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.
14 **
15 ** $Id: where.c,v 1.89.2.2 2004/07/19 19:30:50 drh Exp $
16 */
17 #include "sqliteInt.h"
18
19 /*
20 ** The query generator uses an array of instances of this structure to
21 ** help it analyze the subexpressions of the WHERE clause. Each WHERE
22 ** clause subexpression is separated from the others by an AND operator.
23 */
24 typedef struct ExprInfo ExprInfo;
25 struct ExprInfo {
26 Expr *p; /* Pointer to the subexpression */
27 u8 indexable; /* True if this subexprssion is usable by an index */
28 short int idxLeft; /* p->pLeft is a column in this table number. -1 if
29 ** p->pLeft is not the column of any table */
30 short int idxRight; /* p->pRight is a column in this table number. -1 if
31 ** p->pRight is not the column of any table */
32 unsigned prereqLeft; /* Bitmask of tables referenced by p->pLeft */
33 unsigned prereqRight; /* Bitmask of tables referenced by p->pRight */
34 unsigned prereqAll; /* Bitmask of tables referenced by p */
35 };
36
37 /*
38 ** An instance of the following structure keeps track of a mapping
39 ** between VDBE cursor numbers and bitmasks. The VDBE cursor numbers
40 ** are small integers contained in SrcList_item.iCursor and Expr.iTable
41 ** fields. For any given WHERE clause, we want to track which cursors
42 ** are being used, so we assign a single bit in a 32-bit word to track
43 ** that cursor. Then a 32-bit integer is able to show the set of all
44 ** cursors being used.
45 */
46 typedef struct ExprMaskSet ExprMaskSet;
47 struct ExprMaskSet {
48 int n; /* Number of assigned cursor values */
49 int ix[31]; /* Cursor assigned to each bit */
50 };
51
52 /*
53 ** Determine the number of elements in an array.
54 */
55 #define ARRAYSIZE(X) (sizeof(X)/sizeof(X[0]))
56
57 /*
58 ** This routine is used to divide the WHERE expression into subexpressions
59 ** separated by the AND operator.
60 **
61 ** aSlot[] is an array of subexpressions structures.
62 ** There are nSlot spaces left in this array. This routine attempts to
63 ** split pExpr into subexpressions and fills aSlot[] with those subexpressions.
64 ** The return value is the number of slots filled.
65 */
exprSplit(int nSlot,ExprInfo * aSlot,Expr * pExpr)66 static int exprSplit(int nSlot, ExprInfo *aSlot, Expr *pExpr){
67 int cnt = 0;
68 if( pExpr==0 || nSlot<1 ) return 0;
69 if( nSlot==1 || pExpr->op!=TK_AND ){
70 aSlot[0].p = pExpr;
71 return 1;
72 }
73 if( pExpr->pLeft->op!=TK_AND ){
74 aSlot[0].p = pExpr->pLeft;
75 cnt = 1 + exprSplit(nSlot-1, &aSlot[1], pExpr->pRight);
76 }else{
77 cnt = exprSplit(nSlot, aSlot, pExpr->pLeft);
78 cnt += exprSplit(nSlot-cnt, &aSlot[cnt], pExpr->pRight);
79 }
80 return cnt;
81 }
82
83 /*
84 ** Initialize an expression mask set
85 */
86 #define initMaskSet(P) memset(P, 0, sizeof(*P))
87
88 /*
89 ** Return the bitmask for the given cursor. Assign a new bitmask
90 ** if this is the first time the cursor has been seen.
91 */
getMask(ExprMaskSet * pMaskSet,int iCursor)92 static int getMask(ExprMaskSet *pMaskSet, int iCursor){
93 int i;
94 for(i=0; i<pMaskSet->n; i++){
95 if( pMaskSet->ix[i]==iCursor ) return 1<<i;
96 }
97 if( i==pMaskSet->n && i<ARRAYSIZE(pMaskSet->ix) ){
98 pMaskSet->n++;
99 pMaskSet->ix[i] = iCursor;
100 return 1<<i;
101 }
102 return 0;
103 }
104
105 /*
106 ** Destroy an expression mask set
107 */
108 #define freeMaskSet(P) /* NO-OP */
109
110 /*
111 ** This routine walks (recursively) an expression tree and generates
112 ** a bitmask indicating which tables are used in that expression
113 ** tree.
114 **
115 ** In order for this routine to work, the calling function must have
116 ** previously invoked sqliteExprResolveIds() on the expression. See
117 ** the header comment on that routine for additional information.
118 ** The sqliteExprResolveIds() routines looks for column names and
119 ** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
120 ** the VDBE cursor number of the table.
121 */
exprTableUsage(ExprMaskSet * pMaskSet,Expr * p)122 static int exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
123 unsigned int mask = 0;
124 if( p==0 ) return 0;
125 if( p->op==TK_COLUMN ){
126 mask = getMask(pMaskSet, p->iTable);
127 if( mask==0 ) mask = -1;
128 return mask;
129 }
130 if( p->pRight ){
131 mask = exprTableUsage(pMaskSet, p->pRight);
132 }
133 if( p->pLeft ){
134 mask |= exprTableUsage(pMaskSet, p->pLeft);
135 }
136 if( p->pList ){
137 int i;
138 for(i=0; i<p->pList->nExpr; i++){
139 mask |= exprTableUsage(pMaskSet, p->pList->a[i].pExpr);
140 }
141 }
142 return mask;
143 }
144
145 /*
146 ** Return TRUE if the given operator is one of the operators that is
147 ** allowed for an indexable WHERE clause. The allowed operators are
148 ** "=", "<", ">", "<=", ">=", and "IN".
149 */
allowedOp(int op)150 static int allowedOp(int op){
151 switch( op ){
152 case TK_LT:
153 case TK_LE:
154 case TK_GT:
155 case TK_GE:
156 case TK_EQ:
157 case TK_IN:
158 return 1;
159 default:
160 return 0;
161 }
162 }
163
164 /*
165 ** The input to this routine is an ExprInfo structure with only the
166 ** "p" field filled in. The job of this routine is to analyze the
167 ** subexpression and populate all the other fields of the ExprInfo
168 ** structure.
169 */
exprAnalyze(ExprMaskSet * pMaskSet,ExprInfo * pInfo)170 static void exprAnalyze(ExprMaskSet *pMaskSet, ExprInfo *pInfo){
171 Expr *pExpr = pInfo->p;
172 pInfo->prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
173 pInfo->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
174 pInfo->prereqAll = exprTableUsage(pMaskSet, pExpr);
175 pInfo->indexable = 0;
176 pInfo->idxLeft = -1;
177 pInfo->idxRight = -1;
178 if( allowedOp(pExpr->op) && (pInfo->prereqRight & pInfo->prereqLeft)==0 ){
179 if( pExpr->pRight && pExpr->pRight->op==TK_COLUMN ){
180 pInfo->idxRight = pExpr->pRight->iTable;
181 pInfo->indexable = 1;
182 }
183 if( pExpr->pLeft->op==TK_COLUMN ){
184 pInfo->idxLeft = pExpr->pLeft->iTable;
185 pInfo->indexable = 1;
186 }
187 }
188 }
189
190 /*
191 ** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
192 ** left-most table in the FROM clause of that same SELECT statement and
193 ** the table has a cursor number of "base".
194 **
195 ** This routine attempts to find an index for pTab that generates the
196 ** correct record sequence for the given ORDER BY clause. The return value
197 ** is a pointer to an index that does the job. NULL is returned if the
198 ** table has no index that will generate the correct sort order.
199 **
200 ** If there are two or more indices that generate the correct sort order
201 ** and pPreferredIdx is one of those indices, then return pPreferredIdx.
202 **
203 ** nEqCol is the number of columns of pPreferredIdx that are used as
204 ** equality constraints. Any index returned must have exactly this same
205 ** set of columns. The ORDER BY clause only matches index columns beyond the
206 ** the first nEqCol columns.
207 **
208 ** All terms of the ORDER BY clause must be either ASC or DESC. The
209 ** *pbRev value is set to 1 if the ORDER BY clause is all DESC and it is
210 ** set to 0 if the ORDER BY clause is all ASC.
211 */
findSortingIndex(Table * pTab,int base,ExprList * pOrderBy,Index * pPreferredIdx,int nEqCol,int * pbRev)212 static Index *findSortingIndex(
213 Table *pTab, /* The table to be sorted */
214 int base, /* Cursor number for pTab */
215 ExprList *pOrderBy, /* The ORDER BY clause */
216 Index *pPreferredIdx, /* Use this index, if possible and not NULL */
217 int nEqCol, /* Number of index columns used with == constraints */
218 int *pbRev /* Set to 1 if ORDER BY is DESC */
219 ){
220 int i, j;
221 Index *pMatch;
222 Index *pIdx;
223 int sortOrder;
224
225 assert( pOrderBy!=0 );
226 assert( pOrderBy->nExpr>0 );
227 sortOrder = pOrderBy->a[0].sortOrder & SQLITE_SO_DIRMASK;
228 for(i=0; i<pOrderBy->nExpr; i++){
229 Expr *p;
230 if( (pOrderBy->a[i].sortOrder & SQLITE_SO_DIRMASK)!=sortOrder ){
231 /* Indices can only be used if all ORDER BY terms are either
232 ** DESC or ASC. Indices cannot be used on a mixture. */
233 return 0;
234 }
235 if( (pOrderBy->a[i].sortOrder & SQLITE_SO_TYPEMASK)!=SQLITE_SO_UNK ){
236 /* Do not sort by index if there is a COLLATE clause */
237 return 0;
238 }
239 p = pOrderBy->a[i].pExpr;
240 if( p->op!=TK_COLUMN || p->iTable!=base ){
241 /* Can not use an index sort on anything that is not a column in the
242 ** left-most table of the FROM clause */
243 return 0;
244 }
245 }
246
247 /* If we get this far, it means the ORDER BY clause consists only of
248 ** ascending columns in the left-most table of the FROM clause. Now
249 ** check for a matching index.
250 */
251 pMatch = 0;
252 for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
253 int nExpr = pOrderBy->nExpr;
254 if( pIdx->nColumn < nEqCol || pIdx->nColumn < nExpr ) continue;
255 for(i=j=0; i<nEqCol; i++){
256 if( pPreferredIdx->aiColumn[i]!=pIdx->aiColumn[i] ) break;
257 if( j<nExpr && pOrderBy->a[j].pExpr->iColumn==pIdx->aiColumn[i] ){ j++; }
258 }
259 if( i<nEqCol ) continue;
260 for(i=0; i+j<nExpr; i++){
261 if( pOrderBy->a[i+j].pExpr->iColumn!=pIdx->aiColumn[i+nEqCol] ) break;
262 }
263 if( i+j>=nExpr ){
264 pMatch = pIdx;
265 if( pIdx==pPreferredIdx ) break;
266 }
267 }
268 if( pMatch && pbRev ){
269 *pbRev = sortOrder==SQLITE_SO_DESC;
270 }
271 return pMatch;
272 }
273
274 /*
275 ** Disable a term in the WHERE clause. Except, do not disable the term
276 ** if it controls a LEFT OUTER JOIN and it did not originate in the ON
277 ** or USING clause of that join.
278 **
279 ** Consider the term t2.z='ok' in the following queries:
280 **
281 ** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
282 ** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
283 ** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
284 **
285 ** The t2.z='ok' is disabled in the in (2) because it did not originate
286 ** in the ON clause. The term is disabled in (3) because it is not part
287 ** of a LEFT OUTER JOIN. In (1), the term is not disabled.
288 **
289 ** Disabling a term causes that term to not be tested in the inner loop
290 ** of the join. Disabling is an optimization. We would get the correct
291 ** results if nothing were ever disabled, but joins might run a little
292 ** slower. The trick is to disable as much as we can without disabling
293 ** too much. If we disabled in (1), we'd get the wrong answer.
294 ** See ticket #813.
295 */
disableTerm(WhereLevel * pLevel,Expr ** ppExpr)296 static void disableTerm(WhereLevel *pLevel, Expr **ppExpr){
297 Expr *pExpr = *ppExpr;
298 if( pLevel->iLeftJoin==0 || ExprHasProperty(pExpr, EP_FromJoin) ){
299 *ppExpr = 0;
300 }
301 }
302
303 /*
304 ** Generate the beginning of the loop used for WHERE clause processing.
305 ** The return value is a pointer to an (opaque) structure that contains
306 ** information needed to terminate the loop. Later, the calling routine
307 ** should invoke sqliteWhereEnd() with the return value of this function
308 ** in order to complete the WHERE clause processing.
309 **
310 ** If an error occurs, this routine returns NULL.
311 **
312 ** The basic idea is to do a nested loop, one loop for each table in
313 ** the FROM clause of a select. (INSERT and UPDATE statements are the
314 ** same as a SELECT with only a single table in the FROM clause.) For
315 ** example, if the SQL is this:
316 **
317 ** SELECT * FROM t1, t2, t3 WHERE ...;
318 **
319 ** Then the code generated is conceptually like the following:
320 **
321 ** foreach row1 in t1 do \ Code generated
322 ** foreach row2 in t2 do |-- by sqliteWhereBegin()
323 ** foreach row3 in t3 do /
324 ** ...
325 ** end \ Code generated
326 ** end |-- by sqliteWhereEnd()
327 ** end /
328 **
329 ** There are Btree cursors associated with each table. t1 uses cursor
330 ** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
331 ** And so forth. This routine generates code to open those VDBE cursors
332 ** and sqliteWhereEnd() generates the code to close them.
333 **
334 ** If the WHERE clause is empty, the foreach loops must each scan their
335 ** entire tables. Thus a three-way join is an O(N^3) operation. But if
336 ** the tables have indices and there are terms in the WHERE clause that
337 ** refer to those indices, a complete table scan can be avoided and the
338 ** code will run much faster. Most of the work of this routine is checking
339 ** to see if there are indices that can be used to speed up the loop.
340 **
341 ** Terms of the WHERE clause are also used to limit which rows actually
342 ** make it to the "..." in the middle of the loop. After each "foreach",
343 ** terms of the WHERE clause that use only terms in that loop and outer
344 ** loops are evaluated and if false a jump is made around all subsequent
345 ** inner loops (or around the "..." if the test occurs within the inner-
346 ** most loop)
347 **
348 ** OUTER JOINS
349 **
350 ** An outer join of tables t1 and t2 is conceptally coded as follows:
351 **
352 ** foreach row1 in t1 do
353 ** flag = 0
354 ** foreach row2 in t2 do
355 ** start:
356 ** ...
357 ** flag = 1
358 ** end
359 ** if flag==0 then
360 ** move the row2 cursor to a null row
361 ** goto start
362 ** fi
363 ** end
364 **
365 ** ORDER BY CLAUSE PROCESSING
366 **
367 ** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
368 ** if there is one. If there is no ORDER BY clause or if this routine
369 ** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
370 **
371 ** If an index can be used so that the natural output order of the table
372 ** scan is correct for the ORDER BY clause, then that index is used and
373 ** *ppOrderBy is set to NULL. This is an optimization that prevents an
374 ** unnecessary sort of the result set if an index appropriate for the
375 ** ORDER BY clause already exists.
376 **
377 ** If the where clause loops cannot be arranged to provide the correct
378 ** output order, then the *ppOrderBy is unchanged.
379 */
sqliteWhereBegin(Parse * pParse,SrcList * pTabList,Expr * pWhere,int pushKey,ExprList ** ppOrderBy)380 WhereInfo *sqliteWhereBegin(
381 Parse *pParse, /* The parser context */
382 SrcList *pTabList, /* A list of all tables to be scanned */
383 Expr *pWhere, /* The WHERE clause */
384 int pushKey, /* If TRUE, leave the table key on the stack */
385 ExprList **ppOrderBy /* An ORDER BY clause, or NULL */
386 ){
387 int i; /* Loop counter */
388 WhereInfo *pWInfo; /* Will become the return value of this function */
389 Vdbe *v = pParse->pVdbe; /* The virtual database engine */
390 int brk, cont = 0; /* Addresses used during code generation */
391 int nExpr; /* Number of subexpressions in the WHERE clause */
392 int loopMask; /* One bit set for each outer loop */
393 int haveKey; /* True if KEY is on the stack */
394 ExprMaskSet maskSet; /* The expression mask set */
395 int iDirectEq[32]; /* Term of the form ROWID==X for the N-th table */
396 int iDirectLt[32]; /* Term of the form ROWID<X or ROWID<=X */
397 int iDirectGt[32]; /* Term of the form ROWID>X or ROWID>=X */
398 ExprInfo aExpr[101]; /* The WHERE clause is divided into these expressions */
399
400 /* pushKey is only allowed if there is a single table (as in an INSERT or
401 ** UPDATE statement)
402 */
403 assert( pushKey==0 || pTabList->nSrc==1 );
404
405 /* Split the WHERE clause into separate subexpressions where each
406 ** subexpression is separated by an AND operator. If the aExpr[]
407 ** array fills up, the last entry might point to an expression which
408 ** contains additional unfactored AND operators.
409 */
410 initMaskSet(&maskSet);
411 memset(aExpr, 0, sizeof(aExpr));
412 nExpr = exprSplit(ARRAYSIZE(aExpr), aExpr, pWhere);
413 if( nExpr==ARRAYSIZE(aExpr) ){
414 sqliteErrorMsg(pParse, "WHERE clause too complex - no more "
415 "than %d terms allowed", (int)ARRAYSIZE(aExpr)-1);
416 return 0;
417 }
418
419 /* Allocate and initialize the WhereInfo structure that will become the
420 ** return value.
421 */
422 pWInfo = sqliteMalloc( sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
423 if( sqlite_malloc_failed ){
424 sqliteFree(pWInfo);
425 return 0;
426 }
427 pWInfo->pParse = pParse;
428 pWInfo->pTabList = pTabList;
429 pWInfo->peakNTab = pWInfo->savedNTab = pParse->nTab;
430 pWInfo->iBreak = sqliteVdbeMakeLabel(v);
431
432 /* Special case: a WHERE clause that is constant. Evaluate the
433 ** expression and either jump over all of the code or fall thru.
434 */
435 if( pWhere && (pTabList->nSrc==0 || sqliteExprIsConstant(pWhere)) ){
436 sqliteExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
437 pWhere = 0;
438 }
439
440 /* Analyze all of the subexpressions.
441 */
442 for(i=0; i<nExpr; i++){
443 exprAnalyze(&maskSet, &aExpr[i]);
444
445 /* If we are executing a trigger body, remove all references to
446 ** new.* and old.* tables from the prerequisite masks.
447 */
448 if( pParse->trigStack ){
449 int x;
450 if( (x = pParse->trigStack->newIdx) >= 0 ){
451 int mask = ~getMask(&maskSet, x);
452 aExpr[i].prereqRight &= mask;
453 aExpr[i].prereqLeft &= mask;
454 aExpr[i].prereqAll &= mask;
455 }
456 if( (x = pParse->trigStack->oldIdx) >= 0 ){
457 int mask = ~getMask(&maskSet, x);
458 aExpr[i].prereqRight &= mask;
459 aExpr[i].prereqLeft &= mask;
460 aExpr[i].prereqAll &= mask;
461 }
462 }
463 }
464
465 /* Figure out what index to use (if any) for each nested loop.
466 ** Make pWInfo->a[i].pIdx point to the index to use for the i-th nested
467 ** loop where i==0 is the outer loop and i==pTabList->nSrc-1 is the inner
468 ** loop.
469 **
470 ** If terms exist that use the ROWID of any table, then set the
471 ** iDirectEq[], iDirectLt[], or iDirectGt[] elements for that table
472 ** to the index of the term containing the ROWID. We always prefer
473 ** to use a ROWID which can directly access a table rather than an
474 ** index which requires reading an index first to get the rowid then
475 ** doing a second read of the actual database table.
476 **
477 ** Actually, if there are more than 32 tables in the join, only the
478 ** first 32 tables are candidates for indices. This is (again) due
479 ** to the limit of 32 bits in an integer bitmask.
480 */
481 loopMask = 0;
482 for(i=0; i<pTabList->nSrc && i<ARRAYSIZE(iDirectEq); i++){
483 int j;
484 int iCur = pTabList->a[i].iCursor; /* The cursor for this table */
485 int mask = getMask(&maskSet, iCur); /* Cursor mask for this table */
486 Table *pTab = pTabList->a[i].pTab;
487 Index *pIdx;
488 Index *pBestIdx = 0;
489 int bestScore = 0;
490
491 /* Check to see if there is an expression that uses only the
492 ** ROWID field of this table. For terms of the form ROWID==expr
493 ** set iDirectEq[i] to the index of the term. For terms of the
494 ** form ROWID<expr or ROWID<=expr set iDirectLt[i] to the term index.
495 ** For terms like ROWID>expr or ROWID>=expr set iDirectGt[i].
496 **
497 ** (Added:) Treat ROWID IN expr like ROWID=expr.
498 */
499 pWInfo->a[i].iCur = -1;
500 iDirectEq[i] = -1;
501 iDirectLt[i] = -1;
502 iDirectGt[i] = -1;
503 for(j=0; j<nExpr; j++){
504 if( aExpr[j].idxLeft==iCur && aExpr[j].p->pLeft->iColumn<0
505 && (aExpr[j].prereqRight & loopMask)==aExpr[j].prereqRight ){
506 switch( aExpr[j].p->op ){
507 case TK_IN:
508 case TK_EQ: iDirectEq[i] = j; break;
509 case TK_LE:
510 case TK_LT: iDirectLt[i] = j; break;
511 case TK_GE:
512 case TK_GT: iDirectGt[i] = j; break;
513 }
514 }
515 if( aExpr[j].idxRight==iCur && aExpr[j].p->pRight->iColumn<0
516 && (aExpr[j].prereqLeft & loopMask)==aExpr[j].prereqLeft ){
517 switch( aExpr[j].p->op ){
518 case TK_EQ: iDirectEq[i] = j; break;
519 case TK_LE:
520 case TK_LT: iDirectGt[i] = j; break;
521 case TK_GE:
522 case TK_GT: iDirectLt[i] = j; break;
523 }
524 }
525 }
526 if( iDirectEq[i]>=0 ){
527 loopMask |= mask;
528 pWInfo->a[i].pIdx = 0;
529 continue;
530 }
531
532 /* Do a search for usable indices. Leave pBestIdx pointing to
533 ** the "best" index. pBestIdx is left set to NULL if no indices
534 ** are usable.
535 **
536 ** The best index is determined as follows. For each of the
537 ** left-most terms that is fixed by an equality operator, add
538 ** 8 to the score. The right-most term of the index may be
539 ** constrained by an inequality. Add 1 if for an "x<..." constraint
540 ** and add 2 for an "x>..." constraint. Chose the index that
541 ** gives the best score.
542 **
543 ** This scoring system is designed so that the score can later be
544 ** used to determine how the index is used. If the score&7 is 0
545 ** then all constraints are equalities. If score&1 is not 0 then
546 ** there is an inequality used as a termination key. (ex: "x<...")
547 ** If score&2 is not 0 then there is an inequality used as the
548 ** start key. (ex: "x>..."). A score or 4 is the special case
549 ** of an IN operator constraint. (ex: "x IN ...").
550 **
551 ** The IN operator (as in "<expr> IN (...)") is treated the same as
552 ** an equality comparison except that it can only be used on the
553 ** left-most column of an index and other terms of the WHERE clause
554 ** cannot be used in conjunction with the IN operator to help satisfy
555 ** other columns of the index.
556 */
557 for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
558 int eqMask = 0; /* Index columns covered by an x=... term */
559 int ltMask = 0; /* Index columns covered by an x<... term */
560 int gtMask = 0; /* Index columns covered by an x>... term */
561 int inMask = 0; /* Index columns covered by an x IN .. term */
562 int nEq, m, score;
563
564 if( pIdx->nColumn>32 ) continue; /* Ignore indices too many columns */
565 for(j=0; j<nExpr; j++){
566 if( aExpr[j].idxLeft==iCur
567 && (aExpr[j].prereqRight & loopMask)==aExpr[j].prereqRight ){
568 int iColumn = aExpr[j].p->pLeft->iColumn;
569 int k;
570 for(k=0; k<pIdx->nColumn; k++){
571 if( pIdx->aiColumn[k]==iColumn ){
572 switch( aExpr[j].p->op ){
573 case TK_IN: {
574 if( k==0 ) inMask |= 1;
575 break;
576 }
577 case TK_EQ: {
578 eqMask |= 1<<k;
579 break;
580 }
581 case TK_LE:
582 case TK_LT: {
583 ltMask |= 1<<k;
584 break;
585 }
586 case TK_GE:
587 case TK_GT: {
588 gtMask |= 1<<k;
589 break;
590 }
591 default: {
592 /* CANT_HAPPEN */
593 assert( 0 );
594 break;
595 }
596 }
597 break;
598 }
599 }
600 }
601 if( aExpr[j].idxRight==iCur
602 && (aExpr[j].prereqLeft & loopMask)==aExpr[j].prereqLeft ){
603 int iColumn = aExpr[j].p->pRight->iColumn;
604 int k;
605 for(k=0; k<pIdx->nColumn; k++){
606 if( pIdx->aiColumn[k]==iColumn ){
607 switch( aExpr[j].p->op ){
608 case TK_EQ: {
609 eqMask |= 1<<k;
610 break;
611 }
612 case TK_LE:
613 case TK_LT: {
614 gtMask |= 1<<k;
615 break;
616 }
617 case TK_GE:
618 case TK_GT: {
619 ltMask |= 1<<k;
620 break;
621 }
622 default: {
623 /* CANT_HAPPEN */
624 assert( 0 );
625 break;
626 }
627 }
628 break;
629 }
630 }
631 }
632 }
633
634 /* The following loop ends with nEq set to the number of columns
635 ** on the left of the index with == constraints.
636 */
637 for(nEq=0; nEq<pIdx->nColumn; nEq++){
638 m = (1<<(nEq+1))-1;
639 if( (m & eqMask)!=m ) break;
640 }
641 score = nEq*8; /* Base score is 8 times number of == constraints */
642 m = 1<<nEq;
643 if( m & ltMask ) score++; /* Increase score for a < constraint */
644 if( m & gtMask ) score+=2; /* Increase score for a > constraint */
645 if( score==0 && inMask ) score = 4; /* Default score for IN constraint */
646 if( score>bestScore ){
647 pBestIdx = pIdx;
648 bestScore = score;
649 }
650 }
651 pWInfo->a[i].pIdx = pBestIdx;
652 pWInfo->a[i].score = bestScore;
653 pWInfo->a[i].bRev = 0;
654 loopMask |= mask;
655 if( pBestIdx ){
656 pWInfo->a[i].iCur = pParse->nTab++;
657 pWInfo->peakNTab = pParse->nTab;
658 }
659 }
660
661 /* Check to see if the ORDER BY clause is or can be satisfied by the
662 ** use of an index on the first table.
663 */
664 if( ppOrderBy && *ppOrderBy && pTabList->nSrc>0 ){
665 Index *pSortIdx;
666 Index *pIdx;
667 Table *pTab;
668 int bRev = 0;
669
670 pTab = pTabList->a[0].pTab;
671 pIdx = pWInfo->a[0].pIdx;
672 if( pIdx && pWInfo->a[0].score==4 ){
673 /* If there is already an IN index on the left-most table,
674 ** it will not give the correct sort order.
675 ** So, pretend that no suitable index is found.
676 */
677 pSortIdx = 0;
678 }else if( iDirectEq[0]>=0 || iDirectLt[0]>=0 || iDirectGt[0]>=0 ){
679 /* If the left-most column is accessed using its ROWID, then do
680 ** not try to sort by index.
681 */
682 pSortIdx = 0;
683 }else{
684 int nEqCol = (pWInfo->a[0].score+4)/8;
685 pSortIdx = findSortingIndex(pTab, pTabList->a[0].iCursor,
686 *ppOrderBy, pIdx, nEqCol, &bRev);
687 }
688 if( pSortIdx && (pIdx==0 || pIdx==pSortIdx) ){
689 if( pIdx==0 ){
690 pWInfo->a[0].pIdx = pSortIdx;
691 pWInfo->a[0].iCur = pParse->nTab++;
692 pWInfo->peakNTab = pParse->nTab;
693 }
694 pWInfo->a[0].bRev = bRev;
695 *ppOrderBy = 0;
696 }
697 }
698
699 /* Open all tables in the pTabList and all indices used by those tables.
700 */
701 for(i=0; i<pTabList->nSrc; i++){
702 Table *pTab;
703 Index *pIx;
704
705 pTab = pTabList->a[i].pTab;
706 if( pTab->isTransient || pTab->pSelect ) continue;
707 sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
708 sqliteVdbeOp3(v, OP_OpenRead, pTabList->a[i].iCursor, pTab->tnum,
709 pTab->zName, P3_STATIC);
710 sqliteCodeVerifySchema(pParse, pTab->iDb);
711 if( (pIx = pWInfo->a[i].pIdx)!=0 ){
712 sqliteVdbeAddOp(v, OP_Integer, pIx->iDb, 0);
713 sqliteVdbeOp3(v, OP_OpenRead, pWInfo->a[i].iCur, pIx->tnum, pIx->zName,0);
714 }
715 }
716
717 /* Generate the code to do the search
718 */
719 loopMask = 0;
720 for(i=0; i<pTabList->nSrc; i++){
721 int j, k;
722 int iCur = pTabList->a[i].iCursor;
723 Index *pIdx;
724 WhereLevel *pLevel = &pWInfo->a[i];
725
726 /* If this is the right table of a LEFT OUTER JOIN, allocate and
727 ** initialize a memory cell that records if this table matches any
728 ** row of the left table of the join.
729 */
730 if( i>0 && (pTabList->a[i-1].jointype & JT_LEFT)!=0 ){
731 if( !pParse->nMem ) pParse->nMem++;
732 pLevel->iLeftJoin = pParse->nMem++;
733 sqliteVdbeAddOp(v, OP_String, 0, 0);
734 sqliteVdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
735 }
736
737 pIdx = pLevel->pIdx;
738 pLevel->inOp = OP_Noop;
739 if( i<ARRAYSIZE(iDirectEq) && iDirectEq[i]>=0 ){
740 /* Case 1: We can directly reference a single row using an
741 ** equality comparison against the ROWID field. Or
742 ** we reference multiple rows using a "rowid IN (...)"
743 ** construct.
744 */
745 k = iDirectEq[i];
746 assert( k<nExpr );
747 assert( aExpr[k].p!=0 );
748 assert( aExpr[k].idxLeft==iCur || aExpr[k].idxRight==iCur );
749 brk = pLevel->brk = sqliteVdbeMakeLabel(v);
750 if( aExpr[k].idxLeft==iCur ){
751 Expr *pX = aExpr[k].p;
752 if( pX->op!=TK_IN ){
753 sqliteExprCode(pParse, aExpr[k].p->pRight);
754 }else if( pX->pList ){
755 sqliteVdbeAddOp(v, OP_SetFirst, pX->iTable, brk);
756 pLevel->inOp = OP_SetNext;
757 pLevel->inP1 = pX->iTable;
758 pLevel->inP2 = sqliteVdbeCurrentAddr(v);
759 }else{
760 assert( pX->pSelect );
761 sqliteVdbeAddOp(v, OP_Rewind, pX->iTable, brk);
762 sqliteVdbeAddOp(v, OP_KeyAsData, pX->iTable, 1);
763 pLevel->inP2 = sqliteVdbeAddOp(v, OP_FullKey, pX->iTable, 0);
764 pLevel->inOp = OP_Next;
765 pLevel->inP1 = pX->iTable;
766 }
767 }else{
768 sqliteExprCode(pParse, aExpr[k].p->pLeft);
769 }
770 disableTerm(pLevel, &aExpr[k].p);
771 cont = pLevel->cont = sqliteVdbeMakeLabel(v);
772 sqliteVdbeAddOp(v, OP_MustBeInt, 1, brk);
773 haveKey = 0;
774 sqliteVdbeAddOp(v, OP_NotExists, iCur, brk);
775 pLevel->op = OP_Noop;
776 }else if( pIdx!=0 && pLevel->score>0 && pLevel->score%4==0 ){
777 /* Case 2: There is an index and all terms of the WHERE clause that
778 ** refer to the index use the "==" or "IN" operators.
779 */
780 int start;
781 int testOp;
782 int nColumn = (pLevel->score+4)/8;
783 brk = pLevel->brk = sqliteVdbeMakeLabel(v);
784 for(j=0; j<nColumn; j++){
785 for(k=0; k<nExpr; k++){
786 Expr *pX = aExpr[k].p;
787 if( pX==0 ) continue;
788 if( aExpr[k].idxLeft==iCur
789 && (aExpr[k].prereqRight & loopMask)==aExpr[k].prereqRight
790 && pX->pLeft->iColumn==pIdx->aiColumn[j]
791 ){
792 if( pX->op==TK_EQ ){
793 sqliteExprCode(pParse, pX->pRight);
794 disableTerm(pLevel, &aExpr[k].p);
795 break;
796 }
797 if( pX->op==TK_IN && nColumn==1 ){
798 if( pX->pList ){
799 sqliteVdbeAddOp(v, OP_SetFirst, pX->iTable, brk);
800 pLevel->inOp = OP_SetNext;
801 pLevel->inP1 = pX->iTable;
802 pLevel->inP2 = sqliteVdbeCurrentAddr(v);
803 }else{
804 assert( pX->pSelect );
805 sqliteVdbeAddOp(v, OP_Rewind, pX->iTable, brk);
806 sqliteVdbeAddOp(v, OP_KeyAsData, pX->iTable, 1);
807 pLevel->inP2 = sqliteVdbeAddOp(v, OP_FullKey, pX->iTable, 0);
808 pLevel->inOp = OP_Next;
809 pLevel->inP1 = pX->iTable;
810 }
811 disableTerm(pLevel, &aExpr[k].p);
812 break;
813 }
814 }
815 if( aExpr[k].idxRight==iCur
816 && aExpr[k].p->op==TK_EQ
817 && (aExpr[k].prereqLeft & loopMask)==aExpr[k].prereqLeft
818 && aExpr[k].p->pRight->iColumn==pIdx->aiColumn[j]
819 ){
820 sqliteExprCode(pParse, aExpr[k].p->pLeft);
821 disableTerm(pLevel, &aExpr[k].p);
822 break;
823 }
824 }
825 }
826 pLevel->iMem = pParse->nMem++;
827 cont = pLevel->cont = sqliteVdbeMakeLabel(v);
828 sqliteVdbeAddOp(v, OP_NotNull, -nColumn, sqliteVdbeCurrentAddr(v)+3);
829 sqliteVdbeAddOp(v, OP_Pop, nColumn, 0);
830 sqliteVdbeAddOp(v, OP_Goto, 0, brk);
831 sqliteVdbeAddOp(v, OP_MakeKey, nColumn, 0);
832 sqliteAddIdxKeyType(v, pIdx);
833 if( nColumn==pIdx->nColumn || pLevel->bRev ){
834 sqliteVdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);
835 testOp = OP_IdxGT;
836 }else{
837 sqliteVdbeAddOp(v, OP_Dup, 0, 0);
838 sqliteVdbeAddOp(v, OP_IncrKey, 0, 0);
839 sqliteVdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
840 testOp = OP_IdxGE;
841 }
842 if( pLevel->bRev ){
843 /* Scan in reverse order */
844 sqliteVdbeAddOp(v, OP_IncrKey, 0, 0);
845 sqliteVdbeAddOp(v, OP_MoveLt, pLevel->iCur, brk);
846 start = sqliteVdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
847 sqliteVdbeAddOp(v, OP_IdxLT, pLevel->iCur, brk);
848 pLevel->op = OP_Prev;
849 }else{
850 /* Scan in the forward order */
851 sqliteVdbeAddOp(v, OP_MoveTo, pLevel->iCur, brk);
852 start = sqliteVdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
853 sqliteVdbeAddOp(v, testOp, pLevel->iCur, brk);
854 pLevel->op = OP_Next;
855 }
856 sqliteVdbeAddOp(v, OP_RowKey, pLevel->iCur, 0);
857 sqliteVdbeAddOp(v, OP_IdxIsNull, nColumn, cont);
858 sqliteVdbeAddOp(v, OP_IdxRecno, pLevel->iCur, 0);
859 if( i==pTabList->nSrc-1 && pushKey ){
860 haveKey = 1;
861 }else{
862 sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);
863 haveKey = 0;
864 }
865 pLevel->p1 = pLevel->iCur;
866 pLevel->p2 = start;
867 }else if( i<ARRAYSIZE(iDirectLt) && (iDirectLt[i]>=0 || iDirectGt[i]>=0) ){
868 /* Case 3: We have an inequality comparison against the ROWID field.
869 */
870 int testOp = OP_Noop;
871 int start;
872
873 brk = pLevel->brk = sqliteVdbeMakeLabel(v);
874 cont = pLevel->cont = sqliteVdbeMakeLabel(v);
875 if( iDirectGt[i]>=0 ){
876 k = iDirectGt[i];
877 assert( k<nExpr );
878 assert( aExpr[k].p!=0 );
879 assert( aExpr[k].idxLeft==iCur || aExpr[k].idxRight==iCur );
880 if( aExpr[k].idxLeft==iCur ){
881 sqliteExprCode(pParse, aExpr[k].p->pRight);
882 }else{
883 sqliteExprCode(pParse, aExpr[k].p->pLeft);
884 }
885 sqliteVdbeAddOp(v, OP_ForceInt,
886 aExpr[k].p->op==TK_LT || aExpr[k].p->op==TK_GT, brk);
887 sqliteVdbeAddOp(v, OP_MoveTo, iCur, brk);
888 disableTerm(pLevel, &aExpr[k].p);
889 }else{
890 sqliteVdbeAddOp(v, OP_Rewind, iCur, brk);
891 }
892 if( iDirectLt[i]>=0 ){
893 k = iDirectLt[i];
894 assert( k<nExpr );
895 assert( aExpr[k].p!=0 );
896 assert( aExpr[k].idxLeft==iCur || aExpr[k].idxRight==iCur );
897 if( aExpr[k].idxLeft==iCur ){
898 sqliteExprCode(pParse, aExpr[k].p->pRight);
899 }else{
900 sqliteExprCode(pParse, aExpr[k].p->pLeft);
901 }
902 /* sqliteVdbeAddOp(v, OP_MustBeInt, 0, sqliteVdbeCurrentAddr(v)+1); */
903 pLevel->iMem = pParse->nMem++;
904 sqliteVdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
905 if( aExpr[k].p->op==TK_LT || aExpr[k].p->op==TK_GT ){
906 testOp = OP_Ge;
907 }else{
908 testOp = OP_Gt;
909 }
910 disableTerm(pLevel, &aExpr[k].p);
911 }
912 start = sqliteVdbeCurrentAddr(v);
913 pLevel->op = OP_Next;
914 pLevel->p1 = iCur;
915 pLevel->p2 = start;
916 if( testOp!=OP_Noop ){
917 sqliteVdbeAddOp(v, OP_Recno, iCur, 0);
918 sqliteVdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
919 sqliteVdbeAddOp(v, testOp, 0, brk);
920 }
921 haveKey = 0;
922 }else if( pIdx==0 ){
923 /* Case 4: There is no usable index. We must do a complete
924 ** scan of the entire database table.
925 */
926 int start;
927
928 brk = pLevel->brk = sqliteVdbeMakeLabel(v);
929 cont = pLevel->cont = sqliteVdbeMakeLabel(v);
930 sqliteVdbeAddOp(v, OP_Rewind, iCur, brk);
931 start = sqliteVdbeCurrentAddr(v);
932 pLevel->op = OP_Next;
933 pLevel->p1 = iCur;
934 pLevel->p2 = start;
935 haveKey = 0;
936 }else{
937 /* Case 5: The WHERE clause term that refers to the right-most
938 ** column of the index is an inequality. For example, if
939 ** the index is on (x,y,z) and the WHERE clause is of the
940 ** form "x=5 AND y<10" then this case is used. Only the
941 ** right-most column can be an inequality - the rest must
942 ** use the "==" operator.
943 **
944 ** This case is also used when there are no WHERE clause
945 ** constraints but an index is selected anyway, in order
946 ** to force the output order to conform to an ORDER BY.
947 */
948 int score = pLevel->score;
949 int nEqColumn = score/8;
950 int start;
951 int leFlag, geFlag;
952 int testOp;
953
954 /* Evaluate the equality constraints
955 */
956 for(j=0; j<nEqColumn; j++){
957 for(k=0; k<nExpr; k++){
958 if( aExpr[k].p==0 ) continue;
959 if( aExpr[k].idxLeft==iCur
960 && aExpr[k].p->op==TK_EQ
961 && (aExpr[k].prereqRight & loopMask)==aExpr[k].prereqRight
962 && aExpr[k].p->pLeft->iColumn==pIdx->aiColumn[j]
963 ){
964 sqliteExprCode(pParse, aExpr[k].p->pRight);
965 disableTerm(pLevel, &aExpr[k].p);
966 break;
967 }
968 if( aExpr[k].idxRight==iCur
969 && aExpr[k].p->op==TK_EQ
970 && (aExpr[k].prereqLeft & loopMask)==aExpr[k].prereqLeft
971 && aExpr[k].p->pRight->iColumn==pIdx->aiColumn[j]
972 ){
973 sqliteExprCode(pParse, aExpr[k].p->pLeft);
974 disableTerm(pLevel, &aExpr[k].p);
975 break;
976 }
977 }
978 }
979
980 /* Duplicate the equality term values because they will all be
981 ** used twice: once to make the termination key and once to make the
982 ** start key.
983 */
984 for(j=0; j<nEqColumn; j++){
985 sqliteVdbeAddOp(v, OP_Dup, nEqColumn-1, 0);
986 }
987
988 /* Labels for the beginning and end of the loop
989 */
990 cont = pLevel->cont = sqliteVdbeMakeLabel(v);
991 brk = pLevel->brk = sqliteVdbeMakeLabel(v);
992
993 /* Generate the termination key. This is the key value that
994 ** will end the search. There is no termination key if there
995 ** are no equality terms and no "X<..." term.
996 **
997 ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
998 ** key computed here really ends up being the start key.
999 */
1000 if( (score & 1)!=0 ){
1001 for(k=0; k<nExpr; k++){
1002 Expr *pExpr = aExpr[k].p;
1003 if( pExpr==0 ) continue;
1004 if( aExpr[k].idxLeft==iCur
1005 && (pExpr->op==TK_LT || pExpr->op==TK_LE)
1006 && (aExpr[k].prereqRight & loopMask)==aExpr[k].prereqRight
1007 && pExpr->pLeft->iColumn==pIdx->aiColumn[j]
1008 ){
1009 sqliteExprCode(pParse, pExpr->pRight);
1010 leFlag = pExpr->op==TK_LE;
1011 disableTerm(pLevel, &aExpr[k].p);
1012 break;
1013 }
1014 if( aExpr[k].idxRight==iCur
1015 && (pExpr->op==TK_GT || pExpr->op==TK_GE)
1016 && (aExpr[k].prereqLeft & loopMask)==aExpr[k].prereqLeft
1017 && pExpr->pRight->iColumn==pIdx->aiColumn[j]
1018 ){
1019 sqliteExprCode(pParse, pExpr->pLeft);
1020 leFlag = pExpr->op==TK_GE;
1021 disableTerm(pLevel, &aExpr[k].p);
1022 break;
1023 }
1024 }
1025 testOp = OP_IdxGE;
1026 }else{
1027 testOp = nEqColumn>0 ? OP_IdxGE : OP_Noop;
1028 leFlag = 1;
1029 }
1030 if( testOp!=OP_Noop ){
1031 int nCol = nEqColumn + (score & 1);
1032 pLevel->iMem = pParse->nMem++;
1033 sqliteVdbeAddOp(v, OP_NotNull, -nCol, sqliteVdbeCurrentAddr(v)+3);
1034 sqliteVdbeAddOp(v, OP_Pop, nCol, 0);
1035 sqliteVdbeAddOp(v, OP_Goto, 0, brk);
1036 sqliteVdbeAddOp(v, OP_MakeKey, nCol, 0);
1037 sqliteAddIdxKeyType(v, pIdx);
1038 if( leFlag ){
1039 sqliteVdbeAddOp(v, OP_IncrKey, 0, 0);
1040 }
1041 if( pLevel->bRev ){
1042 sqliteVdbeAddOp(v, OP_MoveLt, pLevel->iCur, brk);
1043 }else{
1044 sqliteVdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1045 }
1046 }else if( pLevel->bRev ){
1047 sqliteVdbeAddOp(v, OP_Last, pLevel->iCur, brk);
1048 }
1049
1050 /* Generate the start key. This is the key that defines the lower
1051 ** bound on the search. There is no start key if there are no
1052 ** equality terms and if there is no "X>..." term. In
1053 ** that case, generate a "Rewind" instruction in place of the
1054 ** start key search.
1055 **
1056 ** 2002-Dec-04: In the case of a reverse-order search, the so-called
1057 ** "start" key really ends up being used as the termination key.
1058 */
1059 if( (score & 2)!=0 ){
1060 for(k=0; k<nExpr; k++){
1061 Expr *pExpr = aExpr[k].p;
1062 if( pExpr==0 ) continue;
1063 if( aExpr[k].idxLeft==iCur
1064 && (pExpr->op==TK_GT || pExpr->op==TK_GE)
1065 && (aExpr[k].prereqRight & loopMask)==aExpr[k].prereqRight
1066 && pExpr->pLeft->iColumn==pIdx->aiColumn[j]
1067 ){
1068 sqliteExprCode(pParse, pExpr->pRight);
1069 geFlag = pExpr->op==TK_GE;
1070 disableTerm(pLevel, &aExpr[k].p);
1071 break;
1072 }
1073 if( aExpr[k].idxRight==iCur
1074 && (pExpr->op==TK_LT || pExpr->op==TK_LE)
1075 && (aExpr[k].prereqLeft & loopMask)==aExpr[k].prereqLeft
1076 && pExpr->pRight->iColumn==pIdx->aiColumn[j]
1077 ){
1078 sqliteExprCode(pParse, pExpr->pLeft);
1079 geFlag = pExpr->op==TK_LE;
1080 disableTerm(pLevel, &aExpr[k].p);
1081 break;
1082 }
1083 }
1084 }else{
1085 geFlag = 1;
1086 }
1087 if( nEqColumn>0 || (score&2)!=0 ){
1088 int nCol = nEqColumn + ((score&2)!=0);
1089 sqliteVdbeAddOp(v, OP_NotNull, -nCol, sqliteVdbeCurrentAddr(v)+3);
1090 sqliteVdbeAddOp(v, OP_Pop, nCol, 0);
1091 sqliteVdbeAddOp(v, OP_Goto, 0, brk);
1092 sqliteVdbeAddOp(v, OP_MakeKey, nCol, 0);
1093 sqliteAddIdxKeyType(v, pIdx);
1094 if( !geFlag ){
1095 sqliteVdbeAddOp(v, OP_IncrKey, 0, 0);
1096 }
1097 if( pLevel->bRev ){
1098 pLevel->iMem = pParse->nMem++;
1099 sqliteVdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1100 testOp = OP_IdxLT;
1101 }else{
1102 sqliteVdbeAddOp(v, OP_MoveTo, pLevel->iCur, brk);
1103 }
1104 }else if( pLevel->bRev ){
1105 testOp = OP_Noop;
1106 }else{
1107 sqliteVdbeAddOp(v, OP_Rewind, pLevel->iCur, brk);
1108 }
1109
1110 /* Generate the the top of the loop. If there is a termination
1111 ** key we have to test for that key and abort at the top of the
1112 ** loop.
1113 */
1114 start = sqliteVdbeCurrentAddr(v);
1115 if( testOp!=OP_Noop ){
1116 sqliteVdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1117 sqliteVdbeAddOp(v, testOp, pLevel->iCur, brk);
1118 }
1119 sqliteVdbeAddOp(v, OP_RowKey, pLevel->iCur, 0);
1120 sqliteVdbeAddOp(v, OP_IdxIsNull, nEqColumn + (score & 1), cont);
1121 sqliteVdbeAddOp(v, OP_IdxRecno, pLevel->iCur, 0);
1122 if( i==pTabList->nSrc-1 && pushKey ){
1123 haveKey = 1;
1124 }else{
1125 sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);
1126 haveKey = 0;
1127 }
1128
1129 /* Record the instruction used to terminate the loop.
1130 */
1131 pLevel->op = pLevel->bRev ? OP_Prev : OP_Next;
1132 pLevel->p1 = pLevel->iCur;
1133 pLevel->p2 = start;
1134 }
1135 loopMask |= getMask(&maskSet, iCur);
1136
1137 /* Insert code to test every subexpression that can be completely
1138 ** computed using the current set of tables.
1139 */
1140 for(j=0; j<nExpr; j++){
1141 if( aExpr[j].p==0 ) continue;
1142 if( (aExpr[j].prereqAll & loopMask)!=aExpr[j].prereqAll ) continue;
1143 if( pLevel->iLeftJoin && !ExprHasProperty(aExpr[j].p,EP_FromJoin) ){
1144 continue;
1145 }
1146 if( haveKey ){
1147 haveKey = 0;
1148 sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);
1149 }
1150 sqliteExprIfFalse(pParse, aExpr[j].p, cont, 1);
1151 aExpr[j].p = 0;
1152 }
1153 brk = cont;
1154
1155 /* For a LEFT OUTER JOIN, generate code that will record the fact that
1156 ** at least one row of the right table has matched the left table.
1157 */
1158 if( pLevel->iLeftJoin ){
1159 pLevel->top = sqliteVdbeCurrentAddr(v);
1160 sqliteVdbeAddOp(v, OP_Integer, 1, 0);
1161 sqliteVdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
1162 for(j=0; j<nExpr; j++){
1163 if( aExpr[j].p==0 ) continue;
1164 if( (aExpr[j].prereqAll & loopMask)!=aExpr[j].prereqAll ) continue;
1165 if( haveKey ){
1166 /* Cannot happen. "haveKey" can only be true if pushKey is true
1167 ** an pushKey can only be true for DELETE and UPDATE and there are
1168 ** no outer joins with DELETE and UPDATE.
1169 */
1170 haveKey = 0;
1171 sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);
1172 }
1173 sqliteExprIfFalse(pParse, aExpr[j].p, cont, 1);
1174 aExpr[j].p = 0;
1175 }
1176 }
1177 }
1178 pWInfo->iContinue = cont;
1179 if( pushKey && !haveKey ){
1180 sqliteVdbeAddOp(v, OP_Recno, pTabList->a[0].iCursor, 0);
1181 }
1182 freeMaskSet(&maskSet);
1183 return pWInfo;
1184 }
1185
1186 /*
1187 ** Generate the end of the WHERE loop. See comments on
1188 ** sqliteWhereBegin() for additional information.
1189 */
sqliteWhereEnd(WhereInfo * pWInfo)1190 void sqliteWhereEnd(WhereInfo *pWInfo){
1191 Vdbe *v = pWInfo->pParse->pVdbe;
1192 int i;
1193 WhereLevel *pLevel;
1194 SrcList *pTabList = pWInfo->pTabList;
1195
1196 for(i=pTabList->nSrc-1; i>=0; i--){
1197 pLevel = &pWInfo->a[i];
1198 sqliteVdbeResolveLabel(v, pLevel->cont);
1199 if( pLevel->op!=OP_Noop ){
1200 sqliteVdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
1201 }
1202 sqliteVdbeResolveLabel(v, pLevel->brk);
1203 if( pLevel->inOp!=OP_Noop ){
1204 sqliteVdbeAddOp(v, pLevel->inOp, pLevel->inP1, pLevel->inP2);
1205 }
1206 if( pLevel->iLeftJoin ){
1207 int addr;
1208 addr = sqliteVdbeAddOp(v, OP_MemLoad, pLevel->iLeftJoin, 0);
1209 sqliteVdbeAddOp(v, OP_NotNull, 1, addr+4 + (pLevel->iCur>=0));
1210 sqliteVdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
1211 if( pLevel->iCur>=0 ){
1212 sqliteVdbeAddOp(v, OP_NullRow, pLevel->iCur, 0);
1213 }
1214 sqliteVdbeAddOp(v, OP_Goto, 0, pLevel->top);
1215 }
1216 }
1217 sqliteVdbeResolveLabel(v, pWInfo->iBreak);
1218 for(i=0; i<pTabList->nSrc; i++){
1219 Table *pTab = pTabList->a[i].pTab;
1220 assert( pTab!=0 );
1221 if( pTab->isTransient || pTab->pSelect ) continue;
1222 pLevel = &pWInfo->a[i];
1223 sqliteVdbeAddOp(v, OP_Close, pTabList->a[i].iCursor, 0);
1224 if( pLevel->pIdx!=0 ){
1225 sqliteVdbeAddOp(v, OP_Close, pLevel->iCur, 0);
1226 }
1227 }
1228 #if 0 /* Never reuse a cursor */
1229 if( pWInfo->pParse->nTab==pWInfo->peakNTab ){
1230 pWInfo->pParse->nTab = pWInfo->savedNTab;
1231 }
1232 #endif
1233 sqliteFree(pWInfo);
1234 return;
1235 }
1236