }else if( pOp->opcode==OP_NullRow ){
2763 pOp->opcode = OP_Noop;
2764 }
2765 }
2766 }
2767 }
2768
2769 /* Final cleanup
2770 */
2771 whereInfoFree(pWInfo);
2772 return;
2773}
generated by cgit v1.1 at 2024-12-22 06:35:26 +0000