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 responsible 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: #include "sqliteInt.h"
20:
21:
22: /*
23: ** Trace output macros
24: */
25: #if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
26: int sqlite3WhereTrace = 0;
27: #endif
28: #if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
29: # define WHERETRACE(X) if(sqlite3WhereTrace) sqlite3DebugPrintf X
30: #else
31: # define WHERETRACE(X)
32: #endif
33:
34: /* Forward reference
35: */
36: typedef struct WhereClause WhereClause;
37: typedef struct WhereMaskSet WhereMaskSet;
38: typedef struct WhereOrInfo WhereOrInfo;
39: typedef struct WhereAndInfo WhereAndInfo;
40: typedef struct WhereCost WhereCost;
41:
42: /*
43: ** The query generator uses an array of instances of this structure to
44: ** help it analyze the subexpressions of the WHERE clause. Each WHERE
45: ** clause subexpression is separated from the others by AND operators,
46: ** usually, or sometimes subexpressions separated by OR.
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.u.leftColumn record the
59: ** cursor number and column number for X. WhereTerm.eOperator 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: ** A WhereTerm might also be two or more subterms connected by OR:
65: **
66: ** (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
67: **
68: ** In this second case, wtFlag as the TERM_ORINFO set and eOperator==WO_OR
69: ** and the WhereTerm.u.pOrInfo field points to auxiliary information that
70: ** is collected about the
71: **
72: ** If a term in the WHERE clause does not match either of the two previous
73: ** categories, then eOperator==0. The WhereTerm.pExpr field is still set
74: ** to the original subexpression content and wtFlags is set up appropriately
75: ** but no other fields in the WhereTerm object are meaningful.
76: **
77: ** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
78: ** but they do so indirectly. A single WhereMaskSet structure translates
79: ** cursor number into bits and the translated bit is stored in the prereq
80: ** fields. The translation is used in order to maximize the number of
81: ** bits that will fit in a Bitmask. The VDBE cursor numbers might be
82: ** spread out over the non-negative integers. For example, the cursor
83: ** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The WhereMaskSet
84: ** translates these sparse cursor numbers into consecutive integers
85: ** beginning with 0 in order to make the best possible use of the available
86: ** bits in the Bitmask. So, in the example above, the cursor numbers
87: ** would be mapped into integers 0 through 7.
88: **
89: ** The number of terms in a join is limited by the number of bits
90: ** in prereqRight and prereqAll. The default is 64 bits, hence SQLite
91: ** is only able to process joins with 64 or fewer tables.
92: */
93: typedef struct WhereTerm WhereTerm;
94: struct WhereTerm {
95: Expr *pExpr; /* Pointer to the subexpression that is this term */
96: int iParent; /* Disable pWC->a[iParent] when this term disabled */
97: int leftCursor; /* Cursor number of X in "X <op> <expr>" */
98: union {
99: int leftColumn; /* Column number of X in "X <op> <expr>" */
100: WhereOrInfo *pOrInfo; /* Extra information if eOperator==WO_OR */
101: WhereAndInfo *pAndInfo; /* Extra information if eOperator==WO_AND */
102: } u;
103: u16 eOperator; /* A WO_xx value describing <op> */
104: u8 wtFlags; /* TERM_xxx bit flags. See below */
105: u8 nChild; /* Number of children that must disable us */
106: WhereClause *pWC; /* The clause this term is part of */
107: Bitmask prereqRight; /* Bitmask of tables used by pExpr->pRight */
108: Bitmask prereqAll; /* Bitmask of tables referenced by pExpr */
109: };
110:
111: /*
112: ** Allowed values of WhereTerm.wtFlags
113: */
114: #define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */
115: #define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */
116: #define TERM_CODED 0x04 /* This term is already coded */
117: #define TERM_COPIED 0x08 /* Has a child */
118: #define TERM_ORINFO 0x10 /* Need to free the WhereTerm.u.pOrInfo object */
119: #define TERM_ANDINFO 0x20 /* Need to free the WhereTerm.u.pAndInfo obj */
120: #define TERM_OR_OK 0x40 /* Used during OR-clause processing */
121: #ifdef SQLITE_ENABLE_STAT3
122: # define TERM_VNULL 0x80 /* Manufactured x>NULL or x<=NULL term */
123: #else
124: # define TERM_VNULL 0x00 /* Disabled if not using stat3 */
125: #endif
126:
127: /*
128: ** An instance of the following structure holds all information about a
129: ** WHERE clause. Mostly this is a container for one or more WhereTerms.
130: **
131: ** Explanation of pOuter: For a WHERE clause of the form
132: **
133: ** a AND ((b AND c) OR (d AND e)) AND f
134: **
135: ** There are separate WhereClause objects for the whole clause and for
136: ** the subclauses "(b AND c)" and "(d AND e)". The pOuter field of the
137: ** subclauses points to the WhereClause object for the whole clause.
138: */
139: struct WhereClause {
140: Parse *pParse; /* The parser context */
141: WhereMaskSet *pMaskSet; /* Mapping of table cursor numbers to bitmasks */
142: Bitmask vmask; /* Bitmask identifying virtual table cursors */
143: WhereClause *pOuter; /* Outer conjunction */
144: u8 op; /* Split operator. TK_AND or TK_OR */
145: u16 wctrlFlags; /* Might include WHERE_AND_ONLY */
146: int nTerm; /* Number of terms */
147: int nSlot; /* Number of entries in a[] */
148: WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
149: #if defined(SQLITE_SMALL_STACK)
150: WhereTerm aStatic[1]; /* Initial static space for a[] */
151: #else
152: WhereTerm aStatic[8]; /* Initial static space for a[] */
153: #endif
154: };
155:
156: /*
157: ** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
158: ** a dynamically allocated instance of the following structure.
159: */
160: struct WhereOrInfo {
161: WhereClause wc; /* Decomposition into subterms */
162: Bitmask indexable; /* Bitmask of all indexable tables in the clause */
163: };
164:
165: /*
166: ** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
167: ** a dynamically allocated instance of the following structure.
168: */
169: struct WhereAndInfo {
170: WhereClause wc; /* The subexpression broken out */
171: };
172:
173: /*
174: ** An instance of the following structure keeps track of a mapping
175: ** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
176: **
177: ** The VDBE cursor numbers are small integers contained in
178: ** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
179: ** clause, the cursor numbers might not begin with 0 and they might
180: ** contain gaps in the numbering sequence. But we want to make maximum
181: ** use of the bits in our bitmasks. This structure provides a mapping
182: ** from the sparse cursor numbers into consecutive integers beginning
183: ** with 0.
184: **
185: ** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
186: ** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
187: **
188: ** For example, if the WHERE clause expression used these VDBE
189: ** cursors: 4, 5, 8, 29, 57, 73. Then the WhereMaskSet structure
190: ** would map those cursor numbers into bits 0 through 5.
191: **
192: ** Note that the mapping is not necessarily ordered. In the example
193: ** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
194: ** 57->5, 73->4. Or one of 719 other combinations might be used. It
195: ** does not really matter. What is important is that sparse cursor
196: ** numbers all get mapped into bit numbers that begin with 0 and contain
197: ** no gaps.
198: */
199: struct WhereMaskSet {
200: int n; /* Number of assigned cursor values */
201: int ix[BMS]; /* Cursor assigned to each bit */
202: };
203:
204: /*
205: ** A WhereCost object records a lookup strategy and the estimated
206: ** cost of pursuing that strategy.
207: */
208: struct WhereCost {
209: WherePlan plan; /* The lookup strategy */
210: double rCost; /* Overall cost of pursuing this search strategy */
211: Bitmask used; /* Bitmask of cursors used by this plan */
212: };
213:
214: /*
215: ** Bitmasks for the operators that indices are able to exploit. An
216: ** OR-ed combination of these values can be used when searching for
217: ** terms in the where clause.
218: */
219: #define WO_IN 0x001
220: #define WO_EQ 0x002
221: #define WO_LT (WO_EQ<<(TK_LT-TK_EQ))
222: #define WO_LE (WO_EQ<<(TK_LE-TK_EQ))
223: #define WO_GT (WO_EQ<<(TK_GT-TK_EQ))
224: #define WO_GE (WO_EQ<<(TK_GE-TK_EQ))
225: #define WO_MATCH 0x040
226: #define WO_ISNULL 0x080
227: #define WO_OR 0x100 /* Two or more OR-connected terms */
228: #define WO_AND 0x200 /* Two or more AND-connected terms */
229: #define WO_NOOP 0x800 /* This term does not restrict search space */
230:
231: #define WO_ALL 0xfff /* Mask of all possible WO_* values */
232: #define WO_SINGLE 0x0ff /* Mask of all non-compound WO_* values */
233:
234: /*
235: ** Value for wsFlags returned by bestIndex() and stored in
236: ** WhereLevel.wsFlags. These flags determine which search
237: ** strategies are appropriate.
238: **
239: ** The least significant 12 bits is reserved as a mask for WO_ values above.
240: ** The WhereLevel.wsFlags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
241: ** But if the table is the right table of a left join, WhereLevel.wsFlags
242: ** is set to WO_IN|WO_EQ. The WhereLevel.wsFlags field can then be used as
243: ** the "op" parameter to findTerm when we are resolving equality constraints.
244: ** ISNULL constraints will then not be used on the right table of a left
245: ** join. Tickets #2177 and #2189.
246: */
247: #define WHERE_ROWID_EQ 0x00001000 /* rowid=EXPR or rowid IN (...) */
248: #define WHERE_ROWID_RANGE 0x00002000 /* rowid<EXPR and/or rowid>EXPR */
249: #define WHERE_COLUMN_EQ 0x00010000 /* x=EXPR or x IN (...) or x IS NULL */
250: #define WHERE_COLUMN_RANGE 0x00020000 /* x<EXPR and/or x>EXPR */
251: #define WHERE_COLUMN_IN 0x00040000 /* x IN (...) */
252: #define WHERE_COLUMN_NULL 0x00080000 /* x IS NULL */
253: #define WHERE_INDEXED 0x000f0000 /* Anything that uses an index */
254: #define WHERE_NOT_FULLSCAN 0x100f3000 /* Does not do a full table scan */
255: #define WHERE_IN_ABLE 0x000f1000 /* Able to support an IN operator */
256: #define WHERE_TOP_LIMIT 0x00100000 /* x<EXPR or x<=EXPR constraint */
257: #define WHERE_BTM_LIMIT 0x00200000 /* x>EXPR or x>=EXPR constraint */
258: #define WHERE_BOTH_LIMIT 0x00300000 /* Both x>EXPR and x<EXPR */
259: #define WHERE_IDX_ONLY 0x00800000 /* Use index only - omit table */
260: #define WHERE_ORDERBY 0x01000000 /* Output will appear in correct order */
261: #define WHERE_REVERSE 0x02000000 /* Scan in reverse order */
262: #define WHERE_UNIQUE 0x04000000 /* Selects no more than one row */
263: #define WHERE_VIRTUALTABLE 0x08000000 /* Use virtual-table processing */
264: #define WHERE_MULTI_OR 0x10000000 /* OR using multiple indices */
265: #define WHERE_TEMP_INDEX 0x20000000 /* Uses an ephemeral index */
266: #define WHERE_DISTINCT 0x40000000 /* Correct order for DISTINCT */
267:
268: /*
269: ** Initialize a preallocated WhereClause structure.
270: */
271: static void whereClauseInit(
272: WhereClause *pWC, /* The WhereClause to be initialized */
273: Parse *pParse, /* The parsing context */
274: WhereMaskSet *pMaskSet, /* Mapping from table cursor numbers to bitmasks */
275: u16 wctrlFlags /* Might include WHERE_AND_ONLY */
276: ){
277: pWC->pParse = pParse;
278: pWC->pMaskSet = pMaskSet;
279: pWC->pOuter = 0;
280: pWC->nTerm = 0;
281: pWC->nSlot = ArraySize(pWC->aStatic);
282: pWC->a = pWC->aStatic;
283: pWC->vmask = 0;
284: pWC->wctrlFlags = wctrlFlags;
285: }
286:
287: /* Forward reference */
288: static void whereClauseClear(WhereClause*);
289:
290: /*
291: ** Deallocate all memory associated with a WhereOrInfo object.
292: */
293: static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
294: whereClauseClear(&p->wc);
295: sqlite3DbFree(db, p);
296: }
297:
298: /*
299: ** Deallocate all memory associated with a WhereAndInfo object.
300: */
301: static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
302: whereClauseClear(&p->wc);
303: sqlite3DbFree(db, p);
304: }
305:
306: /*
307: ** Deallocate a WhereClause structure. The WhereClause structure
308: ** itself is not freed. This routine is the inverse of whereClauseInit().
309: */
310: static void whereClauseClear(WhereClause *pWC){
311: int i;
312: WhereTerm *a;
313: sqlite3 *db = pWC->pParse->db;
314: for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
315: if( a->wtFlags & TERM_DYNAMIC ){
316: sqlite3ExprDelete(db, a->pExpr);
317: }
318: if( a->wtFlags & TERM_ORINFO ){
319: whereOrInfoDelete(db, a->u.pOrInfo);
320: }else if( a->wtFlags & TERM_ANDINFO ){
321: whereAndInfoDelete(db, a->u.pAndInfo);
322: }
323: }
324: if( pWC->a!=pWC->aStatic ){
325: sqlite3DbFree(db, pWC->a);
326: }
327: }
328:
329: /*
330: ** Add a single new WhereTerm entry to the WhereClause object pWC.
331: ** The new WhereTerm object is constructed from Expr p and with wtFlags.
332: ** The index in pWC->a[] of the new WhereTerm is returned on success.
333: ** 0 is returned if the new WhereTerm could not be added due to a memory
334: ** allocation error. The memory allocation failure will be recorded in
335: ** the db->mallocFailed flag so that higher-level functions can detect it.
336: **
337: ** This routine will increase the size of the pWC->a[] array as necessary.
338: **
339: ** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
340: ** for freeing the expression p is assumed by the WhereClause object pWC.
341: ** This is true even if this routine fails to allocate a new WhereTerm.
342: **
343: ** WARNING: This routine might reallocate the space used to store
344: ** WhereTerms. All pointers to WhereTerms should be invalidated after
345: ** calling this routine. Such pointers may be reinitialized by referencing
346: ** the pWC->a[] array.
347: */
348: static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
349: WhereTerm *pTerm;
350: int idx;
351: testcase( wtFlags & TERM_VIRTUAL ); /* EV: R-00211-15100 */
352: if( pWC->nTerm>=pWC->nSlot ){
353: WhereTerm *pOld = pWC->a;
354: sqlite3 *db = pWC->pParse->db;
355: pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
356: if( pWC->a==0 ){
357: if( wtFlags & TERM_DYNAMIC ){
358: sqlite3ExprDelete(db, p);
359: }
360: pWC->a = pOld;
361: return 0;
362: }
363: memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
364: if( pOld!=pWC->aStatic ){
365: sqlite3DbFree(db, pOld);
366: }
367: pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
368: }
369: pTerm = &pWC->a[idx = pWC->nTerm++];
370: pTerm->pExpr = p;
371: pTerm->wtFlags = wtFlags;
372: pTerm->pWC = pWC;
373: pTerm->iParent = -1;
374: return idx;
375: }
376:
377: /*
378: ** This routine identifies subexpressions in the WHERE clause where
379: ** each subexpression is separated by the AND operator or some other
380: ** operator specified in the op parameter. The WhereClause structure
381: ** is filled with pointers to subexpressions. For example:
382: **
383: ** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
384: ** \________/ \_______________/ \________________/
385: ** slot[0] slot[1] slot[2]
386: **
387: ** The original WHERE clause in pExpr is unaltered. All this routine
388: ** does is make slot[] entries point to substructure within pExpr.
389: **
390: ** In the previous sentence and in the diagram, "slot[]" refers to
391: ** the WhereClause.a[] array. The slot[] array grows as needed to contain
392: ** all terms of the WHERE clause.
393: */
394: static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
395: pWC->op = (u8)op;
396: if( pExpr==0 ) return;
397: if( pExpr->op!=op ){
398: whereClauseInsert(pWC, pExpr, 0);
399: }else{
400: whereSplit(pWC, pExpr->pLeft, op);
401: whereSplit(pWC, pExpr->pRight, op);
402: }
403: }
404:
405: /*
406: ** Initialize an expression mask set (a WhereMaskSet object)
407: */
408: #define initMaskSet(P) memset(P, 0, sizeof(*P))
409:
410: /*
411: ** Return the bitmask for the given cursor number. Return 0 if
412: ** iCursor is not in the set.
413: */
414: static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
415: int i;
416: assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
417: for(i=0; i<pMaskSet->n; i++){
418: if( pMaskSet->ix[i]==iCursor ){
419: return ((Bitmask)1)<<i;
420: }
421: }
422: return 0;
423: }
424:
425: /*
426: ** Create a new mask for cursor iCursor.
427: **
428: ** There is one cursor per table in the FROM clause. The number of
429: ** tables in the FROM clause is limited by a test early in the
430: ** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
431: ** array will never overflow.
432: */
433: static void createMask(WhereMaskSet *pMaskSet, int iCursor){
434: assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
435: pMaskSet->ix[pMaskSet->n++] = iCursor;
436: }
437:
438: /*
439: ** This routine walks (recursively) an expression tree and generates
440: ** a bitmask indicating which tables are used in that expression
441: ** tree.
442: **
443: ** In order for this routine to work, the calling function must have
444: ** previously invoked sqlite3ResolveExprNames() on the expression. See
445: ** the header comment on that routine for additional information.
446: ** The sqlite3ResolveExprNames() routines looks for column names and
447: ** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
448: ** the VDBE cursor number of the table. This routine just has to
449: ** translate the cursor numbers into bitmask values and OR all
450: ** the bitmasks together.
451: */
452: static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
453: static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
454: static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
455: Bitmask mask = 0;
456: if( p==0 ) return 0;
457: if( p->op==TK_COLUMN ){
458: mask = getMask(pMaskSet, p->iTable);
459: return mask;
460: }
461: mask = exprTableUsage(pMaskSet, p->pRight);
462: mask |= exprTableUsage(pMaskSet, p->pLeft);
463: if( ExprHasProperty(p, EP_xIsSelect) ){
464: mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
465: }else{
466: mask |= exprListTableUsage(pMaskSet, p->x.pList);
467: }
468: return mask;
469: }
470: static Bitmask exprListTableUsage(WhereMaskSet *pMaskSet, ExprList *pList){
471: int i;
472: Bitmask mask = 0;
473: if( pList ){
474: for(i=0; i<pList->nExpr; i++){
475: mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
476: }
477: }
478: return mask;
479: }
480: static Bitmask exprSelectTableUsage(WhereMaskSet *pMaskSet, Select *pS){
481: Bitmask mask = 0;
482: while( pS ){
483: SrcList *pSrc = pS->pSrc;
484: mask |= exprListTableUsage(pMaskSet, pS->pEList);
485: mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
486: mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
487: mask |= exprTableUsage(pMaskSet, pS->pWhere);
488: mask |= exprTableUsage(pMaskSet, pS->pHaving);
489: if( ALWAYS(pSrc!=0) ){
490: int i;
491: for(i=0; i<pSrc->nSrc; i++){
492: mask |= exprSelectTableUsage(pMaskSet, pSrc->a[i].pSelect);
493: mask |= exprTableUsage(pMaskSet, pSrc->a[i].pOn);
494: }
495: }
496: pS = pS->pPrior;
497: }
498: return mask;
499: }
500:
501: /*
502: ** Return TRUE if the given operator is one of the operators that is
503: ** allowed for an indexable WHERE clause term. The allowed operators are
504: ** "=", "<", ">", "<=", ">=", and "IN".
505: **
506: ** IMPLEMENTATION-OF: R-59926-26393 To be usable by an index a term must be
507: ** of one of the following forms: column = expression column > expression
508: ** column >= expression column < expression column <= expression
509: ** expression = column expression > column expression >= column
510: ** expression < column expression <= column column IN
511: ** (expression-list) column IN (subquery) column IS NULL
512: */
513: static int allowedOp(int op){
514: assert( TK_GT>TK_EQ && TK_GT<TK_GE );
515: assert( TK_LT>TK_EQ && TK_LT<TK_GE );
516: assert( TK_LE>TK_EQ && TK_LE<TK_GE );
517: assert( TK_GE==TK_EQ+4 );
518: return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
519: }
520:
521: /*
522: ** Swap two objects of type TYPE.
523: */
524: #define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
525:
526: /*
527: ** Commute a comparison operator. Expressions of the form "X op Y"
528: ** are converted into "Y op X".
529: **
530: ** If a collation sequence is associated with either the left or right
531: ** side of the comparison, it remains associated with the same side after
532: ** the commutation. So "Y collate NOCASE op X" becomes
533: ** "X collate NOCASE op Y". This is because any collation sequence on
534: ** the left hand side of a comparison overrides any collation sequence
535: ** attached to the right. For the same reason the EP_ExpCollate flag
536: ** is not commuted.
537: */
538: static void exprCommute(Parse *pParse, Expr *pExpr){
539: u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
540: u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
541: assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
542: pExpr->pRight->pColl = sqlite3ExprCollSeq(pParse, pExpr->pRight);
543: pExpr->pLeft->pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
544: SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
545: pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
546: pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
547: SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
548: if( pExpr->op>=TK_GT ){
549: assert( TK_LT==TK_GT+2 );
550: assert( TK_GE==TK_LE+2 );
551: assert( TK_GT>TK_EQ );
552: assert( TK_GT<TK_LE );
553: assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
554: pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
555: }
556: }
557:
558: /*
559: ** Translate from TK_xx operator to WO_xx bitmask.
560: */
561: static u16 operatorMask(int op){
562: u16 c;
563: assert( allowedOp(op) );
564: if( op==TK_IN ){
565: c = WO_IN;
566: }else if( op==TK_ISNULL ){
567: c = WO_ISNULL;
568: }else{
569: assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
570: c = (u16)(WO_EQ<<(op-TK_EQ));
571: }
572: assert( op!=TK_ISNULL || c==WO_ISNULL );
573: assert( op!=TK_IN || c==WO_IN );
574: assert( op!=TK_EQ || c==WO_EQ );
575: assert( op!=TK_LT || c==WO_LT );
576: assert( op!=TK_LE || c==WO_LE );
577: assert( op!=TK_GT || c==WO_GT );
578: assert( op!=TK_GE || c==WO_GE );
579: return c;
580: }
581:
582: /*
583: ** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
584: ** where X is a reference to the iColumn of table iCur and <op> is one of
585: ** the WO_xx operator codes specified by the op parameter.
586: ** Return a pointer to the term. Return 0 if not found.
587: */
588: static WhereTerm *findTerm(
589: WhereClause *pWC, /* The WHERE clause to be searched */
590: int iCur, /* Cursor number of LHS */
591: int iColumn, /* Column number of LHS */
592: Bitmask notReady, /* RHS must not overlap with this mask */
593: u32 op, /* Mask of WO_xx values describing operator */
594: Index *pIdx /* Must be compatible with this index, if not NULL */
595: ){
596: WhereTerm *pTerm;
597: int k;
598: assert( iCur>=0 );
599: op &= WO_ALL;
600: for(; pWC; pWC=pWC->pOuter){
601: for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
602: if( pTerm->leftCursor==iCur
603: && (pTerm->prereqRight & notReady)==0
604: && pTerm->u.leftColumn==iColumn
605: && (pTerm->eOperator & op)!=0
606: ){
607: if( iColumn>=0 && pIdx && pTerm->eOperator!=WO_ISNULL ){
608: Expr *pX = pTerm->pExpr;
609: CollSeq *pColl;
610: char idxaff;
611: int j;
612: Parse *pParse = pWC->pParse;
613:
614: idxaff = pIdx->pTable->aCol[iColumn].affinity;
615: if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
616:
617: /* Figure out the collation sequence required from an index for
618: ** it to be useful for optimising expression pX. Store this
619: ** value in variable pColl.
620: */
621: assert(pX->pLeft);
622: pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
623: assert(pColl || pParse->nErr);
624:
625: for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
626: if( NEVER(j>=pIdx->nColumn) ) return 0;
627: }
628: if( pColl && sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
629: }
630: return pTerm;
631: }
632: }
633: }
634: return 0;
635: }
636:
637: /* Forward reference */
638: static void exprAnalyze(SrcList*, WhereClause*, int);
639:
640: /*
641: ** Call exprAnalyze on all terms in a WHERE clause.
642: **
643: **
644: */
645: static void exprAnalyzeAll(
646: SrcList *pTabList, /* the FROM clause */
647: WhereClause *pWC /* the WHERE clause to be analyzed */
648: ){
649: int i;
650: for(i=pWC->nTerm-1; i>=0; i--){
651: exprAnalyze(pTabList, pWC, i);
652: }
653: }
654:
655: #ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
656: /*
657: ** Check to see if the given expression is a LIKE or GLOB operator that
658: ** can be optimized using inequality constraints. Return TRUE if it is
659: ** so and false if not.
660: **
661: ** In order for the operator to be optimizible, the RHS must be a string
662: ** literal that does not begin with a wildcard.
663: */
664: static int isLikeOrGlob(
665: Parse *pParse, /* Parsing and code generating context */
666: Expr *pExpr, /* Test this expression */
667: Expr **ppPrefix, /* Pointer to TK_STRING expression with pattern prefix */
668: int *pisComplete, /* True if the only wildcard is % in the last character */
669: int *pnoCase /* True if uppercase is equivalent to lowercase */
670: ){
671: const char *z = 0; /* String on RHS of LIKE operator */
672: Expr *pRight, *pLeft; /* Right and left size of LIKE operator */
673: ExprList *pList; /* List of operands to the LIKE operator */
674: int c; /* One character in z[] */
675: int cnt; /* Number of non-wildcard prefix characters */
676: char wc[3]; /* Wildcard characters */
677: sqlite3 *db = pParse->db; /* Database connection */
678: sqlite3_value *pVal = 0;
679: int op; /* Opcode of pRight */
680:
681: if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
682: return 0;
683: }
684: #ifdef SQLITE_EBCDIC
685: if( *pnoCase ) return 0;
686: #endif
687: pList = pExpr->x.pList;
688: pLeft = pList->a[1].pExpr;
689: if( pLeft->op!=TK_COLUMN || sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT ){
690: /* IMP: R-02065-49465 The left-hand side of the LIKE or GLOB operator must
691: ** be the name of an indexed column with TEXT affinity. */
692: return 0;
693: }
694: assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */
695:
696: pRight = pList->a[0].pExpr;
697: op = pRight->op;
698: if( op==TK_REGISTER ){
699: op = pRight->op2;
700: }
701: if( op==TK_VARIABLE ){
702: Vdbe *pReprepare = pParse->pReprepare;
703: int iCol = pRight->iColumn;
704: pVal = sqlite3VdbeGetValue(pReprepare, iCol, SQLITE_AFF_NONE);
705: if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
706: z = (char *)sqlite3_value_text(pVal);
707: }
708: sqlite3VdbeSetVarmask(pParse->pVdbe, iCol);
709: assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER );
710: }else if( op==TK_STRING ){
711: z = pRight->u.zToken;
712: }
713: if( z ){
714: cnt = 0;
715: while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
716: cnt++;
717: }
718: if( cnt!=0 && 255!=(u8)z[cnt-1] ){
719: Expr *pPrefix;
720: *pisComplete = c==wc[0] && z[cnt+1]==0;
721: pPrefix = sqlite3Expr(db, TK_STRING, z);
722: if( pPrefix ) pPrefix->u.zToken[cnt] = 0;
723: *ppPrefix = pPrefix;
724: if( op==TK_VARIABLE ){
725: Vdbe *v = pParse->pVdbe;
726: sqlite3VdbeSetVarmask(v, pRight->iColumn);
727: if( *pisComplete && pRight->u.zToken[1] ){
728: /* If the rhs of the LIKE expression is a variable, and the current
729: ** value of the variable means there is no need to invoke the LIKE
730: ** function, then no OP_Variable will be added to the program.
731: ** This causes problems for the sqlite3_bind_parameter_name()
732: ** API. To workaround them, add a dummy OP_Variable here.
733: */
734: int r1 = sqlite3GetTempReg(pParse);
735: sqlite3ExprCodeTarget(pParse, pRight, r1);
736: sqlite3VdbeChangeP3(v, sqlite3VdbeCurrentAddr(v)-1, 0);
737: sqlite3ReleaseTempReg(pParse, r1);
738: }
739: }
740: }else{
741: z = 0;
742: }
743: }
744:
745: sqlite3ValueFree(pVal);
746: return (z!=0);
747: }
748: #endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
749:
750:
751: #ifndef SQLITE_OMIT_VIRTUALTABLE
752: /*
753: ** Check to see if the given expression is of the form
754: **
755: ** column MATCH expr
756: **
757: ** If it is then return TRUE. If not, return FALSE.
758: */
759: static int isMatchOfColumn(
760: Expr *pExpr /* Test this expression */
761: ){
762: ExprList *pList;
763:
764: if( pExpr->op!=TK_FUNCTION ){
765: return 0;
766: }
767: if( sqlite3StrICmp(pExpr->u.zToken,"match")!=0 ){
768: return 0;
769: }
770: pList = pExpr->x.pList;
771: if( pList->nExpr!=2 ){
772: return 0;
773: }
774: if( pList->a[1].pExpr->op != TK_COLUMN ){
775: return 0;
776: }
777: return 1;
778: }
779: #endif /* SQLITE_OMIT_VIRTUALTABLE */
780:
781: /*
782: ** If the pBase expression originated in the ON or USING clause of
783: ** a join, then transfer the appropriate markings over to derived.
784: */
785: static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
786: pDerived->flags |= pBase->flags & EP_FromJoin;
787: pDerived->iRightJoinTable = pBase->iRightJoinTable;
788: }
789:
790: #if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
791: /*
792: ** Analyze a term that consists of two or more OR-connected
793: ** subterms. So in:
794: **
795: ** ... WHERE (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
796: ** ^^^^^^^^^^^^^^^^^^^^
797: **
798: ** This routine analyzes terms such as the middle term in the above example.
799: ** A WhereOrTerm object is computed and attached to the term under
800: ** analysis, regardless of the outcome of the analysis. Hence:
801: **
802: ** WhereTerm.wtFlags |= TERM_ORINFO
803: ** WhereTerm.u.pOrInfo = a dynamically allocated WhereOrTerm object
804: **
805: ** The term being analyzed must have two or more of OR-connected subterms.
806: ** A single subterm might be a set of AND-connected sub-subterms.
807: ** Examples of terms under analysis:
808: **
809: ** (A) t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
810: ** (B) x=expr1 OR expr2=x OR x=expr3
811: ** (C) t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
812: ** (D) x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
813: ** (E) (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
814: **
815: ** CASE 1:
816: **
817: ** If all subterms are of the form T.C=expr for some single column of C
818: ** a single table T (as shown in example B above) then create a new virtual
819: ** term that is an equivalent IN expression. In other words, if the term
820: ** being analyzed is:
821: **
822: ** x = expr1 OR expr2 = x OR x = expr3
823: **
824: ** then create a new virtual term like this:
825: **
826: ** x IN (expr1,expr2,expr3)
827: **
828: ** CASE 2:
829: **
830: ** If all subterms are indexable by a single table T, then set
831: **
832: ** WhereTerm.eOperator = WO_OR
833: ** WhereTerm.u.pOrInfo->indexable |= the cursor number for table T
834: **
835: ** A subterm is "indexable" if it is of the form
836: ** "T.C <op> <expr>" where C is any column of table T and
837: ** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
838: ** A subterm is also indexable if it is an AND of two or more
839: ** subsubterms at least one of which is indexable. Indexable AND
840: ** subterms have their eOperator set to WO_AND and they have
841: ** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
842: **
843: ** From another point of view, "indexable" means that the subterm could
844: ** potentially be used with an index if an appropriate index exists.
845: ** This analysis does not consider whether or not the index exists; that
846: ** is something the bestIndex() routine will determine. This analysis
847: ** only looks at whether subterms appropriate for indexing exist.
848: **
849: ** All examples A through E above all satisfy case 2. But if a term
850: ** also statisfies case 1 (such as B) we know that the optimizer will
851: ** always prefer case 1, so in that case we pretend that case 2 is not
852: ** satisfied.
853: **
854: ** It might be the case that multiple tables are indexable. For example,
855: ** (E) above is indexable on tables P, Q, and R.
856: **
857: ** Terms that satisfy case 2 are candidates for lookup by using
858: ** separate indices to find rowids for each subterm and composing
859: ** the union of all rowids using a RowSet object. This is similar
860: ** to "bitmap indices" in other database engines.
861: **
862: ** OTHERWISE:
863: **
864: ** If neither case 1 nor case 2 apply, then leave the eOperator set to
865: ** zero. This term is not useful for search.
866: */
867: static void exprAnalyzeOrTerm(
868: SrcList *pSrc, /* the FROM clause */
869: WhereClause *pWC, /* the complete WHERE clause */
870: int idxTerm /* Index of the OR-term to be analyzed */
871: ){
872: Parse *pParse = pWC->pParse; /* Parser context */
873: sqlite3 *db = pParse->db; /* Database connection */
874: WhereTerm *pTerm = &pWC->a[idxTerm]; /* The term to be analyzed */
875: Expr *pExpr = pTerm->pExpr; /* The expression of the term */
876: WhereMaskSet *pMaskSet = pWC->pMaskSet; /* Table use masks */
877: int i; /* Loop counters */
878: WhereClause *pOrWc; /* Breakup of pTerm into subterms */
879: WhereTerm *pOrTerm; /* A Sub-term within the pOrWc */
880: WhereOrInfo *pOrInfo; /* Additional information associated with pTerm */
881: Bitmask chngToIN; /* Tables that might satisfy case 1 */
882: Bitmask indexable; /* Tables that are indexable, satisfying case 2 */
883:
884: /*
885: ** Break the OR clause into its separate subterms. The subterms are
886: ** stored in a WhereClause structure containing within the WhereOrInfo
887: ** object that is attached to the original OR clause term.
888: */
889: assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
890: assert( pExpr->op==TK_OR );
891: pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
892: if( pOrInfo==0 ) return;
893: pTerm->wtFlags |= TERM_ORINFO;
894: pOrWc = &pOrInfo->wc;
895: whereClauseInit(pOrWc, pWC->pParse, pMaskSet, pWC->wctrlFlags);
896: whereSplit(pOrWc, pExpr, TK_OR);
897: exprAnalyzeAll(pSrc, pOrWc);
898: if( db->mallocFailed ) return;
899: assert( pOrWc->nTerm>=2 );
900:
901: /*
902: ** Compute the set of tables that might satisfy cases 1 or 2.
903: */
904: indexable = ~(Bitmask)0;
905: chngToIN = ~(pWC->vmask);
906: for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
907: if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
908: WhereAndInfo *pAndInfo;
909: assert( pOrTerm->eOperator==0 );
910: assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
911: chngToIN = 0;
912: pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
913: if( pAndInfo ){
914: WhereClause *pAndWC;
915: WhereTerm *pAndTerm;
916: int j;
917: Bitmask b = 0;
918: pOrTerm->u.pAndInfo = pAndInfo;
919: pOrTerm->wtFlags |= TERM_ANDINFO;
920: pOrTerm->eOperator = WO_AND;
921: pAndWC = &pAndInfo->wc;
922: whereClauseInit(pAndWC, pWC->pParse, pMaskSet, pWC->wctrlFlags);
923: whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
924: exprAnalyzeAll(pSrc, pAndWC);
925: pAndWC->pOuter = pWC;
926: testcase( db->mallocFailed );
927: if( !db->mallocFailed ){
928: for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
929: assert( pAndTerm->pExpr );
930: if( allowedOp(pAndTerm->pExpr->op) ){
931: b |= getMask(pMaskSet, pAndTerm->leftCursor);
932: }
933: }
934: }
935: indexable &= b;
936: }
937: }else if( pOrTerm->wtFlags & TERM_COPIED ){
938: /* Skip this term for now. We revisit it when we process the
939: ** corresponding TERM_VIRTUAL term */
940: }else{
941: Bitmask b;
942: b = getMask(pMaskSet, pOrTerm->leftCursor);
943: if( pOrTerm->wtFlags & TERM_VIRTUAL ){
944: WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
945: b |= getMask(pMaskSet, pOther->leftCursor);
946: }
947: indexable &= b;
948: if( pOrTerm->eOperator!=WO_EQ ){
949: chngToIN = 0;
950: }else{
951: chngToIN &= b;
952: }
953: }
954: }
955:
956: /*
957: ** Record the set of tables that satisfy case 2. The set might be
958: ** empty.
959: */
960: pOrInfo->indexable = indexable;
961: pTerm->eOperator = indexable==0 ? 0 : WO_OR;
962:
963: /*
964: ** chngToIN holds a set of tables that *might* satisfy case 1. But
965: ** we have to do some additional checking to see if case 1 really
966: ** is satisfied.
967: **
968: ** chngToIN will hold either 0, 1, or 2 bits. The 0-bit case means
969: ** that there is no possibility of transforming the OR clause into an
970: ** IN operator because one or more terms in the OR clause contain
971: ** something other than == on a column in the single table. The 1-bit
972: ** case means that every term of the OR clause is of the form
973: ** "table.column=expr" for some single table. The one bit that is set
974: ** will correspond to the common table. We still need to check to make
975: ** sure the same column is used on all terms. The 2-bit case is when
976: ** the all terms are of the form "table1.column=table2.column". It
977: ** might be possible to form an IN operator with either table1.column
978: ** or table2.column as the LHS if either is common to every term of
979: ** the OR clause.
980: **
981: ** Note that terms of the form "table.column1=table.column2" (the
982: ** same table on both sizes of the ==) cannot be optimized.
983: */
984: if( chngToIN ){
985: int okToChngToIN = 0; /* True if the conversion to IN is valid */
986: int iColumn = -1; /* Column index on lhs of IN operator */
987: int iCursor = -1; /* Table cursor common to all terms */
988: int j = 0; /* Loop counter */
989:
990: /* Search for a table and column that appears on one side or the
991: ** other of the == operator in every subterm. That table and column
992: ** will be recorded in iCursor and iColumn. There might not be any
993: ** such table and column. Set okToChngToIN if an appropriate table
994: ** and column is found but leave okToChngToIN false if not found.
995: */
996: for(j=0; j<2 && !okToChngToIN; j++){
997: pOrTerm = pOrWc->a;
998: for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
999: assert( pOrTerm->eOperator==WO_EQ );
1000: pOrTerm->wtFlags &= ~TERM_OR_OK;
1001: if( pOrTerm->leftCursor==iCursor ){
1002: /* This is the 2-bit case and we are on the second iteration and
1003: ** current term is from the first iteration. So skip this term. */
1004: assert( j==1 );
1005: continue;
1006: }
1007: if( (chngToIN & getMask(pMaskSet, pOrTerm->leftCursor))==0 ){
1008: /* This term must be of the form t1.a==t2.b where t2 is in the
1009: ** chngToIN set but t1 is not. This term will be either preceeded
1010: ** or follwed by an inverted copy (t2.b==t1.a). Skip this term
1011: ** and use its inversion. */
1012: testcase( pOrTerm->wtFlags & TERM_COPIED );
1013: testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
1014: assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
1015: continue;
1016: }
1017: iColumn = pOrTerm->u.leftColumn;
1018: iCursor = pOrTerm->leftCursor;
1019: break;
1020: }
1021: if( i<0 ){
1022: /* No candidate table+column was found. This can only occur
1023: ** on the second iteration */
1024: assert( j==1 );
1025: assert( (chngToIN&(chngToIN-1))==0 );
1026: assert( chngToIN==getMask(pMaskSet, iCursor) );
1027: break;
1028: }
1029: testcase( j==1 );
1030:
1031: /* We have found a candidate table and column. Check to see if that
1032: ** table and column is common to every term in the OR clause */
1033: okToChngToIN = 1;
1034: for(; i>=0 && okToChngToIN; i--, pOrTerm++){
1035: assert( pOrTerm->eOperator==WO_EQ );
1036: if( pOrTerm->leftCursor!=iCursor ){
1037: pOrTerm->wtFlags &= ~TERM_OR_OK;
1038: }else if( pOrTerm->u.leftColumn!=iColumn ){
1039: okToChngToIN = 0;
1040: }else{
1041: int affLeft, affRight;
1042: /* If the right-hand side is also a column, then the affinities
1043: ** of both right and left sides must be such that no type
1044: ** conversions are required on the right. (Ticket #2249)
1045: */
1046: affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
1047: affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
1048: if( affRight!=0 && affRight!=affLeft ){
1049: okToChngToIN = 0;
1050: }else{
1051: pOrTerm->wtFlags |= TERM_OR_OK;
1052: }
1053: }
1054: }
1055: }
1056:
1057: /* At this point, okToChngToIN is true if original pTerm satisfies
1058: ** case 1. In that case, construct a new virtual term that is
1059: ** pTerm converted into an IN operator.
1060: **
1061: ** EV: R-00211-15100
1062: */
1063: if( okToChngToIN ){
1064: Expr *pDup; /* A transient duplicate expression */
1065: ExprList *pList = 0; /* The RHS of the IN operator */
1066: Expr *pLeft = 0; /* The LHS of the IN operator */
1067: Expr *pNew; /* The complete IN operator */
1068:
1069: for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
1070: if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
1071: assert( pOrTerm->eOperator==WO_EQ );
1072: assert( pOrTerm->leftCursor==iCursor );
1073: assert( pOrTerm->u.leftColumn==iColumn );
1074: pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
1075: pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup);
1076: pLeft = pOrTerm->pExpr->pLeft;
1077: }
1078: assert( pLeft!=0 );
1079: pDup = sqlite3ExprDup(db, pLeft, 0);
1080: pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0, 0);
1081: if( pNew ){
1082: int idxNew;
1083: transferJoinMarkings(pNew, pExpr);
1084: assert( !ExprHasProperty(pNew, EP_xIsSelect) );
1085: pNew->x.pList = pList;
1086: idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
1087: testcase( idxNew==0 );
1088: exprAnalyze(pSrc, pWC, idxNew);
1089: pTerm = &pWC->a[idxTerm];
1090: pWC->a[idxNew].iParent = idxTerm;
1091: pTerm->nChild = 1;
1092: }else{
1093: sqlite3ExprListDelete(db, pList);
1094: }
1095: pTerm->eOperator = WO_NOOP; /* case 1 trumps case 2 */
1096: }
1097: }
1098: }
1099: #endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
1100:
1101:
1102: /*
1103: ** The input to this routine is an WhereTerm structure with only the
1104: ** "pExpr" field filled in. The job of this routine is to analyze the
1105: ** subexpression and populate all the other fields of the WhereTerm
1106: ** structure.
1107: **
1108: ** If the expression is of the form "<expr> <op> X" it gets commuted
1109: ** to the standard form of "X <op> <expr>".
1110: **
1111: ** If the expression is of the form "X <op> Y" where both X and Y are
1112: ** columns, then the original expression is unchanged and a new virtual
1113: ** term of the form "Y <op> X" is added to the WHERE clause and
1114: ** analyzed separately. The original term is marked with TERM_COPIED
1115: ** and the new term is marked with TERM_DYNAMIC (because it's pExpr
1116: ** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
1117: ** is a commuted copy of a prior term.) The original term has nChild=1
1118: ** and the copy has idxParent set to the index of the original term.
1119: */
1120: static void exprAnalyze(
1121: SrcList *pSrc, /* the FROM clause */
1122: WhereClause *pWC, /* the WHERE clause */
1123: int idxTerm /* Index of the term to be analyzed */
1124: ){
1125: WhereTerm *pTerm; /* The term to be analyzed */
1126: WhereMaskSet *pMaskSet; /* Set of table index masks */
1127: Expr *pExpr; /* The expression to be analyzed */
1128: Bitmask prereqLeft; /* Prerequesites of the pExpr->pLeft */
1129: Bitmask prereqAll; /* Prerequesites of pExpr */
1130: Bitmask extraRight = 0; /* Extra dependencies on LEFT JOIN */
1131: Expr *pStr1 = 0; /* RHS of LIKE/GLOB operator */
1132: int isComplete = 0; /* RHS of LIKE/GLOB ends with wildcard */
1133: int noCase = 0; /* LIKE/GLOB distinguishes case */
1134: int op; /* Top-level operator. pExpr->op */
1135: Parse *pParse = pWC->pParse; /* Parsing context */
1136: sqlite3 *db = pParse->db; /* Database connection */
1137:
1138: if( db->mallocFailed ){
1139: return;
1140: }
1141: pTerm = &pWC->a[idxTerm];
1142: pMaskSet = pWC->pMaskSet;
1143: pExpr = pTerm->pExpr;
1144: prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
1145: op = pExpr->op;
1146: if( op==TK_IN ){
1147: assert( pExpr->pRight==0 );
1148: if( ExprHasProperty(pExpr, EP_xIsSelect) ){
1149: pTerm->prereqRight = exprSelectTableUsage(pMaskSet, pExpr->x.pSelect);
1150: }else{
1151: pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->x.pList);
1152: }
1153: }else if( op==TK_ISNULL ){
1154: pTerm->prereqRight = 0;
1155: }else{
1156: pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
1157: }
1158: prereqAll = exprTableUsage(pMaskSet, pExpr);
1159: if( ExprHasProperty(pExpr, EP_FromJoin) ){
1160: Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
1161: prereqAll |= x;
1162: extraRight = x-1; /* ON clause terms may not be used with an index
1163: ** on left table of a LEFT JOIN. Ticket #3015 */
1164: }
1165: pTerm->prereqAll = prereqAll;
1166: pTerm->leftCursor = -1;
1167: pTerm->iParent = -1;
1168: pTerm->eOperator = 0;
1169: if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
1170: Expr *pLeft = pExpr->pLeft;
1171: Expr *pRight = pExpr->pRight;
1172: if( pLeft->op==TK_COLUMN ){
1173: pTerm->leftCursor = pLeft->iTable;
1174: pTerm->u.leftColumn = pLeft->iColumn;
1175: pTerm->eOperator = operatorMask(op);
1176: }
1177: if( pRight && pRight->op==TK_COLUMN ){
1178: WhereTerm *pNew;
1179: Expr *pDup;
1180: if( pTerm->leftCursor>=0 ){
1181: int idxNew;
1182: pDup = sqlite3ExprDup(db, pExpr, 0);
1183: if( db->mallocFailed ){
1184: sqlite3ExprDelete(db, pDup);
1185: return;
1186: }
1187: idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
1188: if( idxNew==0 ) return;
1189: pNew = &pWC->a[idxNew];
1190: pNew->iParent = idxTerm;
1191: pTerm = &pWC->a[idxTerm];
1192: pTerm->nChild = 1;
1193: pTerm->wtFlags |= TERM_COPIED;
1194: }else{
1195: pDup = pExpr;
1196: pNew = pTerm;
1197: }
1198: exprCommute(pParse, pDup);
1199: pLeft = pDup->pLeft;
1200: pNew->leftCursor = pLeft->iTable;
1201: pNew->u.leftColumn = pLeft->iColumn;
1202: testcase( (prereqLeft | extraRight) != prereqLeft );
1203: pNew->prereqRight = prereqLeft | extraRight;
1204: pNew->prereqAll = prereqAll;
1205: pNew->eOperator = operatorMask(pDup->op);
1206: }
1207: }
1208:
1209: #ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
1210: /* If a term is the BETWEEN operator, create two new virtual terms
1211: ** that define the range that the BETWEEN implements. For example:
1212: **
1213: ** a BETWEEN b AND c
1214: **
1215: ** is converted into:
1216: **
1217: ** (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
1218: **
1219: ** The two new terms are added onto the end of the WhereClause object.
1220: ** The new terms are "dynamic" and are children of the original BETWEEN
1221: ** term. That means that if the BETWEEN term is coded, the children are
1222: ** skipped. Or, if the children are satisfied by an index, the original
1223: ** BETWEEN term is skipped.
1224: */
1225: else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
1226: ExprList *pList = pExpr->x.pList;
1227: int i;
1228: static const u8 ops[] = {TK_GE, TK_LE};
1229: assert( pList!=0 );
1230: assert( pList->nExpr==2 );
1231: for(i=0; i<2; i++){
1232: Expr *pNewExpr;
1233: int idxNew;
1234: pNewExpr = sqlite3PExpr(pParse, ops[i],
1235: sqlite3ExprDup(db, pExpr->pLeft, 0),
1236: sqlite3ExprDup(db, pList->a[i].pExpr, 0), 0);
1237: idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
1238: testcase( idxNew==0 );
1239: exprAnalyze(pSrc, pWC, idxNew);
1240: pTerm = &pWC->a[idxTerm];
1241: pWC->a[idxNew].iParent = idxTerm;
1242: }
1243: pTerm->nChild = 2;
1244: }
1245: #endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
1246:
1247: #if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
1248: /* Analyze a term that is composed of two or more subterms connected by
1249: ** an OR operator.
1250: */
1251: else if( pExpr->op==TK_OR ){
1252: assert( pWC->op==TK_AND );
1253: exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
1254: pTerm = &pWC->a[idxTerm];
1255: }
1256: #endif /* SQLITE_OMIT_OR_OPTIMIZATION */
1257:
1258: #ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
1259: /* Add constraints to reduce the search space on a LIKE or GLOB
1260: ** operator.
1261: **
1262: ** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
1263: **
1264: ** x>='abc' AND x<'abd' AND x LIKE 'abc%'
1265: **
1266: ** The last character of the prefix "abc" is incremented to form the
1267: ** termination condition "abd".
1268: */
1269: if( pWC->op==TK_AND
1270: && isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
1271: ){
1272: Expr *pLeft; /* LHS of LIKE/GLOB operator */
1273: Expr *pStr2; /* Copy of pStr1 - RHS of LIKE/GLOB operator */
1274: Expr *pNewExpr1;
1275: Expr *pNewExpr2;
1276: int idxNew1;
1277: int idxNew2;
1278: CollSeq *pColl; /* Collating sequence to use */
1279:
1280: pLeft = pExpr->x.pList->a[1].pExpr;
1281: pStr2 = sqlite3ExprDup(db, pStr1, 0);
1282: if( !db->mallocFailed ){
1283: u8 c, *pC; /* Last character before the first wildcard */
1284: pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
1285: c = *pC;
1286: if( noCase ){
1287: /* The point is to increment the last character before the first
1288: ** wildcard. But if we increment '@', that will push it into the
1289: ** alphabetic range where case conversions will mess up the
1290: ** inequality. To avoid this, make sure to also run the full
1291: ** LIKE on all candidate expressions by clearing the isComplete flag
1292: */
1293: if( c=='A'-1 ) isComplete = 0; /* EV: R-64339-08207 */
1294:
1295:
1296: c = sqlite3UpperToLower[c];
1297: }
1298: *pC = c + 1;
1299: }
1300: pColl = sqlite3FindCollSeq(db, SQLITE_UTF8, noCase ? "NOCASE" : "BINARY",0);
1301: pNewExpr1 = sqlite3PExpr(pParse, TK_GE,
1302: sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
1303: pStr1, 0);
1304: idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
1305: testcase( idxNew1==0 );
1306: exprAnalyze(pSrc, pWC, idxNew1);
1307: pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
1308: sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
1309: pStr2, 0);
1310: idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
1311: testcase( idxNew2==0 );
1312: exprAnalyze(pSrc, pWC, idxNew2);
1313: pTerm = &pWC->a[idxTerm];
1314: if( isComplete ){
1315: pWC->a[idxNew1].iParent = idxTerm;
1316: pWC->a[idxNew2].iParent = idxTerm;
1317: pTerm->nChild = 2;
1318: }
1319: }
1320: #endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
1321:
1322: #ifndef SQLITE_OMIT_VIRTUALTABLE
1323: /* Add a WO_MATCH auxiliary term to the constraint set if the
1324: ** current expression is of the form: column MATCH expr.
1325: ** This information is used by the xBestIndex methods of
1326: ** virtual tables. The native query optimizer does not attempt
1327: ** to do anything with MATCH functions.
1328: */
1329: if( isMatchOfColumn(pExpr) ){
1330: int idxNew;
1331: Expr *pRight, *pLeft;
1332: WhereTerm *pNewTerm;
1333: Bitmask prereqColumn, prereqExpr;
1334:
1335: pRight = pExpr->x.pList->a[0].pExpr;
1336: pLeft = pExpr->x.pList->a[1].pExpr;
1337: prereqExpr = exprTableUsage(pMaskSet, pRight);
1338: prereqColumn = exprTableUsage(pMaskSet, pLeft);
1339: if( (prereqExpr & prereqColumn)==0 ){
1340: Expr *pNewExpr;
1341: pNewExpr = sqlite3PExpr(pParse, TK_MATCH,
1342: 0, sqlite3ExprDup(db, pRight, 0), 0);
1343: idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
1344: testcase( idxNew==0 );
1345: pNewTerm = &pWC->a[idxNew];
1346: pNewTerm->prereqRight = prereqExpr;
1347: pNewTerm->leftCursor = pLeft->iTable;
1348: pNewTerm->u.leftColumn = pLeft->iColumn;
1349: pNewTerm->eOperator = WO_MATCH;
1350: pNewTerm->iParent = idxTerm;
1351: pTerm = &pWC->a[idxTerm];
1352: pTerm->nChild = 1;
1353: pTerm->wtFlags |= TERM_COPIED;
1354: pNewTerm->prereqAll = pTerm->prereqAll;
1355: }
1356: }
1357: #endif /* SQLITE_OMIT_VIRTUALTABLE */
1358:
1359: #ifdef SQLITE_ENABLE_STAT3
1360: /* When sqlite_stat3 histogram data is available an operator of the
1361: ** form "x IS NOT NULL" can sometimes be evaluated more efficiently
1362: ** as "x>NULL" if x is not an INTEGER PRIMARY KEY. So construct a
1363: ** virtual term of that form.
1364: **
1365: ** Note that the virtual term must be tagged with TERM_VNULL. This
1366: ** TERM_VNULL tag will suppress the not-null check at the beginning
1367: ** of the loop. Without the TERM_VNULL flag, the not-null check at
1368: ** the start of the loop will prevent any results from being returned.
1369: */
1370: if( pExpr->op==TK_NOTNULL
1371: && pExpr->pLeft->op==TK_COLUMN
1372: && pExpr->pLeft->iColumn>=0
1373: ){
1374: Expr *pNewExpr;
1375: Expr *pLeft = pExpr->pLeft;
1376: int idxNew;
1377: WhereTerm *pNewTerm;
1378:
1379: pNewExpr = sqlite3PExpr(pParse, TK_GT,
1380: sqlite3ExprDup(db, pLeft, 0),
1381: sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
1382:
1383: idxNew = whereClauseInsert(pWC, pNewExpr,
1384: TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
1385: if( idxNew ){
1386: pNewTerm = &pWC->a[idxNew];
1387: pNewTerm->prereqRight = 0;
1388: pNewTerm->leftCursor = pLeft->iTable;
1389: pNewTerm->u.leftColumn = pLeft->iColumn;
1390: pNewTerm->eOperator = WO_GT;
1391: pNewTerm->iParent = idxTerm;
1392: pTerm = &pWC->a[idxTerm];
1393: pTerm->nChild = 1;
1394: pTerm->wtFlags |= TERM_COPIED;
1395: pNewTerm->prereqAll = pTerm->prereqAll;
1396: }
1397: }
1398: #endif /* SQLITE_ENABLE_STAT */
1399:
1400: /* Prevent ON clause terms of a LEFT JOIN from being used to drive
1401: ** an index for tables to the left of the join.
1402: */
1403: pTerm->prereqRight |= extraRight;
1404: }
1405:
1406: /*
1407: ** Return TRUE if any of the expressions in pList->a[iFirst...] contain
1408: ** a reference to any table other than the iBase table.
1409: */
1410: static int referencesOtherTables(
1411: ExprList *pList, /* Search expressions in ths list */
1412: WhereMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
1413: int iFirst, /* Be searching with the iFirst-th expression */
1414: int iBase /* Ignore references to this table */
1415: ){
1416: Bitmask allowed = ~getMask(pMaskSet, iBase);
1417: while( iFirst<pList->nExpr ){
1418: if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
1419: return 1;
1420: }
1421: }
1422: return 0;
1423: }
1424:
1425: /*
1426: ** This function searches the expression list passed as the second argument
1427: ** for an expression of type TK_COLUMN that refers to the same column and
1428: ** uses the same collation sequence as the iCol'th column of index pIdx.
1429: ** Argument iBase is the cursor number used for the table that pIdx refers
1430: ** to.
1431: **
1432: ** If such an expression is found, its index in pList->a[] is returned. If
1433: ** no expression is found, -1 is returned.
1434: */
1435: static int findIndexCol(
1436: Parse *pParse, /* Parse context */
1437: ExprList *pList, /* Expression list to search */
1438: int iBase, /* Cursor for table associated with pIdx */
1439: Index *pIdx, /* Index to match column of */
1440: int iCol /* Column of index to match */
1441: ){
1442: int i;
1443: const char *zColl = pIdx->azColl[iCol];
1444:
1445: for(i=0; i<pList->nExpr; i++){
1446: Expr *p = pList->a[i].pExpr;
1447: if( p->op==TK_COLUMN
1448: && p->iColumn==pIdx->aiColumn[iCol]
1449: && p->iTable==iBase
1450: ){
1451: CollSeq *pColl = sqlite3ExprCollSeq(pParse, p);
1452: if( ALWAYS(pColl) && 0==sqlite3StrICmp(pColl->zName, zColl) ){
1453: return i;
1454: }
1455: }
1456: }
1457:
1458: return -1;
1459: }
1460:
1461: /*
1462: ** This routine determines if pIdx can be used to assist in processing a
1463: ** DISTINCT qualifier. In other words, it tests whether or not using this
1464: ** index for the outer loop guarantees that rows with equal values for
1465: ** all expressions in the pDistinct list are delivered grouped together.
1466: **
1467: ** For example, the query
1468: **
1469: ** SELECT DISTINCT a, b, c FROM tbl WHERE a = ?
1470: **
1471: ** can benefit from any index on columns "b" and "c".
1472: */
1473: static int isDistinctIndex(
1474: Parse *pParse, /* Parsing context */
1475: WhereClause *pWC, /* The WHERE clause */
1476: Index *pIdx, /* The index being considered */
1477: int base, /* Cursor number for the table pIdx is on */
1478: ExprList *pDistinct, /* The DISTINCT expressions */
1479: int nEqCol /* Number of index columns with == */
1480: ){
1481: Bitmask mask = 0; /* Mask of unaccounted for pDistinct exprs */
1482: int i; /* Iterator variable */
1483:
1484: if( pIdx->zName==0 || pDistinct==0 || pDistinct->nExpr>=BMS ) return 0;
1485: testcase( pDistinct->nExpr==BMS-1 );
1486:
1487: /* Loop through all the expressions in the distinct list. If any of them
1488: ** are not simple column references, return early. Otherwise, test if the
1489: ** WHERE clause contains a "col=X" clause. If it does, the expression
1490: ** can be ignored. If it does not, and the column does not belong to the
1491: ** same table as index pIdx, return early. Finally, if there is no
1492: ** matching "col=X" expression and the column is on the same table as pIdx,
1493: ** set the corresponding bit in variable mask.
1494: */
1495: for(i=0; i<pDistinct->nExpr; i++){
1496: WhereTerm *pTerm;
1497: Expr *p = pDistinct->a[i].pExpr;
1498: if( p->op!=TK_COLUMN ) return 0;
1499: pTerm = findTerm(pWC, p->iTable, p->iColumn, ~(Bitmask)0, WO_EQ, 0);
1500: if( pTerm ){
1501: Expr *pX = pTerm->pExpr;
1502: CollSeq *p1 = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
1503: CollSeq *p2 = sqlite3ExprCollSeq(pParse, p);
1504: if( p1==p2 ) continue;
1505: }
1506: if( p->iTable!=base ) return 0;
1507: mask |= (((Bitmask)1) << i);
1508: }
1509:
1510: for(i=nEqCol; mask && i<pIdx->nColumn; i++){
1511: int iExpr = findIndexCol(pParse, pDistinct, base, pIdx, i);
1512: if( iExpr<0 ) break;
1513: mask &= ~(((Bitmask)1) << iExpr);
1514: }
1515:
1516: return (mask==0);
1517: }
1518:
1519:
1520: /*
1521: ** Return true if the DISTINCT expression-list passed as the third argument
1522: ** is redundant. A DISTINCT list is redundant if the database contains a
1523: ** UNIQUE index that guarantees that the result of the query will be distinct
1524: ** anyway.
1525: */
1526: static int isDistinctRedundant(
1527: Parse *pParse,
1528: SrcList *pTabList,
1529: WhereClause *pWC,
1530: ExprList *pDistinct
1531: ){
1532: Table *pTab;
1533: Index *pIdx;
1534: int i;
1535: int iBase;
1536:
1537: /* If there is more than one table or sub-select in the FROM clause of
1538: ** this query, then it will not be possible to show that the DISTINCT
1539: ** clause is redundant. */
1540: if( pTabList->nSrc!=1 ) return 0;
1541: iBase = pTabList->a[0].iCursor;
1542: pTab = pTabList->a[0].pTab;
1543:
1544: /* If any of the expressions is an IPK column on table iBase, then return
1545: ** true. Note: The (p->iTable==iBase) part of this test may be false if the
1546: ** current SELECT is a correlated sub-query.
1547: */
1548: for(i=0; i<pDistinct->nExpr; i++){
1549: Expr *p = pDistinct->a[i].pExpr;
1550: if( p->op==TK_COLUMN && p->iTable==iBase && p->iColumn<0 ) return 1;
1551: }
1552:
1553: /* Loop through all indices on the table, checking each to see if it makes
1554: ** the DISTINCT qualifier redundant. It does so if:
1555: **
1556: ** 1. The index is itself UNIQUE, and
1557: **
1558: ** 2. All of the columns in the index are either part of the pDistinct
1559: ** list, or else the WHERE clause contains a term of the form "col=X",
1560: ** where X is a constant value. The collation sequences of the
1561: ** comparison and select-list expressions must match those of the index.
1562: */
1563: for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
1564: if( pIdx->onError==OE_None ) continue;
1565: for(i=0; i<pIdx->nColumn; i++){
1566: int iCol = pIdx->aiColumn[i];
1567: if( 0==findTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx)
1568: && 0>findIndexCol(pParse, pDistinct, iBase, pIdx, i)
1569: ){
1570: break;
1571: }
1572: }
1573: if( i==pIdx->nColumn ){
1574: /* This index implies that the DISTINCT qualifier is redundant. */
1575: return 1;
1576: }
1577: }
1578:
1579: return 0;
1580: }
1581:
1582: /*
1583: ** This routine decides if pIdx can be used to satisfy the ORDER BY
1584: ** clause. If it can, it returns 1. If pIdx cannot satisfy the
1585: ** ORDER BY clause, this routine returns 0.
1586: **
1587: ** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
1588: ** left-most table in the FROM clause of that same SELECT statement and
1589: ** the table has a cursor number of "base". pIdx is an index on pTab.
1590: **
1591: ** nEqCol is the number of columns of pIdx that are used as equality
1592: ** constraints. Any of these columns may be missing from the ORDER BY
1593: ** clause and the match can still be a success.
1594: **
1595: ** All terms of the ORDER BY that match against the index must be either
1596: ** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
1597: ** index do not need to satisfy this constraint.) The *pbRev value is
1598: ** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
1599: ** the ORDER BY clause is all ASC.
1600: */
1601: static int isSortingIndex(
1602: Parse *pParse, /* Parsing context */
1603: WhereMaskSet *pMaskSet, /* Mapping from table cursor numbers to bitmaps */
1604: Index *pIdx, /* The index we are testing */
1605: int base, /* Cursor number for the table to be sorted */
1606: ExprList *pOrderBy, /* The ORDER BY clause */
1607: int nEqCol, /* Number of index columns with == constraints */
1608: int wsFlags, /* Index usages flags */
1609: int *pbRev /* Set to 1 if ORDER BY is DESC */
1610: ){
1611: int i, j; /* Loop counters */
1612: int sortOrder = 0; /* XOR of index and ORDER BY sort direction */
1613: int nTerm; /* Number of ORDER BY terms */
1614: struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
1615: sqlite3 *db = pParse->db;
1616:
1617: if( !pOrderBy ) return 0;
1618: if( wsFlags & WHERE_COLUMN_IN ) return 0;
1619: if( pIdx->bUnordered ) return 0;
1620:
1621: nTerm = pOrderBy->nExpr;
1622: assert( nTerm>0 );
1623:
1624: /* Argument pIdx must either point to a 'real' named index structure,
1625: ** or an index structure allocated on the stack by bestBtreeIndex() to
1626: ** represent the rowid index that is part of every table. */
1627: assert( pIdx->zName || (pIdx->nColumn==1 && pIdx->aiColumn[0]==-1) );
1628:
1629: /* Match terms of the ORDER BY clause against columns of
1630: ** the index.
1631: **
1632: ** Note that indices have pIdx->nColumn regular columns plus
1633: ** one additional column containing the rowid. The rowid column
1634: ** of the index is also allowed to match against the ORDER BY
1635: ** clause.
1636: */
1637: for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
1638: Expr *pExpr; /* The expression of the ORDER BY pTerm */
1639: CollSeq *pColl; /* The collating sequence of pExpr */
1640: int termSortOrder; /* Sort order for this term */
1641: int iColumn; /* The i-th column of the index. -1 for rowid */
1642: int iSortOrder; /* 1 for DESC, 0 for ASC on the i-th index term */
1643: const char *zColl; /* Name of the collating sequence for i-th index term */
1644:
1645: pExpr = pTerm->pExpr;
1646: if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
1647: /* Can not use an index sort on anything that is not a column in the
1648: ** left-most table of the FROM clause */
1649: break;
1650: }
1651: pColl = sqlite3ExprCollSeq(pParse, pExpr);
1652: if( !pColl ){
1653: pColl = db->pDfltColl;
1654: }
1655: if( pIdx->zName && i<pIdx->nColumn ){
1656: iColumn = pIdx->aiColumn[i];
1657: if( iColumn==pIdx->pTable->iPKey ){
1658: iColumn = -1;
1659: }
1660: iSortOrder = pIdx->aSortOrder[i];
1661: zColl = pIdx->azColl[i];
1662: }else{
1663: iColumn = -1;
1664: iSortOrder = 0;
1665: zColl = pColl->zName;
1666: }
1667: if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
1668: /* Term j of the ORDER BY clause does not match column i of the index */
1669: if( i<nEqCol ){
1670: /* If an index column that is constrained by == fails to match an
1671: ** ORDER BY term, that is OK. Just ignore that column of the index
1672: */
1673: continue;
1674: }else if( i==pIdx->nColumn ){
1675: /* Index column i is the rowid. All other terms match. */
1676: break;
1677: }else{
1678: /* If an index column fails to match and is not constrained by ==
1679: ** then the index cannot satisfy the ORDER BY constraint.
1680: */
1681: return 0;
1682: }
1683: }
1684: assert( pIdx->aSortOrder!=0 || iColumn==-1 );
1685: assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
1686: assert( iSortOrder==0 || iSortOrder==1 );
1687: termSortOrder = iSortOrder ^ pTerm->sortOrder;
1688: if( i>nEqCol ){
1689: if( termSortOrder!=sortOrder ){
1690: /* Indices can only be used if all ORDER BY terms past the
1691: ** equality constraints are all either DESC or ASC. */
1692: return 0;
1693: }
1694: }else{
1695: sortOrder = termSortOrder;
1696: }
1697: j++;
1698: pTerm++;
1699: if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1700: /* If the indexed column is the primary key and everything matches
1701: ** so far and none of the ORDER BY terms to the right reference other
1702: ** tables in the join, then we are assured that the index can be used
1703: ** to sort because the primary key is unique and so none of the other
1704: ** columns will make any difference
1705: */
1706: j = nTerm;
1707: }
1708: }
1709:
1710: *pbRev = sortOrder!=0;
1711: if( j>=nTerm ){
1712: /* All terms of the ORDER BY clause are covered by this index so
1713: ** this index can be used for sorting. */
1714: return 1;
1715: }
1716: if( pIdx->onError!=OE_None && i==pIdx->nColumn
1717: && (wsFlags & WHERE_COLUMN_NULL)==0
1718: && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1719: /* All terms of this index match some prefix of the ORDER BY clause
1720: ** and the index is UNIQUE and no terms on the tail of the ORDER BY
1721: ** clause reference other tables in a join. If this is all true then
1722: ** the order by clause is superfluous. Not that if the matching
1723: ** condition is IS NULL then the result is not necessarily unique
1724: ** even on a UNIQUE index, so disallow those cases. */
1725: return 1;
1726: }
1727: return 0;
1728: }
1729:
1730: /*
1731: ** Prepare a crude estimate of the logarithm of the input value.
1732: ** The results need not be exact. This is only used for estimating
1733: ** the total cost of performing operations with O(logN) or O(NlogN)
1734: ** complexity. Because N is just a guess, it is no great tragedy if
1735: ** logN is a little off.
1736: */
1737: static double estLog(double N){
1738: double logN = 1;
1739: double x = 10;
1740: while( N>x ){
1741: logN += 1;
1742: x *= 10;
1743: }
1744: return logN;
1745: }
1746:
1747: /*
1748: ** Two routines for printing the content of an sqlite3_index_info
1749: ** structure. Used for testing and debugging only. If neither
1750: ** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
1751: ** are no-ops.
1752: */
1753: #if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
1754: static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
1755: int i;
1756: if( !sqlite3WhereTrace ) return;
1757: for(i=0; i<p->nConstraint; i++){
1758: sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
1759: i,
1760: p->aConstraint[i].iColumn,
1761: p->aConstraint[i].iTermOffset,
1762: p->aConstraint[i].op,
1763: p->aConstraint[i].usable);
1764: }
1765: for(i=0; i<p->nOrderBy; i++){
1766: sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
1767: i,
1768: p->aOrderBy[i].iColumn,
1769: p->aOrderBy[i].desc);
1770: }
1771: }
1772: static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
1773: int i;
1774: if( !sqlite3WhereTrace ) return;
1775: for(i=0; i<p->nConstraint; i++){
1776: sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
1777: i,
1778: p->aConstraintUsage[i].argvIndex,
1779: p->aConstraintUsage[i].omit);
1780: }
1781: sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
1782: sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
1783: sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
1784: sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
1785: }
1786: #else
1787: #define TRACE_IDX_INPUTS(A)
1788: #define TRACE_IDX_OUTPUTS(A)
1789: #endif
1790:
1791: /*
1792: ** Required because bestIndex() is called by bestOrClauseIndex()
1793: */
1794: static void bestIndex(
1795: Parse*, WhereClause*, struct SrcList_item*,
1796: Bitmask, Bitmask, ExprList*, WhereCost*);
1797:
1798: /*
1799: ** This routine attempts to find an scanning strategy that can be used
1800: ** to optimize an 'OR' expression that is part of a WHERE clause.
1801: **
1802: ** The table associated with FROM clause term pSrc may be either a
1803: ** regular B-Tree table or a virtual table.
1804: */
1805: static void bestOrClauseIndex(
1806: Parse *pParse, /* The parsing context */
1807: WhereClause *pWC, /* The WHERE clause */
1808: struct SrcList_item *pSrc, /* The FROM clause term to search */
1809: Bitmask notReady, /* Mask of cursors not available for indexing */
1810: Bitmask notValid, /* Cursors not available for any purpose */
1811: ExprList *pOrderBy, /* The ORDER BY clause */
1812: WhereCost *pCost /* Lowest cost query plan */
1813: ){
1814: #ifndef SQLITE_OMIT_OR_OPTIMIZATION
1815: const int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
1816: const Bitmask maskSrc = getMask(pWC->pMaskSet, iCur); /* Bitmask for pSrc */
1817: WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm]; /* End of pWC->a[] */
1818: WhereTerm *pTerm; /* A single term of the WHERE clause */
1819:
1820: /* The OR-clause optimization is disallowed if the INDEXED BY or
1821: ** NOT INDEXED clauses are used or if the WHERE_AND_ONLY bit is set. */
1822: if( pSrc->notIndexed || pSrc->pIndex!=0 ){
1823: return;
1824: }
1825: if( pWC->wctrlFlags & WHERE_AND_ONLY ){
1826: return;
1827: }
1828:
1829: /* Search the WHERE clause terms for a usable WO_OR term. */
1830: for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
1831: if( pTerm->eOperator==WO_OR
1832: && ((pTerm->prereqAll & ~maskSrc) & notReady)==0
1833: && (pTerm->u.pOrInfo->indexable & maskSrc)!=0
1834: ){
1835: WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
1836: WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
1837: WhereTerm *pOrTerm;
1838: int flags = WHERE_MULTI_OR;
1839: double rTotal = 0;
1840: double nRow = 0;
1841: Bitmask used = 0;
1842:
1843: for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
1844: WhereCost sTermCost;
1845: WHERETRACE(("... Multi-index OR testing for term %d of %d....\n",
1846: (pOrTerm - pOrWC->a), (pTerm - pWC->a)
1847: ));
1848: if( pOrTerm->eOperator==WO_AND ){
1849: WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
1850: bestIndex(pParse, pAndWC, pSrc, notReady, notValid, 0, &sTermCost);
1851: }else if( pOrTerm->leftCursor==iCur ){
1852: WhereClause tempWC;
1853: tempWC.pParse = pWC->pParse;
1854: tempWC.pMaskSet = pWC->pMaskSet;
1855: tempWC.pOuter = pWC;
1856: tempWC.op = TK_AND;
1857: tempWC.a = pOrTerm;
1858: tempWC.wctrlFlags = 0;
1859: tempWC.nTerm = 1;
1860: bestIndex(pParse, &tempWC, pSrc, notReady, notValid, 0, &sTermCost);
1861: }else{
1862: continue;
1863: }
1864: rTotal += sTermCost.rCost;
1865: nRow += sTermCost.plan.nRow;
1866: used |= sTermCost.used;
1867: if( rTotal>=pCost->rCost ) break;
1868: }
1869:
1870: /* If there is an ORDER BY clause, increase the scan cost to account
1871: ** for the cost of the sort. */
1872: if( pOrderBy!=0 ){
1873: WHERETRACE(("... sorting increases OR cost %.9g to %.9g\n",
1874: rTotal, rTotal+nRow*estLog(nRow)));
1875: rTotal += nRow*estLog(nRow);
1876: }
1877:
1878: /* If the cost of scanning using this OR term for optimization is
1879: ** less than the current cost stored in pCost, replace the contents
1880: ** of pCost. */
1881: WHERETRACE(("... multi-index OR cost=%.9g nrow=%.9g\n", rTotal, nRow));
1882: if( rTotal<pCost->rCost ){
1883: pCost->rCost = rTotal;
1884: pCost->used = used;
1885: pCost->plan.nRow = nRow;
1886: pCost->plan.wsFlags = flags;
1887: pCost->plan.u.pTerm = pTerm;
1888: }
1889: }
1890: }
1891: #endif /* SQLITE_OMIT_OR_OPTIMIZATION */
1892: }
1893:
1894: #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
1895: /*
1896: ** Return TRUE if the WHERE clause term pTerm is of a form where it
1897: ** could be used with an index to access pSrc, assuming an appropriate
1898: ** index existed.
1899: */
1900: static int termCanDriveIndex(
1901: WhereTerm *pTerm, /* WHERE clause term to check */
1902: struct SrcList_item *pSrc, /* Table we are trying to access */
1903: Bitmask notReady /* Tables in outer loops of the join */
1904: ){
1905: char aff;
1906: if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
1907: if( pTerm->eOperator!=WO_EQ ) return 0;
1908: if( (pTerm->prereqRight & notReady)!=0 ) return 0;
1909: aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
1910: if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
1911: return 1;
1912: }
1913: #endif
1914:
1915: #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
1916: /*
1917: ** If the query plan for pSrc specified in pCost is a full table scan
1918: ** and indexing is allows (if there is no NOT INDEXED clause) and it
1919: ** possible to construct a transient index that would perform better
1920: ** than a full table scan even when the cost of constructing the index
1921: ** is taken into account, then alter the query plan to use the
1922: ** transient index.
1923: */
1924: static void bestAutomaticIndex(
1925: Parse *pParse, /* The parsing context */
1926: WhereClause *pWC, /* The WHERE clause */
1927: struct SrcList_item *pSrc, /* The FROM clause term to search */
1928: Bitmask notReady, /* Mask of cursors that are not available */
1929: WhereCost *pCost /* Lowest cost query plan */
1930: ){
1931: double nTableRow; /* Rows in the input table */
1932: double logN; /* log(nTableRow) */
1933: double costTempIdx; /* per-query cost of the transient index */
1934: WhereTerm *pTerm; /* A single term of the WHERE clause */
1935: WhereTerm *pWCEnd; /* End of pWC->a[] */
1936: Table *pTable; /* Table tht might be indexed */
1937:
1938: if( pParse->nQueryLoop<=(double)1 ){
1939: /* There is no point in building an automatic index for a single scan */
1940: return;
1941: }
1942: if( (pParse->db->flags & SQLITE_AutoIndex)==0 ){
1943: /* Automatic indices are disabled at run-time */
1944: return;
1945: }
1946: if( (pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)!=0 ){
1947: /* We already have some kind of index in use for this query. */
1948: return;
1949: }
1950: if( pSrc->notIndexed ){
1951: /* The NOT INDEXED clause appears in the SQL. */
1952: return;
1953: }
1954: if( pSrc->isCorrelated ){
1955: /* The source is a correlated sub-query. No point in indexing it. */
1956: return;
1957: }
1958:
1959: assert( pParse->nQueryLoop >= (double)1 );
1960: pTable = pSrc->pTab;
1961: nTableRow = pTable->nRowEst;
1962: logN = estLog(nTableRow);
1963: costTempIdx = 2*logN*(nTableRow/pParse->nQueryLoop + 1);
1964: if( costTempIdx>=pCost->rCost ){
1965: /* The cost of creating the transient table would be greater than
1966: ** doing the full table scan */
1967: return;
1968: }
1969:
1970: /* Search for any equality comparison term */
1971: pWCEnd = &pWC->a[pWC->nTerm];
1972: for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
1973: if( termCanDriveIndex(pTerm, pSrc, notReady) ){
1974: WHERETRACE(("auto-index reduces cost from %.1f to %.1f\n",
1975: pCost->rCost, costTempIdx));
1976: pCost->rCost = costTempIdx;
1977: pCost->plan.nRow = logN + 1;
1978: pCost->plan.wsFlags = WHERE_TEMP_INDEX;
1979: pCost->used = pTerm->prereqRight;
1980: break;
1981: }
1982: }
1983: }
1984: #else
1985: # define bestAutomaticIndex(A,B,C,D,E) /* no-op */
1986: #endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
1987:
1988:
1989: #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
1990: /*
1991: ** Generate code to construct the Index object for an automatic index
1992: ** and to set up the WhereLevel object pLevel so that the code generator
1993: ** makes use of the automatic index.
1994: */
1995: static void constructAutomaticIndex(
1996: Parse *pParse, /* The parsing context */
1997: WhereClause *pWC, /* The WHERE clause */
1998: struct SrcList_item *pSrc, /* The FROM clause term to get the next index */
1999: Bitmask notReady, /* Mask of cursors that are not available */
2000: WhereLevel *pLevel /* Write new index here */
2001: ){
2002: int nColumn; /* Number of columns in the constructed index */
2003: WhereTerm *pTerm; /* A single term of the WHERE clause */
2004: WhereTerm *pWCEnd; /* End of pWC->a[] */
2005: int nByte; /* Byte of memory needed for pIdx */
2006: Index *pIdx; /* Object describing the transient index */
2007: Vdbe *v; /* Prepared statement under construction */
2008: int addrInit; /* Address of the initialization bypass jump */
2009: Table *pTable; /* The table being indexed */
2010: KeyInfo *pKeyinfo; /* Key information for the index */
2011: int addrTop; /* Top of the index fill loop */
2012: int regRecord; /* Register holding an index record */
2013: int n; /* Column counter */
2014: int i; /* Loop counter */
2015: int mxBitCol; /* Maximum column in pSrc->colUsed */
2016: CollSeq *pColl; /* Collating sequence to on a column */
2017: Bitmask idxCols; /* Bitmap of columns used for indexing */
2018: Bitmask extraCols; /* Bitmap of additional columns */
2019:
2020: /* Generate code to skip over the creation and initialization of the
2021: ** transient index on 2nd and subsequent iterations of the loop. */
2022: v = pParse->pVdbe;
2023: assert( v!=0 );
2024: addrInit = sqlite3CodeOnce(pParse);
2025:
2026: /* Count the number of columns that will be added to the index
2027: ** and used to match WHERE clause constraints */
2028: nColumn = 0;
2029: pTable = pSrc->pTab;
2030: pWCEnd = &pWC->a[pWC->nTerm];
2031: idxCols = 0;
2032: for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
2033: if( termCanDriveIndex(pTerm, pSrc, notReady) ){
2034: int iCol = pTerm->u.leftColumn;
2035: Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
2036: testcase( iCol==BMS );
2037: testcase( iCol==BMS-1 );
2038: if( (idxCols & cMask)==0 ){
2039: nColumn++;
2040: idxCols |= cMask;
2041: }
2042: }
2043: }
2044: assert( nColumn>0 );
2045: pLevel->plan.nEq = nColumn;
2046:
2047: /* Count the number of additional columns needed to create a
2048: ** covering index. A "covering index" is an index that contains all
2049: ** columns that are needed by the query. With a covering index, the
2050: ** original table never needs to be accessed. Automatic indices must
2051: ** be a covering index because the index will not be updated if the
2052: ** original table changes and the index and table cannot both be used
2053: ** if they go out of sync.
2054: */
2055: extraCols = pSrc->colUsed & (~idxCols | (((Bitmask)1)<<(BMS-1)));
2056: mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
2057: testcase( pTable->nCol==BMS-1 );
2058: testcase( pTable->nCol==BMS-2 );
2059: for(i=0; i<mxBitCol; i++){
2060: if( extraCols & (((Bitmask)1)<<i) ) nColumn++;
2061: }
2062: if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
2063: nColumn += pTable->nCol - BMS + 1;
2064: }
2065: pLevel->plan.wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WO_EQ;
2066:
2067: /* Construct the Index object to describe this index */
2068: nByte = sizeof(Index);
2069: nByte += nColumn*sizeof(int); /* Index.aiColumn */
2070: nByte += nColumn*sizeof(char*); /* Index.azColl */
2071: nByte += nColumn; /* Index.aSortOrder */
2072: pIdx = sqlite3DbMallocZero(pParse->db, nByte);
2073: if( pIdx==0 ) return;
2074: pLevel->plan.u.pIdx = pIdx;
2075: pIdx->azColl = (char**)&pIdx[1];
2076: pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
2077: pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
2078: pIdx->zName = "auto-index";
2079: pIdx->nColumn = nColumn;
2080: pIdx->pTable = pTable;
2081: n = 0;
2082: idxCols = 0;
2083: for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
2084: if( termCanDriveIndex(pTerm, pSrc, notReady) ){
2085: int iCol = pTerm->u.leftColumn;
2086: Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
2087: if( (idxCols & cMask)==0 ){
2088: Expr *pX = pTerm->pExpr;
2089: idxCols |= cMask;
2090: pIdx->aiColumn[n] = pTerm->u.leftColumn;
2091: pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
2092: pIdx->azColl[n] = ALWAYS(pColl) ? pColl->zName : "BINARY";
2093: n++;
2094: }
2095: }
2096: }
2097: assert( (u32)n==pLevel->plan.nEq );
2098:
2099: /* Add additional columns needed to make the automatic index into
2100: ** a covering index */
2101: for(i=0; i<mxBitCol; i++){
2102: if( extraCols & (((Bitmask)1)<<i) ){
2103: pIdx->aiColumn[n] = i;
2104: pIdx->azColl[n] = "BINARY";
2105: n++;
2106: }
2107: }
2108: if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
2109: for(i=BMS-1; i<pTable->nCol; i++){
2110: pIdx->aiColumn[n] = i;
2111: pIdx->azColl[n] = "BINARY";
2112: n++;
2113: }
2114: }
2115: assert( n==nColumn );
2116:
2117: /* Create the automatic index */
2118: pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
2119: assert( pLevel->iIdxCur>=0 );
2120: sqlite3VdbeAddOp4(v, OP_OpenAutoindex, pLevel->iIdxCur, nColumn+1, 0,
2121: (char*)pKeyinfo, P4_KEYINFO_HANDOFF);
2122: VdbeComment((v, "for %s", pTable->zName));
2123:
2124: /* Fill the automatic index with content */
2125: addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur);
2126: regRecord = sqlite3GetTempReg(pParse);
2127: sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 1);
2128: sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
2129: sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
2130: sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1);
2131: sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
2132: sqlite3VdbeJumpHere(v, addrTop);
2133: sqlite3ReleaseTempReg(pParse, regRecord);
2134:
2135: /* Jump here when skipping the initialization */
2136: sqlite3VdbeJumpHere(v, addrInit);
2137: }
2138: #endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
2139:
2140: #ifndef SQLITE_OMIT_VIRTUALTABLE
2141: /*
2142: ** Allocate and populate an sqlite3_index_info structure. It is the
2143: ** responsibility of the caller to eventually release the structure
2144: ** by passing the pointer returned by this function to sqlite3_free().
2145: */
2146: static sqlite3_index_info *allocateIndexInfo(
2147: Parse *pParse,
2148: WhereClause *pWC,
2149: struct SrcList_item *pSrc,
2150: ExprList *pOrderBy
2151: ){
2152: int i, j;
2153: int nTerm;
2154: struct sqlite3_index_constraint *pIdxCons;
2155: struct sqlite3_index_orderby *pIdxOrderBy;
2156: struct sqlite3_index_constraint_usage *pUsage;
2157: WhereTerm *pTerm;
2158: int nOrderBy;
2159: sqlite3_index_info *pIdxInfo;
2160:
2161: WHERETRACE(("Recomputing index info for %s...\n", pSrc->pTab->zName));
2162:
2163: /* Count the number of possible WHERE clause constraints referring
2164: ** to this virtual table */
2165: for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
2166: if( pTerm->leftCursor != pSrc->iCursor ) continue;
2167: assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
2168: testcase( pTerm->eOperator==WO_IN );
2169: testcase( pTerm->eOperator==WO_ISNULL );
2170: if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
2171: if( pTerm->wtFlags & TERM_VNULL ) continue;
2172: nTerm++;
2173: }
2174:
2175: /* If the ORDER BY clause contains only columns in the current
2176: ** virtual table then allocate space for the aOrderBy part of
2177: ** the sqlite3_index_info structure.
2178: */
2179: nOrderBy = 0;
2180: if( pOrderBy ){
2181: for(i=0; i<pOrderBy->nExpr; i++){
2182: Expr *pExpr = pOrderBy->a[i].pExpr;
2183: if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
2184: }
2185: if( i==pOrderBy->nExpr ){
2186: nOrderBy = pOrderBy->nExpr;
2187: }
2188: }
2189:
2190: /* Allocate the sqlite3_index_info structure
2191: */
2192: pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
2193: + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
2194: + sizeof(*pIdxOrderBy)*nOrderBy );
2195: if( pIdxInfo==0 ){
2196: sqlite3ErrorMsg(pParse, "out of memory");
2197: /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
2198: return 0;
2199: }
2200:
2201: /* Initialize the structure. The sqlite3_index_info structure contains
2202: ** many fields that are declared "const" to prevent xBestIndex from
2203: ** changing them. We have to do some funky casting in order to
2204: ** initialize those fields.
2205: */
2206: pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
2207: pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
2208: pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
2209: *(int*)&pIdxInfo->nConstraint = nTerm;
2210: *(int*)&pIdxInfo->nOrderBy = nOrderBy;
2211: *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
2212: *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
2213: *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
2214: pUsage;
2215:
2216: for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
2217: if( pTerm->leftCursor != pSrc->iCursor ) continue;
2218: assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
2219: testcase( pTerm->eOperator==WO_IN );
2220: testcase( pTerm->eOperator==WO_ISNULL );
2221: if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
2222: if( pTerm->wtFlags & TERM_VNULL ) continue;
2223: pIdxCons[j].iColumn = pTerm->u.leftColumn;
2224: pIdxCons[j].iTermOffset = i;
2225: pIdxCons[j].op = (u8)pTerm->eOperator;
2226: /* The direct assignment in the previous line is possible only because
2227: ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
2228: ** following asserts verify this fact. */
2229: assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
2230: assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
2231: assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
2232: assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
2233: assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
2234: assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
2235: assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
2236: j++;
2237: }
2238: for(i=0; i<nOrderBy; i++){
2239: Expr *pExpr = pOrderBy->a[i].pExpr;
2240: pIdxOrderBy[i].iColumn = pExpr->iColumn;
2241: pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
2242: }
2243:
2244: return pIdxInfo;
2245: }
2246:
2247: /*
2248: ** The table object reference passed as the second argument to this function
2249: ** must represent a virtual table. This function invokes the xBestIndex()
2250: ** method of the virtual table with the sqlite3_index_info pointer passed
2251: ** as the argument.
2252: **
2253: ** If an error occurs, pParse is populated with an error message and a
2254: ** non-zero value is returned. Otherwise, 0 is returned and the output
2255: ** part of the sqlite3_index_info structure is left populated.
2256: **
2257: ** Whether or not an error is returned, it is the responsibility of the
2258: ** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
2259: ** that this is required.
2260: */
2261: static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
2262: sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
2263: int i;
2264: int rc;
2265:
2266: WHERETRACE(("xBestIndex for %s\n", pTab->zName));
2267: TRACE_IDX_INPUTS(p);
2268: rc = pVtab->pModule->xBestIndex(pVtab, p);
2269: TRACE_IDX_OUTPUTS(p);
2270:
2271: if( rc!=SQLITE_OK ){
2272: if( rc==SQLITE_NOMEM ){
2273: pParse->db->mallocFailed = 1;
2274: }else if( !pVtab->zErrMsg ){
2275: sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
2276: }else{
2277: sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
2278: }
2279: }
2280: sqlite3_free(pVtab->zErrMsg);
2281: pVtab->zErrMsg = 0;
2282:
2283: for(i=0; i<p->nConstraint; i++){
2284: if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
2285: sqlite3ErrorMsg(pParse,
2286: "table %s: xBestIndex returned an invalid plan", pTab->zName);
2287: }
2288: }
2289:
2290: return pParse->nErr;
2291: }
2292:
2293:
2294: /*
2295: ** Compute the best index for a virtual table.
2296: **
2297: ** The best index is computed by the xBestIndex method of the virtual
2298: ** table module. This routine is really just a wrapper that sets up
2299: ** the sqlite3_index_info structure that is used to communicate with
2300: ** xBestIndex.
2301: **
2302: ** In a join, this routine might be called multiple times for the
2303: ** same virtual table. The sqlite3_index_info structure is created
2304: ** and initialized on the first invocation and reused on all subsequent
2305: ** invocations. The sqlite3_index_info structure is also used when
2306: ** code is generated to access the virtual table. The whereInfoDelete()
2307: ** routine takes care of freeing the sqlite3_index_info structure after
2308: ** everybody has finished with it.
2309: */
2310: static void bestVirtualIndex(
2311: Parse *pParse, /* The parsing context */
2312: WhereClause *pWC, /* The WHERE clause */
2313: struct SrcList_item *pSrc, /* The FROM clause term to search */
2314: Bitmask notReady, /* Mask of cursors not available for index */
2315: Bitmask notValid, /* Cursors not valid for any purpose */
2316: ExprList *pOrderBy, /* The order by clause */
2317: WhereCost *pCost, /* Lowest cost query plan */
2318: sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
2319: ){
2320: Table *pTab = pSrc->pTab;
2321: sqlite3_index_info *pIdxInfo;
2322: struct sqlite3_index_constraint *pIdxCons;
2323: struct sqlite3_index_constraint_usage *pUsage;
2324: WhereTerm *pTerm;
2325: int i, j;
2326: int nOrderBy;
2327: double rCost;
2328:
2329: /* Make sure wsFlags is initialized to some sane value. Otherwise, if the
2330: ** malloc in allocateIndexInfo() fails and this function returns leaving
2331: ** wsFlags in an uninitialized state, the caller may behave unpredictably.
2332: */
2333: memset(pCost, 0, sizeof(*pCost));
2334: pCost->plan.wsFlags = WHERE_VIRTUALTABLE;
2335:
2336: /* If the sqlite3_index_info structure has not been previously
2337: ** allocated and initialized, then allocate and initialize it now.
2338: */
2339: pIdxInfo = *ppIdxInfo;
2340: if( pIdxInfo==0 ){
2341: *ppIdxInfo = pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pOrderBy);
2342: }
2343: if( pIdxInfo==0 ){
2344: return;
2345: }
2346:
2347: /* At this point, the sqlite3_index_info structure that pIdxInfo points
2348: ** to will have been initialized, either during the current invocation or
2349: ** during some prior invocation. Now we just have to customize the
2350: ** details of pIdxInfo for the current invocation and pass it to
2351: ** xBestIndex.
2352: */
2353:
2354: /* The module name must be defined. Also, by this point there must
2355: ** be a pointer to an sqlite3_vtab structure. Otherwise
2356: ** sqlite3ViewGetColumnNames() would have picked up the error.
2357: */
2358: assert( pTab->azModuleArg && pTab->azModuleArg[0] );
2359: assert( sqlite3GetVTable(pParse->db, pTab) );
2360:
2361: /* Set the aConstraint[].usable fields and initialize all
2362: ** output variables to zero.
2363: **
2364: ** aConstraint[].usable is true for constraints where the right-hand
2365: ** side contains only references to tables to the left of the current
2366: ** table. In other words, if the constraint is of the form:
2367: **
2368: ** column = expr
2369: **
2370: ** and we are evaluating a join, then the constraint on column is
2371: ** only valid if all tables referenced in expr occur to the left
2372: ** of the table containing column.
2373: **
2374: ** The aConstraints[] array contains entries for all constraints
2375: ** on the current table. That way we only have to compute it once
2376: ** even though we might try to pick the best index multiple times.
2377: ** For each attempt at picking an index, the order of tables in the
2378: ** join might be different so we have to recompute the usable flag
2379: ** each time.
2380: */
2381: pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
2382: pUsage = pIdxInfo->aConstraintUsage;
2383: for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
2384: j = pIdxCons->iTermOffset;
2385: pTerm = &pWC->a[j];
2386: pIdxCons->usable = (pTerm->prereqRight¬Ready) ? 0 : 1;
2387: }
2388: memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
2389: if( pIdxInfo->needToFreeIdxStr ){
2390: sqlite3_free(pIdxInfo->idxStr);
2391: }
2392: pIdxInfo->idxStr = 0;
2393: pIdxInfo->idxNum = 0;
2394: pIdxInfo->needToFreeIdxStr = 0;
2395: pIdxInfo->orderByConsumed = 0;
2396: /* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
2397: pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
2398: nOrderBy = pIdxInfo->nOrderBy;
2399: if( !pOrderBy ){
2400: pIdxInfo->nOrderBy = 0;
2401: }
2402:
2403: if( vtabBestIndex(pParse, pTab, pIdxInfo) ){
2404: return;
2405: }
2406:
2407: pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
2408: for(i=0; i<pIdxInfo->nConstraint; i++){
2409: if( pUsage[i].argvIndex>0 ){
2410: pCost->used |= pWC->a[pIdxCons[i].iTermOffset].prereqRight;
2411: }
2412: }
2413:
2414: /* If there is an ORDER BY clause, and the selected virtual table index
2415: ** does not satisfy it, increase the cost of the scan accordingly. This
2416: ** matches the processing for non-virtual tables in bestBtreeIndex().
2417: */
2418: rCost = pIdxInfo->estimatedCost;
2419: if( pOrderBy && pIdxInfo->orderByConsumed==0 ){
2420: rCost += estLog(rCost)*rCost;
2421: }
2422:
2423: /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
2424: ** inital value of lowestCost in this loop. If it is, then the
2425: ** (cost<lowestCost) test below will never be true.
2426: **
2427: ** Use "(double)2" instead of "2.0" in case OMIT_FLOATING_POINT
2428: ** is defined.
2429: */
2430: if( (SQLITE_BIG_DBL/((double)2))<rCost ){
2431: pCost->rCost = (SQLITE_BIG_DBL/((double)2));
2432: }else{
2433: pCost->rCost = rCost;
2434: }
2435: pCost->plan.u.pVtabIdx = pIdxInfo;
2436: if( pIdxInfo->orderByConsumed ){
2437: pCost->plan.wsFlags |= WHERE_ORDERBY;
2438: }
2439: pCost->plan.nEq = 0;
2440: pIdxInfo->nOrderBy = nOrderBy;
2441:
2442: /* Try to find a more efficient access pattern by using multiple indexes
2443: ** to optimize an OR expression within the WHERE clause.
2444: */
2445: bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
2446: }
2447: #endif /* SQLITE_OMIT_VIRTUALTABLE */
2448:
2449: #ifdef SQLITE_ENABLE_STAT3
2450: /*
2451: ** Estimate the location of a particular key among all keys in an
2452: ** index. Store the results in aStat as follows:
2453: **
2454: ** aStat[0] Est. number of rows less than pVal
2455: ** aStat[1] Est. number of rows equal to pVal
2456: **
2457: ** Return SQLITE_OK on success.
2458: */
2459: static int whereKeyStats(
2460: Parse *pParse, /* Database connection */
2461: Index *pIdx, /* Index to consider domain of */
2462: sqlite3_value *pVal, /* Value to consider */
2463: int roundUp, /* Round up if true. Round down if false */
2464: tRowcnt *aStat /* OUT: stats written here */
2465: ){
2466: tRowcnt n;
2467: IndexSample *aSample;
2468: int i, eType;
2469: int isEq = 0;
2470: i64 v;
2471: double r, rS;
2472:
2473: assert( roundUp==0 || roundUp==1 );
2474: assert( pIdx->nSample>0 );
2475: if( pVal==0 ) return SQLITE_ERROR;
2476: n = pIdx->aiRowEst[0];
2477: aSample = pIdx->aSample;
2478: eType = sqlite3_value_type(pVal);
2479:
2480: if( eType==SQLITE_INTEGER ){
2481: v = sqlite3_value_int64(pVal);
2482: r = (i64)v;
2483: for(i=0; i<pIdx->nSample; i++){
2484: if( aSample[i].eType==SQLITE_NULL ) continue;
2485: if( aSample[i].eType>=SQLITE_TEXT ) break;
2486: if( aSample[i].eType==SQLITE_INTEGER ){
2487: if( aSample[i].u.i>=v ){
2488: isEq = aSample[i].u.i==v;
2489: break;
2490: }
2491: }else{
2492: assert( aSample[i].eType==SQLITE_FLOAT );
2493: if( aSample[i].u.r>=r ){
2494: isEq = aSample[i].u.r==r;
2495: break;
2496: }
2497: }
2498: }
2499: }else if( eType==SQLITE_FLOAT ){
2500: r = sqlite3_value_double(pVal);
2501: for(i=0; i<pIdx->nSample; i++){
2502: if( aSample[i].eType==SQLITE_NULL ) continue;
2503: if( aSample[i].eType>=SQLITE_TEXT ) break;
2504: if( aSample[i].eType==SQLITE_FLOAT ){
2505: rS = aSample[i].u.r;
2506: }else{
2507: rS = aSample[i].u.i;
2508: }
2509: if( rS>=r ){
2510: isEq = rS==r;
2511: break;
2512: }
2513: }
2514: }else if( eType==SQLITE_NULL ){
2515: i = 0;
2516: if( aSample[0].eType==SQLITE_NULL ) isEq = 1;
2517: }else{
2518: assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
2519: for(i=0; i<pIdx->nSample; i++){
2520: if( aSample[i].eType==SQLITE_TEXT || aSample[i].eType==SQLITE_BLOB ){
2521: break;
2522: }
2523: }
2524: if( i<pIdx->nSample ){
2525: sqlite3 *db = pParse->db;
2526: CollSeq *pColl;
2527: const u8 *z;
2528: if( eType==SQLITE_BLOB ){
2529: z = (const u8 *)sqlite3_value_blob(pVal);
2530: pColl = db->pDfltColl;
2531: assert( pColl->enc==SQLITE_UTF8 );
2532: }else{
2533: pColl = sqlite3GetCollSeq(db, SQLITE_UTF8, 0, *pIdx->azColl);
2534: if( pColl==0 ){
2535: sqlite3ErrorMsg(pParse, "no such collation sequence: %s",
2536: *pIdx->azColl);
2537: return SQLITE_ERROR;
2538: }
2539: z = (const u8 *)sqlite3ValueText(pVal, pColl->enc);
2540: if( !z ){
2541: return SQLITE_NOMEM;
2542: }
2543: assert( z && pColl && pColl->xCmp );
2544: }
2545: n = sqlite3ValueBytes(pVal, pColl->enc);
2546:
2547: for(; i<pIdx->nSample; i++){
2548: int c;
2549: int eSampletype = aSample[i].eType;
2550: if( eSampletype<eType ) continue;
2551: if( eSampletype!=eType ) break;
2552: #ifndef SQLITE_OMIT_UTF16
2553: if( pColl->enc!=SQLITE_UTF8 ){
2554: int nSample;
2555: char *zSample = sqlite3Utf8to16(
2556: db, pColl->enc, aSample[i].u.z, aSample[i].nByte, &nSample
2557: );
2558: if( !zSample ){
2559: assert( db->mallocFailed );
2560: return SQLITE_NOMEM;
2561: }
2562: c = pColl->xCmp(pColl->pUser, nSample, zSample, n, z);
2563: sqlite3DbFree(db, zSample);
2564: }else
2565: #endif
2566: {
2567: c = pColl->xCmp(pColl->pUser, aSample[i].nByte, aSample[i].u.z, n, z);
2568: }
2569: if( c>=0 ){
2570: if( c==0 ) isEq = 1;
2571: break;
2572: }
2573: }
2574: }
2575: }
2576:
2577: /* At this point, aSample[i] is the first sample that is greater than
2578: ** or equal to pVal. Or if i==pIdx->nSample, then all samples are less
2579: ** than pVal. If aSample[i]==pVal, then isEq==1.
2580: */
2581: if( isEq ){
2582: assert( i<pIdx->nSample );
2583: aStat[0] = aSample[i].nLt;
2584: aStat[1] = aSample[i].nEq;
2585: }else{
2586: tRowcnt iLower, iUpper, iGap;
2587: if( i==0 ){
2588: iLower = 0;
2589: iUpper = aSample[0].nLt;
2590: }else{
2591: iUpper = i>=pIdx->nSample ? n : aSample[i].nLt;
2592: iLower = aSample[i-1].nEq + aSample[i-1].nLt;
2593: }
2594: aStat[1] = pIdx->avgEq;
2595: if( iLower>=iUpper ){
2596: iGap = 0;
2597: }else{
2598: iGap = iUpper - iLower;
2599: }
2600: if( roundUp ){
2601: iGap = (iGap*2)/3;
2602: }else{
2603: iGap = iGap/3;
2604: }
2605: aStat[0] = iLower + iGap;
2606: }
2607: return SQLITE_OK;
2608: }
2609: #endif /* SQLITE_ENABLE_STAT3 */
2610:
2611: /*
2612: ** If expression pExpr represents a literal value, set *pp to point to
2613: ** an sqlite3_value structure containing the same value, with affinity
2614: ** aff applied to it, before returning. It is the responsibility of the
2615: ** caller to eventually release this structure by passing it to
2616: ** sqlite3ValueFree().
2617: **
2618: ** If the current parse is a recompile (sqlite3Reprepare()) and pExpr
2619: ** is an SQL variable that currently has a non-NULL value bound to it,
2620: ** create an sqlite3_value structure containing this value, again with
2621: ** affinity aff applied to it, instead.
2622: **
2623: ** If neither of the above apply, set *pp to NULL.
2624: **
2625: ** If an error occurs, return an error code. Otherwise, SQLITE_OK.
2626: */
2627: #ifdef SQLITE_ENABLE_STAT3
2628: static int valueFromExpr(
2629: Parse *pParse,
2630: Expr *pExpr,
2631: u8 aff,
2632: sqlite3_value **pp
2633: ){
2634: if( pExpr->op==TK_VARIABLE
2635: || (pExpr->op==TK_REGISTER && pExpr->op2==TK_VARIABLE)
2636: ){
2637: int iVar = pExpr->iColumn;
2638: sqlite3VdbeSetVarmask(pParse->pVdbe, iVar);
2639: *pp = sqlite3VdbeGetValue(pParse->pReprepare, iVar, aff);
2640: return SQLITE_OK;
2641: }
2642: return sqlite3ValueFromExpr(pParse->db, pExpr, SQLITE_UTF8, aff, pp);
2643: }
2644: #endif
2645:
2646: /*
2647: ** This function is used to estimate the number of rows that will be visited
2648: ** by scanning an index for a range of values. The range may have an upper
2649: ** bound, a lower bound, or both. The WHERE clause terms that set the upper
2650: ** and lower bounds are represented by pLower and pUpper respectively. For
2651: ** example, assuming that index p is on t1(a):
2652: **
2653: ** ... FROM t1 WHERE a > ? AND a < ? ...
2654: ** |_____| |_____|
2655: ** | |
2656: ** pLower pUpper
2657: **
2658: ** If either of the upper or lower bound is not present, then NULL is passed in
2659: ** place of the corresponding WhereTerm.
2660: **
2661: ** The nEq parameter is passed the index of the index column subject to the
2662: ** range constraint. Or, equivalently, the number of equality constraints
2663: ** optimized by the proposed index scan. For example, assuming index p is
2664: ** on t1(a, b), and the SQL query is:
2665: **
2666: ** ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
2667: **
2668: ** then nEq should be passed the value 1 (as the range restricted column,
2669: ** b, is the second left-most column of the index). Or, if the query is:
2670: **
2671: ** ... FROM t1 WHERE a > ? AND a < ? ...
2672: **
2673: ** then nEq should be passed 0.
2674: **
2675: ** The returned value is an integer divisor to reduce the estimated
2676: ** search space. A return value of 1 means that range constraints are
2677: ** no help at all. A return value of 2 means range constraints are
2678: ** expected to reduce the search space by half. And so forth...
2679: **
2680: ** In the absence of sqlite_stat3 ANALYZE data, each range inequality
2681: ** reduces the search space by a factor of 4. Hence a single constraint (x>?)
2682: ** results in a return of 4 and a range constraint (x>? AND x<?) results
2683: ** in a return of 16.
2684: */
2685: static int whereRangeScanEst(
2686: Parse *pParse, /* Parsing & code generating context */
2687: Index *p, /* The index containing the range-compared column; "x" */
2688: int nEq, /* index into p->aCol[] of the range-compared column */
2689: WhereTerm *pLower, /* Lower bound on the range. ex: "x>123" Might be NULL */
2690: WhereTerm *pUpper, /* Upper bound on the range. ex: "x<455" Might be NULL */
2691: double *pRangeDiv /* OUT: Reduce search space by this divisor */
2692: ){
2693: int rc = SQLITE_OK;
2694:
2695: #ifdef SQLITE_ENABLE_STAT3
2696:
2697: if( nEq==0 && p->nSample ){
2698: sqlite3_value *pRangeVal;
2699: tRowcnt iLower = 0;
2700: tRowcnt iUpper = p->aiRowEst[0];
2701: tRowcnt a[2];
2702: u8 aff = p->pTable->aCol[p->aiColumn[0]].affinity;
2703:
2704: if( pLower ){
2705: Expr *pExpr = pLower->pExpr->pRight;
2706: rc = valueFromExpr(pParse, pExpr, aff, &pRangeVal);
2707: assert( pLower->eOperator==WO_GT || pLower->eOperator==WO_GE );
2708: if( rc==SQLITE_OK
2709: && whereKeyStats(pParse, p, pRangeVal, 0, a)==SQLITE_OK
2710: ){
2711: iLower = a[0];
2712: if( pLower->eOperator==WO_GT ) iLower += a[1];
2713: }
2714: sqlite3ValueFree(pRangeVal);
2715: }
2716: if( rc==SQLITE_OK && pUpper ){
2717: Expr *pExpr = pUpper->pExpr->pRight;
2718: rc = valueFromExpr(pParse, pExpr, aff, &pRangeVal);
2719: assert( pUpper->eOperator==WO_LT || pUpper->eOperator==WO_LE );
2720: if( rc==SQLITE_OK
2721: && whereKeyStats(pParse, p, pRangeVal, 1, a)==SQLITE_OK
2722: ){
2723: iUpper = a[0];
2724: if( pUpper->eOperator==WO_LE ) iUpper += a[1];
2725: }
2726: sqlite3ValueFree(pRangeVal);
2727: }
2728: if( rc==SQLITE_OK ){
2729: if( iUpper<=iLower ){
2730: *pRangeDiv = (double)p->aiRowEst[0];
2731: }else{
2732: *pRangeDiv = (double)p->aiRowEst[0]/(double)(iUpper - iLower);
2733: }
2734: WHERETRACE(("range scan regions: %u..%u div=%g\n",
2735: (u32)iLower, (u32)iUpper, *pRangeDiv));
2736: return SQLITE_OK;
2737: }
2738: }
2739: #else
2740: UNUSED_PARAMETER(pParse);
2741: UNUSED_PARAMETER(p);
2742: UNUSED_PARAMETER(nEq);
2743: #endif
2744: assert( pLower || pUpper );
2745: *pRangeDiv = (double)1;
2746: if( pLower && (pLower->wtFlags & TERM_VNULL)==0 ) *pRangeDiv *= (double)4;
2747: if( pUpper ) *pRangeDiv *= (double)4;
2748: return rc;
2749: }
2750:
2751: #ifdef SQLITE_ENABLE_STAT3
2752: /*
2753: ** Estimate the number of rows that will be returned based on
2754: ** an equality constraint x=VALUE and where that VALUE occurs in
2755: ** the histogram data. This only works when x is the left-most
2756: ** column of an index and sqlite_stat3 histogram data is available
2757: ** for that index. When pExpr==NULL that means the constraint is
2758: ** "x IS NULL" instead of "x=VALUE".
2759: **
2760: ** Write the estimated row count into *pnRow and return SQLITE_OK.
2761: ** If unable to make an estimate, leave *pnRow unchanged and return
2762: ** non-zero.
2763: **
2764: ** This routine can fail if it is unable to load a collating sequence
2765: ** required for string comparison, or if unable to allocate memory
2766: ** for a UTF conversion required for comparison. The error is stored
2767: ** in the pParse structure.
2768: */
2769: static int whereEqualScanEst(
2770: Parse *pParse, /* Parsing & code generating context */
2771: Index *p, /* The index whose left-most column is pTerm */
2772: Expr *pExpr, /* Expression for VALUE in the x=VALUE constraint */
2773: double *pnRow /* Write the revised row estimate here */
2774: ){
2775: sqlite3_value *pRhs = 0; /* VALUE on right-hand side of pTerm */
2776: u8 aff; /* Column affinity */
2777: int rc; /* Subfunction return code */
2778: tRowcnt a[2]; /* Statistics */
2779:
2780: assert( p->aSample!=0 );
2781: assert( p->nSample>0 );
2782: aff = p->pTable->aCol[p->aiColumn[0]].affinity;
2783: if( pExpr ){
2784: rc = valueFromExpr(pParse, pExpr, aff, &pRhs);
2785: if( rc ) goto whereEqualScanEst_cancel;
2786: }else{
2787: pRhs = sqlite3ValueNew(pParse->db);
2788: }
2789: if( pRhs==0 ) return SQLITE_NOTFOUND;
2790: rc = whereKeyStats(pParse, p, pRhs, 0, a);
2791: if( rc==SQLITE_OK ){
2792: WHERETRACE(("equality scan regions: %d\n", (int)a[1]));
2793: *pnRow = a[1];
2794: }
2795: whereEqualScanEst_cancel:
2796: sqlite3ValueFree(pRhs);
2797: return rc;
2798: }
2799: #endif /* defined(SQLITE_ENABLE_STAT3) */
2800:
2801: #ifdef SQLITE_ENABLE_STAT3
2802: /*
2803: ** Estimate the number of rows that will be returned based on
2804: ** an IN constraint where the right-hand side of the IN operator
2805: ** is a list of values. Example:
2806: **
2807: ** WHERE x IN (1,2,3,4)
2808: **
2809: ** Write the estimated row count into *pnRow and return SQLITE_OK.
2810: ** If unable to make an estimate, leave *pnRow unchanged and return
2811: ** non-zero.
2812: **
2813: ** This routine can fail if it is unable to load a collating sequence
2814: ** required for string comparison, or if unable to allocate memory
2815: ** for a UTF conversion required for comparison. The error is stored
2816: ** in the pParse structure.
2817: */
2818: static int whereInScanEst(
2819: Parse *pParse, /* Parsing & code generating context */
2820: Index *p, /* The index whose left-most column is pTerm */
2821: ExprList *pList, /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
2822: double *pnRow /* Write the revised row estimate here */
2823: ){
2824: int rc = SQLITE_OK; /* Subfunction return code */
2825: double nEst; /* Number of rows for a single term */
2826: double nRowEst = (double)0; /* New estimate of the number of rows */
2827: int i; /* Loop counter */
2828:
2829: assert( p->aSample!=0 );
2830: for(i=0; rc==SQLITE_OK && i<pList->nExpr; i++){
2831: nEst = p->aiRowEst[0];
2832: rc = whereEqualScanEst(pParse, p, pList->a[i].pExpr, &nEst);
2833: nRowEst += nEst;
2834: }
2835: if( rc==SQLITE_OK ){
2836: if( nRowEst > p->aiRowEst[0] ) nRowEst = p->aiRowEst[0];
2837: *pnRow = nRowEst;
2838: WHERETRACE(("IN row estimate: est=%g\n", nRowEst));
2839: }
2840: return rc;
2841: }
2842: #endif /* defined(SQLITE_ENABLE_STAT3) */
2843:
2844:
2845: /*
2846: ** Find the best query plan for accessing a particular table. Write the
2847: ** best query plan and its cost into the WhereCost object supplied as the
2848: ** last parameter.
2849: **
2850: ** The lowest cost plan wins. The cost is an estimate of the amount of
2851: ** CPU and disk I/O needed to process the requested result.
2852: ** Factors that influence cost include:
2853: **
2854: ** * The estimated number of rows that will be retrieved. (The
2855: ** fewer the better.)
2856: **
2857: ** * Whether or not sorting must occur.
2858: **
2859: ** * Whether or not there must be separate lookups in the
2860: ** index and in the main table.
2861: **
2862: ** If there was an INDEXED BY clause (pSrc->pIndex) attached to the table in
2863: ** the SQL statement, then this function only considers plans using the
2864: ** named index. If no such plan is found, then the returned cost is
2865: ** SQLITE_BIG_DBL. If a plan is found that uses the named index,
2866: ** then the cost is calculated in the usual way.
2867: **
2868: ** If a NOT INDEXED clause (pSrc->notIndexed!=0) was attached to the table
2869: ** in the SELECT statement, then no indexes are considered. However, the
2870: ** selected plan may still take advantage of the built-in rowid primary key
2871: ** index.
2872: */
2873: static void bestBtreeIndex(
2874: Parse *pParse, /* The parsing context */
2875: WhereClause *pWC, /* The WHERE clause */
2876: struct SrcList_item *pSrc, /* The FROM clause term to search */
2877: Bitmask notReady, /* Mask of cursors not available for indexing */
2878: Bitmask notValid, /* Cursors not available for any purpose */
2879: ExprList *pOrderBy, /* The ORDER BY clause */
2880: ExprList *pDistinct, /* The select-list if query is DISTINCT */
2881: WhereCost *pCost /* Lowest cost query plan */
2882: ){
2883: int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
2884: Index *pProbe; /* An index we are evaluating */
2885: Index *pIdx; /* Copy of pProbe, or zero for IPK index */
2886: int eqTermMask; /* Current mask of valid equality operators */
2887: int idxEqTermMask; /* Index mask of valid equality operators */
2888: Index sPk; /* A fake index object for the primary key */
2889: tRowcnt aiRowEstPk[2]; /* The aiRowEst[] value for the sPk index */
2890: int aiColumnPk = -1; /* The aColumn[] value for the sPk index */
2891: int wsFlagMask; /* Allowed flags in pCost->plan.wsFlag */
2892:
2893: /* Initialize the cost to a worst-case value */
2894: memset(pCost, 0, sizeof(*pCost));
2895: pCost->rCost = SQLITE_BIG_DBL;
2896:
2897: /* If the pSrc table is the right table of a LEFT JOIN then we may not
2898: ** use an index to satisfy IS NULL constraints on that table. This is
2899: ** because columns might end up being NULL if the table does not match -
2900: ** a circumstance which the index cannot help us discover. Ticket #2177.
2901: */
2902: if( pSrc->jointype & JT_LEFT ){
2903: idxEqTermMask = WO_EQ|WO_IN;
2904: }else{
2905: idxEqTermMask = WO_EQ|WO_IN|WO_ISNULL;
2906: }
2907:
2908: if( pSrc->pIndex ){
2909: /* An INDEXED BY clause specifies a particular index to use */
2910: pIdx = pProbe = pSrc->pIndex;
2911: wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
2912: eqTermMask = idxEqTermMask;
2913: }else{
2914: /* There is no INDEXED BY clause. Create a fake Index object in local
2915: ** variable sPk to represent the rowid primary key index. Make this
2916: ** fake index the first in a chain of Index objects with all of the real
2917: ** indices to follow */
2918: Index *pFirst; /* First of real indices on the table */
2919: memset(&sPk, 0, sizeof(Index));
2920: sPk.nColumn = 1;
2921: sPk.aiColumn = &aiColumnPk;
2922: sPk.aiRowEst = aiRowEstPk;
2923: sPk.onError = OE_Replace;
2924: sPk.pTable = pSrc->pTab;
2925: aiRowEstPk[0] = pSrc->pTab->nRowEst;
2926: aiRowEstPk[1] = 1;
2927: pFirst = pSrc->pTab->pIndex;
2928: if( pSrc->notIndexed==0 ){
2929: /* The real indices of the table are only considered if the
2930: ** NOT INDEXED qualifier is omitted from the FROM clause */
2931: sPk.pNext = pFirst;
2932: }
2933: pProbe = &sPk;
2934: wsFlagMask = ~(
2935: WHERE_COLUMN_IN|WHERE_COLUMN_EQ|WHERE_COLUMN_NULL|WHERE_COLUMN_RANGE
2936: );
2937: eqTermMask = WO_EQ|WO_IN;
2938: pIdx = 0;
2939: }
2940:
2941: /* Loop over all indices looking for the best one to use
2942: */
2943: for(; pProbe; pIdx=pProbe=pProbe->pNext){
2944: const tRowcnt * const aiRowEst = pProbe->aiRowEst;
2945: double cost; /* Cost of using pProbe */
2946: double nRow; /* Estimated number of rows in result set */
2947: double log10N = (double)1; /* base-10 logarithm of nRow (inexact) */
2948: int rev; /* True to scan in reverse order */
2949: int wsFlags = 0;
2950: Bitmask used = 0;
2951:
2952: /* The following variables are populated based on the properties of
2953: ** index being evaluated. They are then used to determine the expected
2954: ** cost and number of rows returned.
2955: **
2956: ** nEq:
2957: ** Number of equality terms that can be implemented using the index.
2958: ** In other words, the number of initial fields in the index that
2959: ** are used in == or IN or NOT NULL constraints of the WHERE clause.
2960: **
2961: ** nInMul:
2962: ** The "in-multiplier". This is an estimate of how many seek operations
2963: ** SQLite must perform on the index in question. For example, if the
2964: ** WHERE clause is:
2965: **
2966: ** WHERE a IN (1, 2, 3) AND b IN (4, 5, 6)
2967: **
2968: ** SQLite must perform 9 lookups on an index on (a, b), so nInMul is
2969: ** set to 9. Given the same schema and either of the following WHERE
2970: ** clauses:
2971: **
2972: ** WHERE a = 1
2973: ** WHERE a >= 2
2974: **
2975: ** nInMul is set to 1.
2976: **
2977: ** If there exists a WHERE term of the form "x IN (SELECT ...)", then
2978: ** the sub-select is assumed to return 25 rows for the purposes of
2979: ** determining nInMul.
2980: **
2981: ** bInEst:
2982: ** Set to true if there was at least one "x IN (SELECT ...)" term used
2983: ** in determining the value of nInMul. Note that the RHS of the
2984: ** IN operator must be a SELECT, not a value list, for this variable
2985: ** to be true.
2986: **
2987: ** rangeDiv:
2988: ** An estimate of a divisor by which to reduce the search space due
2989: ** to inequality constraints. In the absence of sqlite_stat3 ANALYZE
2990: ** data, a single inequality reduces the search space to 1/4rd its
2991: ** original size (rangeDiv==4). Two inequalities reduce the search
2992: ** space to 1/16th of its original size (rangeDiv==16).
2993: **
2994: ** bSort:
2995: ** Boolean. True if there is an ORDER BY clause that will require an
2996: ** external sort (i.e. scanning the index being evaluated will not
2997: ** correctly order records).
2998: **
2999: ** bLookup:
3000: ** Boolean. True if a table lookup is required for each index entry
3001: ** visited. In other words, true if this is not a covering index.
3002: ** This is always false for the rowid primary key index of a table.
3003: ** For other indexes, it is true unless all the columns of the table
3004: ** used by the SELECT statement are present in the index (such an
3005: ** index is sometimes described as a covering index).
3006: ** For example, given the index on (a, b), the second of the following
3007: ** two queries requires table b-tree lookups in order to find the value
3008: ** of column c, but the first does not because columns a and b are
3009: ** both available in the index.
3010: **
3011: ** SELECT a, b FROM tbl WHERE a = 1;
3012: ** SELECT a, b, c FROM tbl WHERE a = 1;
3013: */
3014: int nEq; /* Number of == or IN terms matching index */
3015: int bInEst = 0; /* True if "x IN (SELECT...)" seen */
3016: int nInMul = 1; /* Number of distinct equalities to lookup */
3017: double rangeDiv = (double)1; /* Estimated reduction in search space */
3018: int nBound = 0; /* Number of range constraints seen */
3019: int bSort = !!pOrderBy; /* True if external sort required */
3020: int bDist = !!pDistinct; /* True if index cannot help with DISTINCT */
3021: int bLookup = 0; /* True if not a covering index */
3022: WhereTerm *pTerm; /* A single term of the WHERE clause */
3023: #ifdef SQLITE_ENABLE_STAT3
3024: WhereTerm *pFirstTerm = 0; /* First term matching the index */
3025: #endif
3026:
3027: /* Determine the values of nEq and nInMul */
3028: for(nEq=0; nEq<pProbe->nColumn; nEq++){
3029: int j = pProbe->aiColumn[nEq];
3030: pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pIdx);
3031: if( pTerm==0 ) break;
3032: wsFlags |= (WHERE_COLUMN_EQ|WHERE_ROWID_EQ);
3033: testcase( pTerm->pWC!=pWC );
3034: if( pTerm->eOperator & WO_IN ){
3035: Expr *pExpr = pTerm->pExpr;
3036: wsFlags |= WHERE_COLUMN_IN;
3037: if( ExprHasProperty(pExpr, EP_xIsSelect) ){
3038: /* "x IN (SELECT ...)": Assume the SELECT returns 25 rows */
3039: nInMul *= 25;
3040: bInEst = 1;
3041: }else if( ALWAYS(pExpr->x.pList && pExpr->x.pList->nExpr) ){
3042: /* "x IN (value, value, ...)" */
3043: nInMul *= pExpr->x.pList->nExpr;
3044: }
3045: }else if( pTerm->eOperator & WO_ISNULL ){
3046: wsFlags |= WHERE_COLUMN_NULL;
3047: }
3048: #ifdef SQLITE_ENABLE_STAT3
3049: if( nEq==0 && pProbe->aSample ) pFirstTerm = pTerm;
3050: #endif
3051: used |= pTerm->prereqRight;
3052: }
3053:
3054: /* If the index being considered is UNIQUE, and there is an equality
3055: ** constraint for all columns in the index, then this search will find
3056: ** at most a single row. In this case set the WHERE_UNIQUE flag to
3057: ** indicate this to the caller.
3058: **
3059: ** Otherwise, if the search may find more than one row, test to see if
3060: ** there is a range constraint on indexed column (nEq+1) that can be
3061: ** optimized using the index.
3062: */
3063: if( nEq==pProbe->nColumn && pProbe->onError!=OE_None ){
3064: testcase( wsFlags & WHERE_COLUMN_IN );
3065: testcase( wsFlags & WHERE_COLUMN_NULL );
3066: if( (wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_NULL))==0 ){
3067: wsFlags |= WHERE_UNIQUE;
3068: }
3069: }else if( pProbe->bUnordered==0 ){
3070: int j = (nEq==pProbe->nColumn ? -1 : pProbe->aiColumn[nEq]);
3071: if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pIdx) ){
3072: WhereTerm *pTop = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pIdx);
3073: WhereTerm *pBtm = findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pIdx);
3074: whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &rangeDiv);
3075: if( pTop ){
3076: nBound = 1;
3077: wsFlags |= WHERE_TOP_LIMIT;
3078: used |= pTop->prereqRight;
3079: testcase( pTop->pWC!=pWC );
3080: }
3081: if( pBtm ){
3082: nBound++;
3083: wsFlags |= WHERE_BTM_LIMIT;
3084: used |= pBtm->prereqRight;
3085: testcase( pBtm->pWC!=pWC );
3086: }
3087: wsFlags |= (WHERE_COLUMN_RANGE|WHERE_ROWID_RANGE);
3088: }
3089: }
3090:
3091: /* If there is an ORDER BY clause and the index being considered will
3092: ** naturally scan rows in the required order, set the appropriate flags
3093: ** in wsFlags. Otherwise, if there is an ORDER BY clause but the index
3094: ** will scan rows in a different order, set the bSort variable. */
3095: if( isSortingIndex(
3096: pParse, pWC->pMaskSet, pProbe, iCur, pOrderBy, nEq, wsFlags, &rev)
3097: ){
3098: bSort = 0;
3099: wsFlags |= WHERE_ROWID_RANGE|WHERE_COLUMN_RANGE|WHERE_ORDERBY;
3100: wsFlags |= (rev ? WHERE_REVERSE : 0);
3101: }
3102:
3103: /* If there is a DISTINCT qualifier and this index will scan rows in
3104: ** order of the DISTINCT expressions, clear bDist and set the appropriate
3105: ** flags in wsFlags. */
3106: if( isDistinctIndex(pParse, pWC, pProbe, iCur, pDistinct, nEq) ){
3107: bDist = 0;
3108: wsFlags |= WHERE_ROWID_RANGE|WHERE_COLUMN_RANGE|WHERE_DISTINCT;
3109: }
3110:
3111: /* If currently calculating the cost of using an index (not the IPK
3112: ** index), determine if all required column data may be obtained without
3113: ** using the main table (i.e. if the index is a covering
3114: ** index for this query). If it is, set the WHERE_IDX_ONLY flag in
3115: ** wsFlags. Otherwise, set the bLookup variable to true. */
3116: if( pIdx && wsFlags ){
3117: Bitmask m = pSrc->colUsed;
3118: int j;
3119: for(j=0; j<pIdx->nColumn; j++){
3120: int x = pIdx->aiColumn[j];
3121: if( x<BMS-1 ){
3122: m &= ~(((Bitmask)1)<<x);
3123: }
3124: }
3125: if( m==0 ){
3126: wsFlags |= WHERE_IDX_ONLY;
3127: }else{
3128: bLookup = 1;
3129: }
3130: }
3131:
3132: /*
3133: ** Estimate the number of rows of output. For an "x IN (SELECT...)"
3134: ** constraint, do not let the estimate exceed half the rows in the table.
3135: */
3136: nRow = (double)(aiRowEst[nEq] * nInMul);
3137: if( bInEst && nRow*2>aiRowEst[0] ){
3138: nRow = aiRowEst[0]/2;
3139: nInMul = (int)(nRow / aiRowEst[nEq]);
3140: }
3141:
3142: #ifdef SQLITE_ENABLE_STAT3
3143: /* If the constraint is of the form x=VALUE or x IN (E1,E2,...)
3144: ** and we do not think that values of x are unique and if histogram
3145: ** data is available for column x, then it might be possible
3146: ** to get a better estimate on the number of rows based on
3147: ** VALUE and how common that value is according to the histogram.
3148: */
3149: if( nRow>(double)1 && nEq==1 && pFirstTerm!=0 && aiRowEst[1]>1 ){
3150: assert( (pFirstTerm->eOperator & (WO_EQ|WO_ISNULL|WO_IN))!=0 );
3151: if( pFirstTerm->eOperator & (WO_EQ|WO_ISNULL) ){
3152: testcase( pFirstTerm->eOperator==WO_EQ );
3153: testcase( pFirstTerm->eOperator==WO_ISNULL );
3154: whereEqualScanEst(pParse, pProbe, pFirstTerm->pExpr->pRight, &nRow);
3155: }else if( bInEst==0 ){
3156: assert( pFirstTerm->eOperator==WO_IN );
3157: whereInScanEst(pParse, pProbe, pFirstTerm->pExpr->x.pList, &nRow);
3158: }
3159: }
3160: #endif /* SQLITE_ENABLE_STAT3 */
3161:
3162: /* Adjust the number of output rows and downward to reflect rows
3163: ** that are excluded by range constraints.
3164: */
3165: nRow = nRow/rangeDiv;
3166: if( nRow<1 ) nRow = 1;
3167:
3168: /* Experiments run on real SQLite databases show that the time needed
3169: ** to do a binary search to locate a row in a table or index is roughly
3170: ** log10(N) times the time to move from one row to the next row within
3171: ** a table or index. The actual times can vary, with the size of
3172: ** records being an important factor. Both moves and searches are
3173: ** slower with larger records, presumably because fewer records fit
3174: ** on one page and hence more pages have to be fetched.
3175: **
3176: ** The ANALYZE command and the sqlite_stat1 and sqlite_stat3 tables do
3177: ** not give us data on the relative sizes of table and index records.
3178: ** So this computation assumes table records are about twice as big
3179: ** as index records
3180: */
3181: if( (wsFlags & WHERE_NOT_FULLSCAN)==0 ){
3182: /* The cost of a full table scan is a number of move operations equal
3183: ** to the number of rows in the table.
3184: **
3185: ** We add an additional 4x penalty to full table scans. This causes
3186: ** the cost function to err on the side of choosing an index over
3187: ** choosing a full scan. This 4x full-scan penalty is an arguable
3188: ** decision and one which we expect to revisit in the future. But
3189: ** it seems to be working well enough at the moment.
3190: */
3191: cost = aiRowEst[0]*4;
3192: }else{
3193: log10N = estLog(aiRowEst[0]);
3194: cost = nRow;
3195: if( pIdx ){
3196: if( bLookup ){
3197: /* For an index lookup followed by a table lookup:
3198: ** nInMul index searches to find the start of each index range
3199: ** + nRow steps through the index
3200: ** + nRow table searches to lookup the table entry using the rowid
3201: */
3202: cost += (nInMul + nRow)*log10N;
3203: }else{
3204: /* For a covering index:
3205: ** nInMul index searches to find the initial entry
3206: ** + nRow steps through the index
3207: */
3208: cost += nInMul*log10N;
3209: }
3210: }else{
3211: /* For a rowid primary key lookup:
3212: ** nInMult table searches to find the initial entry for each range
3213: ** + nRow steps through the table
3214: */
3215: cost += nInMul*log10N;
3216: }
3217: }
3218:
3219: /* Add in the estimated cost of sorting the result. Actual experimental
3220: ** measurements of sorting performance in SQLite show that sorting time
3221: ** adds C*N*log10(N) to the cost, where N is the number of rows to be
3222: ** sorted and C is a factor between 1.95 and 4.3. We will split the
3223: ** difference and select C of 3.0.
3224: */
3225: if( bSort ){
3226: cost += nRow*estLog(nRow)*3;
3227: }
3228: if( bDist ){
3229: cost += nRow*estLog(nRow)*3;
3230: }
3231:
3232: /**** Cost of using this index has now been computed ****/
3233:
3234: /* If there are additional constraints on this table that cannot
3235: ** be used with the current index, but which might lower the number
3236: ** of output rows, adjust the nRow value accordingly. This only
3237: ** matters if the current index is the least costly, so do not bother
3238: ** with this step if we already know this index will not be chosen.
3239: ** Also, never reduce the output row count below 2 using this step.
3240: **
3241: ** It is critical that the notValid mask be used here instead of
3242: ** the notReady mask. When computing an "optimal" index, the notReady
3243: ** mask will only have one bit set - the bit for the current table.
3244: ** The notValid mask, on the other hand, always has all bits set for
3245: ** tables that are not in outer loops. If notReady is used here instead
3246: ** of notValid, then a optimal index that depends on inner joins loops
3247: ** might be selected even when there exists an optimal index that has
3248: ** no such dependency.
3249: */
3250: if( nRow>2 && cost<=pCost->rCost ){
3251: int k; /* Loop counter */
3252: int nSkipEq = nEq; /* Number of == constraints to skip */
3253: int nSkipRange = nBound; /* Number of < constraints to skip */
3254: Bitmask thisTab; /* Bitmap for pSrc */
3255:
3256: thisTab = getMask(pWC->pMaskSet, iCur);
3257: for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
3258: if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
3259: if( (pTerm->prereqAll & notValid)!=thisTab ) continue;
3260: if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
3261: if( nSkipEq ){
3262: /* Ignore the first nEq equality matches since the index
3263: ** has already accounted for these */
3264: nSkipEq--;
3265: }else{
3266: /* Assume each additional equality match reduces the result
3267: ** set size by a factor of 10 */
3268: nRow /= 10;
3269: }
3270: }else if( pTerm->eOperator & (WO_LT|WO_LE|WO_GT|WO_GE) ){
3271: if( nSkipRange ){
3272: /* Ignore the first nSkipRange range constraints since the index
3273: ** has already accounted for these */
3274: nSkipRange--;
3275: }else{
3276: /* Assume each additional range constraint reduces the result
3277: ** set size by a factor of 3. Indexed range constraints reduce
3278: ** the search space by a larger factor: 4. We make indexed range
3279: ** more selective intentionally because of the subjective
3280: ** observation that indexed range constraints really are more
3281: ** selective in practice, on average. */
3282: nRow /= 3;
3283: }
3284: }else if( pTerm->eOperator!=WO_NOOP ){
3285: /* Any other expression lowers the output row count by half */
3286: nRow /= 2;
3287: }
3288: }
3289: if( nRow<2 ) nRow = 2;
3290: }
3291:
3292:
3293: WHERETRACE((
3294: "%s(%s): nEq=%d nInMul=%d rangeDiv=%d bSort=%d bLookup=%d wsFlags=0x%x\n"
3295: " notReady=0x%llx log10N=%.1f nRow=%.1f cost=%.1f used=0x%llx\n",
3296: pSrc->pTab->zName, (pIdx ? pIdx->zName : "ipk"),
3297: nEq, nInMul, (int)rangeDiv, bSort, bLookup, wsFlags,
3298: notReady, log10N, nRow, cost, used
3299: ));
3300:
3301: /* If this index is the best we have seen so far, then record this
3302: ** index and its cost in the pCost structure.
3303: */
3304: if( (!pIdx || wsFlags)
3305: && (cost<pCost->rCost || (cost<=pCost->rCost && nRow<pCost->plan.nRow))
3306: ){
3307: pCost->rCost = cost;
3308: pCost->used = used;
3309: pCost->plan.nRow = nRow;
3310: pCost->plan.wsFlags = (wsFlags&wsFlagMask);
3311: pCost->plan.nEq = nEq;
3312: pCost->plan.u.pIdx = pIdx;
3313: }
3314:
3315: /* If there was an INDEXED BY clause, then only that one index is
3316: ** considered. */
3317: if( pSrc->pIndex ) break;
3318:
3319: /* Reset masks for the next index in the loop */
3320: wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
3321: eqTermMask = idxEqTermMask;
3322: }
3323:
3324: /* If there is no ORDER BY clause and the SQLITE_ReverseOrder flag
3325: ** is set, then reverse the order that the index will be scanned
3326: ** in. This is used for application testing, to help find cases
3327: ** where application behaviour depends on the (undefined) order that
3328: ** SQLite outputs rows in in the absence of an ORDER BY clause. */
3329: if( !pOrderBy && pParse->db->flags & SQLITE_ReverseOrder ){
3330: pCost->plan.wsFlags |= WHERE_REVERSE;
3331: }
3332:
3333: assert( pOrderBy || (pCost->plan.wsFlags&WHERE_ORDERBY)==0 );
3334: assert( pCost->plan.u.pIdx==0 || (pCost->plan.wsFlags&WHERE_ROWID_EQ)==0 );
3335: assert( pSrc->pIndex==0
3336: || pCost->plan.u.pIdx==0
3337: || pCost->plan.u.pIdx==pSrc->pIndex
3338: );
3339:
3340: WHERETRACE(("best index is: %s\n",
3341: ((pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ? "none" :
3342: pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
3343: ));
3344:
3345: bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
3346: bestAutomaticIndex(pParse, pWC, pSrc, notReady, pCost);
3347: pCost->plan.wsFlags |= eqTermMask;
3348: }
3349:
3350: /*
3351: ** Find the query plan for accessing table pSrc->pTab. Write the
3352: ** best query plan and its cost into the WhereCost object supplied
3353: ** as the last parameter. This function may calculate the cost of
3354: ** both real and virtual table scans.
3355: */
3356: static void bestIndex(
3357: Parse *pParse, /* The parsing context */
3358: WhereClause *pWC, /* The WHERE clause */
3359: struct SrcList_item *pSrc, /* The FROM clause term to search */
3360: Bitmask notReady, /* Mask of cursors not available for indexing */
3361: Bitmask notValid, /* Cursors not available for any purpose */
3362: ExprList *pOrderBy, /* The ORDER BY clause */
3363: WhereCost *pCost /* Lowest cost query plan */
3364: ){
3365: #ifndef SQLITE_OMIT_VIRTUALTABLE
3366: if( IsVirtual(pSrc->pTab) ){
3367: sqlite3_index_info *p = 0;
3368: bestVirtualIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost,&p);
3369: if( p->needToFreeIdxStr ){
3370: sqlite3_free(p->idxStr);
3371: }
3372: sqlite3DbFree(pParse->db, p);
3373: }else
3374: #endif
3375: {
3376: bestBtreeIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, 0, pCost);
3377: }
3378: }
3379:
3380: /*
3381: ** Disable a term in the WHERE clause. Except, do not disable the term
3382: ** if it controls a LEFT OUTER JOIN and it did not originate in the ON
3383: ** or USING clause of that join.
3384: **
3385: ** Consider the term t2.z='ok' in the following queries:
3386: **
3387: ** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
3388: ** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
3389: ** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
3390: **
3391: ** The t2.z='ok' is disabled in the in (2) because it originates
3392: ** in the ON clause. The term is disabled in (3) because it is not part
3393: ** of a LEFT OUTER JOIN. In (1), the term is not disabled.
3394: **
3395: ** IMPLEMENTATION-OF: R-24597-58655 No tests are done for terms that are
3396: ** completely satisfied by indices.
3397: **
3398: ** Disabling a term causes that term to not be tested in the inner loop
3399: ** of the join. Disabling is an optimization. When terms are satisfied
3400: ** by indices, we disable them to prevent redundant tests in the inner
3401: ** loop. We would get the correct results if nothing were ever disabled,
3402: ** but joins might run a little slower. The trick is to disable as much
3403: ** as we can without disabling too much. If we disabled in (1), we'd get
3404: ** the wrong answer. See ticket #813.
3405: */
3406: static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
3407: if( pTerm
3408: && (pTerm->wtFlags & TERM_CODED)==0
3409: && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
3410: ){
3411: pTerm->wtFlags |= TERM_CODED;
3412: if( pTerm->iParent>=0 ){
3413: WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
3414: if( (--pOther->nChild)==0 ){
3415: disableTerm(pLevel, pOther);
3416: }
3417: }
3418: }
3419: }
3420:
3421: /*
3422: ** Code an OP_Affinity opcode to apply the column affinity string zAff
3423: ** to the n registers starting at base.
3424: **
3425: ** As an optimization, SQLITE_AFF_NONE entries (which are no-ops) at the
3426: ** beginning and end of zAff are ignored. If all entries in zAff are
3427: ** SQLITE_AFF_NONE, then no code gets generated.
3428: **
3429: ** This routine makes its own copy of zAff so that the caller is free
3430: ** to modify zAff after this routine returns.
3431: */
3432: static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
3433: Vdbe *v = pParse->pVdbe;
3434: if( zAff==0 ){
3435: assert( pParse->db->mallocFailed );
3436: return;
3437: }
3438: assert( v!=0 );
3439:
3440: /* Adjust base and n to skip over SQLITE_AFF_NONE entries at the beginning
3441: ** and end of the affinity string.
3442: */
3443: while( n>0 && zAff[0]==SQLITE_AFF_NONE ){
3444: n--;
3445: base++;
3446: zAff++;
3447: }
3448: while( n>1 && zAff[n-1]==SQLITE_AFF_NONE ){
3449: n--;
3450: }
3451:
3452: /* Code the OP_Affinity opcode if there is anything left to do. */
3453: if( n>0 ){
3454: sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
3455: sqlite3VdbeChangeP4(v, -1, zAff, n);
3456: sqlite3ExprCacheAffinityChange(pParse, base, n);
3457: }
3458: }
3459:
3460:
3461: /*
3462: ** Generate code for a single equality term of the WHERE clause. An equality
3463: ** term can be either X=expr or X IN (...). pTerm is the term to be
3464: ** coded.
3465: **
3466: ** The current value for the constraint is left in register iReg.
3467: **
3468: ** For a constraint of the form X=expr, the expression is evaluated and its
3469: ** result is left on the stack. For constraints of the form X IN (...)
3470: ** this routine sets up a loop that will iterate over all values of X.
3471: */
3472: static int codeEqualityTerm(
3473: Parse *pParse, /* The parsing context */
3474: WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
3475: WhereLevel *pLevel, /* When level of the FROM clause we are working on */
3476: int iTarget /* Attempt to leave results in this register */
3477: ){
3478: Expr *pX = pTerm->pExpr;
3479: Vdbe *v = pParse->pVdbe;
3480: int iReg; /* Register holding results */
3481:
3482: assert( iTarget>0 );
3483: if( pX->op==TK_EQ ){
3484: iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
3485: }else if( pX->op==TK_ISNULL ){
3486: iReg = iTarget;
3487: sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
3488: #ifndef SQLITE_OMIT_SUBQUERY
3489: }else{
3490: int eType;
3491: int iTab;
3492: struct InLoop *pIn;
3493:
3494: assert( pX->op==TK_IN );
3495: iReg = iTarget;
3496: eType = sqlite3FindInIndex(pParse, pX, 0);
3497: iTab = pX->iTable;
3498: sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
3499: assert( pLevel->plan.wsFlags & WHERE_IN_ABLE );
3500: if( pLevel->u.in.nIn==0 ){
3501: pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
3502: }
3503: pLevel->u.in.nIn++;
3504: pLevel->u.in.aInLoop =
3505: sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
3506: sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
3507: pIn = pLevel->u.in.aInLoop;
3508: if( pIn ){
3509: pIn += pLevel->u.in.nIn - 1;
3510: pIn->iCur = iTab;
3511: if( eType==IN_INDEX_ROWID ){
3512: pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
3513: }else{
3514: pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
3515: }
3516: sqlite3VdbeAddOp1(v, OP_IsNull, iReg);
3517: }else{
3518: pLevel->u.in.nIn = 0;
3519: }
3520: #endif
3521: }
3522: disableTerm(pLevel, pTerm);
3523: return iReg;
3524: }
3525:
3526: /*
3527: ** Generate code that will evaluate all == and IN constraints for an
3528: ** index.
3529: **
3530: ** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
3531: ** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
3532: ** The index has as many as three equality constraints, but in this
3533: ** example, the third "c" value is an inequality. So only two
3534: ** constraints are coded. This routine will generate code to evaluate
3535: ** a==5 and b IN (1,2,3). The current values for a and b will be stored
3536: ** in consecutive registers and the index of the first register is returned.
3537: **
3538: ** In the example above nEq==2. But this subroutine works for any value
3539: ** of nEq including 0. If nEq==0, this routine is nearly a no-op.
3540: ** The only thing it does is allocate the pLevel->iMem memory cell and
3541: ** compute the affinity string.
3542: **
3543: ** This routine always allocates at least one memory cell and returns
3544: ** the index of that memory cell. The code that
3545: ** calls this routine will use that memory cell to store the termination
3546: ** key value of the loop. If one or more IN operators appear, then
3547: ** this routine allocates an additional nEq memory cells for internal
3548: ** use.
3549: **
3550: ** Before returning, *pzAff is set to point to a buffer containing a
3551: ** copy of the column affinity string of the index allocated using
3552: ** sqlite3DbMalloc(). Except, entries in the copy of the string associated
3553: ** with equality constraints that use NONE affinity are set to
3554: ** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
3555: **
3556: ** CREATE TABLE t1(a TEXT PRIMARY KEY, b);
3557: ** SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
3558: **
3559: ** In the example above, the index on t1(a) has TEXT affinity. But since
3560: ** the right hand side of the equality constraint (t2.b) has NONE affinity,
3561: ** no conversion should be attempted before using a t2.b value as part of
3562: ** a key to search the index. Hence the first byte in the returned affinity
3563: ** string in this example would be set to SQLITE_AFF_NONE.
3564: */
3565: static int codeAllEqualityTerms(
3566: Parse *pParse, /* Parsing context */
3567: WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
3568: WhereClause *pWC, /* The WHERE clause */
3569: Bitmask notReady, /* Which parts of FROM have not yet been coded */
3570: int nExtraReg, /* Number of extra registers to allocate */
3571: char **pzAff /* OUT: Set to point to affinity string */
3572: ){
3573: int nEq = pLevel->plan.nEq; /* The number of == or IN constraints to code */
3574: Vdbe *v = pParse->pVdbe; /* The vm under construction */
3575: Index *pIdx; /* The index being used for this loop */
3576: int iCur = pLevel->iTabCur; /* The cursor of the table */
3577: WhereTerm *pTerm; /* A single constraint term */
3578: int j; /* Loop counter */
3579: int regBase; /* Base register */
3580: int nReg; /* Number of registers to allocate */
3581: char *zAff; /* Affinity string to return */
3582:
3583: /* This module is only called on query plans that use an index. */
3584: assert( pLevel->plan.wsFlags & WHERE_INDEXED );
3585: pIdx = pLevel->plan.u.pIdx;
3586:
3587: /* Figure out how many memory cells we will need then allocate them.
3588: */
3589: regBase = pParse->nMem + 1;
3590: nReg = pLevel->plan.nEq + nExtraReg;
3591: pParse->nMem += nReg;
3592:
3593: zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
3594: if( !zAff ){
3595: pParse->db->mallocFailed = 1;
3596: }
3597:
3598: /* Evaluate the equality constraints
3599: */
3600: assert( pIdx->nColumn>=nEq );
3601: for(j=0; j<nEq; j++){
3602: int r1;
3603: int k = pIdx->aiColumn[j];
3604: pTerm = findTerm(pWC, iCur, k, notReady, pLevel->plan.wsFlags, pIdx);
3605: if( NEVER(pTerm==0) ) break;
3606: /* The following true for indices with redundant columns.
3607: ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
3608: testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
3609: testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
3610: r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
3611: if( r1!=regBase+j ){
3612: if( nReg==1 ){
3613: sqlite3ReleaseTempReg(pParse, regBase);
3614: regBase = r1;
3615: }else{
3616: sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
3617: }
3618: }
3619: testcase( pTerm->eOperator & WO_ISNULL );
3620: testcase( pTerm->eOperator & WO_IN );
3621: if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
3622: Expr *pRight = pTerm->pExpr->pRight;
3623: sqlite3ExprCodeIsNullJump(v, pRight, regBase+j, pLevel->addrBrk);
3624: if( zAff ){
3625: if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
3626: zAff[j] = SQLITE_AFF_NONE;
3627: }
3628: if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
3629: zAff[j] = SQLITE_AFF_NONE;
3630: }
3631: }
3632: }
3633: }
3634: *pzAff = zAff;
3635: return regBase;
3636: }
3637:
3638: #ifndef SQLITE_OMIT_EXPLAIN
3639: /*
3640: ** This routine is a helper for explainIndexRange() below
3641: **
3642: ** pStr holds the text of an expression that we are building up one term
3643: ** at a time. This routine adds a new term to the end of the expression.
3644: ** Terms are separated by AND so add the "AND" text for second and subsequent
3645: ** terms only.
3646: */
3647: static void explainAppendTerm(
3648: StrAccum *pStr, /* The text expression being built */
3649: int iTerm, /* Index of this term. First is zero */
3650: const char *zColumn, /* Name of the column */
3651: const char *zOp /* Name of the operator */
3652: ){
3653: if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
3654: sqlite3StrAccumAppend(pStr, zColumn, -1);
3655: sqlite3StrAccumAppend(pStr, zOp, 1);
3656: sqlite3StrAccumAppend(pStr, "?", 1);
3657: }
3658:
3659: /*
3660: ** Argument pLevel describes a strategy for scanning table pTab. This
3661: ** function returns a pointer to a string buffer containing a description
3662: ** of the subset of table rows scanned by the strategy in the form of an
3663: ** SQL expression. Or, if all rows are scanned, NULL is returned.
3664: **
3665: ** For example, if the query:
3666: **
3667: ** SELECT * FROM t1 WHERE a=1 AND b>2;
3668: **
3669: ** is run and there is an index on (a, b), then this function returns a
3670: ** string similar to:
3671: **
3672: ** "a=? AND b>?"
3673: **
3674: ** The returned pointer points to memory obtained from sqlite3DbMalloc().
3675: ** It is the responsibility of the caller to free the buffer when it is
3676: ** no longer required.
3677: */
3678: static char *explainIndexRange(sqlite3 *db, WhereLevel *pLevel, Table *pTab){
3679: WherePlan *pPlan = &pLevel->plan;
3680: Index *pIndex = pPlan->u.pIdx;
3681: int nEq = pPlan->nEq;
3682: int i, j;
3683: Column *aCol = pTab->aCol;
3684: int *aiColumn = pIndex->aiColumn;
3685: StrAccum txt;
3686:
3687: if( nEq==0 && (pPlan->wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ){
3688: return 0;
3689: }
3690: sqlite3StrAccumInit(&txt, 0, 0, SQLITE_MAX_LENGTH);
3691: txt.db = db;
3692: sqlite3StrAccumAppend(&txt, " (", 2);
3693: for(i=0; i<nEq; i++){
3694: explainAppendTerm(&txt, i, aCol[aiColumn[i]].zName, "=");
3695: }
3696:
3697: j = i;
3698: if( pPlan->wsFlags&WHERE_BTM_LIMIT ){
3699: char *z = (j==pIndex->nColumn ) ? "rowid" : aCol[aiColumn[j]].zName;
3700: explainAppendTerm(&txt, i++, z, ">");
3701: }
3702: if( pPlan->wsFlags&WHERE_TOP_LIMIT ){
3703: char *z = (j==pIndex->nColumn ) ? "rowid" : aCol[aiColumn[j]].zName;
3704: explainAppendTerm(&txt, i, z, "<");
3705: }
3706: sqlite3StrAccumAppend(&txt, ")", 1);
3707: return sqlite3StrAccumFinish(&txt);
3708: }
3709:
3710: /*
3711: ** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
3712: ** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
3713: ** record is added to the output to describe the table scan strategy in
3714: ** pLevel.
3715: */
3716: static void explainOneScan(
3717: Parse *pParse, /* Parse context */
3718: SrcList *pTabList, /* Table list this loop refers to */
3719: WhereLevel *pLevel, /* Scan to write OP_Explain opcode for */
3720: int iLevel, /* Value for "level" column of output */
3721: int iFrom, /* Value for "from" column of output */
3722: u16 wctrlFlags /* Flags passed to sqlite3WhereBegin() */
3723: ){
3724: if( pParse->explain==2 ){
3725: u32 flags = pLevel->plan.wsFlags;
3726: struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
3727: Vdbe *v = pParse->pVdbe; /* VM being constructed */
3728: sqlite3 *db = pParse->db; /* Database handle */
3729: char *zMsg; /* Text to add to EQP output */
3730: sqlite3_int64 nRow; /* Expected number of rows visited by scan */
3731: int iId = pParse->iSelectId; /* Select id (left-most output column) */
3732: int isSearch; /* True for a SEARCH. False for SCAN. */
3733:
3734: if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return;
3735:
3736: isSearch = (pLevel->plan.nEq>0)
3737: || (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
3738: || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
3739:
3740: zMsg = sqlite3MPrintf(db, "%s", isSearch?"SEARCH":"SCAN");
3741: if( pItem->pSelect ){
3742: zMsg = sqlite3MAppendf(db, zMsg, "%s SUBQUERY %d", zMsg,pItem->iSelectId);
3743: }else{
3744: zMsg = sqlite3MAppendf(db, zMsg, "%s TABLE %s", zMsg, pItem->zName);
3745: }
3746:
3747: if( pItem->zAlias ){
3748: zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
3749: }
3750: if( (flags & WHERE_INDEXED)!=0 ){
3751: char *zWhere = explainIndexRange(db, pLevel, pItem->pTab);
3752: zMsg = sqlite3MAppendf(db, zMsg, "%s USING %s%sINDEX%s%s%s", zMsg,
3753: ((flags & WHERE_TEMP_INDEX)?"AUTOMATIC ":""),
3754: ((flags & WHERE_IDX_ONLY)?"COVERING ":""),
3755: ((flags & WHERE_TEMP_INDEX)?"":" "),
3756: ((flags & WHERE_TEMP_INDEX)?"": pLevel->plan.u.pIdx->zName),
3757: zWhere
3758: );
3759: sqlite3DbFree(db, zWhere);
3760: }else if( flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
3761: zMsg = sqlite3MAppendf(db, zMsg, "%s USING INTEGER PRIMARY KEY", zMsg);
3762:
3763: if( flags&WHERE_ROWID_EQ ){
3764: zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid=?)", zMsg);
3765: }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
3766: zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>? AND rowid<?)", zMsg);
3767: }else if( flags&WHERE_BTM_LIMIT ){
3768: zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>?)", zMsg);
3769: }else if( flags&WHERE_TOP_LIMIT ){
3770: zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid<?)", zMsg);
3771: }
3772: }
3773: #ifndef SQLITE_OMIT_VIRTUALTABLE
3774: else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
3775: sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
3776: zMsg = sqlite3MAppendf(db, zMsg, "%s VIRTUAL TABLE INDEX %d:%s", zMsg,
3777: pVtabIdx->idxNum, pVtabIdx->idxStr);
3778: }
3779: #endif
3780: if( wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX) ){
3781: testcase( wctrlFlags & WHERE_ORDERBY_MIN );
3782: nRow = 1;
3783: }else{
3784: nRow = (sqlite3_int64)pLevel->plan.nRow;
3785: }
3786: zMsg = sqlite3MAppendf(db, zMsg, "%s (~%lld rows)", zMsg, nRow);
3787: sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg, P4_DYNAMIC);
3788: }
3789: }
3790: #else
3791: # define explainOneScan(u,v,w,x,y,z)
3792: #endif /* SQLITE_OMIT_EXPLAIN */
3793:
3794:
3795: /*
3796: ** Generate code for the start of the iLevel-th loop in the WHERE clause
3797: ** implementation described by pWInfo.
3798: */
3799: static Bitmask codeOneLoopStart(
3800: WhereInfo *pWInfo, /* Complete information about the WHERE clause */
3801: int iLevel, /* Which level of pWInfo->a[] should be coded */
3802: u16 wctrlFlags, /* One of the WHERE_* flags defined in sqliteInt.h */
3803: Bitmask notReady, /* Which tables are currently available */
3804: Expr *pWhere /* Complete WHERE clause */
3805: ){
3806: int j, k; /* Loop counters */
3807: int iCur; /* The VDBE cursor for the table */
3808: int addrNxt; /* Where to jump to continue with the next IN case */
3809: int omitTable; /* True if we use the index only */
3810: int bRev; /* True if we need to scan in reverse order */
3811: WhereLevel *pLevel; /* The where level to be coded */
3812: WhereClause *pWC; /* Decomposition of the entire WHERE clause */
3813: WhereTerm *pTerm; /* A WHERE clause term */
3814: Parse *pParse; /* Parsing context */
3815: Vdbe *v; /* The prepared stmt under constructions */
3816: struct SrcList_item *pTabItem; /* FROM clause term being coded */
3817: int addrBrk; /* Jump here to break out of the loop */
3818: int addrCont; /* Jump here to continue with next cycle */
3819: int iRowidReg = 0; /* Rowid is stored in this register, if not zero */
3820: int iReleaseReg = 0; /* Temp register to free before returning */
3821:
3822: pParse = pWInfo->pParse;
3823: v = pParse->pVdbe;
3824: pWC = pWInfo->pWC;
3825: pLevel = &pWInfo->a[iLevel];
3826: pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
3827: iCur = pTabItem->iCursor;
3828: bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;
3829: omitTable = (pLevel->plan.wsFlags & WHERE_IDX_ONLY)!=0
3830: && (wctrlFlags & WHERE_FORCE_TABLE)==0;
3831:
3832: /* Create labels for the "break" and "continue" instructions
3833: ** for the current loop. Jump to addrBrk to break out of a loop.
3834: ** Jump to cont to go immediately to the next iteration of the
3835: ** loop.
3836: **
3837: ** When there is an IN operator, we also have a "addrNxt" label that
3838: ** means to continue with the next IN value combination. When
3839: ** there are no IN operators in the constraints, the "addrNxt" label
3840: ** is the same as "addrBrk".
3841: */
3842: addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
3843: addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
3844:
3845: /* If this is the right table of a LEFT OUTER JOIN, allocate and
3846: ** initialize a memory cell that records if this table matches any
3847: ** row of the left table of the join.
3848: */
3849: if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
3850: pLevel->iLeftJoin = ++pParse->nMem;
3851: sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
3852: VdbeComment((v, "init LEFT JOIN no-match flag"));
3853: }
3854:
3855: #ifndef SQLITE_OMIT_VIRTUALTABLE
3856: if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
3857: /* Case 0: The table is a virtual-table. Use the VFilter and VNext
3858: ** to access the data.
3859: */
3860: int iReg; /* P3 Value for OP_VFilter */
3861: sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
3862: int nConstraint = pVtabIdx->nConstraint;
3863: struct sqlite3_index_constraint_usage *aUsage =
3864: pVtabIdx->aConstraintUsage;
3865: const struct sqlite3_index_constraint *aConstraint =
3866: pVtabIdx->aConstraint;
3867:
3868: sqlite3ExprCachePush(pParse);
3869: iReg = sqlite3GetTempRange(pParse, nConstraint+2);
3870: for(j=1; j<=nConstraint; j++){
3871: for(k=0; k<nConstraint; k++){
3872: if( aUsage[k].argvIndex==j ){
3873: int iTerm = aConstraint[k].iTermOffset;
3874: sqlite3ExprCode(pParse, pWC->a[iTerm].pExpr->pRight, iReg+j+1);
3875: break;
3876: }
3877: }
3878: if( k==nConstraint ) break;
3879: }
3880: sqlite3VdbeAddOp2(v, OP_Integer, pVtabIdx->idxNum, iReg);
3881: sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
3882: sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrBrk, iReg, pVtabIdx->idxStr,
3883: pVtabIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
3884: pVtabIdx->needToFreeIdxStr = 0;
3885: for(j=0; j<nConstraint; j++){
3886: if( aUsage[j].omit ){
3887: int iTerm = aConstraint[j].iTermOffset;
3888: disableTerm(pLevel, &pWC->a[iTerm]);
3889: }
3890: }
3891: pLevel->op = OP_VNext;
3892: pLevel->p1 = iCur;
3893: pLevel->p2 = sqlite3VdbeCurrentAddr(v);
3894: sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
3895: sqlite3ExprCachePop(pParse, 1);
3896: }else
3897: #endif /* SQLITE_OMIT_VIRTUALTABLE */
3898:
3899: if( pLevel->plan.wsFlags & WHERE_ROWID_EQ ){
3900: /* Case 1: We can directly reference a single row using an
3901: ** equality comparison against the ROWID field. Or
3902: ** we reference multiple rows using a "rowid IN (...)"
3903: ** construct.
3904: */
3905: iReleaseReg = sqlite3GetTempReg(pParse);
3906: pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
3907: assert( pTerm!=0 );
3908: assert( pTerm->pExpr!=0 );
3909: assert( pTerm->leftCursor==iCur );
3910: assert( omitTable==0 );
3911: testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
3912: iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, iReleaseReg);
3913: addrNxt = pLevel->addrNxt;
3914: sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt);
3915: sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
3916: sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
3917: VdbeComment((v, "pk"));
3918: pLevel->op = OP_Noop;
3919: }else if( pLevel->plan.wsFlags & WHERE_ROWID_RANGE ){
3920: /* Case 2: We have an inequality comparison against the ROWID field.
3921: */
3922: int testOp = OP_Noop;
3923: int start;
3924: int memEndValue = 0;
3925: WhereTerm *pStart, *pEnd;
3926:
3927: assert( omitTable==0 );
3928: pStart = findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0);
3929: pEnd = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0);
3930: if( bRev ){
3931: pTerm = pStart;
3932: pStart = pEnd;
3933: pEnd = pTerm;
3934: }
3935: if( pStart ){
3936: Expr *pX; /* The expression that defines the start bound */
3937: int r1, rTemp; /* Registers for holding the start boundary */
3938:
3939: /* The following constant maps TK_xx codes into corresponding
3940: ** seek opcodes. It depends on a particular ordering of TK_xx
3941: */
3942: const u8 aMoveOp[] = {
3943: /* TK_GT */ OP_SeekGt,
3944: /* TK_LE */ OP_SeekLe,
3945: /* TK_LT */ OP_SeekLt,
3946: /* TK_GE */ OP_SeekGe
3947: };
3948: assert( TK_LE==TK_GT+1 ); /* Make sure the ordering.. */
3949: assert( TK_LT==TK_GT+2 ); /* ... of the TK_xx values... */
3950: assert( TK_GE==TK_GT+3 ); /* ... is correcct. */
3951:
3952: testcase( pStart->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
3953: pX = pStart->pExpr;
3954: assert( pX!=0 );
3955: assert( pStart->leftCursor==iCur );
3956: r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
3957: sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
3958: VdbeComment((v, "pk"));
3959: sqlite3ExprCacheAffinityChange(pParse, r1, 1);
3960: sqlite3ReleaseTempReg(pParse, rTemp);
3961: disableTerm(pLevel, pStart);
3962: }else{
3963: sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
3964: }
3965: if( pEnd ){
3966: Expr *pX;
3967: pX = pEnd->pExpr;
3968: assert( pX!=0 );
3969: assert( pEnd->leftCursor==iCur );
3970: testcase( pEnd->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
3971: memEndValue = ++pParse->nMem;
3972: sqlite3ExprCode(pParse, pX->pRight, memEndValue);
3973: if( pX->op==TK_LT || pX->op==TK_GT ){
3974: testOp = bRev ? OP_Le : OP_Ge;
3975: }else{
3976: testOp = bRev ? OP_Lt : OP_Gt;
3977: }
3978: disableTerm(pLevel, pEnd);
3979: }
3980: start = sqlite3VdbeCurrentAddr(v);
3981: pLevel->op = bRev ? OP_Prev : OP_Next;
3982: pLevel->p1 = iCur;
3983: pLevel->p2 = start;
3984: if( pStart==0 && pEnd==0 ){
3985: pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
3986: }else{
3987: assert( pLevel->p5==0 );
3988: }
3989: if( testOp!=OP_Noop ){
3990: iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
3991: sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
3992: sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
3993: sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
3994: sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
3995: }
3996: }else if( pLevel->plan.wsFlags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
3997: /* Case 3: A scan using an index.
3998: **
3999: ** The WHERE clause may contain zero or more equality
4000: ** terms ("==" or "IN" operators) that refer to the N
4001: ** left-most columns of the index. It may also contain
4002: ** inequality constraints (>, <, >= or <=) on the indexed
4003: ** column that immediately follows the N equalities. Only
4004: ** the right-most column can be an inequality - the rest must
4005: ** use the "==" and "IN" operators. For example, if the
4006: ** index is on (x,y,z), then the following clauses are all
4007: ** optimized:
4008: **
4009: ** x=5
4010: ** x=5 AND y=10
4011: ** x=5 AND y<10
4012: ** x=5 AND y>5 AND y<10
4013: ** x=5 AND y=5 AND z<=10
4014: **
4015: ** The z<10 term of the following cannot be used, only
4016: ** the x=5 term:
4017: **
4018: ** x=5 AND z<10
4019: **
4020: ** N may be zero if there are inequality constraints.
4021: ** If there are no inequality constraints, then N is at
4022: ** least one.
4023: **
4024: ** This case is also used when there are no WHERE clause
4025: ** constraints but an index is selected anyway, in order
4026: ** to force the output order to conform to an ORDER BY.
4027: */
4028: static const u8 aStartOp[] = {
4029: 0,
4030: 0,
4031: OP_Rewind, /* 2: (!start_constraints && startEq && !bRev) */
4032: OP_Last, /* 3: (!start_constraints && startEq && bRev) */
4033: OP_SeekGt, /* 4: (start_constraints && !startEq && !bRev) */
4034: OP_SeekLt, /* 5: (start_constraints && !startEq && bRev) */
4035: OP_SeekGe, /* 6: (start_constraints && startEq && !bRev) */
4036: OP_SeekLe /* 7: (start_constraints && startEq && bRev) */
4037: };
4038: static const u8 aEndOp[] = {
4039: OP_Noop, /* 0: (!end_constraints) */
4040: OP_IdxGE, /* 1: (end_constraints && !bRev) */
4041: OP_IdxLT /* 2: (end_constraints && bRev) */
4042: };
4043: int nEq = pLevel->plan.nEq; /* Number of == or IN terms */
4044: int isMinQuery = 0; /* If this is an optimized SELECT min(x).. */
4045: int regBase; /* Base register holding constraint values */
4046: int r1; /* Temp register */
4047: WhereTerm *pRangeStart = 0; /* Inequality constraint at range start */
4048: WhereTerm *pRangeEnd = 0; /* Inequality constraint at range end */
4049: int startEq; /* True if range start uses ==, >= or <= */
4050: int endEq; /* True if range end uses ==, >= or <= */
4051: int start_constraints; /* Start of range is constrained */
4052: int nConstraint; /* Number of constraint terms */
4053: Index *pIdx; /* The index we will be using */
4054: int iIdxCur; /* The VDBE cursor for the index */
4055: int nExtraReg = 0; /* Number of extra registers needed */
4056: int op; /* Instruction opcode */
4057: char *zStartAff; /* Affinity for start of range constraint */
4058: char *zEndAff; /* Affinity for end of range constraint */
4059:
4060: pIdx = pLevel->plan.u.pIdx;
4061: iIdxCur = pLevel->iIdxCur;
4062: k = (nEq==pIdx->nColumn ? -1 : pIdx->aiColumn[nEq]);
4063:
4064: /* If this loop satisfies a sort order (pOrderBy) request that
4065: ** was passed to this function to implement a "SELECT min(x) ..."
4066: ** query, then the caller will only allow the loop to run for
4067: ** a single iteration. This means that the first row returned
4068: ** should not have a NULL value stored in 'x'. If column 'x' is
4069: ** the first one after the nEq equality constraints in the index,
4070: ** this requires some special handling.
4071: */
4072: if( (wctrlFlags&WHERE_ORDERBY_MIN)!=0
4073: && (pLevel->plan.wsFlags&WHERE_ORDERBY)
4074: && (pIdx->nColumn>nEq)
4075: ){
4076: /* assert( pOrderBy->nExpr==1 ); */
4077: /* assert( pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq] ); */
4078: isMinQuery = 1;
4079: nExtraReg = 1;
4080: }
4081:
4082: /* Find any inequality constraint terms for the start and end
4083: ** of the range.
4084: */
4085: if( pLevel->plan.wsFlags & WHERE_TOP_LIMIT ){
4086: pRangeEnd = findTerm(pWC, iCur, k, notReady, (WO_LT|WO_LE), pIdx);
4087: nExtraReg = 1;
4088: }
4089: if( pLevel->plan.wsFlags & WHERE_BTM_LIMIT ){
4090: pRangeStart = findTerm(pWC, iCur, k, notReady, (WO_GT|WO_GE), pIdx);
4091: nExtraReg = 1;
4092: }
4093:
4094: /* Generate code to evaluate all constraint terms using == or IN
4095: ** and store the values of those terms in an array of registers
4096: ** starting at regBase.
4097: */
4098: regBase = codeAllEqualityTerms(
4099: pParse, pLevel, pWC, notReady, nExtraReg, &zStartAff
4100: );
4101: zEndAff = sqlite3DbStrDup(pParse->db, zStartAff);
4102: addrNxt = pLevel->addrNxt;
4103:
4104: /* If we are doing a reverse order scan on an ascending index, or
4105: ** a forward order scan on a descending index, interchange the
4106: ** start and end terms (pRangeStart and pRangeEnd).
4107: */
4108: if( (nEq<pIdx->nColumn && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
4109: || (bRev && pIdx->nColumn==nEq)
4110: ){
4111: SWAP(WhereTerm *, pRangeEnd, pRangeStart);
4112: }
4113:
4114: testcase( pRangeStart && pRangeStart->eOperator & WO_LE );
4115: testcase( pRangeStart && pRangeStart->eOperator & WO_GE );
4116: testcase( pRangeEnd && pRangeEnd->eOperator & WO_LE );
4117: testcase( pRangeEnd && pRangeEnd->eOperator & WO_GE );
4118: startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
4119: endEq = !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
4120: start_constraints = pRangeStart || nEq>0;
4121:
4122: /* Seek the index cursor to the start of the range. */
4123: nConstraint = nEq;
4124: if( pRangeStart ){
4125: Expr *pRight = pRangeStart->pExpr->pRight;
4126: sqlite3ExprCode(pParse, pRight, regBase+nEq);
4127: if( (pRangeStart->wtFlags & TERM_VNULL)==0 ){
4128: sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
4129: }
4130: if( zStartAff ){
4131: if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
4132: /* Since the comparison is to be performed with no conversions
4133: ** applied to the operands, set the affinity to apply to pRight to
4134: ** SQLITE_AFF_NONE. */
4135: zStartAff[nEq] = SQLITE_AFF_NONE;
4136: }
4137: if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
4138: zStartAff[nEq] = SQLITE_AFF_NONE;
4139: }
4140: }
4141: nConstraint++;
4142: testcase( pRangeStart->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
4143: }else if( isMinQuery ){
4144: sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
4145: nConstraint++;
4146: startEq = 0;
4147: start_constraints = 1;
4148: }
4149: codeApplyAffinity(pParse, regBase, nConstraint, zStartAff);
4150: op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
4151: assert( op!=0 );
4152: testcase( op==OP_Rewind );
4153: testcase( op==OP_Last );
4154: testcase( op==OP_SeekGt );
4155: testcase( op==OP_SeekGe );
4156: testcase( op==OP_SeekLe );
4157: testcase( op==OP_SeekLt );
4158: sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
4159:
4160: /* Load the value for the inequality constraint at the end of the
4161: ** range (if any).
4162: */
4163: nConstraint = nEq;
4164: if( pRangeEnd ){
4165: Expr *pRight = pRangeEnd->pExpr->pRight;
4166: sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
4167: sqlite3ExprCode(pParse, pRight, regBase+nEq);
4168: if( (pRangeEnd->wtFlags & TERM_VNULL)==0 ){
4169: sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
4170: }
4171: if( zEndAff ){
4172: if( sqlite3CompareAffinity(pRight, zEndAff[nEq])==SQLITE_AFF_NONE){
4173: /* Since the comparison is to be performed with no conversions
4174: ** applied to the operands, set the affinity to apply to pRight to
4175: ** SQLITE_AFF_NONE. */
4176: zEndAff[nEq] = SQLITE_AFF_NONE;
4177: }
4178: if( sqlite3ExprNeedsNoAffinityChange(pRight, zEndAff[nEq]) ){
4179: zEndAff[nEq] = SQLITE_AFF_NONE;
4180: }
4181: }
4182: codeApplyAffinity(pParse, regBase, nEq+1, zEndAff);
4183: nConstraint++;
4184: testcase( pRangeEnd->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
4185: }
4186: sqlite3DbFree(pParse->db, zStartAff);
4187: sqlite3DbFree(pParse->db, zEndAff);
4188:
4189: /* Top of the loop body */
4190: pLevel->p2 = sqlite3VdbeCurrentAddr(v);
4191:
4192: /* Check if the index cursor is past the end of the range. */
4193: op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
4194: testcase( op==OP_Noop );
4195: testcase( op==OP_IdxGE );
4196: testcase( op==OP_IdxLT );
4197: if( op!=OP_Noop ){
4198: sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
4199: sqlite3VdbeChangeP5(v, endEq!=bRev ?1:0);
4200: }
4201:
4202: /* If there are inequality constraints, check that the value
4203: ** of the table column that the inequality contrains is not NULL.
4204: ** If it is, jump to the next iteration of the loop.
4205: */
4206: r1 = sqlite3GetTempReg(pParse);
4207: testcase( pLevel->plan.wsFlags & WHERE_BTM_LIMIT );
4208: testcase( pLevel->plan.wsFlags & WHERE_TOP_LIMIT );
4209: if( (pLevel->plan.wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0 ){
4210: sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
4211: sqlite3VdbeAddOp2(v, OP_IsNull, r1, addrCont);
4212: }
4213: sqlite3ReleaseTempReg(pParse, r1);
4214:
4215: /* Seek the table cursor, if required */
4216: disableTerm(pLevel, pRangeStart);
4217: disableTerm(pLevel, pRangeEnd);
4218: if( !omitTable ){
4219: iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
4220: sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
4221: sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
4222: sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg); /* Deferred seek */
4223: }
4224:
4225: /* Record the instruction used to terminate the loop. Disable
4226: ** WHERE clause terms made redundant by the index range scan.
4227: */
4228: if( pLevel->plan.wsFlags & WHERE_UNIQUE ){
4229: pLevel->op = OP_Noop;
4230: }else if( bRev ){
4231: pLevel->op = OP_Prev;
4232: }else{
4233: pLevel->op = OP_Next;
4234: }
4235: pLevel->p1 = iIdxCur;
4236: }else
4237:
4238: #ifndef SQLITE_OMIT_OR_OPTIMIZATION
4239: if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
4240: /* Case 4: Two or more separately indexed terms connected by OR
4241: **
4242: ** Example:
4243: **
4244: ** CREATE TABLE t1(a,b,c,d);
4245: ** CREATE INDEX i1 ON t1(a);
4246: ** CREATE INDEX i2 ON t1(b);
4247: ** CREATE INDEX i3 ON t1(c);
4248: **
4249: ** SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
4250: **
4251: ** In the example, there are three indexed terms connected by OR.
4252: ** The top of the loop looks like this:
4253: **
4254: ** Null 1 # Zero the rowset in reg 1
4255: **
4256: ** Then, for each indexed term, the following. The arguments to
4257: ** RowSetTest are such that the rowid of the current row is inserted
4258: ** into the RowSet. If it is already present, control skips the
4259: ** Gosub opcode and jumps straight to the code generated by WhereEnd().
4260: **
4261: ** sqlite3WhereBegin(<term>)
4262: ** RowSetTest # Insert rowid into rowset
4263: ** Gosub 2 A
4264: ** sqlite3WhereEnd()
4265: **
4266: ** Following the above, code to terminate the loop. Label A, the target
4267: ** of the Gosub above, jumps to the instruction right after the Goto.
4268: **
4269: ** Null 1 # Zero the rowset in reg 1
4270: ** Goto B # The loop is finished.
4271: **
4272: ** A: <loop body> # Return data, whatever.
4273: **
4274: ** Return 2 # Jump back to the Gosub
4275: **
4276: ** B: <after the loop>
4277: **
4278: */
4279: WhereClause *pOrWc; /* The OR-clause broken out into subterms */
4280: SrcList *pOrTab; /* Shortened table list or OR-clause generation */
4281:
4282: int regReturn = ++pParse->nMem; /* Register used with OP_Gosub */
4283: int regRowset = 0; /* Register for RowSet object */
4284: int regRowid = 0; /* Register holding rowid */
4285: int iLoopBody = sqlite3VdbeMakeLabel(v); /* Start of loop body */
4286: int iRetInit; /* Address of regReturn init */
4287: int untestedTerms = 0; /* Some terms not completely tested */
4288: int ii; /* Loop counter */
4289: Expr *pAndExpr = 0; /* An ".. AND (...)" expression */
4290:
4291: pTerm = pLevel->plan.u.pTerm;
4292: assert( pTerm!=0 );
4293: assert( pTerm->eOperator==WO_OR );
4294: assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
4295: pOrWc = &pTerm->u.pOrInfo->wc;
4296: pLevel->op = OP_Return;
4297: pLevel->p1 = regReturn;
4298:
4299: /* Set up a new SrcList ni pOrTab containing the table being scanned
4300: ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
4301: ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
4302: */
4303: if( pWInfo->nLevel>1 ){
4304: int nNotReady; /* The number of notReady tables */
4305: struct SrcList_item *origSrc; /* Original list of tables */
4306: nNotReady = pWInfo->nLevel - iLevel - 1;
4307: pOrTab = sqlite3StackAllocRaw(pParse->db,
4308: sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
4309: if( pOrTab==0 ) return notReady;
4310: pOrTab->nAlloc = (i16)(nNotReady + 1);
4311: pOrTab->nSrc = pOrTab->nAlloc;
4312: memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
4313: origSrc = pWInfo->pTabList->a;
4314: for(k=1; k<=nNotReady; k++){
4315: memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
4316: }
4317: }else{
4318: pOrTab = pWInfo->pTabList;
4319: }
4320:
4321: /* Initialize the rowset register to contain NULL. An SQL NULL is
4322: ** equivalent to an empty rowset.
4323: **
4324: ** Also initialize regReturn to contain the address of the instruction
4325: ** immediately following the OP_Return at the bottom of the loop. This
4326: ** is required in a few obscure LEFT JOIN cases where control jumps
4327: ** over the top of the loop into the body of it. In this case the
4328: ** correct response for the end-of-loop code (the OP_Return) is to
4329: ** fall through to the next instruction, just as an OP_Next does if
4330: ** called on an uninitialized cursor.
4331: */
4332: if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
4333: regRowset = ++pParse->nMem;
4334: regRowid = ++pParse->nMem;
4335: sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
4336: }
4337: iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
4338:
4339: /* If the original WHERE clause is z of the form: (x1 OR x2 OR ...) AND y
4340: ** Then for every term xN, evaluate as the subexpression: xN AND z
4341: ** That way, terms in y that are factored into the disjunction will
4342: ** be picked up by the recursive calls to sqlite3WhereBegin() below.
4343: */
4344: if( pWC->nTerm>1 ){
4345: pAndExpr = sqlite3ExprAlloc(pParse->db, TK_AND, 0, 0);
4346: pAndExpr->pRight = pWhere;
4347: }
4348:
4349: for(ii=0; ii<pOrWc->nTerm; ii++){
4350: WhereTerm *pOrTerm = &pOrWc->a[ii];
4351: if( pOrTerm->leftCursor==iCur || pOrTerm->eOperator==WO_AND ){
4352: WhereInfo *pSubWInfo; /* Info for single OR-term scan */
4353: Expr *pOrExpr = pOrTerm->pExpr;
4354: if( pAndExpr ){
4355: pAndExpr->pLeft = pOrExpr;
4356: pOrExpr = pAndExpr;
4357: }
4358: /* Loop through table entries that match term pOrTerm. */
4359: pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
4360: WHERE_OMIT_OPEN_CLOSE | WHERE_AND_ONLY |
4361: WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY);
4362: if( pSubWInfo ){
4363: explainOneScan(
4364: pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
4365: );
4366: if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
4367: int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
4368: int r;
4369: r = sqlite3ExprCodeGetColumn(pParse, pTabItem->pTab, -1, iCur,
4370: regRowid);
4371: sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset,
4372: sqlite3VdbeCurrentAddr(v)+2, r, iSet);
4373: }
4374: sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
4375:
4376: /* The pSubWInfo->untestedTerms flag means that this OR term
4377: ** contained one or more AND term from a notReady table. The
4378: ** terms from the notReady table could not be tested and will
4379: ** need to be tested later.
4380: */
4381: if( pSubWInfo->untestedTerms ) untestedTerms = 1;
4382:
4383: /* Finish the loop through table entries that match term pOrTerm. */
4384: sqlite3WhereEnd(pSubWInfo);
4385: }
4386: }
4387: }
4388: sqlite3DbFree(pParse->db, pAndExpr);
4389: sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
4390: sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
4391: sqlite3VdbeResolveLabel(v, iLoopBody);
4392:
4393: if( pWInfo->nLevel>1 ) sqlite3StackFree(pParse->db, pOrTab);
4394: if( !untestedTerms ) disableTerm(pLevel, pTerm);
4395: }else
4396: #endif /* SQLITE_OMIT_OR_OPTIMIZATION */
4397:
4398: {
4399: /* Case 5: There is no usable index. We must do a complete
4400: ** scan of the entire table.
4401: */
4402: static const u8 aStep[] = { OP_Next, OP_Prev };
4403: static const u8 aStart[] = { OP_Rewind, OP_Last };
4404: assert( bRev==0 || bRev==1 );
4405: assert( omitTable==0 );
4406: pLevel->op = aStep[bRev];
4407: pLevel->p1 = iCur;
4408: pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
4409: pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
4410: }
4411: notReady &= ~getMask(pWC->pMaskSet, iCur);
4412:
4413: /* Insert code to test every subexpression that can be completely
4414: ** computed using the current set of tables.
4415: **
4416: ** IMPLEMENTATION-OF: R-49525-50935 Terms that cannot be satisfied through
4417: ** the use of indices become tests that are evaluated against each row of
4418: ** the relevant input tables.
4419: */
4420: for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
4421: Expr *pE;
4422: testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* IMP: R-30575-11662 */
4423: testcase( pTerm->wtFlags & TERM_CODED );
4424: if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
4425: if( (pTerm->prereqAll & notReady)!=0 ){
4426: testcase( pWInfo->untestedTerms==0
4427: && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
4428: pWInfo->untestedTerms = 1;
4429: continue;
4430: }
4431: pE = pTerm->pExpr;
4432: assert( pE!=0 );
4433: if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
4434: continue;
4435: }
4436: sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
4437: pTerm->wtFlags |= TERM_CODED;
4438: }
4439:
4440: /* For a LEFT OUTER JOIN, generate code that will record the fact that
4441: ** at least one row of the right table has matched the left table.
4442: */
4443: if( pLevel->iLeftJoin ){
4444: pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
4445: sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
4446: VdbeComment((v, "record LEFT JOIN hit"));
4447: sqlite3ExprCacheClear(pParse);
4448: for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
4449: testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* IMP: R-30575-11662 */
4450: testcase( pTerm->wtFlags & TERM_CODED );
4451: if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
4452: if( (pTerm->prereqAll & notReady)!=0 ){
4453: assert( pWInfo->untestedTerms );
4454: continue;
4455: }
4456: assert( pTerm->pExpr );
4457: sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
4458: pTerm->wtFlags |= TERM_CODED;
4459: }
4460: }
4461: sqlite3ReleaseTempReg(pParse, iReleaseReg);
4462:
4463: return notReady;
4464: }
4465:
4466: #if defined(SQLITE_TEST)
4467: /*
4468: ** The following variable holds a text description of query plan generated
4469: ** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin
4470: ** overwrites the previous. This information is used for testing and
4471: ** analysis only.
4472: */
4473: char sqlite3_query_plan[BMS*2*40]; /* Text of the join */
4474: static int nQPlan = 0; /* Next free slow in _query_plan[] */
4475:
4476: #endif /* SQLITE_TEST */
4477:
4478:
4479: /*
4480: ** Free a WhereInfo structure
4481: */
4482: static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
4483: if( ALWAYS(pWInfo) ){
4484: int i;
4485: for(i=0; i<pWInfo->nLevel; i++){
4486: sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
4487: if( pInfo ){
4488: /* assert( pInfo->needToFreeIdxStr==0 || db->mallocFailed ); */
4489: if( pInfo->needToFreeIdxStr ){
4490: sqlite3_free(pInfo->idxStr);
4491: }
4492: sqlite3DbFree(db, pInfo);
4493: }
4494: if( pWInfo->a[i].plan.wsFlags & WHERE_TEMP_INDEX ){
4495: Index *pIdx = pWInfo->a[i].plan.u.pIdx;
4496: if( pIdx ){
4497: sqlite3DbFree(db, pIdx->zColAff);
4498: sqlite3DbFree(db, pIdx);
4499: }
4500: }
4501: }
4502: whereClauseClear(pWInfo->pWC);
4503: sqlite3DbFree(db, pWInfo);
4504: }
4505: }
4506:
4507:
4508: /*
4509: ** Generate the beginning of the loop used for WHERE clause processing.
4510: ** The return value is a pointer to an opaque structure that contains
4511: ** information needed to terminate the loop. Later, the calling routine
4512: ** should invoke sqlite3WhereEnd() with the return value of this function
4513: ** in order to complete the WHERE clause processing.
4514: **
4515: ** If an error occurs, this routine returns NULL.
4516: **
4517: ** The basic idea is to do a nested loop, one loop for each table in
4518: ** the FROM clause of a select. (INSERT and UPDATE statements are the
4519: ** same as a SELECT with only a single table in the FROM clause.) For
4520: ** example, if the SQL is this:
4521: **
4522: ** SELECT * FROM t1, t2, t3 WHERE ...;
4523: **
4524: ** Then the code generated is conceptually like the following:
4525: **
4526: ** foreach row1 in t1 do \ Code generated
4527: ** foreach row2 in t2 do |-- by sqlite3WhereBegin()
4528: ** foreach row3 in t3 do /
4529: ** ...
4530: ** end \ Code generated
4531: ** end |-- by sqlite3WhereEnd()
4532: ** end /
4533: **
4534: ** Note that the loops might not be nested in the order in which they
4535: ** appear in the FROM clause if a different order is better able to make
4536: ** use of indices. Note also that when the IN operator appears in
4537: ** the WHERE clause, it might result in additional nested loops for
4538: ** scanning through all values on the right-hand side of the IN.
4539: **
4540: ** There are Btree cursors associated with each table. t1 uses cursor
4541: ** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
4542: ** And so forth. This routine generates code to open those VDBE cursors
4543: ** and sqlite3WhereEnd() generates the code to close them.
4544: **
4545: ** The code that sqlite3WhereBegin() generates leaves the cursors named
4546: ** in pTabList pointing at their appropriate entries. The [...] code
4547: ** can use OP_Column and OP_Rowid opcodes on these cursors to extract
4548: ** data from the various tables of the loop.
4549: **
4550: ** If the WHERE clause is empty, the foreach loops must each scan their
4551: ** entire tables. Thus a three-way join is an O(N^3) operation. But if
4552: ** the tables have indices and there are terms in the WHERE clause that
4553: ** refer to those indices, a complete table scan can be avoided and the
4554: ** code will run much faster. Most of the work of this routine is checking
4555: ** to see if there are indices that can be used to speed up the loop.
4556: **
4557: ** Terms of the WHERE clause are also used to limit which rows actually
4558: ** make it to the "..." in the middle of the loop. After each "foreach",
4559: ** terms of the WHERE clause that use only terms in that loop and outer
4560: ** loops are evaluated and if false a jump is made around all subsequent
4561: ** inner loops (or around the "..." if the test occurs within the inner-
4562: ** most loop)
4563: **
4564: ** OUTER JOINS
4565: **
4566: ** An outer join of tables t1 and t2 is conceptally coded as follows:
4567: **
4568: ** foreach row1 in t1 do
4569: ** flag = 0
4570: ** foreach row2 in t2 do
4571: ** start:
4572: ** ...
4573: ** flag = 1
4574: ** end
4575: ** if flag==0 then
4576: ** move the row2 cursor to a null row
4577: ** goto start
4578: ** fi
4579: ** end
4580: **
4581: ** ORDER BY CLAUSE PROCESSING
4582: **
4583: ** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
4584: ** if there is one. If there is no ORDER BY clause or if this routine
4585: ** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
4586: **
4587: ** If an index can be used so that the natural output order of the table
4588: ** scan is correct for the ORDER BY clause, then that index is used and
4589: ** *ppOrderBy is set to NULL. This is an optimization that prevents an
4590: ** unnecessary sort of the result set if an index appropriate for the
4591: ** ORDER BY clause already exists.
4592: **
4593: ** If the where clause loops cannot be arranged to provide the correct
4594: ** output order, then the *ppOrderBy is unchanged.
4595: */
4596: WhereInfo *sqlite3WhereBegin(
4597: Parse *pParse, /* The parser context */
4598: SrcList *pTabList, /* A list of all tables to be scanned */
4599: Expr *pWhere, /* The WHERE clause */
4600: ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
4601: ExprList *pDistinct, /* The select-list for DISTINCT queries - or NULL */
4602: u16 wctrlFlags /* One of the WHERE_* flags defined in sqliteInt.h */
4603: ){
4604: int i; /* Loop counter */
4605: int nByteWInfo; /* Num. bytes allocated for WhereInfo struct */
4606: int nTabList; /* Number of elements in pTabList */
4607: WhereInfo *pWInfo; /* Will become the return value of this function */
4608: Vdbe *v = pParse->pVdbe; /* The virtual database engine */
4609: Bitmask notReady; /* Cursors that are not yet positioned */
4610: WhereMaskSet *pMaskSet; /* The expression mask set */
4611: WhereClause *pWC; /* Decomposition of the WHERE clause */
4612: struct SrcList_item *pTabItem; /* A single entry from pTabList */
4613: WhereLevel *pLevel; /* A single level in the pWInfo list */
4614: int iFrom; /* First unused FROM clause element */
4615: int andFlags; /* AND-ed combination of all pWC->a[].wtFlags */
4616: sqlite3 *db; /* Database connection */
4617:
4618: /* The number of tables in the FROM clause is limited by the number of
4619: ** bits in a Bitmask
4620: */
4621: testcase( pTabList->nSrc==BMS );
4622: if( pTabList->nSrc>BMS ){
4623: sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
4624: return 0;
4625: }
4626:
4627: /* This function normally generates a nested loop for all tables in
4628: ** pTabList. But if the WHERE_ONETABLE_ONLY flag is set, then we should
4629: ** only generate code for the first table in pTabList and assume that
4630: ** any cursors associated with subsequent tables are uninitialized.
4631: */
4632: nTabList = (wctrlFlags & WHERE_ONETABLE_ONLY) ? 1 : pTabList->nSrc;
4633:
4634: /* Allocate and initialize the WhereInfo structure that will become the
4635: ** return value. A single allocation is used to store the WhereInfo
4636: ** struct, the contents of WhereInfo.a[], the WhereClause structure
4637: ** and the WhereMaskSet structure. Since WhereClause contains an 8-byte
4638: ** field (type Bitmask) it must be aligned on an 8-byte boundary on
4639: ** some architectures. Hence the ROUND8() below.
4640: */
4641: db = pParse->db;
4642: nByteWInfo = ROUND8(sizeof(WhereInfo)+(nTabList-1)*sizeof(WhereLevel));
4643: pWInfo = sqlite3DbMallocZero(db,
4644: nByteWInfo +
4645: sizeof(WhereClause) +
4646: sizeof(WhereMaskSet)
4647: );
4648: if( db->mallocFailed ){
4649: sqlite3DbFree(db, pWInfo);
4650: pWInfo = 0;
4651: goto whereBeginError;
4652: }
4653: pWInfo->nLevel = nTabList;
4654: pWInfo->pParse = pParse;
4655: pWInfo->pTabList = pTabList;
4656: pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
4657: pWInfo->pWC = pWC = (WhereClause *)&((u8 *)pWInfo)[nByteWInfo];
4658: pWInfo->wctrlFlags = wctrlFlags;
4659: pWInfo->savedNQueryLoop = pParse->nQueryLoop;
4660: pMaskSet = (WhereMaskSet*)&pWC[1];
4661:
4662: /* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via
4663: ** sqlite3_test_ctrl(SQLITE_TESTCTRL_OPTIMIZATIONS,...) */
4664: if( db->flags & SQLITE_DistinctOpt ) pDistinct = 0;
4665:
4666: /* Split the WHERE clause into separate subexpressions where each
4667: ** subexpression is separated by an AND operator.
4668: */
4669: initMaskSet(pMaskSet);
4670: whereClauseInit(pWC, pParse, pMaskSet, wctrlFlags);
4671: sqlite3ExprCodeConstants(pParse, pWhere);
4672: whereSplit(pWC, pWhere, TK_AND); /* IMP: R-15842-53296 */
4673:
4674: /* Special case: a WHERE clause that is constant. Evaluate the
4675: ** expression and either jump over all of the code or fall thru.
4676: */
4677: if( pWhere && (nTabList==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
4678: sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, SQLITE_JUMPIFNULL);
4679: pWhere = 0;
4680: }
4681:
4682: /* Assign a bit from the bitmask to every term in the FROM clause.
4683: **
4684: ** When assigning bitmask values to FROM clause cursors, it must be
4685: ** the case that if X is the bitmask for the N-th FROM clause term then
4686: ** the bitmask for all FROM clause terms to the left of the N-th term
4687: ** is (X-1). An expression from the ON clause of a LEFT JOIN can use
4688: ** its Expr.iRightJoinTable value to find the bitmask of the right table
4689: ** of the join. Subtracting one from the right table bitmask gives a
4690: ** bitmask for all tables to the left of the join. Knowing the bitmask
4691: ** for all tables to the left of a left join is important. Ticket #3015.
4692: **
4693: ** Configure the WhereClause.vmask variable so that bits that correspond
4694: ** to virtual table cursors are set. This is used to selectively disable
4695: ** the OR-to-IN transformation in exprAnalyzeOrTerm(). It is not helpful
4696: ** with virtual tables.
4697: **
4698: ** Note that bitmasks are created for all pTabList->nSrc tables in
4699: ** pTabList, not just the first nTabList tables. nTabList is normally
4700: ** equal to pTabList->nSrc but might be shortened to 1 if the
4701: ** WHERE_ONETABLE_ONLY flag is set.
4702: */
4703: assert( pWC->vmask==0 && pMaskSet->n==0 );
4704: for(i=0; i<pTabList->nSrc; i++){
4705: createMask(pMaskSet, pTabList->a[i].iCursor);
4706: #ifndef SQLITE_OMIT_VIRTUALTABLE
4707: if( ALWAYS(pTabList->a[i].pTab) && IsVirtual(pTabList->a[i].pTab) ){
4708: pWC->vmask |= ((Bitmask)1 << i);
4709: }
4710: #endif
4711: }
4712: #ifndef NDEBUG
4713: {
4714: Bitmask toTheLeft = 0;
4715: for(i=0; i<pTabList->nSrc; i++){
4716: Bitmask m = getMask(pMaskSet, pTabList->a[i].iCursor);
4717: assert( (m-1)==toTheLeft );
4718: toTheLeft |= m;
4719: }
4720: }
4721: #endif
4722:
4723: /* Analyze all of the subexpressions. Note that exprAnalyze() might
4724: ** add new virtual terms onto the end of the WHERE clause. We do not
4725: ** want to analyze these virtual terms, so start analyzing at the end
4726: ** and work forward so that the added virtual terms are never processed.
4727: */
4728: exprAnalyzeAll(pTabList, pWC);
4729: if( db->mallocFailed ){
4730: goto whereBeginError;
4731: }
4732:
4733: /* Check if the DISTINCT qualifier, if there is one, is redundant.
4734: ** If it is, then set pDistinct to NULL and WhereInfo.eDistinct to
4735: ** WHERE_DISTINCT_UNIQUE to tell the caller to ignore the DISTINCT.
4736: */
4737: if( pDistinct && isDistinctRedundant(pParse, pTabList, pWC, pDistinct) ){
4738: pDistinct = 0;
4739: pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
4740: }
4741:
4742: /* Chose the best index to use for each table in the FROM clause.
4743: **
4744: ** This loop fills in the following fields:
4745: **
4746: ** pWInfo->a[].pIdx The index to use for this level of the loop.
4747: ** pWInfo->a[].wsFlags WHERE_xxx flags associated with pIdx
4748: ** pWInfo->a[].nEq The number of == and IN constraints
4749: ** pWInfo->a[].iFrom Which term of the FROM clause is being coded
4750: ** pWInfo->a[].iTabCur The VDBE cursor for the database table
4751: ** pWInfo->a[].iIdxCur The VDBE cursor for the index
4752: ** pWInfo->a[].pTerm When wsFlags==WO_OR, the OR-clause term
4753: **
4754: ** This loop also figures out the nesting order of tables in the FROM
4755: ** clause.
4756: */
4757: notReady = ~(Bitmask)0;
4758: andFlags = ~0;
4759: WHERETRACE(("*** Optimizer Start ***\n"));
4760: for(i=iFrom=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
4761: WhereCost bestPlan; /* Most efficient plan seen so far */
4762: Index *pIdx; /* Index for FROM table at pTabItem */
4763: int j; /* For looping over FROM tables */
4764: int bestJ = -1; /* The value of j */
4765: Bitmask m; /* Bitmask value for j or bestJ */
4766: int isOptimal; /* Iterator for optimal/non-optimal search */
4767: int nUnconstrained; /* Number tables without INDEXED BY */
4768: Bitmask notIndexed; /* Mask of tables that cannot use an index */
4769:
4770: memset(&bestPlan, 0, sizeof(bestPlan));
4771: bestPlan.rCost = SQLITE_BIG_DBL;
4772: WHERETRACE(("*** Begin search for loop %d ***\n", i));
4773:
4774: /* Loop through the remaining entries in the FROM clause to find the
4775: ** next nested loop. The loop tests all FROM clause entries
4776: ** either once or twice.
4777: **
4778: ** The first test is always performed if there are two or more entries
4779: ** remaining and never performed if there is only one FROM clause entry
4780: ** to choose from. The first test looks for an "optimal" scan. In
4781: ** this context an optimal scan is one that uses the same strategy
4782: ** for the given FROM clause entry as would be selected if the entry
4783: ** were used as the innermost nested loop. In other words, a table
4784: ** is chosen such that the cost of running that table cannot be reduced
4785: ** by waiting for other tables to run first. This "optimal" test works
4786: ** by first assuming that the FROM clause is on the inner loop and finding
4787: ** its query plan, then checking to see if that query plan uses any
4788: ** other FROM clause terms that are notReady. If no notReady terms are
4789: ** used then the "optimal" query plan works.
4790: **
4791: ** Note that the WhereCost.nRow parameter for an optimal scan might
4792: ** not be as small as it would be if the table really were the innermost
4793: ** join. The nRow value can be reduced by WHERE clause constraints
4794: ** that do not use indices. But this nRow reduction only happens if the
4795: ** table really is the innermost join.
4796: **
4797: ** The second loop iteration is only performed if no optimal scan
4798: ** strategies were found by the first iteration. This second iteration
4799: ** is used to search for the lowest cost scan overall.
4800: **
4801: ** Previous versions of SQLite performed only the second iteration -
4802: ** the next outermost loop was always that with the lowest overall
4803: ** cost. However, this meant that SQLite could select the wrong plan
4804: ** for scripts such as the following:
4805: **
4806: ** CREATE TABLE t1(a, b);
4807: ** CREATE TABLE t2(c, d);
4808: ** SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
4809: **
4810: ** The best strategy is to iterate through table t1 first. However it
4811: ** is not possible to determine this with a simple greedy algorithm.
4812: ** Since the cost of a linear scan through table t2 is the same
4813: ** as the cost of a linear scan through table t1, a simple greedy
4814: ** algorithm may choose to use t2 for the outer loop, which is a much
4815: ** costlier approach.
4816: */
4817: nUnconstrained = 0;
4818: notIndexed = 0;
4819: for(isOptimal=(iFrom<nTabList-1); isOptimal>=0 && bestJ<0; isOptimal--){
4820: Bitmask mask; /* Mask of tables not yet ready */
4821: for(j=iFrom, pTabItem=&pTabList->a[j]; j<nTabList; j++, pTabItem++){
4822: int doNotReorder; /* True if this table should not be reordered */
4823: WhereCost sCost; /* Cost information from best[Virtual]Index() */
4824: ExprList *pOrderBy; /* ORDER BY clause for index to optimize */
4825: ExprList *pDist; /* DISTINCT clause for index to optimize */
4826:
4827: doNotReorder = (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
4828: if( j!=iFrom && doNotReorder ) break;
4829: m = getMask(pMaskSet, pTabItem->iCursor);
4830: if( (m & notReady)==0 ){
4831: if( j==iFrom ) iFrom++;
4832: continue;
4833: }
4834: mask = (isOptimal ? m : notReady);
4835: pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
4836: pDist = (i==0 ? pDistinct : 0);
4837: if( pTabItem->pIndex==0 ) nUnconstrained++;
4838:
4839: WHERETRACE(("=== trying table %d with isOptimal=%d ===\n",
4840: j, isOptimal));
4841: assert( pTabItem->pTab );
4842: #ifndef SQLITE_OMIT_VIRTUALTABLE
4843: if( IsVirtual(pTabItem->pTab) ){
4844: sqlite3_index_info **pp = &pWInfo->a[j].pIdxInfo;
4845: bestVirtualIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
4846: &sCost, pp);
4847: }else
4848: #endif
4849: {
4850: bestBtreeIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
4851: pDist, &sCost);
4852: }
4853: assert( isOptimal || (sCost.used¬Ready)==0 );
4854:
4855: /* If an INDEXED BY clause is present, then the plan must use that
4856: ** index if it uses any index at all */
4857: assert( pTabItem->pIndex==0
4858: || (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0
4859: || sCost.plan.u.pIdx==pTabItem->pIndex );
4860:
4861: if( isOptimal && (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ){
4862: notIndexed |= m;
4863: }
4864:
4865: /* Conditions under which this table becomes the best so far:
4866: **
4867: ** (1) The table must not depend on other tables that have not
4868: ** yet run.
4869: **
4870: ** (2) A full-table-scan plan cannot supercede indexed plan unless
4871: ** the full-table-scan is an "optimal" plan as defined above.
4872: **
4873: ** (3) All tables have an INDEXED BY clause or this table lacks an
4874: ** INDEXED BY clause or this table uses the specific
4875: ** index specified by its INDEXED BY clause. This rule ensures
4876: ** that a best-so-far is always selected even if an impossible
4877: ** combination of INDEXED BY clauses are given. The error
4878: ** will be detected and relayed back to the application later.
4879: ** The NEVER() comes about because rule (2) above prevents
4880: ** An indexable full-table-scan from reaching rule (3).
4881: **
4882: ** (4) The plan cost must be lower than prior plans or else the
4883: ** cost must be the same and the number of rows must be lower.
4884: */
4885: if( (sCost.used¬Ready)==0 /* (1) */
4886: && (bestJ<0 || (notIndexed&m)!=0 /* (2) */
4887: || (bestPlan.plan.wsFlags & WHERE_NOT_FULLSCAN)==0
4888: || (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0)
4889: && (nUnconstrained==0 || pTabItem->pIndex==0 /* (3) */
4890: || NEVER((sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0))
4891: && (bestJ<0 || sCost.rCost<bestPlan.rCost /* (4) */
4892: || (sCost.rCost<=bestPlan.rCost
4893: && sCost.plan.nRow<bestPlan.plan.nRow))
4894: ){
4895: WHERETRACE(("=== table %d is best so far"
4896: " with cost=%g and nRow=%g\n",
4897: j, sCost.rCost, sCost.plan.nRow));
4898: bestPlan = sCost;
4899: bestJ = j;
4900: }
4901: if( doNotReorder ) break;
4902: }
4903: }
4904: assert( bestJ>=0 );
4905: assert( notReady & getMask(pMaskSet, pTabList->a[bestJ].iCursor) );
4906: WHERETRACE(("*** Optimizer selects table %d for loop %d"
4907: " with cost=%g and nRow=%g\n",
4908: bestJ, pLevel-pWInfo->a, bestPlan.rCost, bestPlan.plan.nRow));
4909: /* The ALWAYS() that follows was added to hush up clang scan-build */
4910: if( (bestPlan.plan.wsFlags & WHERE_ORDERBY)!=0 && ALWAYS(ppOrderBy) ){
4911: *ppOrderBy = 0;
4912: }
4913: if( (bestPlan.plan.wsFlags & WHERE_DISTINCT)!=0 ){
4914: assert( pWInfo->eDistinct==0 );
4915: pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
4916: }
4917: andFlags &= bestPlan.plan.wsFlags;
4918: pLevel->plan = bestPlan.plan;
4919: testcase( bestPlan.plan.wsFlags & WHERE_INDEXED );
4920: testcase( bestPlan.plan.wsFlags & WHERE_TEMP_INDEX );
4921: if( bestPlan.plan.wsFlags & (WHERE_INDEXED|WHERE_TEMP_INDEX) ){
4922: pLevel->iIdxCur = pParse->nTab++;
4923: }else{
4924: pLevel->iIdxCur = -1;
4925: }
4926: notReady &= ~getMask(pMaskSet, pTabList->a[bestJ].iCursor);
4927: pLevel->iFrom = (u8)bestJ;
4928: if( bestPlan.plan.nRow>=(double)1 ){
4929: pParse->nQueryLoop *= bestPlan.plan.nRow;
4930: }
4931:
4932: /* Check that if the table scanned by this loop iteration had an
4933: ** INDEXED BY clause attached to it, that the named index is being
4934: ** used for the scan. If not, then query compilation has failed.
4935: ** Return an error.
4936: */
4937: pIdx = pTabList->a[bestJ].pIndex;
4938: if( pIdx ){
4939: if( (bestPlan.plan.wsFlags & WHERE_INDEXED)==0 ){
4940: sqlite3ErrorMsg(pParse, "cannot use index: %s", pIdx->zName);
4941: goto whereBeginError;
4942: }else{
4943: /* If an INDEXED BY clause is used, the bestIndex() function is
4944: ** guaranteed to find the index specified in the INDEXED BY clause
4945: ** if it find an index at all. */
4946: assert( bestPlan.plan.u.pIdx==pIdx );
4947: }
4948: }
4949: }
4950: WHERETRACE(("*** Optimizer Finished ***\n"));
4951: if( pParse->nErr || db->mallocFailed ){
4952: goto whereBeginError;
4953: }
4954:
4955: /* If the total query only selects a single row, then the ORDER BY
4956: ** clause is irrelevant.
4957: */
4958: if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
4959: *ppOrderBy = 0;
4960: }
4961:
4962: /* If the caller is an UPDATE or DELETE statement that is requesting
4963: ** to use a one-pass algorithm, determine if this is appropriate.
4964: ** The one-pass algorithm only works if the WHERE clause constraints
4965: ** the statement to update a single row.
4966: */
4967: assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
4968: if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
4969: pWInfo->okOnePass = 1;
4970: pWInfo->a[0].plan.wsFlags &= ~WHERE_IDX_ONLY;
4971: }
4972:
4973: /* Open all tables in the pTabList and any indices selected for
4974: ** searching those tables.
4975: */
4976: sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
4977: notReady = ~(Bitmask)0;
4978: pWInfo->nRowOut = (double)1;
4979: for(i=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
4980: Table *pTab; /* Table to open */
4981: int iDb; /* Index of database containing table/index */
4982:
4983: pTabItem = &pTabList->a[pLevel->iFrom];
4984: pTab = pTabItem->pTab;
4985: pLevel->iTabCur = pTabItem->iCursor;
4986: pWInfo->nRowOut *= pLevel->plan.nRow;
4987: iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
4988: if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
4989: /* Do nothing */
4990: }else
4991: #ifndef SQLITE_OMIT_VIRTUALTABLE
4992: if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
4993: const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
4994: int iCur = pTabItem->iCursor;
4995: sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
4996: }else
4997: #endif
4998: if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
4999: && (wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0 ){
5000: int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
5001: sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
5002: testcase( pTab->nCol==BMS-1 );
5003: testcase( pTab->nCol==BMS );
5004: if( !pWInfo->okOnePass && pTab->nCol<BMS ){
5005: Bitmask b = pTabItem->colUsed;
5006: int n = 0;
5007: for(; b; b=b>>1, n++){}
5008: sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1,
5009: SQLITE_INT_TO_PTR(n), P4_INT32);
5010: assert( n<=pTab->nCol );
5011: }
5012: }else{
5013: sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
5014: }
5015: #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
5016: if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
5017: constructAutomaticIndex(pParse, pWC, pTabItem, notReady, pLevel);
5018: }else
5019: #endif
5020: if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
5021: Index *pIx = pLevel->plan.u.pIdx;
5022: KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
5023: int iIdxCur = pLevel->iIdxCur;
5024: assert( pIx->pSchema==pTab->pSchema );
5025: assert( iIdxCur>=0 );
5026: sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIx->tnum, iDb,
5027: (char*)pKey, P4_KEYINFO_HANDOFF);
5028: VdbeComment((v, "%s", pIx->zName));
5029: }
5030: sqlite3CodeVerifySchema(pParse, iDb);
5031: notReady &= ~getMask(pWC->pMaskSet, pTabItem->iCursor);
5032: }
5033: pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
5034: if( db->mallocFailed ) goto whereBeginError;
5035:
5036: /* Generate the code to do the search. Each iteration of the for
5037: ** loop below generates code for a single nested loop of the VM
5038: ** program.
5039: */
5040: notReady = ~(Bitmask)0;
5041: for(i=0; i<nTabList; i++){
5042: pLevel = &pWInfo->a[i];
5043: explainOneScan(pParse, pTabList, pLevel, i, pLevel->iFrom, wctrlFlags);
5044: notReady = codeOneLoopStart(pWInfo, i, wctrlFlags, notReady, pWhere);
5045: pWInfo->iContinue = pLevel->addrCont;
5046: }
5047:
5048: #ifdef SQLITE_TEST /* For testing and debugging use only */
5049: /* Record in the query plan information about the current table
5050: ** and the index used to access it (if any). If the table itself
5051: ** is not used, its name is just '{}'. If no index is used
5052: ** the index is listed as "{}". If the primary key is used the
5053: ** index name is '*'.
5054: */
5055: for(i=0; i<nTabList; i++){
5056: char *z;
5057: int n;
5058: pLevel = &pWInfo->a[i];
5059: pTabItem = &pTabList->a[pLevel->iFrom];
5060: z = pTabItem->zAlias;
5061: if( z==0 ) z = pTabItem->pTab->zName;
5062: n = sqlite3Strlen30(z);
5063: if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
5064: if( pLevel->plan.wsFlags & WHERE_IDX_ONLY ){
5065: memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
5066: nQPlan += 2;
5067: }else{
5068: memcpy(&sqlite3_query_plan[nQPlan], z, n);
5069: nQPlan += n;
5070: }
5071: sqlite3_query_plan[nQPlan++] = ' ';
5072: }
5073: testcase( pLevel->plan.wsFlags & WHERE_ROWID_EQ );
5074: testcase( pLevel->plan.wsFlags & WHERE_ROWID_RANGE );
5075: if( pLevel->plan.wsFlags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
5076: memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
5077: nQPlan += 2;
5078: }else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
5079: n = sqlite3Strlen30(pLevel->plan.u.pIdx->zName);
5080: if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
5081: memcpy(&sqlite3_query_plan[nQPlan], pLevel->plan.u.pIdx->zName, n);
5082: nQPlan += n;
5083: sqlite3_query_plan[nQPlan++] = ' ';
5084: }
5085: }else{
5086: memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
5087: nQPlan += 3;
5088: }
5089: }
5090: while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
5091: sqlite3_query_plan[--nQPlan] = 0;
5092: }
5093: sqlite3_query_plan[nQPlan] = 0;
5094: nQPlan = 0;
5095: #endif /* SQLITE_TEST // Testing and debugging use only */
5096:
5097: /* Record the continuation address in the WhereInfo structure. Then
5098: ** clean up and return.
5099: */
5100: return pWInfo;
5101:
5102: /* Jump here if malloc fails */
5103: whereBeginError:
5104: if( pWInfo ){
5105: pParse->nQueryLoop = pWInfo->savedNQueryLoop;
5106: whereInfoFree(db, pWInfo);
5107: }
5108: return 0;
5109: }
5110:
5111: /*
5112: ** Generate the end of the WHERE loop. See comments on
5113: ** sqlite3WhereBegin() for additional information.
5114: */
5115: void sqlite3WhereEnd(WhereInfo *pWInfo){
5116: Parse *pParse = pWInfo->pParse;
5117: Vdbe *v = pParse->pVdbe;
5118: int i;
5119: WhereLevel *pLevel;
5120: SrcList *pTabList = pWInfo->pTabList;
5121: sqlite3 *db = pParse->db;
5122:
5123: /* Generate loop termination code.
5124: */
5125: sqlite3ExprCacheClear(pParse);
5126: for(i=pWInfo->nLevel-1; i>=0; i--){
5127: pLevel = &pWInfo->a[i];
5128: sqlite3VdbeResolveLabel(v, pLevel->addrCont);
5129: if( pLevel->op!=OP_Noop ){
5130: sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
5131: sqlite3VdbeChangeP5(v, pLevel->p5);
5132: }
5133: if( pLevel->plan.wsFlags & WHERE_IN_ABLE && pLevel->u.in.nIn>0 ){
5134: struct InLoop *pIn;
5135: int j;
5136: sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
5137: for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
5138: sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
5139: sqlite3VdbeAddOp2(v, OP_Next, pIn->iCur, pIn->addrInTop);
5140: sqlite3VdbeJumpHere(v, pIn->addrInTop-1);
5141: }
5142: sqlite3DbFree(db, pLevel->u.in.aInLoop);
5143: }
5144: sqlite3VdbeResolveLabel(v, pLevel->addrBrk);
5145: if( pLevel->iLeftJoin ){
5146: int addr;
5147: addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin);
5148: assert( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
5149: || (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 );
5150: if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0 ){
5151: sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
5152: }
5153: if( pLevel->iIdxCur>=0 ){
5154: sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
5155: }
5156: if( pLevel->op==OP_Return ){
5157: sqlite3VdbeAddOp2(v, OP_Gosub, pLevel->p1, pLevel->addrFirst);
5158: }else{
5159: sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrFirst);
5160: }
5161: sqlite3VdbeJumpHere(v, addr);
5162: }
5163: }
5164:
5165: /* The "break" point is here, just past the end of the outer loop.
5166: ** Set it.
5167: */
5168: sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
5169:
5170: /* Close all of the cursors that were opened by sqlite3WhereBegin.
5171: */
5172: assert( pWInfo->nLevel==1 || pWInfo->nLevel==pTabList->nSrc );
5173: for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
5174: struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
5175: Table *pTab = pTabItem->pTab;
5176: assert( pTab!=0 );
5177: if( (pTab->tabFlags & TF_Ephemeral)==0
5178: && pTab->pSelect==0
5179: && (pWInfo->wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0
5180: ){
5181: int ws = pLevel->plan.wsFlags;
5182: if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
5183: sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
5184: }
5185: if( (ws & WHERE_INDEXED)!=0 && (ws & WHERE_TEMP_INDEX)==0 ){
5186: sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
5187: }
5188: }
5189:
5190: /* If this scan uses an index, make code substitutions to read data
5191: ** from the index in preference to the table. Sometimes, this means
5192: ** the table need never be read from. This is a performance boost,
5193: ** as the vdbe level waits until the table is read before actually
5194: ** seeking the table cursor to the record corresponding to the current
5195: ** position in the index.
5196: **
5197: ** Calls to the code generator in between sqlite3WhereBegin and
5198: ** sqlite3WhereEnd will have created code that references the table
5199: ** directly. This loop scans all that code looking for opcodes
5200: ** that reference the table and converts them into opcodes that
5201: ** reference the index.
5202: */
5203: if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 && !db->mallocFailed){
5204: int k, j, last;
5205: VdbeOp *pOp;
5206: Index *pIdx = pLevel->plan.u.pIdx;
5207:
5208: assert( pIdx!=0 );
5209: pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
5210: last = sqlite3VdbeCurrentAddr(v);
5211: for(k=pWInfo->iTop; k<last; k++, pOp++){
5212: if( pOp->p1!=pLevel->iTabCur ) continue;
5213: if( pOp->opcode==OP_Column ){
5214: for(j=0; j<pIdx->nColumn; j++){
5215: if( pOp->p2==pIdx->aiColumn[j] ){
5216: pOp->p2 = j;
5217: pOp->p1 = pLevel->iIdxCur;
5218: break;
5219: }
5220: }
5221: assert( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
5222: || j<pIdx->nColumn );
5223: }else if( pOp->opcode==OP_Rowid ){
5224: pOp->p1 = pLevel->iIdxCur;
5225: pOp->opcode = OP_IdxRowid;
5226: }
5227: }
5228: }
5229: }
5230:
5231: /* Final cleanup
5232: */
5233: pParse->nQueryLoop = pWInfo->savedNQueryLoop;
5234: whereInfoFree(db, pWInfo);
5235: return;
5236: }
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