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 file contains C code routines that are called by the parser
13: ** to handle SELECT statements in SQLite.
14: */
15: #include "sqliteInt.h"
16:
17:
18: /*
19: ** Delete all the content of a Select structure but do not deallocate
20: ** the select structure itself.
21: */
22: static void clearSelect(sqlite3 *db, Select *p){
23: sqlite3ExprListDelete(db, p->pEList);
24: sqlite3SrcListDelete(db, p->pSrc);
25: sqlite3ExprDelete(db, p->pWhere);
26: sqlite3ExprListDelete(db, p->pGroupBy);
27: sqlite3ExprDelete(db, p->pHaving);
28: sqlite3ExprListDelete(db, p->pOrderBy);
29: sqlite3SelectDelete(db, p->pPrior);
30: sqlite3ExprDelete(db, p->pLimit);
31: sqlite3ExprDelete(db, p->pOffset);
32: }
33:
34: /*
35: ** Initialize a SelectDest structure.
36: */
37: void sqlite3SelectDestInit(SelectDest *pDest, int eDest, int iParm){
38: pDest->eDest = (u8)eDest;
39: pDest->iParm = iParm;
40: pDest->affinity = 0;
41: pDest->iMem = 0;
42: pDest->nMem = 0;
43: }
44:
45:
46: /*
47: ** Allocate a new Select structure and return a pointer to that
48: ** structure.
49: */
50: Select *sqlite3SelectNew(
51: Parse *pParse, /* Parsing context */
52: ExprList *pEList, /* which columns to include in the result */
53: SrcList *pSrc, /* the FROM clause -- which tables to scan */
54: Expr *pWhere, /* the WHERE clause */
55: ExprList *pGroupBy, /* the GROUP BY clause */
56: Expr *pHaving, /* the HAVING clause */
57: ExprList *pOrderBy, /* the ORDER BY clause */
58: int isDistinct, /* true if the DISTINCT keyword is present */
59: Expr *pLimit, /* LIMIT value. NULL means not used */
60: Expr *pOffset /* OFFSET value. NULL means no offset */
61: ){
62: Select *pNew;
63: Select standin;
64: sqlite3 *db = pParse->db;
65: pNew = sqlite3DbMallocZero(db, sizeof(*pNew) );
66: assert( db->mallocFailed || !pOffset || pLimit ); /* OFFSET implies LIMIT */
67: if( pNew==0 ){
68: assert( db->mallocFailed );
69: pNew = &standin;
70: memset(pNew, 0, sizeof(*pNew));
71: }
72: if( pEList==0 ){
73: pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db,TK_ALL,0));
74: }
75: pNew->pEList = pEList;
76: pNew->pSrc = pSrc;
77: pNew->pWhere = pWhere;
78: pNew->pGroupBy = pGroupBy;
79: pNew->pHaving = pHaving;
80: pNew->pOrderBy = pOrderBy;
81: pNew->selFlags = isDistinct ? SF_Distinct : 0;
82: pNew->op = TK_SELECT;
83: pNew->pLimit = pLimit;
84: pNew->pOffset = pOffset;
85: assert( pOffset==0 || pLimit!=0 );
86: pNew->addrOpenEphm[0] = -1;
87: pNew->addrOpenEphm[1] = -1;
88: pNew->addrOpenEphm[2] = -1;
89: if( db->mallocFailed ) {
90: clearSelect(db, pNew);
91: if( pNew!=&standin ) sqlite3DbFree(db, pNew);
92: pNew = 0;
93: }else{
94: assert( pNew->pSrc!=0 || pParse->nErr>0 );
95: }
96: assert( pNew!=&standin );
97: return pNew;
98: }
99:
100: /*
101: ** Delete the given Select structure and all of its substructures.
102: */
103: void sqlite3SelectDelete(sqlite3 *db, Select *p){
104: if( p ){
105: clearSelect(db, p);
106: sqlite3DbFree(db, p);
107: }
108: }
109:
110: /*
111: ** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
112: ** type of join. Return an integer constant that expresses that type
113: ** in terms of the following bit values:
114: **
115: ** JT_INNER
116: ** JT_CROSS
117: ** JT_OUTER
118: ** JT_NATURAL
119: ** JT_LEFT
120: ** JT_RIGHT
121: **
122: ** A full outer join is the combination of JT_LEFT and JT_RIGHT.
123: **
124: ** If an illegal or unsupported join type is seen, then still return
125: ** a join type, but put an error in the pParse structure.
126: */
127: int sqlite3JoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
128: int jointype = 0;
129: Token *apAll[3];
130: Token *p;
131: /* 0123456789 123456789 123456789 123 */
132: static const char zKeyText[] = "naturaleftouterightfullinnercross";
133: static const struct {
134: u8 i; /* Beginning of keyword text in zKeyText[] */
135: u8 nChar; /* Length of the keyword in characters */
136: u8 code; /* Join type mask */
137: } aKeyword[] = {
138: /* natural */ { 0, 7, JT_NATURAL },
139: /* left */ { 6, 4, JT_LEFT|JT_OUTER },
140: /* outer */ { 10, 5, JT_OUTER },
141: /* right */ { 14, 5, JT_RIGHT|JT_OUTER },
142: /* full */ { 19, 4, JT_LEFT|JT_RIGHT|JT_OUTER },
143: /* inner */ { 23, 5, JT_INNER },
144: /* cross */ { 28, 5, JT_INNER|JT_CROSS },
145: };
146: int i, j;
147: apAll[0] = pA;
148: apAll[1] = pB;
149: apAll[2] = pC;
150: for(i=0; i<3 && apAll[i]; i++){
151: p = apAll[i];
152: for(j=0; j<ArraySize(aKeyword); j++){
153: if( p->n==aKeyword[j].nChar
154: && sqlite3StrNICmp((char*)p->z, &zKeyText[aKeyword[j].i], p->n)==0 ){
155: jointype |= aKeyword[j].code;
156: break;
157: }
158: }
159: testcase( j==0 || j==1 || j==2 || j==3 || j==4 || j==5 || j==6 );
160: if( j>=ArraySize(aKeyword) ){
161: jointype |= JT_ERROR;
162: break;
163: }
164: }
165: if(
166: (jointype & (JT_INNER|JT_OUTER))==(JT_INNER|JT_OUTER) ||
167: (jointype & JT_ERROR)!=0
168: ){
169: const char *zSp = " ";
170: assert( pB!=0 );
171: if( pC==0 ){ zSp++; }
172: sqlite3ErrorMsg(pParse, "unknown or unsupported join type: "
173: "%T %T%s%T", pA, pB, zSp, pC);
174: jointype = JT_INNER;
175: }else if( (jointype & JT_OUTER)!=0
176: && (jointype & (JT_LEFT|JT_RIGHT))!=JT_LEFT ){
177: sqlite3ErrorMsg(pParse,
178: "RIGHT and FULL OUTER JOINs are not currently supported");
179: jointype = JT_INNER;
180: }
181: return jointype;
182: }
183:
184: /*
185: ** Return the index of a column in a table. Return -1 if the column
186: ** is not contained in the table.
187: */
188: static int columnIndex(Table *pTab, const char *zCol){
189: int i;
190: for(i=0; i<pTab->nCol; i++){
191: if( sqlite3StrICmp(pTab->aCol[i].zName, zCol)==0 ) return i;
192: }
193: return -1;
194: }
195:
196: /*
197: ** Search the first N tables in pSrc, from left to right, looking for a
198: ** table that has a column named zCol.
199: **
200: ** When found, set *piTab and *piCol to the table index and column index
201: ** of the matching column and return TRUE.
202: **
203: ** If not found, return FALSE.
204: */
205: static int tableAndColumnIndex(
206: SrcList *pSrc, /* Array of tables to search */
207: int N, /* Number of tables in pSrc->a[] to search */
208: const char *zCol, /* Name of the column we are looking for */
209: int *piTab, /* Write index of pSrc->a[] here */
210: int *piCol /* Write index of pSrc->a[*piTab].pTab->aCol[] here */
211: ){
212: int i; /* For looping over tables in pSrc */
213: int iCol; /* Index of column matching zCol */
214:
215: assert( (piTab==0)==(piCol==0) ); /* Both or neither are NULL */
216: for(i=0; i<N; i++){
217: iCol = columnIndex(pSrc->a[i].pTab, zCol);
218: if( iCol>=0 ){
219: if( piTab ){
220: *piTab = i;
221: *piCol = iCol;
222: }
223: return 1;
224: }
225: }
226: return 0;
227: }
228:
229: /*
230: ** This function is used to add terms implied by JOIN syntax to the
231: ** WHERE clause expression of a SELECT statement. The new term, which
232: ** is ANDed with the existing WHERE clause, is of the form:
233: **
234: ** (tab1.col1 = tab2.col2)
235: **
236: ** where tab1 is the iSrc'th table in SrcList pSrc and tab2 is the
237: ** (iSrc+1)'th. Column col1 is column iColLeft of tab1, and col2 is
238: ** column iColRight of tab2.
239: */
240: static void addWhereTerm(
241: Parse *pParse, /* Parsing context */
242: SrcList *pSrc, /* List of tables in FROM clause */
243: int iLeft, /* Index of first table to join in pSrc */
244: int iColLeft, /* Index of column in first table */
245: int iRight, /* Index of second table in pSrc */
246: int iColRight, /* Index of column in second table */
247: int isOuterJoin, /* True if this is an OUTER join */
248: Expr **ppWhere /* IN/OUT: The WHERE clause to add to */
249: ){
250: sqlite3 *db = pParse->db;
251: Expr *pE1;
252: Expr *pE2;
253: Expr *pEq;
254:
255: assert( iLeft<iRight );
256: assert( pSrc->nSrc>iRight );
257: assert( pSrc->a[iLeft].pTab );
258: assert( pSrc->a[iRight].pTab );
259:
260: pE1 = sqlite3CreateColumnExpr(db, pSrc, iLeft, iColLeft);
261: pE2 = sqlite3CreateColumnExpr(db, pSrc, iRight, iColRight);
262:
263: pEq = sqlite3PExpr(pParse, TK_EQ, pE1, pE2, 0);
264: if( pEq && isOuterJoin ){
265: ExprSetProperty(pEq, EP_FromJoin);
266: assert( !ExprHasAnyProperty(pEq, EP_TokenOnly|EP_Reduced) );
267: ExprSetIrreducible(pEq);
268: pEq->iRightJoinTable = (i16)pE2->iTable;
269: }
270: *ppWhere = sqlite3ExprAnd(db, *ppWhere, pEq);
271: }
272:
273: /*
274: ** Set the EP_FromJoin property on all terms of the given expression.
275: ** And set the Expr.iRightJoinTable to iTable for every term in the
276: ** expression.
277: **
278: ** The EP_FromJoin property is used on terms of an expression to tell
279: ** the LEFT OUTER JOIN processing logic that this term is part of the
280: ** join restriction specified in the ON or USING clause and not a part
281: ** of the more general WHERE clause. These terms are moved over to the
282: ** WHERE clause during join processing but we need to remember that they
283: ** originated in the ON or USING clause.
284: **
285: ** The Expr.iRightJoinTable tells the WHERE clause processing that the
286: ** expression depends on table iRightJoinTable even if that table is not
287: ** explicitly mentioned in the expression. That information is needed
288: ** for cases like this:
289: **
290: ** SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.b AND t1.x=5
291: **
292: ** The where clause needs to defer the handling of the t1.x=5
293: ** term until after the t2 loop of the join. In that way, a
294: ** NULL t2 row will be inserted whenever t1.x!=5. If we do not
295: ** defer the handling of t1.x=5, it will be processed immediately
296: ** after the t1 loop and rows with t1.x!=5 will never appear in
297: ** the output, which is incorrect.
298: */
299: static void setJoinExpr(Expr *p, int iTable){
300: while( p ){
301: ExprSetProperty(p, EP_FromJoin);
302: assert( !ExprHasAnyProperty(p, EP_TokenOnly|EP_Reduced) );
303: ExprSetIrreducible(p);
304: p->iRightJoinTable = (i16)iTable;
305: setJoinExpr(p->pLeft, iTable);
306: p = p->pRight;
307: }
308: }
309:
310: /*
311: ** This routine processes the join information for a SELECT statement.
312: ** ON and USING clauses are converted into extra terms of the WHERE clause.
313: ** NATURAL joins also create extra WHERE clause terms.
314: **
315: ** The terms of a FROM clause are contained in the Select.pSrc structure.
316: ** The left most table is the first entry in Select.pSrc. The right-most
317: ** table is the last entry. The join operator is held in the entry to
318: ** the left. Thus entry 0 contains the join operator for the join between
319: ** entries 0 and 1. Any ON or USING clauses associated with the join are
320: ** also attached to the left entry.
321: **
322: ** This routine returns the number of errors encountered.
323: */
324: static int sqliteProcessJoin(Parse *pParse, Select *p){
325: SrcList *pSrc; /* All tables in the FROM clause */
326: int i, j; /* Loop counters */
327: struct SrcList_item *pLeft; /* Left table being joined */
328: struct SrcList_item *pRight; /* Right table being joined */
329:
330: pSrc = p->pSrc;
331: pLeft = &pSrc->a[0];
332: pRight = &pLeft[1];
333: for(i=0; i<pSrc->nSrc-1; i++, pRight++, pLeft++){
334: Table *pLeftTab = pLeft->pTab;
335: Table *pRightTab = pRight->pTab;
336: int isOuter;
337:
338: if( NEVER(pLeftTab==0 || pRightTab==0) ) continue;
339: isOuter = (pRight->jointype & JT_OUTER)!=0;
340:
341: /* When the NATURAL keyword is present, add WHERE clause terms for
342: ** every column that the two tables have in common.
343: */
344: if( pRight->jointype & JT_NATURAL ){
345: if( pRight->pOn || pRight->pUsing ){
346: sqlite3ErrorMsg(pParse, "a NATURAL join may not have "
347: "an ON or USING clause", 0);
348: return 1;
349: }
350: for(j=0; j<pRightTab->nCol; j++){
351: char *zName; /* Name of column in the right table */
352: int iLeft; /* Matching left table */
353: int iLeftCol; /* Matching column in the left table */
354:
355: zName = pRightTab->aCol[j].zName;
356: if( tableAndColumnIndex(pSrc, i+1, zName, &iLeft, &iLeftCol) ){
357: addWhereTerm(pParse, pSrc, iLeft, iLeftCol, i+1, j,
358: isOuter, &p->pWhere);
359: }
360: }
361: }
362:
363: /* Disallow both ON and USING clauses in the same join
364: */
365: if( pRight->pOn && pRight->pUsing ){
366: sqlite3ErrorMsg(pParse, "cannot have both ON and USING "
367: "clauses in the same join");
368: return 1;
369: }
370:
371: /* Add the ON clause to the end of the WHERE clause, connected by
372: ** an AND operator.
373: */
374: if( pRight->pOn ){
375: if( isOuter ) setJoinExpr(pRight->pOn, pRight->iCursor);
376: p->pWhere = sqlite3ExprAnd(pParse->db, p->pWhere, pRight->pOn);
377: pRight->pOn = 0;
378: }
379:
380: /* Create extra terms on the WHERE clause for each column named
381: ** in the USING clause. Example: If the two tables to be joined are
382: ** A and B and the USING clause names X, Y, and Z, then add this
383: ** to the WHERE clause: A.X=B.X AND A.Y=B.Y AND A.Z=B.Z
384: ** Report an error if any column mentioned in the USING clause is
385: ** not contained in both tables to be joined.
386: */
387: if( pRight->pUsing ){
388: IdList *pList = pRight->pUsing;
389: for(j=0; j<pList->nId; j++){
390: char *zName; /* Name of the term in the USING clause */
391: int iLeft; /* Table on the left with matching column name */
392: int iLeftCol; /* Column number of matching column on the left */
393: int iRightCol; /* Column number of matching column on the right */
394:
395: zName = pList->a[j].zName;
396: iRightCol = columnIndex(pRightTab, zName);
397: if( iRightCol<0
398: || !tableAndColumnIndex(pSrc, i+1, zName, &iLeft, &iLeftCol)
399: ){
400: sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
401: "not present in both tables", zName);
402: return 1;
403: }
404: addWhereTerm(pParse, pSrc, iLeft, iLeftCol, i+1, iRightCol,
405: isOuter, &p->pWhere);
406: }
407: }
408: }
409: return 0;
410: }
411:
412: /*
413: ** Insert code into "v" that will push the record on the top of the
414: ** stack into the sorter.
415: */
416: static void pushOntoSorter(
417: Parse *pParse, /* Parser context */
418: ExprList *pOrderBy, /* The ORDER BY clause */
419: Select *pSelect, /* The whole SELECT statement */
420: int regData /* Register holding data to be sorted */
421: ){
422: Vdbe *v = pParse->pVdbe;
423: int nExpr = pOrderBy->nExpr;
424: int regBase = sqlite3GetTempRange(pParse, nExpr+2);
425: int regRecord = sqlite3GetTempReg(pParse);
426: int op;
427: sqlite3ExprCacheClear(pParse);
428: sqlite3ExprCodeExprList(pParse, pOrderBy, regBase, 0);
429: sqlite3VdbeAddOp2(v, OP_Sequence, pOrderBy->iECursor, regBase+nExpr);
430: sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+1, 1);
431: sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nExpr + 2, regRecord);
432: if( pSelect->selFlags & SF_UseSorter ){
433: op = OP_SorterInsert;
434: }else{
435: op = OP_IdxInsert;
436: }
437: sqlite3VdbeAddOp2(v, op, pOrderBy->iECursor, regRecord);
438: sqlite3ReleaseTempReg(pParse, regRecord);
439: sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
440: if( pSelect->iLimit ){
441: int addr1, addr2;
442: int iLimit;
443: if( pSelect->iOffset ){
444: iLimit = pSelect->iOffset+1;
445: }else{
446: iLimit = pSelect->iLimit;
447: }
448: addr1 = sqlite3VdbeAddOp1(v, OP_IfZero, iLimit);
449: sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
450: addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
451: sqlite3VdbeJumpHere(v, addr1);
452: sqlite3VdbeAddOp1(v, OP_Last, pOrderBy->iECursor);
453: sqlite3VdbeAddOp1(v, OP_Delete, pOrderBy->iECursor);
454: sqlite3VdbeJumpHere(v, addr2);
455: }
456: }
457:
458: /*
459: ** Add code to implement the OFFSET
460: */
461: static void codeOffset(
462: Vdbe *v, /* Generate code into this VM */
463: Select *p, /* The SELECT statement being coded */
464: int iContinue /* Jump here to skip the current record */
465: ){
466: if( p->iOffset && iContinue!=0 ){
467: int addr;
468: sqlite3VdbeAddOp2(v, OP_AddImm, p->iOffset, -1);
469: addr = sqlite3VdbeAddOp1(v, OP_IfNeg, p->iOffset);
470: sqlite3VdbeAddOp2(v, OP_Goto, 0, iContinue);
471: VdbeComment((v, "skip OFFSET records"));
472: sqlite3VdbeJumpHere(v, addr);
473: }
474: }
475:
476: /*
477: ** Add code that will check to make sure the N registers starting at iMem
478: ** form a distinct entry. iTab is a sorting index that holds previously
479: ** seen combinations of the N values. A new entry is made in iTab
480: ** if the current N values are new.
481: **
482: ** A jump to addrRepeat is made and the N+1 values are popped from the
483: ** stack if the top N elements are not distinct.
484: */
485: static void codeDistinct(
486: Parse *pParse, /* Parsing and code generating context */
487: int iTab, /* A sorting index used to test for distinctness */
488: int addrRepeat, /* Jump to here if not distinct */
489: int N, /* Number of elements */
490: int iMem /* First element */
491: ){
492: Vdbe *v;
493: int r1;
494:
495: v = pParse->pVdbe;
496: r1 = sqlite3GetTempReg(pParse);
497: sqlite3VdbeAddOp4Int(v, OP_Found, iTab, addrRepeat, iMem, N);
498: sqlite3VdbeAddOp3(v, OP_MakeRecord, iMem, N, r1);
499: sqlite3VdbeAddOp2(v, OP_IdxInsert, iTab, r1);
500: sqlite3ReleaseTempReg(pParse, r1);
501: }
502:
503: #ifndef SQLITE_OMIT_SUBQUERY
504: /*
505: ** Generate an error message when a SELECT is used within a subexpression
506: ** (example: "a IN (SELECT * FROM table)") but it has more than 1 result
507: ** column. We do this in a subroutine because the error used to occur
508: ** in multiple places. (The error only occurs in one place now, but we
509: ** retain the subroutine to minimize code disruption.)
510: */
511: static int checkForMultiColumnSelectError(
512: Parse *pParse, /* Parse context. */
513: SelectDest *pDest, /* Destination of SELECT results */
514: int nExpr /* Number of result columns returned by SELECT */
515: ){
516: int eDest = pDest->eDest;
517: if( nExpr>1 && (eDest==SRT_Mem || eDest==SRT_Set) ){
518: sqlite3ErrorMsg(pParse, "only a single result allowed for "
519: "a SELECT that is part of an expression");
520: return 1;
521: }else{
522: return 0;
523: }
524: }
525: #endif
526:
527: /*
528: ** This routine generates the code for the inside of the inner loop
529: ** of a SELECT.
530: **
531: ** If srcTab and nColumn are both zero, then the pEList expressions
532: ** are evaluated in order to get the data for this row. If nColumn>0
533: ** then data is pulled from srcTab and pEList is used only to get the
534: ** datatypes for each column.
535: */
536: static void selectInnerLoop(
537: Parse *pParse, /* The parser context */
538: Select *p, /* The complete select statement being coded */
539: ExprList *pEList, /* List of values being extracted */
540: int srcTab, /* Pull data from this table */
541: int nColumn, /* Number of columns in the source table */
542: ExprList *pOrderBy, /* If not NULL, sort results using this key */
543: int distinct, /* If >=0, make sure results are distinct */
544: SelectDest *pDest, /* How to dispose of the results */
545: int iContinue, /* Jump here to continue with next row */
546: int iBreak /* Jump here to break out of the inner loop */
547: ){
548: Vdbe *v = pParse->pVdbe;
549: int i;
550: int hasDistinct; /* True if the DISTINCT keyword is present */
551: int regResult; /* Start of memory holding result set */
552: int eDest = pDest->eDest; /* How to dispose of results */
553: int iParm = pDest->iParm; /* First argument to disposal method */
554: int nResultCol; /* Number of result columns */
555:
556: assert( v );
557: if( NEVER(v==0) ) return;
558: assert( pEList!=0 );
559: hasDistinct = distinct>=0;
560: if( pOrderBy==0 && !hasDistinct ){
561: codeOffset(v, p, iContinue);
562: }
563:
564: /* Pull the requested columns.
565: */
566: if( nColumn>0 ){
567: nResultCol = nColumn;
568: }else{
569: nResultCol = pEList->nExpr;
570: }
571: if( pDest->iMem==0 ){
572: pDest->iMem = pParse->nMem+1;
573: pDest->nMem = nResultCol;
574: pParse->nMem += nResultCol;
575: }else{
576: assert( pDest->nMem==nResultCol );
577: }
578: regResult = pDest->iMem;
579: if( nColumn>0 ){
580: for(i=0; i<nColumn; i++){
581: sqlite3VdbeAddOp3(v, OP_Column, srcTab, i, regResult+i);
582: }
583: }else if( eDest!=SRT_Exists ){
584: /* If the destination is an EXISTS(...) expression, the actual
585: ** values returned by the SELECT are not required.
586: */
587: sqlite3ExprCacheClear(pParse);
588: sqlite3ExprCodeExprList(pParse, pEList, regResult, eDest==SRT_Output);
589: }
590: nColumn = nResultCol;
591:
592: /* If the DISTINCT keyword was present on the SELECT statement
593: ** and this row has been seen before, then do not make this row
594: ** part of the result.
595: */
596: if( hasDistinct ){
597: assert( pEList!=0 );
598: assert( pEList->nExpr==nColumn );
599: codeDistinct(pParse, distinct, iContinue, nColumn, regResult);
600: if( pOrderBy==0 ){
601: codeOffset(v, p, iContinue);
602: }
603: }
604:
605: switch( eDest ){
606: /* In this mode, write each query result to the key of the temporary
607: ** table iParm.
608: */
609: #ifndef SQLITE_OMIT_COMPOUND_SELECT
610: case SRT_Union: {
611: int r1;
612: r1 = sqlite3GetTempReg(pParse);
613: sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
614: sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
615: sqlite3ReleaseTempReg(pParse, r1);
616: break;
617: }
618:
619: /* Construct a record from the query result, but instead of
620: ** saving that record, use it as a key to delete elements from
621: ** the temporary table iParm.
622: */
623: case SRT_Except: {
624: sqlite3VdbeAddOp3(v, OP_IdxDelete, iParm, regResult, nColumn);
625: break;
626: }
627: #endif
628:
629: /* Store the result as data using a unique key.
630: */
631: case SRT_Table:
632: case SRT_EphemTab: {
633: int r1 = sqlite3GetTempReg(pParse);
634: testcase( eDest==SRT_Table );
635: testcase( eDest==SRT_EphemTab );
636: sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
637: if( pOrderBy ){
638: pushOntoSorter(pParse, pOrderBy, p, r1);
639: }else{
640: int r2 = sqlite3GetTempReg(pParse);
641: sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
642: sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
643: sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
644: sqlite3ReleaseTempReg(pParse, r2);
645: }
646: sqlite3ReleaseTempReg(pParse, r1);
647: break;
648: }
649:
650: #ifndef SQLITE_OMIT_SUBQUERY
651: /* If we are creating a set for an "expr IN (SELECT ...)" construct,
652: ** then there should be a single item on the stack. Write this
653: ** item into the set table with bogus data.
654: */
655: case SRT_Set: {
656: assert( nColumn==1 );
657: p->affinity = sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affinity);
658: if( pOrderBy ){
659: /* At first glance you would think we could optimize out the
660: ** ORDER BY in this case since the order of entries in the set
661: ** does not matter. But there might be a LIMIT clause, in which
662: ** case the order does matter */
663: pushOntoSorter(pParse, pOrderBy, p, regResult);
664: }else{
665: int r1 = sqlite3GetTempReg(pParse);
666: sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult, 1, r1, &p->affinity, 1);
667: sqlite3ExprCacheAffinityChange(pParse, regResult, 1);
668: sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
669: sqlite3ReleaseTempReg(pParse, r1);
670: }
671: break;
672: }
673:
674: /* If any row exist in the result set, record that fact and abort.
675: */
676: case SRT_Exists: {
677: sqlite3VdbeAddOp2(v, OP_Integer, 1, iParm);
678: /* The LIMIT clause will terminate the loop for us */
679: break;
680: }
681:
682: /* If this is a scalar select that is part of an expression, then
683: ** store the results in the appropriate memory cell and break out
684: ** of the scan loop.
685: */
686: case SRT_Mem: {
687: assert( nColumn==1 );
688: if( pOrderBy ){
689: pushOntoSorter(pParse, pOrderBy, p, regResult);
690: }else{
691: sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
692: /* The LIMIT clause will jump out of the loop for us */
693: }
694: break;
695: }
696: #endif /* #ifndef SQLITE_OMIT_SUBQUERY */
697:
698: /* Send the data to the callback function or to a subroutine. In the
699: ** case of a subroutine, the subroutine itself is responsible for
700: ** popping the data from the stack.
701: */
702: case SRT_Coroutine:
703: case SRT_Output: {
704: testcase( eDest==SRT_Coroutine );
705: testcase( eDest==SRT_Output );
706: if( pOrderBy ){
707: int r1 = sqlite3GetTempReg(pParse);
708: sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
709: pushOntoSorter(pParse, pOrderBy, p, r1);
710: sqlite3ReleaseTempReg(pParse, r1);
711: }else if( eDest==SRT_Coroutine ){
712: sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
713: }else{
714: sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nColumn);
715: sqlite3ExprCacheAffinityChange(pParse, regResult, nColumn);
716: }
717: break;
718: }
719:
720: #if !defined(SQLITE_OMIT_TRIGGER)
721: /* Discard the results. This is used for SELECT statements inside
722: ** the body of a TRIGGER. The purpose of such selects is to call
723: ** user-defined functions that have side effects. We do not care
724: ** about the actual results of the select.
725: */
726: default: {
727: assert( eDest==SRT_Discard );
728: break;
729: }
730: #endif
731: }
732:
733: /* Jump to the end of the loop if the LIMIT is reached. Except, if
734: ** there is a sorter, in which case the sorter has already limited
735: ** the output for us.
736: */
737: if( pOrderBy==0 && p->iLimit ){
738: sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
739: }
740: }
741:
742: /*
743: ** Given an expression list, generate a KeyInfo structure that records
744: ** the collating sequence for each expression in that expression list.
745: **
746: ** If the ExprList is an ORDER BY or GROUP BY clause then the resulting
747: ** KeyInfo structure is appropriate for initializing a virtual index to
748: ** implement that clause. If the ExprList is the result set of a SELECT
749: ** then the KeyInfo structure is appropriate for initializing a virtual
750: ** index to implement a DISTINCT test.
751: **
752: ** Space to hold the KeyInfo structure is obtain from malloc. The calling
753: ** function is responsible for seeing that this structure is eventually
754: ** freed. Add the KeyInfo structure to the P4 field of an opcode using
755: ** P4_KEYINFO_HANDOFF is the usual way of dealing with this.
756: */
757: static KeyInfo *keyInfoFromExprList(Parse *pParse, ExprList *pList){
758: sqlite3 *db = pParse->db;
759: int nExpr;
760: KeyInfo *pInfo;
761: struct ExprList_item *pItem;
762: int i;
763:
764: nExpr = pList->nExpr;
765: pInfo = sqlite3DbMallocZero(db, sizeof(*pInfo) + nExpr*(sizeof(CollSeq*)+1) );
766: if( pInfo ){
767: pInfo->aSortOrder = (u8*)&pInfo->aColl[nExpr];
768: pInfo->nField = (u16)nExpr;
769: pInfo->enc = ENC(db);
770: pInfo->db = db;
771: for(i=0, pItem=pList->a; i<nExpr; i++, pItem++){
772: CollSeq *pColl;
773: pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
774: if( !pColl ){
775: pColl = db->pDfltColl;
776: }
777: pInfo->aColl[i] = pColl;
778: pInfo->aSortOrder[i] = pItem->sortOrder;
779: }
780: }
781: return pInfo;
782: }
783:
784: #ifndef SQLITE_OMIT_COMPOUND_SELECT
785: /*
786: ** Name of the connection operator, used for error messages.
787: */
788: static const char *selectOpName(int id){
789: char *z;
790: switch( id ){
791: case TK_ALL: z = "UNION ALL"; break;
792: case TK_INTERSECT: z = "INTERSECT"; break;
793: case TK_EXCEPT: z = "EXCEPT"; break;
794: default: z = "UNION"; break;
795: }
796: return z;
797: }
798: #endif /* SQLITE_OMIT_COMPOUND_SELECT */
799:
800: #ifndef SQLITE_OMIT_EXPLAIN
801: /*
802: ** Unless an "EXPLAIN QUERY PLAN" command is being processed, this function
803: ** is a no-op. Otherwise, it adds a single row of output to the EQP result,
804: ** where the caption is of the form:
805: **
806: ** "USE TEMP B-TREE FOR xxx"
807: **
808: ** where xxx is one of "DISTINCT", "ORDER BY" or "GROUP BY". Exactly which
809: ** is determined by the zUsage argument.
810: */
811: static void explainTempTable(Parse *pParse, const char *zUsage){
812: if( pParse->explain==2 ){
813: Vdbe *v = pParse->pVdbe;
814: char *zMsg = sqlite3MPrintf(pParse->db, "USE TEMP B-TREE FOR %s", zUsage);
815: sqlite3VdbeAddOp4(v, OP_Explain, pParse->iSelectId, 0, 0, zMsg, P4_DYNAMIC);
816: }
817: }
818:
819: /*
820: ** Assign expression b to lvalue a. A second, no-op, version of this macro
821: ** is provided when SQLITE_OMIT_EXPLAIN is defined. This allows the code
822: ** in sqlite3Select() to assign values to structure member variables that
823: ** only exist if SQLITE_OMIT_EXPLAIN is not defined without polluting the
824: ** code with #ifndef directives.
825: */
826: # define explainSetInteger(a, b) a = b
827:
828: #else
829: /* No-op versions of the explainXXX() functions and macros. */
830: # define explainTempTable(y,z)
831: # define explainSetInteger(y,z)
832: #endif
833:
834: #if !defined(SQLITE_OMIT_EXPLAIN) && !defined(SQLITE_OMIT_COMPOUND_SELECT)
835: /*
836: ** Unless an "EXPLAIN QUERY PLAN" command is being processed, this function
837: ** is a no-op. Otherwise, it adds a single row of output to the EQP result,
838: ** where the caption is of one of the two forms:
839: **
840: ** "COMPOSITE SUBQUERIES iSub1 and iSub2 (op)"
841: ** "COMPOSITE SUBQUERIES iSub1 and iSub2 USING TEMP B-TREE (op)"
842: **
843: ** where iSub1 and iSub2 are the integers passed as the corresponding
844: ** function parameters, and op is the text representation of the parameter
845: ** of the same name. The parameter "op" must be one of TK_UNION, TK_EXCEPT,
846: ** TK_INTERSECT or TK_ALL. The first form is used if argument bUseTmp is
847: ** false, or the second form if it is true.
848: */
849: static void explainComposite(
850: Parse *pParse, /* Parse context */
851: int op, /* One of TK_UNION, TK_EXCEPT etc. */
852: int iSub1, /* Subquery id 1 */
853: int iSub2, /* Subquery id 2 */
854: int bUseTmp /* True if a temp table was used */
855: ){
856: assert( op==TK_UNION || op==TK_EXCEPT || op==TK_INTERSECT || op==TK_ALL );
857: if( pParse->explain==2 ){
858: Vdbe *v = pParse->pVdbe;
859: char *zMsg = sqlite3MPrintf(
860: pParse->db, "COMPOUND SUBQUERIES %d AND %d %s(%s)", iSub1, iSub2,
861: bUseTmp?"USING TEMP B-TREE ":"", selectOpName(op)
862: );
863: sqlite3VdbeAddOp4(v, OP_Explain, pParse->iSelectId, 0, 0, zMsg, P4_DYNAMIC);
864: }
865: }
866: #else
867: /* No-op versions of the explainXXX() functions and macros. */
868: # define explainComposite(v,w,x,y,z)
869: #endif
870:
871: /*
872: ** If the inner loop was generated using a non-null pOrderBy argument,
873: ** then the results were placed in a sorter. After the loop is terminated
874: ** we need to run the sorter and output the results. The following
875: ** routine generates the code needed to do that.
876: */
877: static void generateSortTail(
878: Parse *pParse, /* Parsing context */
879: Select *p, /* The SELECT statement */
880: Vdbe *v, /* Generate code into this VDBE */
881: int nColumn, /* Number of columns of data */
882: SelectDest *pDest /* Write the sorted results here */
883: ){
884: int addrBreak = sqlite3VdbeMakeLabel(v); /* Jump here to exit loop */
885: int addrContinue = sqlite3VdbeMakeLabel(v); /* Jump here for next cycle */
886: int addr;
887: int iTab;
888: int pseudoTab = 0;
889: ExprList *pOrderBy = p->pOrderBy;
890:
891: int eDest = pDest->eDest;
892: int iParm = pDest->iParm;
893:
894: int regRow;
895: int regRowid;
896:
897: iTab = pOrderBy->iECursor;
898: regRow = sqlite3GetTempReg(pParse);
899: if( eDest==SRT_Output || eDest==SRT_Coroutine ){
900: pseudoTab = pParse->nTab++;
901: sqlite3VdbeAddOp3(v, OP_OpenPseudo, pseudoTab, regRow, nColumn);
902: regRowid = 0;
903: }else{
904: regRowid = sqlite3GetTempReg(pParse);
905: }
906: if( p->selFlags & SF_UseSorter ){
907: int regSortOut = ++pParse->nMem;
908: int ptab2 = pParse->nTab++;
909: sqlite3VdbeAddOp3(v, OP_OpenPseudo, ptab2, regSortOut, pOrderBy->nExpr+2);
910: addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
911: codeOffset(v, p, addrContinue);
912: sqlite3VdbeAddOp2(v, OP_SorterData, iTab, regSortOut);
913: sqlite3VdbeAddOp3(v, OP_Column, ptab2, pOrderBy->nExpr+1, regRow);
914: sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
915: }else{
916: addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak);
917: codeOffset(v, p, addrContinue);
918: sqlite3VdbeAddOp3(v, OP_Column, iTab, pOrderBy->nExpr+1, regRow);
919: }
920: switch( eDest ){
921: case SRT_Table:
922: case SRT_EphemTab: {
923: testcase( eDest==SRT_Table );
924: testcase( eDest==SRT_EphemTab );
925: sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, regRowid);
926: sqlite3VdbeAddOp3(v, OP_Insert, iParm, regRow, regRowid);
927: sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
928: break;
929: }
930: #ifndef SQLITE_OMIT_SUBQUERY
931: case SRT_Set: {
932: assert( nColumn==1 );
933: sqlite3VdbeAddOp4(v, OP_MakeRecord, regRow, 1, regRowid, &p->affinity, 1);
934: sqlite3ExprCacheAffinityChange(pParse, regRow, 1);
935: sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, regRowid);
936: break;
937: }
938: case SRT_Mem: {
939: assert( nColumn==1 );
940: sqlite3ExprCodeMove(pParse, regRow, iParm, 1);
941: /* The LIMIT clause will terminate the loop for us */
942: break;
943: }
944: #endif
945: default: {
946: int i;
947: assert( eDest==SRT_Output || eDest==SRT_Coroutine );
948: testcase( eDest==SRT_Output );
949: testcase( eDest==SRT_Coroutine );
950: for(i=0; i<nColumn; i++){
951: assert( regRow!=pDest->iMem+i );
952: sqlite3VdbeAddOp3(v, OP_Column, pseudoTab, i, pDest->iMem+i);
953: if( i==0 ){
954: sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
955: }
956: }
957: if( eDest==SRT_Output ){
958: sqlite3VdbeAddOp2(v, OP_ResultRow, pDest->iMem, nColumn);
959: sqlite3ExprCacheAffinityChange(pParse, pDest->iMem, nColumn);
960: }else{
961: sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
962: }
963: break;
964: }
965: }
966: sqlite3ReleaseTempReg(pParse, regRow);
967: sqlite3ReleaseTempReg(pParse, regRowid);
968:
969: /* The bottom of the loop
970: */
971: sqlite3VdbeResolveLabel(v, addrContinue);
972: if( p->selFlags & SF_UseSorter ){
973: sqlite3VdbeAddOp2(v, OP_SorterNext, iTab, addr);
974: }else{
975: sqlite3VdbeAddOp2(v, OP_Next, iTab, addr);
976: }
977: sqlite3VdbeResolveLabel(v, addrBreak);
978: if( eDest==SRT_Output || eDest==SRT_Coroutine ){
979: sqlite3VdbeAddOp2(v, OP_Close, pseudoTab, 0);
980: }
981: }
982:
983: /*
984: ** Return a pointer to a string containing the 'declaration type' of the
985: ** expression pExpr. The string may be treated as static by the caller.
986: **
987: ** The declaration type is the exact datatype definition extracted from the
988: ** original CREATE TABLE statement if the expression is a column. The
989: ** declaration type for a ROWID field is INTEGER. Exactly when an expression
990: ** is considered a column can be complex in the presence of subqueries. The
991: ** result-set expression in all of the following SELECT statements is
992: ** considered a column by this function.
993: **
994: ** SELECT col FROM tbl;
995: ** SELECT (SELECT col FROM tbl;
996: ** SELECT (SELECT col FROM tbl);
997: ** SELECT abc FROM (SELECT col AS abc FROM tbl);
998: **
999: ** The declaration type for any expression other than a column is NULL.
1000: */
1001: static const char *columnType(
1002: NameContext *pNC,
1003: Expr *pExpr,
1004: const char **pzOriginDb,
1005: const char **pzOriginTab,
1006: const char **pzOriginCol
1007: ){
1008: char const *zType = 0;
1009: char const *zOriginDb = 0;
1010: char const *zOriginTab = 0;
1011: char const *zOriginCol = 0;
1012: int j;
1013: if( NEVER(pExpr==0) || pNC->pSrcList==0 ) return 0;
1014:
1015: switch( pExpr->op ){
1016: case TK_AGG_COLUMN:
1017: case TK_COLUMN: {
1018: /* The expression is a column. Locate the table the column is being
1019: ** extracted from in NameContext.pSrcList. This table may be real
1020: ** database table or a subquery.
1021: */
1022: Table *pTab = 0; /* Table structure column is extracted from */
1023: Select *pS = 0; /* Select the column is extracted from */
1024: int iCol = pExpr->iColumn; /* Index of column in pTab */
1025: testcase( pExpr->op==TK_AGG_COLUMN );
1026: testcase( pExpr->op==TK_COLUMN );
1027: while( pNC && !pTab ){
1028: SrcList *pTabList = pNC->pSrcList;
1029: for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
1030: if( j<pTabList->nSrc ){
1031: pTab = pTabList->a[j].pTab;
1032: pS = pTabList->a[j].pSelect;
1033: }else{
1034: pNC = pNC->pNext;
1035: }
1036: }
1037:
1038: if( pTab==0 ){
1039: /* At one time, code such as "SELECT new.x" within a trigger would
1040: ** cause this condition to run. Since then, we have restructured how
1041: ** trigger code is generated and so this condition is no longer
1042: ** possible. However, it can still be true for statements like
1043: ** the following:
1044: **
1045: ** CREATE TABLE t1(col INTEGER);
1046: ** SELECT (SELECT t1.col) FROM FROM t1;
1047: **
1048: ** when columnType() is called on the expression "t1.col" in the
1049: ** sub-select. In this case, set the column type to NULL, even
1050: ** though it should really be "INTEGER".
1051: **
1052: ** This is not a problem, as the column type of "t1.col" is never
1053: ** used. When columnType() is called on the expression
1054: ** "(SELECT t1.col)", the correct type is returned (see the TK_SELECT
1055: ** branch below. */
1056: break;
1057: }
1058:
1059: assert( pTab && pExpr->pTab==pTab );
1060: if( pS ){
1061: /* The "table" is actually a sub-select or a view in the FROM clause
1062: ** of the SELECT statement. Return the declaration type and origin
1063: ** data for the result-set column of the sub-select.
1064: */
1065: if( iCol>=0 && ALWAYS(iCol<pS->pEList->nExpr) ){
1066: /* If iCol is less than zero, then the expression requests the
1067: ** rowid of the sub-select or view. This expression is legal (see
1068: ** test case misc2.2.2) - it always evaluates to NULL.
1069: */
1070: NameContext sNC;
1071: Expr *p = pS->pEList->a[iCol].pExpr;
1072: sNC.pSrcList = pS->pSrc;
1073: sNC.pNext = pNC;
1074: sNC.pParse = pNC->pParse;
1075: zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol);
1076: }
1077: }else if( ALWAYS(pTab->pSchema) ){
1078: /* A real table */
1079: assert( !pS );
1080: if( iCol<0 ) iCol = pTab->iPKey;
1081: assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
1082: if( iCol<0 ){
1083: zType = "INTEGER";
1084: zOriginCol = "rowid";
1085: }else{
1086: zType = pTab->aCol[iCol].zType;
1087: zOriginCol = pTab->aCol[iCol].zName;
1088: }
1089: zOriginTab = pTab->zName;
1090: if( pNC->pParse ){
1091: int iDb = sqlite3SchemaToIndex(pNC->pParse->db, pTab->pSchema);
1092: zOriginDb = pNC->pParse->db->aDb[iDb].zName;
1093: }
1094: }
1095: break;
1096: }
1097: #ifndef SQLITE_OMIT_SUBQUERY
1098: case TK_SELECT: {
1099: /* The expression is a sub-select. Return the declaration type and
1100: ** origin info for the single column in the result set of the SELECT
1101: ** statement.
1102: */
1103: NameContext sNC;
1104: Select *pS = pExpr->x.pSelect;
1105: Expr *p = pS->pEList->a[0].pExpr;
1106: assert( ExprHasProperty(pExpr, EP_xIsSelect) );
1107: sNC.pSrcList = pS->pSrc;
1108: sNC.pNext = pNC;
1109: sNC.pParse = pNC->pParse;
1110: zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol);
1111: break;
1112: }
1113: #endif
1114: }
1115:
1116: if( pzOriginDb ){
1117: assert( pzOriginTab && pzOriginCol );
1118: *pzOriginDb = zOriginDb;
1119: *pzOriginTab = zOriginTab;
1120: *pzOriginCol = zOriginCol;
1121: }
1122: return zType;
1123: }
1124:
1125: /*
1126: ** Generate code that will tell the VDBE the declaration types of columns
1127: ** in the result set.
1128: */
1129: static void generateColumnTypes(
1130: Parse *pParse, /* Parser context */
1131: SrcList *pTabList, /* List of tables */
1132: ExprList *pEList /* Expressions defining the result set */
1133: ){
1134: #ifndef SQLITE_OMIT_DECLTYPE
1135: Vdbe *v = pParse->pVdbe;
1136: int i;
1137: NameContext sNC;
1138: sNC.pSrcList = pTabList;
1139: sNC.pParse = pParse;
1140: for(i=0; i<pEList->nExpr; i++){
1141: Expr *p = pEList->a[i].pExpr;
1142: const char *zType;
1143: #ifdef SQLITE_ENABLE_COLUMN_METADATA
1144: const char *zOrigDb = 0;
1145: const char *zOrigTab = 0;
1146: const char *zOrigCol = 0;
1147: zType = columnType(&sNC, p, &zOrigDb, &zOrigTab, &zOrigCol);
1148:
1149: /* The vdbe must make its own copy of the column-type and other
1150: ** column specific strings, in case the schema is reset before this
1151: ** virtual machine is deleted.
1152: */
1153: sqlite3VdbeSetColName(v, i, COLNAME_DATABASE, zOrigDb, SQLITE_TRANSIENT);
1154: sqlite3VdbeSetColName(v, i, COLNAME_TABLE, zOrigTab, SQLITE_TRANSIENT);
1155: sqlite3VdbeSetColName(v, i, COLNAME_COLUMN, zOrigCol, SQLITE_TRANSIENT);
1156: #else
1157: zType = columnType(&sNC, p, 0, 0, 0);
1158: #endif
1159: sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, SQLITE_TRANSIENT);
1160: }
1161: #endif /* SQLITE_OMIT_DECLTYPE */
1162: }
1163:
1164: /*
1165: ** Generate code that will tell the VDBE the names of columns
1166: ** in the result set. This information is used to provide the
1167: ** azCol[] values in the callback.
1168: */
1169: static void generateColumnNames(
1170: Parse *pParse, /* Parser context */
1171: SrcList *pTabList, /* List of tables */
1172: ExprList *pEList /* Expressions defining the result set */
1173: ){
1174: Vdbe *v = pParse->pVdbe;
1175: int i, j;
1176: sqlite3 *db = pParse->db;
1177: int fullNames, shortNames;
1178:
1179: #ifndef SQLITE_OMIT_EXPLAIN
1180: /* If this is an EXPLAIN, skip this step */
1181: if( pParse->explain ){
1182: return;
1183: }
1184: #endif
1185:
1186: if( pParse->colNamesSet || NEVER(v==0) || db->mallocFailed ) return;
1187: pParse->colNamesSet = 1;
1188: fullNames = (db->flags & SQLITE_FullColNames)!=0;
1189: shortNames = (db->flags & SQLITE_ShortColNames)!=0;
1190: sqlite3VdbeSetNumCols(v, pEList->nExpr);
1191: for(i=0; i<pEList->nExpr; i++){
1192: Expr *p;
1193: p = pEList->a[i].pExpr;
1194: if( NEVER(p==0) ) continue;
1195: if( pEList->a[i].zName ){
1196: char *zName = pEList->a[i].zName;
1197: sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT);
1198: }else if( (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN) && pTabList ){
1199: Table *pTab;
1200: char *zCol;
1201: int iCol = p->iColumn;
1202: for(j=0; ALWAYS(j<pTabList->nSrc); j++){
1203: if( pTabList->a[j].iCursor==p->iTable ) break;
1204: }
1205: assert( j<pTabList->nSrc );
1206: pTab = pTabList->a[j].pTab;
1207: if( iCol<0 ) iCol = pTab->iPKey;
1208: assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
1209: if( iCol<0 ){
1210: zCol = "rowid";
1211: }else{
1212: zCol = pTab->aCol[iCol].zName;
1213: }
1214: if( !shortNames && !fullNames ){
1215: sqlite3VdbeSetColName(v, i, COLNAME_NAME,
1216: sqlite3DbStrDup(db, pEList->a[i].zSpan), SQLITE_DYNAMIC);
1217: }else if( fullNames ){
1218: char *zName = 0;
1219: zName = sqlite3MPrintf(db, "%s.%s", pTab->zName, zCol);
1220: sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_DYNAMIC);
1221: }else{
1222: sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, SQLITE_TRANSIENT);
1223: }
1224: }else{
1225: sqlite3VdbeSetColName(v, i, COLNAME_NAME,
1226: sqlite3DbStrDup(db, pEList->a[i].zSpan), SQLITE_DYNAMIC);
1227: }
1228: }
1229: generateColumnTypes(pParse, pTabList, pEList);
1230: }
1231:
1232: /*
1233: ** Given a an expression list (which is really the list of expressions
1234: ** that form the result set of a SELECT statement) compute appropriate
1235: ** column names for a table that would hold the expression list.
1236: **
1237: ** All column names will be unique.
1238: **
1239: ** Only the column names are computed. Column.zType, Column.zColl,
1240: ** and other fields of Column are zeroed.
1241: **
1242: ** Return SQLITE_OK on success. If a memory allocation error occurs,
1243: ** store NULL in *paCol and 0 in *pnCol and return SQLITE_NOMEM.
1244: */
1245: static int selectColumnsFromExprList(
1246: Parse *pParse, /* Parsing context */
1247: ExprList *pEList, /* Expr list from which to derive column names */
1248: int *pnCol, /* Write the number of columns here */
1249: Column **paCol /* Write the new column list here */
1250: ){
1251: sqlite3 *db = pParse->db; /* Database connection */
1252: int i, j; /* Loop counters */
1253: int cnt; /* Index added to make the name unique */
1254: Column *aCol, *pCol; /* For looping over result columns */
1255: int nCol; /* Number of columns in the result set */
1256: Expr *p; /* Expression for a single result column */
1257: char *zName; /* Column name */
1258: int nName; /* Size of name in zName[] */
1259:
1260: *pnCol = nCol = pEList->nExpr;
1261: aCol = *paCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol);
1262: if( aCol==0 ) return SQLITE_NOMEM;
1263: for(i=0, pCol=aCol; i<nCol; i++, pCol++){
1264: /* Get an appropriate name for the column
1265: */
1266: p = pEList->a[i].pExpr;
1267: assert( p->pRight==0 || ExprHasProperty(p->pRight, EP_IntValue)
1268: || p->pRight->u.zToken==0 || p->pRight->u.zToken[0]!=0 );
1269: if( (zName = pEList->a[i].zName)!=0 ){
1270: /* If the column contains an "AS <name>" phrase, use <name> as the name */
1271: zName = sqlite3DbStrDup(db, zName);
1272: }else{
1273: Expr *pColExpr = p; /* The expression that is the result column name */
1274: Table *pTab; /* Table associated with this expression */
1275: while( pColExpr->op==TK_DOT ){
1276: pColExpr = pColExpr->pRight;
1277: assert( pColExpr!=0 );
1278: }
1279: if( pColExpr->op==TK_COLUMN && ALWAYS(pColExpr->pTab!=0) ){
1280: /* For columns use the column name name */
1281: int iCol = pColExpr->iColumn;
1282: pTab = pColExpr->pTab;
1283: if( iCol<0 ) iCol = pTab->iPKey;
1284: zName = sqlite3MPrintf(db, "%s",
1285: iCol>=0 ? pTab->aCol[iCol].zName : "rowid");
1286: }else if( pColExpr->op==TK_ID ){
1287: assert( !ExprHasProperty(pColExpr, EP_IntValue) );
1288: zName = sqlite3MPrintf(db, "%s", pColExpr->u.zToken);
1289: }else{
1290: /* Use the original text of the column expression as its name */
1291: zName = sqlite3MPrintf(db, "%s", pEList->a[i].zSpan);
1292: }
1293: }
1294: if( db->mallocFailed ){
1295: sqlite3DbFree(db, zName);
1296: break;
1297: }
1298:
1299: /* Make sure the column name is unique. If the name is not unique,
1300: ** append a integer to the name so that it becomes unique.
1301: */
1302: nName = sqlite3Strlen30(zName);
1303: for(j=cnt=0; j<i; j++){
1304: if( sqlite3StrICmp(aCol[j].zName, zName)==0 ){
1305: char *zNewName;
1306: zName[nName] = 0;
1307: zNewName = sqlite3MPrintf(db, "%s:%d", zName, ++cnt);
1308: sqlite3DbFree(db, zName);
1309: zName = zNewName;
1310: j = -1;
1311: if( zName==0 ) break;
1312: }
1313: }
1314: pCol->zName = zName;
1315: }
1316: if( db->mallocFailed ){
1317: for(j=0; j<i; j++){
1318: sqlite3DbFree(db, aCol[j].zName);
1319: }
1320: sqlite3DbFree(db, aCol);
1321: *paCol = 0;
1322: *pnCol = 0;
1323: return SQLITE_NOMEM;
1324: }
1325: return SQLITE_OK;
1326: }
1327:
1328: /*
1329: ** Add type and collation information to a column list based on
1330: ** a SELECT statement.
1331: **
1332: ** The column list presumably came from selectColumnNamesFromExprList().
1333: ** The column list has only names, not types or collations. This
1334: ** routine goes through and adds the types and collations.
1335: **
1336: ** This routine requires that all identifiers in the SELECT
1337: ** statement be resolved.
1338: */
1339: static void selectAddColumnTypeAndCollation(
1340: Parse *pParse, /* Parsing contexts */
1341: int nCol, /* Number of columns */
1342: Column *aCol, /* List of columns */
1343: Select *pSelect /* SELECT used to determine types and collations */
1344: ){
1345: sqlite3 *db = pParse->db;
1346: NameContext sNC;
1347: Column *pCol;
1348: CollSeq *pColl;
1349: int i;
1350: Expr *p;
1351: struct ExprList_item *a;
1352:
1353: assert( pSelect!=0 );
1354: assert( (pSelect->selFlags & SF_Resolved)!=0 );
1355: assert( nCol==pSelect->pEList->nExpr || db->mallocFailed );
1356: if( db->mallocFailed ) return;
1357: memset(&sNC, 0, sizeof(sNC));
1358: sNC.pSrcList = pSelect->pSrc;
1359: a = pSelect->pEList->a;
1360: for(i=0, pCol=aCol; i<nCol; i++, pCol++){
1361: p = a[i].pExpr;
1362: pCol->zType = sqlite3DbStrDup(db, columnType(&sNC, p, 0, 0, 0));
1363: pCol->affinity = sqlite3ExprAffinity(p);
1364: if( pCol->affinity==0 ) pCol->affinity = SQLITE_AFF_NONE;
1365: pColl = sqlite3ExprCollSeq(pParse, p);
1366: if( pColl ){
1367: pCol->zColl = sqlite3DbStrDup(db, pColl->zName);
1368: }
1369: }
1370: }
1371:
1372: /*
1373: ** Given a SELECT statement, generate a Table structure that describes
1374: ** the result set of that SELECT.
1375: */
1376: Table *sqlite3ResultSetOfSelect(Parse *pParse, Select *pSelect){
1377: Table *pTab;
1378: sqlite3 *db = pParse->db;
1379: int savedFlags;
1380:
1381: savedFlags = db->flags;
1382: db->flags &= ~SQLITE_FullColNames;
1383: db->flags |= SQLITE_ShortColNames;
1384: sqlite3SelectPrep(pParse, pSelect, 0);
1385: if( pParse->nErr ) return 0;
1386: while( pSelect->pPrior ) pSelect = pSelect->pPrior;
1387: db->flags = savedFlags;
1388: pTab = sqlite3DbMallocZero(db, sizeof(Table) );
1389: if( pTab==0 ){
1390: return 0;
1391: }
1392: /* The sqlite3ResultSetOfSelect() is only used n contexts where lookaside
1393: ** is disabled */
1394: assert( db->lookaside.bEnabled==0 );
1395: pTab->nRef = 1;
1396: pTab->zName = 0;
1397: pTab->nRowEst = 1000000;
1398: selectColumnsFromExprList(pParse, pSelect->pEList, &pTab->nCol, &pTab->aCol);
1399: selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSelect);
1400: pTab->iPKey = -1;
1401: if( db->mallocFailed ){
1402: sqlite3DeleteTable(db, pTab);
1403: return 0;
1404: }
1405: return pTab;
1406: }
1407:
1408: /*
1409: ** Get a VDBE for the given parser context. Create a new one if necessary.
1410: ** If an error occurs, return NULL and leave a message in pParse.
1411: */
1412: Vdbe *sqlite3GetVdbe(Parse *pParse){
1413: Vdbe *v = pParse->pVdbe;
1414: if( v==0 ){
1415: v = pParse->pVdbe = sqlite3VdbeCreate(pParse->db);
1416: #ifndef SQLITE_OMIT_TRACE
1417: if( v ){
1418: sqlite3VdbeAddOp0(v, OP_Trace);
1419: }
1420: #endif
1421: }
1422: return v;
1423: }
1424:
1425:
1426: /*
1427: ** Compute the iLimit and iOffset fields of the SELECT based on the
1428: ** pLimit and pOffset expressions. pLimit and pOffset hold the expressions
1429: ** that appear in the original SQL statement after the LIMIT and OFFSET
1430: ** keywords. Or NULL if those keywords are omitted. iLimit and iOffset
1431: ** are the integer memory register numbers for counters used to compute
1432: ** the limit and offset. If there is no limit and/or offset, then
1433: ** iLimit and iOffset are negative.
1434: **
1435: ** This routine changes the values of iLimit and iOffset only if
1436: ** a limit or offset is defined by pLimit and pOffset. iLimit and
1437: ** iOffset should have been preset to appropriate default values
1438: ** (usually but not always -1) prior to calling this routine.
1439: ** Only if pLimit!=0 or pOffset!=0 do the limit registers get
1440: ** redefined. The UNION ALL operator uses this property to force
1441: ** the reuse of the same limit and offset registers across multiple
1442: ** SELECT statements.
1443: */
1444: static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
1445: Vdbe *v = 0;
1446: int iLimit = 0;
1447: int iOffset;
1448: int addr1, n;
1449: if( p->iLimit ) return;
1450:
1451: /*
1452: ** "LIMIT -1" always shows all rows. There is some
1453: ** contraversy about what the correct behavior should be.
1454: ** The current implementation interprets "LIMIT 0" to mean
1455: ** no rows.
1456: */
1457: sqlite3ExprCacheClear(pParse);
1458: assert( p->pOffset==0 || p->pLimit!=0 );
1459: if( p->pLimit ){
1460: p->iLimit = iLimit = ++pParse->nMem;
1461: v = sqlite3GetVdbe(pParse);
1462: if( NEVER(v==0) ) return; /* VDBE should have already been allocated */
1463: if( sqlite3ExprIsInteger(p->pLimit, &n) ){
1464: sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
1465: VdbeComment((v, "LIMIT counter"));
1466: if( n==0 ){
1467: sqlite3VdbeAddOp2(v, OP_Goto, 0, iBreak);
1468: }else{
1469: if( p->nSelectRow > (double)n ) p->nSelectRow = (double)n;
1470: }
1471: }else{
1472: sqlite3ExprCode(pParse, p->pLimit, iLimit);
1473: sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit);
1474: VdbeComment((v, "LIMIT counter"));
1475: sqlite3VdbeAddOp2(v, OP_IfZero, iLimit, iBreak);
1476: }
1477: if( p->pOffset ){
1478: p->iOffset = iOffset = ++pParse->nMem;
1479: pParse->nMem++; /* Allocate an extra register for limit+offset */
1480: sqlite3ExprCode(pParse, p->pOffset, iOffset);
1481: sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset);
1482: VdbeComment((v, "OFFSET counter"));
1483: addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iOffset);
1484: sqlite3VdbeAddOp2(v, OP_Integer, 0, iOffset);
1485: sqlite3VdbeJumpHere(v, addr1);
1486: sqlite3VdbeAddOp3(v, OP_Add, iLimit, iOffset, iOffset+1);
1487: VdbeComment((v, "LIMIT+OFFSET"));
1488: addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iLimit);
1489: sqlite3VdbeAddOp2(v, OP_Integer, -1, iOffset+1);
1490: sqlite3VdbeJumpHere(v, addr1);
1491: }
1492: }
1493: }
1494:
1495: #ifndef SQLITE_OMIT_COMPOUND_SELECT
1496: /*
1497: ** Return the appropriate collating sequence for the iCol-th column of
1498: ** the result set for the compound-select statement "p". Return NULL if
1499: ** the column has no default collating sequence.
1500: **
1501: ** The collating sequence for the compound select is taken from the
1502: ** left-most term of the select that has a collating sequence.
1503: */
1504: static CollSeq *multiSelectCollSeq(Parse *pParse, Select *p, int iCol){
1505: CollSeq *pRet;
1506: if( p->pPrior ){
1507: pRet = multiSelectCollSeq(pParse, p->pPrior, iCol);
1508: }else{
1509: pRet = 0;
1510: }
1511: assert( iCol>=0 );
1512: if( pRet==0 && iCol<p->pEList->nExpr ){
1513: pRet = sqlite3ExprCollSeq(pParse, p->pEList->a[iCol].pExpr);
1514: }
1515: return pRet;
1516: }
1517: #endif /* SQLITE_OMIT_COMPOUND_SELECT */
1518:
1519: /* Forward reference */
1520: static int multiSelectOrderBy(
1521: Parse *pParse, /* Parsing context */
1522: Select *p, /* The right-most of SELECTs to be coded */
1523: SelectDest *pDest /* What to do with query results */
1524: );
1525:
1526:
1527: #ifndef SQLITE_OMIT_COMPOUND_SELECT
1528: /*
1529: ** This routine is called to process a compound query form from
1530: ** two or more separate queries using UNION, UNION ALL, EXCEPT, or
1531: ** INTERSECT
1532: **
1533: ** "p" points to the right-most of the two queries. the query on the
1534: ** left is p->pPrior. The left query could also be a compound query
1535: ** in which case this routine will be called recursively.
1536: **
1537: ** The results of the total query are to be written into a destination
1538: ** of type eDest with parameter iParm.
1539: **
1540: ** Example 1: Consider a three-way compound SQL statement.
1541: **
1542: ** SELECT a FROM t1 UNION SELECT b FROM t2 UNION SELECT c FROM t3
1543: **
1544: ** This statement is parsed up as follows:
1545: **
1546: ** SELECT c FROM t3
1547: ** |
1548: ** `-----> SELECT b FROM t2
1549: ** |
1550: ** `------> SELECT a FROM t1
1551: **
1552: ** The arrows in the diagram above represent the Select.pPrior pointer.
1553: ** So if this routine is called with p equal to the t3 query, then
1554: ** pPrior will be the t2 query. p->op will be TK_UNION in this case.
1555: **
1556: ** Notice that because of the way SQLite parses compound SELECTs, the
1557: ** individual selects always group from left to right.
1558: */
1559: static int multiSelect(
1560: Parse *pParse, /* Parsing context */
1561: Select *p, /* The right-most of SELECTs to be coded */
1562: SelectDest *pDest /* What to do with query results */
1563: ){
1564: int rc = SQLITE_OK; /* Success code from a subroutine */
1565: Select *pPrior; /* Another SELECT immediately to our left */
1566: Vdbe *v; /* Generate code to this VDBE */
1567: SelectDest dest; /* Alternative data destination */
1568: Select *pDelete = 0; /* Chain of simple selects to delete */
1569: sqlite3 *db; /* Database connection */
1570: #ifndef SQLITE_OMIT_EXPLAIN
1571: int iSub1; /* EQP id of left-hand query */
1572: int iSub2; /* EQP id of right-hand query */
1573: #endif
1574:
1575: /* Make sure there is no ORDER BY or LIMIT clause on prior SELECTs. Only
1576: ** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
1577: */
1578: assert( p && p->pPrior ); /* Calling function guarantees this much */
1579: db = pParse->db;
1580: pPrior = p->pPrior;
1581: assert( pPrior->pRightmost!=pPrior );
1582: assert( pPrior->pRightmost==p->pRightmost );
1583: dest = *pDest;
1584: if( pPrior->pOrderBy ){
1585: sqlite3ErrorMsg(pParse,"ORDER BY clause should come after %s not before",
1586: selectOpName(p->op));
1587: rc = 1;
1588: goto multi_select_end;
1589: }
1590: if( pPrior->pLimit ){
1591: sqlite3ErrorMsg(pParse,"LIMIT clause should come after %s not before",
1592: selectOpName(p->op));
1593: rc = 1;
1594: goto multi_select_end;
1595: }
1596:
1597: v = sqlite3GetVdbe(pParse);
1598: assert( v!=0 ); /* The VDBE already created by calling function */
1599:
1600: /* Create the destination temporary table if necessary
1601: */
1602: if( dest.eDest==SRT_EphemTab ){
1603: assert( p->pEList );
1604: sqlite3VdbeAddOp2(v, OP_OpenEphemeral, dest.iParm, p->pEList->nExpr);
1605: sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
1606: dest.eDest = SRT_Table;
1607: }
1608:
1609: /* Make sure all SELECTs in the statement have the same number of elements
1610: ** in their result sets.
1611: */
1612: assert( p->pEList && pPrior->pEList );
1613: if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
1614: sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
1615: " do not have the same number of result columns", selectOpName(p->op));
1616: rc = 1;
1617: goto multi_select_end;
1618: }
1619:
1620: /* Compound SELECTs that have an ORDER BY clause are handled separately.
1621: */
1622: if( p->pOrderBy ){
1623: return multiSelectOrderBy(pParse, p, pDest);
1624: }
1625:
1626: /* Generate code for the left and right SELECT statements.
1627: */
1628: switch( p->op ){
1629: case TK_ALL: {
1630: int addr = 0;
1631: int nLimit;
1632: assert( !pPrior->pLimit );
1633: pPrior->pLimit = p->pLimit;
1634: pPrior->pOffset = p->pOffset;
1635: explainSetInteger(iSub1, pParse->iNextSelectId);
1636: rc = sqlite3Select(pParse, pPrior, &dest);
1637: p->pLimit = 0;
1638: p->pOffset = 0;
1639: if( rc ){
1640: goto multi_select_end;
1641: }
1642: p->pPrior = 0;
1643: p->iLimit = pPrior->iLimit;
1644: p->iOffset = pPrior->iOffset;
1645: if( p->iLimit ){
1646: addr = sqlite3VdbeAddOp1(v, OP_IfZero, p->iLimit);
1647: VdbeComment((v, "Jump ahead if LIMIT reached"));
1648: }
1649: explainSetInteger(iSub2, pParse->iNextSelectId);
1650: rc = sqlite3Select(pParse, p, &dest);
1651: testcase( rc!=SQLITE_OK );
1652: pDelete = p->pPrior;
1653: p->pPrior = pPrior;
1654: p->nSelectRow += pPrior->nSelectRow;
1655: if( pPrior->pLimit
1656: && sqlite3ExprIsInteger(pPrior->pLimit, &nLimit)
1657: && p->nSelectRow > (double)nLimit
1658: ){
1659: p->nSelectRow = (double)nLimit;
1660: }
1661: if( addr ){
1662: sqlite3VdbeJumpHere(v, addr);
1663: }
1664: break;
1665: }
1666: case TK_EXCEPT:
1667: case TK_UNION: {
1668: int unionTab; /* Cursor number of the temporary table holding result */
1669: u8 op = 0; /* One of the SRT_ operations to apply to self */
1670: int priorOp; /* The SRT_ operation to apply to prior selects */
1671: Expr *pLimit, *pOffset; /* Saved values of p->nLimit and p->nOffset */
1672: int addr;
1673: SelectDest uniondest;
1674:
1675: testcase( p->op==TK_EXCEPT );
1676: testcase( p->op==TK_UNION );
1677: priorOp = SRT_Union;
1678: if( dest.eDest==priorOp && ALWAYS(!p->pLimit &&!p->pOffset) ){
1679: /* We can reuse a temporary table generated by a SELECT to our
1680: ** right.
1681: */
1682: assert( p->pRightmost!=p ); /* Can only happen for leftward elements
1683: ** of a 3-way or more compound */
1684: assert( p->pLimit==0 ); /* Not allowed on leftward elements */
1685: assert( p->pOffset==0 ); /* Not allowed on leftward elements */
1686: unionTab = dest.iParm;
1687: }else{
1688: /* We will need to create our own temporary table to hold the
1689: ** intermediate results.
1690: */
1691: unionTab = pParse->nTab++;
1692: assert( p->pOrderBy==0 );
1693: addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, unionTab, 0);
1694: assert( p->addrOpenEphm[0] == -1 );
1695: p->addrOpenEphm[0] = addr;
1696: p->pRightmost->selFlags |= SF_UsesEphemeral;
1697: assert( p->pEList );
1698: }
1699:
1700: /* Code the SELECT statements to our left
1701: */
1702: assert( !pPrior->pOrderBy );
1703: sqlite3SelectDestInit(&uniondest, priorOp, unionTab);
1704: explainSetInteger(iSub1, pParse->iNextSelectId);
1705: rc = sqlite3Select(pParse, pPrior, &uniondest);
1706: if( rc ){
1707: goto multi_select_end;
1708: }
1709:
1710: /* Code the current SELECT statement
1711: */
1712: if( p->op==TK_EXCEPT ){
1713: op = SRT_Except;
1714: }else{
1715: assert( p->op==TK_UNION );
1716: op = SRT_Union;
1717: }
1718: p->pPrior = 0;
1719: pLimit = p->pLimit;
1720: p->pLimit = 0;
1721: pOffset = p->pOffset;
1722: p->pOffset = 0;
1723: uniondest.eDest = op;
1724: explainSetInteger(iSub2, pParse->iNextSelectId);
1725: rc = sqlite3Select(pParse, p, &uniondest);
1726: testcase( rc!=SQLITE_OK );
1727: /* Query flattening in sqlite3Select() might refill p->pOrderBy.
1728: ** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */
1729: sqlite3ExprListDelete(db, p->pOrderBy);
1730: pDelete = p->pPrior;
1731: p->pPrior = pPrior;
1732: p->pOrderBy = 0;
1733: if( p->op==TK_UNION ) p->nSelectRow += pPrior->nSelectRow;
1734: sqlite3ExprDelete(db, p->pLimit);
1735: p->pLimit = pLimit;
1736: p->pOffset = pOffset;
1737: p->iLimit = 0;
1738: p->iOffset = 0;
1739:
1740: /* Convert the data in the temporary table into whatever form
1741: ** it is that we currently need.
1742: */
1743: assert( unionTab==dest.iParm || dest.eDest!=priorOp );
1744: if( dest.eDest!=priorOp ){
1745: int iCont, iBreak, iStart;
1746: assert( p->pEList );
1747: if( dest.eDest==SRT_Output ){
1748: Select *pFirst = p;
1749: while( pFirst->pPrior ) pFirst = pFirst->pPrior;
1750: generateColumnNames(pParse, 0, pFirst->pEList);
1751: }
1752: iBreak = sqlite3VdbeMakeLabel(v);
1753: iCont = sqlite3VdbeMakeLabel(v);
1754: computeLimitRegisters(pParse, p, iBreak);
1755: sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak);
1756: iStart = sqlite3VdbeCurrentAddr(v);
1757: selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
1758: 0, -1, &dest, iCont, iBreak);
1759: sqlite3VdbeResolveLabel(v, iCont);
1760: sqlite3VdbeAddOp2(v, OP_Next, unionTab, iStart);
1761: sqlite3VdbeResolveLabel(v, iBreak);
1762: sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
1763: }
1764: break;
1765: }
1766: default: assert( p->op==TK_INTERSECT ); {
1767: int tab1, tab2;
1768: int iCont, iBreak, iStart;
1769: Expr *pLimit, *pOffset;
1770: int addr;
1771: SelectDest intersectdest;
1772: int r1;
1773:
1774: /* INTERSECT is different from the others since it requires
1775: ** two temporary tables. Hence it has its own case. Begin
1776: ** by allocating the tables we will need.
1777: */
1778: tab1 = pParse->nTab++;
1779: tab2 = pParse->nTab++;
1780: assert( p->pOrderBy==0 );
1781:
1782: addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab1, 0);
1783: assert( p->addrOpenEphm[0] == -1 );
1784: p->addrOpenEphm[0] = addr;
1785: p->pRightmost->selFlags |= SF_UsesEphemeral;
1786: assert( p->pEList );
1787:
1788: /* Code the SELECTs to our left into temporary table "tab1".
1789: */
1790: sqlite3SelectDestInit(&intersectdest, SRT_Union, tab1);
1791: explainSetInteger(iSub1, pParse->iNextSelectId);
1792: rc = sqlite3Select(pParse, pPrior, &intersectdest);
1793: if( rc ){
1794: goto multi_select_end;
1795: }
1796:
1797: /* Code the current SELECT into temporary table "tab2"
1798: */
1799: addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab2, 0);
1800: assert( p->addrOpenEphm[1] == -1 );
1801: p->addrOpenEphm[1] = addr;
1802: p->pPrior = 0;
1803: pLimit = p->pLimit;
1804: p->pLimit = 0;
1805: pOffset = p->pOffset;
1806: p->pOffset = 0;
1807: intersectdest.iParm = tab2;
1808: explainSetInteger(iSub2, pParse->iNextSelectId);
1809: rc = sqlite3Select(pParse, p, &intersectdest);
1810: testcase( rc!=SQLITE_OK );
1811: pDelete = p->pPrior;
1812: p->pPrior = pPrior;
1813: if( p->nSelectRow>pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
1814: sqlite3ExprDelete(db, p->pLimit);
1815: p->pLimit = pLimit;
1816: p->pOffset = pOffset;
1817:
1818: /* Generate code to take the intersection of the two temporary
1819: ** tables.
1820: */
1821: assert( p->pEList );
1822: if( dest.eDest==SRT_Output ){
1823: Select *pFirst = p;
1824: while( pFirst->pPrior ) pFirst = pFirst->pPrior;
1825: generateColumnNames(pParse, 0, pFirst->pEList);
1826: }
1827: iBreak = sqlite3VdbeMakeLabel(v);
1828: iCont = sqlite3VdbeMakeLabel(v);
1829: computeLimitRegisters(pParse, p, iBreak);
1830: sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak);
1831: r1 = sqlite3GetTempReg(pParse);
1832: iStart = sqlite3VdbeAddOp2(v, OP_RowKey, tab1, r1);
1833: sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0);
1834: sqlite3ReleaseTempReg(pParse, r1);
1835: selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
1836: 0, -1, &dest, iCont, iBreak);
1837: sqlite3VdbeResolveLabel(v, iCont);
1838: sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart);
1839: sqlite3VdbeResolveLabel(v, iBreak);
1840: sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
1841: sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
1842: break;
1843: }
1844: }
1845:
1846: explainComposite(pParse, p->op, iSub1, iSub2, p->op!=TK_ALL);
1847:
1848: /* Compute collating sequences used by
1849: ** temporary tables needed to implement the compound select.
1850: ** Attach the KeyInfo structure to all temporary tables.
1851: **
1852: ** This section is run by the right-most SELECT statement only.
1853: ** SELECT statements to the left always skip this part. The right-most
1854: ** SELECT might also skip this part if it has no ORDER BY clause and
1855: ** no temp tables are required.
1856: */
1857: if( p->selFlags & SF_UsesEphemeral ){
1858: int i; /* Loop counter */
1859: KeyInfo *pKeyInfo; /* Collating sequence for the result set */
1860: Select *pLoop; /* For looping through SELECT statements */
1861: CollSeq **apColl; /* For looping through pKeyInfo->aColl[] */
1862: int nCol; /* Number of columns in result set */
1863:
1864: assert( p->pRightmost==p );
1865: nCol = p->pEList->nExpr;
1866: pKeyInfo = sqlite3DbMallocZero(db,
1867: sizeof(*pKeyInfo)+nCol*(sizeof(CollSeq*) + 1));
1868: if( !pKeyInfo ){
1869: rc = SQLITE_NOMEM;
1870: goto multi_select_end;
1871: }
1872:
1873: pKeyInfo->enc = ENC(db);
1874: pKeyInfo->nField = (u16)nCol;
1875:
1876: for(i=0, apColl=pKeyInfo->aColl; i<nCol; i++, apColl++){
1877: *apColl = multiSelectCollSeq(pParse, p, i);
1878: if( 0==*apColl ){
1879: *apColl = db->pDfltColl;
1880: }
1881: }
1882:
1883: for(pLoop=p; pLoop; pLoop=pLoop->pPrior){
1884: for(i=0; i<2; i++){
1885: int addr = pLoop->addrOpenEphm[i];
1886: if( addr<0 ){
1887: /* If [0] is unused then [1] is also unused. So we can
1888: ** always safely abort as soon as the first unused slot is found */
1889: assert( pLoop->addrOpenEphm[1]<0 );
1890: break;
1891: }
1892: sqlite3VdbeChangeP2(v, addr, nCol);
1893: sqlite3VdbeChangeP4(v, addr, (char*)pKeyInfo, P4_KEYINFO);
1894: pLoop->addrOpenEphm[i] = -1;
1895: }
1896: }
1897: sqlite3DbFree(db, pKeyInfo);
1898: }
1899:
1900: multi_select_end:
1901: pDest->iMem = dest.iMem;
1902: pDest->nMem = dest.nMem;
1903: sqlite3SelectDelete(db, pDelete);
1904: return rc;
1905: }
1906: #endif /* SQLITE_OMIT_COMPOUND_SELECT */
1907:
1908: /*
1909: ** Code an output subroutine for a coroutine implementation of a
1910: ** SELECT statment.
1911: **
1912: ** The data to be output is contained in pIn->iMem. There are
1913: ** pIn->nMem columns to be output. pDest is where the output should
1914: ** be sent.
1915: **
1916: ** regReturn is the number of the register holding the subroutine
1917: ** return address.
1918: **
1919: ** If regPrev>0 then it is the first register in a vector that
1920: ** records the previous output. mem[regPrev] is a flag that is false
1921: ** if there has been no previous output. If regPrev>0 then code is
1922: ** generated to suppress duplicates. pKeyInfo is used for comparing
1923: ** keys.
1924: **
1925: ** If the LIMIT found in p->iLimit is reached, jump immediately to
1926: ** iBreak.
1927: */
1928: static int generateOutputSubroutine(
1929: Parse *pParse, /* Parsing context */
1930: Select *p, /* The SELECT statement */
1931: SelectDest *pIn, /* Coroutine supplying data */
1932: SelectDest *pDest, /* Where to send the data */
1933: int regReturn, /* The return address register */
1934: int regPrev, /* Previous result register. No uniqueness if 0 */
1935: KeyInfo *pKeyInfo, /* For comparing with previous entry */
1936: int p4type, /* The p4 type for pKeyInfo */
1937: int iBreak /* Jump here if we hit the LIMIT */
1938: ){
1939: Vdbe *v = pParse->pVdbe;
1940: int iContinue;
1941: int addr;
1942:
1943: addr = sqlite3VdbeCurrentAddr(v);
1944: iContinue = sqlite3VdbeMakeLabel(v);
1945:
1946: /* Suppress duplicates for UNION, EXCEPT, and INTERSECT
1947: */
1948: if( regPrev ){
1949: int j1, j2;
1950: j1 = sqlite3VdbeAddOp1(v, OP_IfNot, regPrev);
1951: j2 = sqlite3VdbeAddOp4(v, OP_Compare, pIn->iMem, regPrev+1, pIn->nMem,
1952: (char*)pKeyInfo, p4type);
1953: sqlite3VdbeAddOp3(v, OP_Jump, j2+2, iContinue, j2+2);
1954: sqlite3VdbeJumpHere(v, j1);
1955: sqlite3ExprCodeCopy(pParse, pIn->iMem, regPrev+1, pIn->nMem);
1956: sqlite3VdbeAddOp2(v, OP_Integer, 1, regPrev);
1957: }
1958: if( pParse->db->mallocFailed ) return 0;
1959:
1960: /* Suppress the the first OFFSET entries if there is an OFFSET clause
1961: */
1962: codeOffset(v, p, iContinue);
1963:
1964: switch( pDest->eDest ){
1965: /* Store the result as data using a unique key.
1966: */
1967: case SRT_Table:
1968: case SRT_EphemTab: {
1969: int r1 = sqlite3GetTempReg(pParse);
1970: int r2 = sqlite3GetTempReg(pParse);
1971: testcase( pDest->eDest==SRT_Table );
1972: testcase( pDest->eDest==SRT_EphemTab );
1973: sqlite3VdbeAddOp3(v, OP_MakeRecord, pIn->iMem, pIn->nMem, r1);
1974: sqlite3VdbeAddOp2(v, OP_NewRowid, pDest->iParm, r2);
1975: sqlite3VdbeAddOp3(v, OP_Insert, pDest->iParm, r1, r2);
1976: sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
1977: sqlite3ReleaseTempReg(pParse, r2);
1978: sqlite3ReleaseTempReg(pParse, r1);
1979: break;
1980: }
1981:
1982: #ifndef SQLITE_OMIT_SUBQUERY
1983: /* If we are creating a set for an "expr IN (SELECT ...)" construct,
1984: ** then there should be a single item on the stack. Write this
1985: ** item into the set table with bogus data.
1986: */
1987: case SRT_Set: {
1988: int r1;
1989: assert( pIn->nMem==1 );
1990: p->affinity =
1991: sqlite3CompareAffinity(p->pEList->a[0].pExpr, pDest->affinity);
1992: r1 = sqlite3GetTempReg(pParse);
1993: sqlite3VdbeAddOp4(v, OP_MakeRecord, pIn->iMem, 1, r1, &p->affinity, 1);
1994: sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, 1);
1995: sqlite3VdbeAddOp2(v, OP_IdxInsert, pDest->iParm, r1);
1996: sqlite3ReleaseTempReg(pParse, r1);
1997: break;
1998: }
1999:
2000: #if 0 /* Never occurs on an ORDER BY query */
2001: /* If any row exist in the result set, record that fact and abort.
2002: */
2003: case SRT_Exists: {
2004: sqlite3VdbeAddOp2(v, OP_Integer, 1, pDest->iParm);
2005: /* The LIMIT clause will terminate the loop for us */
2006: break;
2007: }
2008: #endif
2009:
2010: /* If this is a scalar select that is part of an expression, then
2011: ** store the results in the appropriate memory cell and break out
2012: ** of the scan loop.
2013: */
2014: case SRT_Mem: {
2015: assert( pIn->nMem==1 );
2016: sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iParm, 1);
2017: /* The LIMIT clause will jump out of the loop for us */
2018: break;
2019: }
2020: #endif /* #ifndef SQLITE_OMIT_SUBQUERY */
2021:
2022: /* The results are stored in a sequence of registers
2023: ** starting at pDest->iMem. Then the co-routine yields.
2024: */
2025: case SRT_Coroutine: {
2026: if( pDest->iMem==0 ){
2027: pDest->iMem = sqlite3GetTempRange(pParse, pIn->nMem);
2028: pDest->nMem = pIn->nMem;
2029: }
2030: sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iMem, pDest->nMem);
2031: sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
2032: break;
2033: }
2034:
2035: /* If none of the above, then the result destination must be
2036: ** SRT_Output. This routine is never called with any other
2037: ** destination other than the ones handled above or SRT_Output.
2038: **
2039: ** For SRT_Output, results are stored in a sequence of registers.
2040: ** Then the OP_ResultRow opcode is used to cause sqlite3_step() to
2041: ** return the next row of result.
2042: */
2043: default: {
2044: assert( pDest->eDest==SRT_Output );
2045: sqlite3VdbeAddOp2(v, OP_ResultRow, pIn->iMem, pIn->nMem);
2046: sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, pIn->nMem);
2047: break;
2048: }
2049: }
2050:
2051: /* Jump to the end of the loop if the LIMIT is reached.
2052: */
2053: if( p->iLimit ){
2054: sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
2055: }
2056:
2057: /* Generate the subroutine return
2058: */
2059: sqlite3VdbeResolveLabel(v, iContinue);
2060: sqlite3VdbeAddOp1(v, OP_Return, regReturn);
2061:
2062: return addr;
2063: }
2064:
2065: /*
2066: ** Alternative compound select code generator for cases when there
2067: ** is an ORDER BY clause.
2068: **
2069: ** We assume a query of the following form:
2070: **
2071: ** <selectA> <operator> <selectB> ORDER BY <orderbylist>
2072: **
2073: ** <operator> is one of UNION ALL, UNION, EXCEPT, or INTERSECT. The idea
2074: ** is to code both <selectA> and <selectB> with the ORDER BY clause as
2075: ** co-routines. Then run the co-routines in parallel and merge the results
2076: ** into the output. In addition to the two coroutines (called selectA and
2077: ** selectB) there are 7 subroutines:
2078: **
2079: ** outA: Move the output of the selectA coroutine into the output
2080: ** of the compound query.
2081: **
2082: ** outB: Move the output of the selectB coroutine into the output
2083: ** of the compound query. (Only generated for UNION and
2084: ** UNION ALL. EXCEPT and INSERTSECT never output a row that
2085: ** appears only in B.)
2086: **
2087: ** AltB: Called when there is data from both coroutines and A<B.
2088: **
2089: ** AeqB: Called when there is data from both coroutines and A==B.
2090: **
2091: ** AgtB: Called when there is data from both coroutines and A>B.
2092: **
2093: ** EofA: Called when data is exhausted from selectA.
2094: **
2095: ** EofB: Called when data is exhausted from selectB.
2096: **
2097: ** The implementation of the latter five subroutines depend on which
2098: ** <operator> is used:
2099: **
2100: **
2101: ** UNION ALL UNION EXCEPT INTERSECT
2102: ** ------------- ----------------- -------------- -----------------
2103: ** AltB: outA, nextA outA, nextA outA, nextA nextA
2104: **
2105: ** AeqB: outA, nextA nextA nextA outA, nextA
2106: **
2107: ** AgtB: outB, nextB outB, nextB nextB nextB
2108: **
2109: ** EofA: outB, nextB outB, nextB halt halt
2110: **
2111: ** EofB: outA, nextA outA, nextA outA, nextA halt
2112: **
2113: ** In the AltB, AeqB, and AgtB subroutines, an EOF on A following nextA
2114: ** causes an immediate jump to EofA and an EOF on B following nextB causes
2115: ** an immediate jump to EofB. Within EofA and EofB, and EOF on entry or
2116: ** following nextX causes a jump to the end of the select processing.
2117: **
2118: ** Duplicate removal in the UNION, EXCEPT, and INTERSECT cases is handled
2119: ** within the output subroutine. The regPrev register set holds the previously
2120: ** output value. A comparison is made against this value and the output
2121: ** is skipped if the next results would be the same as the previous.
2122: **
2123: ** The implementation plan is to implement the two coroutines and seven
2124: ** subroutines first, then put the control logic at the bottom. Like this:
2125: **
2126: ** goto Init
2127: ** coA: coroutine for left query (A)
2128: ** coB: coroutine for right query (B)
2129: ** outA: output one row of A
2130: ** outB: output one row of B (UNION and UNION ALL only)
2131: ** EofA: ...
2132: ** EofB: ...
2133: ** AltB: ...
2134: ** AeqB: ...
2135: ** AgtB: ...
2136: ** Init: initialize coroutine registers
2137: ** yield coA
2138: ** if eof(A) goto EofA
2139: ** yield coB
2140: ** if eof(B) goto EofB
2141: ** Cmpr: Compare A, B
2142: ** Jump AltB, AeqB, AgtB
2143: ** End: ...
2144: **
2145: ** We call AltB, AeqB, AgtB, EofA, and EofB "subroutines" but they are not
2146: ** actually called using Gosub and they do not Return. EofA and EofB loop
2147: ** until all data is exhausted then jump to the "end" labe. AltB, AeqB,
2148: ** and AgtB jump to either L2 or to one of EofA or EofB.
2149: */
2150: #ifndef SQLITE_OMIT_COMPOUND_SELECT
2151: static int multiSelectOrderBy(
2152: Parse *pParse, /* Parsing context */
2153: Select *p, /* The right-most of SELECTs to be coded */
2154: SelectDest *pDest /* What to do with query results */
2155: ){
2156: int i, j; /* Loop counters */
2157: Select *pPrior; /* Another SELECT immediately to our left */
2158: Vdbe *v; /* Generate code to this VDBE */
2159: SelectDest destA; /* Destination for coroutine A */
2160: SelectDest destB; /* Destination for coroutine B */
2161: int regAddrA; /* Address register for select-A coroutine */
2162: int regEofA; /* Flag to indicate when select-A is complete */
2163: int regAddrB; /* Address register for select-B coroutine */
2164: int regEofB; /* Flag to indicate when select-B is complete */
2165: int addrSelectA; /* Address of the select-A coroutine */
2166: int addrSelectB; /* Address of the select-B coroutine */
2167: int regOutA; /* Address register for the output-A subroutine */
2168: int regOutB; /* Address register for the output-B subroutine */
2169: int addrOutA; /* Address of the output-A subroutine */
2170: int addrOutB = 0; /* Address of the output-B subroutine */
2171: int addrEofA; /* Address of the select-A-exhausted subroutine */
2172: int addrEofB; /* Address of the select-B-exhausted subroutine */
2173: int addrAltB; /* Address of the A<B subroutine */
2174: int addrAeqB; /* Address of the A==B subroutine */
2175: int addrAgtB; /* Address of the A>B subroutine */
2176: int regLimitA; /* Limit register for select-A */
2177: int regLimitB; /* Limit register for select-A */
2178: int regPrev; /* A range of registers to hold previous output */
2179: int savedLimit; /* Saved value of p->iLimit */
2180: int savedOffset; /* Saved value of p->iOffset */
2181: int labelCmpr; /* Label for the start of the merge algorithm */
2182: int labelEnd; /* Label for the end of the overall SELECT stmt */
2183: int j1; /* Jump instructions that get retargetted */
2184: int op; /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
2185: KeyInfo *pKeyDup = 0; /* Comparison information for duplicate removal */
2186: KeyInfo *pKeyMerge; /* Comparison information for merging rows */
2187: sqlite3 *db; /* Database connection */
2188: ExprList *pOrderBy; /* The ORDER BY clause */
2189: int nOrderBy; /* Number of terms in the ORDER BY clause */
2190: int *aPermute; /* Mapping from ORDER BY terms to result set columns */
2191: #ifndef SQLITE_OMIT_EXPLAIN
2192: int iSub1; /* EQP id of left-hand query */
2193: int iSub2; /* EQP id of right-hand query */
2194: #endif
2195:
2196: assert( p->pOrderBy!=0 );
2197: assert( pKeyDup==0 ); /* "Managed" code needs this. Ticket #3382. */
2198: db = pParse->db;
2199: v = pParse->pVdbe;
2200: assert( v!=0 ); /* Already thrown the error if VDBE alloc failed */
2201: labelEnd = sqlite3VdbeMakeLabel(v);
2202: labelCmpr = sqlite3VdbeMakeLabel(v);
2203:
2204:
2205: /* Patch up the ORDER BY clause
2206: */
2207: op = p->op;
2208: pPrior = p->pPrior;
2209: assert( pPrior->pOrderBy==0 );
2210: pOrderBy = p->pOrderBy;
2211: assert( pOrderBy );
2212: nOrderBy = pOrderBy->nExpr;
2213:
2214: /* For operators other than UNION ALL we have to make sure that
2215: ** the ORDER BY clause covers every term of the result set. Add
2216: ** terms to the ORDER BY clause as necessary.
2217: */
2218: if( op!=TK_ALL ){
2219: for(i=1; db->mallocFailed==0 && i<=p->pEList->nExpr; i++){
2220: struct ExprList_item *pItem;
2221: for(j=0, pItem=pOrderBy->a; j<nOrderBy; j++, pItem++){
2222: assert( pItem->iOrderByCol>0 );
2223: if( pItem->iOrderByCol==i ) break;
2224: }
2225: if( j==nOrderBy ){
2226: Expr *pNew = sqlite3Expr(db, TK_INTEGER, 0);
2227: if( pNew==0 ) return SQLITE_NOMEM;
2228: pNew->flags |= EP_IntValue;
2229: pNew->u.iValue = i;
2230: pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew);
2231: pOrderBy->a[nOrderBy++].iOrderByCol = (u16)i;
2232: }
2233: }
2234: }
2235:
2236: /* Compute the comparison permutation and keyinfo that is used with
2237: ** the permutation used to determine if the next
2238: ** row of results comes from selectA or selectB. Also add explicit
2239: ** collations to the ORDER BY clause terms so that when the subqueries
2240: ** to the right and the left are evaluated, they use the correct
2241: ** collation.
2242: */
2243: aPermute = sqlite3DbMallocRaw(db, sizeof(int)*nOrderBy);
2244: if( aPermute ){
2245: struct ExprList_item *pItem;
2246: for(i=0, pItem=pOrderBy->a; i<nOrderBy; i++, pItem++){
2247: assert( pItem->iOrderByCol>0 && pItem->iOrderByCol<=p->pEList->nExpr );
2248: aPermute[i] = pItem->iOrderByCol - 1;
2249: }
2250: pKeyMerge =
2251: sqlite3DbMallocRaw(db, sizeof(*pKeyMerge)+nOrderBy*(sizeof(CollSeq*)+1));
2252: if( pKeyMerge ){
2253: pKeyMerge->aSortOrder = (u8*)&pKeyMerge->aColl[nOrderBy];
2254: pKeyMerge->nField = (u16)nOrderBy;
2255: pKeyMerge->enc = ENC(db);
2256: for(i=0; i<nOrderBy; i++){
2257: CollSeq *pColl;
2258: Expr *pTerm = pOrderBy->a[i].pExpr;
2259: if( pTerm->flags & EP_ExpCollate ){
2260: pColl = pTerm->pColl;
2261: }else{
2262: pColl = multiSelectCollSeq(pParse, p, aPermute[i]);
2263: pTerm->flags |= EP_ExpCollate;
2264: pTerm->pColl = pColl;
2265: }
2266: pKeyMerge->aColl[i] = pColl;
2267: pKeyMerge->aSortOrder[i] = pOrderBy->a[i].sortOrder;
2268: }
2269: }
2270: }else{
2271: pKeyMerge = 0;
2272: }
2273:
2274: /* Reattach the ORDER BY clause to the query.
2275: */
2276: p->pOrderBy = pOrderBy;
2277: pPrior->pOrderBy = sqlite3ExprListDup(pParse->db, pOrderBy, 0);
2278:
2279: /* Allocate a range of temporary registers and the KeyInfo needed
2280: ** for the logic that removes duplicate result rows when the
2281: ** operator is UNION, EXCEPT, or INTERSECT (but not UNION ALL).
2282: */
2283: if( op==TK_ALL ){
2284: regPrev = 0;
2285: }else{
2286: int nExpr = p->pEList->nExpr;
2287: assert( nOrderBy>=nExpr || db->mallocFailed );
2288: regPrev = sqlite3GetTempRange(pParse, nExpr+1);
2289: sqlite3VdbeAddOp2(v, OP_Integer, 0, regPrev);
2290: pKeyDup = sqlite3DbMallocZero(db,
2291: sizeof(*pKeyDup) + nExpr*(sizeof(CollSeq*)+1) );
2292: if( pKeyDup ){
2293: pKeyDup->aSortOrder = (u8*)&pKeyDup->aColl[nExpr];
2294: pKeyDup->nField = (u16)nExpr;
2295: pKeyDup->enc = ENC(db);
2296: for(i=0; i<nExpr; i++){
2297: pKeyDup->aColl[i] = multiSelectCollSeq(pParse, p, i);
2298: pKeyDup->aSortOrder[i] = 0;
2299: }
2300: }
2301: }
2302:
2303: /* Separate the left and the right query from one another
2304: */
2305: p->pPrior = 0;
2306: sqlite3ResolveOrderGroupBy(pParse, p, p->pOrderBy, "ORDER");
2307: if( pPrior->pPrior==0 ){
2308: sqlite3ResolveOrderGroupBy(pParse, pPrior, pPrior->pOrderBy, "ORDER");
2309: }
2310:
2311: /* Compute the limit registers */
2312: computeLimitRegisters(pParse, p, labelEnd);
2313: if( p->iLimit && op==TK_ALL ){
2314: regLimitA = ++pParse->nMem;
2315: regLimitB = ++pParse->nMem;
2316: sqlite3VdbeAddOp2(v, OP_Copy, p->iOffset ? p->iOffset+1 : p->iLimit,
2317: regLimitA);
2318: sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
2319: }else{
2320: regLimitA = regLimitB = 0;
2321: }
2322: sqlite3ExprDelete(db, p->pLimit);
2323: p->pLimit = 0;
2324: sqlite3ExprDelete(db, p->pOffset);
2325: p->pOffset = 0;
2326:
2327: regAddrA = ++pParse->nMem;
2328: regEofA = ++pParse->nMem;
2329: regAddrB = ++pParse->nMem;
2330: regEofB = ++pParse->nMem;
2331: regOutA = ++pParse->nMem;
2332: regOutB = ++pParse->nMem;
2333: sqlite3SelectDestInit(&destA, SRT_Coroutine, regAddrA);
2334: sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);
2335:
2336: /* Jump past the various subroutines and coroutines to the main
2337: ** merge loop
2338: */
2339: j1 = sqlite3VdbeAddOp0(v, OP_Goto);
2340: addrSelectA = sqlite3VdbeCurrentAddr(v);
2341:
2342:
2343: /* Generate a coroutine to evaluate the SELECT statement to the
2344: ** left of the compound operator - the "A" select.
2345: */
2346: VdbeNoopComment((v, "Begin coroutine for left SELECT"));
2347: pPrior->iLimit = regLimitA;
2348: explainSetInteger(iSub1, pParse->iNextSelectId);
2349: sqlite3Select(pParse, pPrior, &destA);
2350: sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofA);
2351: sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
2352: VdbeNoopComment((v, "End coroutine for left SELECT"));
2353:
2354: /* Generate a coroutine to evaluate the SELECT statement on
2355: ** the right - the "B" select
2356: */
2357: addrSelectB = sqlite3VdbeCurrentAddr(v);
2358: VdbeNoopComment((v, "Begin coroutine for right SELECT"));
2359: savedLimit = p->iLimit;
2360: savedOffset = p->iOffset;
2361: p->iLimit = regLimitB;
2362: p->iOffset = 0;
2363: explainSetInteger(iSub2, pParse->iNextSelectId);
2364: sqlite3Select(pParse, p, &destB);
2365: p->iLimit = savedLimit;
2366: p->iOffset = savedOffset;
2367: sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofB);
2368: sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
2369: VdbeNoopComment((v, "End coroutine for right SELECT"));
2370:
2371: /* Generate a subroutine that outputs the current row of the A
2372: ** select as the next output row of the compound select.
2373: */
2374: VdbeNoopComment((v, "Output routine for A"));
2375: addrOutA = generateOutputSubroutine(pParse,
2376: p, &destA, pDest, regOutA,
2377: regPrev, pKeyDup, P4_KEYINFO_HANDOFF, labelEnd);
2378:
2379: /* Generate a subroutine that outputs the current row of the B
2380: ** select as the next output row of the compound select.
2381: */
2382: if( op==TK_ALL || op==TK_UNION ){
2383: VdbeNoopComment((v, "Output routine for B"));
2384: addrOutB = generateOutputSubroutine(pParse,
2385: p, &destB, pDest, regOutB,
2386: regPrev, pKeyDup, P4_KEYINFO_STATIC, labelEnd);
2387: }
2388:
2389: /* Generate a subroutine to run when the results from select A
2390: ** are exhausted and only data in select B remains.
2391: */
2392: VdbeNoopComment((v, "eof-A subroutine"));
2393: if( op==TK_EXCEPT || op==TK_INTERSECT ){
2394: addrEofA = sqlite3VdbeAddOp2(v, OP_Goto, 0, labelEnd);
2395: }else{
2396: addrEofA = sqlite3VdbeAddOp2(v, OP_If, regEofB, labelEnd);
2397: sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
2398: sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
2399: sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofA);
2400: p->nSelectRow += pPrior->nSelectRow;
2401: }
2402:
2403: /* Generate a subroutine to run when the results from select B
2404: ** are exhausted and only data in select A remains.
2405: */
2406: if( op==TK_INTERSECT ){
2407: addrEofB = addrEofA;
2408: if( p->nSelectRow > pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
2409: }else{
2410: VdbeNoopComment((v, "eof-B subroutine"));
2411: addrEofB = sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
2412: sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
2413: sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
2414: sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofB);
2415: }
2416:
2417: /* Generate code to handle the case of A<B
2418: */
2419: VdbeNoopComment((v, "A-lt-B subroutine"));
2420: addrAltB = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
2421: sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
2422: sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
2423: sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
2424:
2425: /* Generate code to handle the case of A==B
2426: */
2427: if( op==TK_ALL ){
2428: addrAeqB = addrAltB;
2429: }else if( op==TK_INTERSECT ){
2430: addrAeqB = addrAltB;
2431: addrAltB++;
2432: }else{
2433: VdbeNoopComment((v, "A-eq-B subroutine"));
2434: addrAeqB =
2435: sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
2436: sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
2437: sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
2438: }
2439:
2440: /* Generate code to handle the case of A>B
2441: */
2442: VdbeNoopComment((v, "A-gt-B subroutine"));
2443: addrAgtB = sqlite3VdbeCurrentAddr(v);
2444: if( op==TK_ALL || op==TK_UNION ){
2445: sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
2446: }
2447: sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
2448: sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
2449: sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
2450:
2451: /* This code runs once to initialize everything.
2452: */
2453: sqlite3VdbeJumpHere(v, j1);
2454: sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofA);
2455: sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofB);
2456: sqlite3VdbeAddOp2(v, OP_Gosub, regAddrA, addrSelectA);
2457: sqlite3VdbeAddOp2(v, OP_Gosub, regAddrB, addrSelectB);
2458: sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
2459: sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
2460:
2461: /* Implement the main merge loop
2462: */
2463: sqlite3VdbeResolveLabel(v, labelCmpr);
2464: sqlite3VdbeAddOp4(v, OP_Permutation, 0, 0, 0, (char*)aPermute, P4_INTARRAY);
2465: sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, nOrderBy,
2466: (char*)pKeyMerge, P4_KEYINFO_HANDOFF);
2467: sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB);
2468:
2469: /* Release temporary registers
2470: */
2471: if( regPrev ){
2472: sqlite3ReleaseTempRange(pParse, regPrev, nOrderBy+1);
2473: }
2474:
2475: /* Jump to the this point in order to terminate the query.
2476: */
2477: sqlite3VdbeResolveLabel(v, labelEnd);
2478:
2479: /* Set the number of output columns
2480: */
2481: if( pDest->eDest==SRT_Output ){
2482: Select *pFirst = pPrior;
2483: while( pFirst->pPrior ) pFirst = pFirst->pPrior;
2484: generateColumnNames(pParse, 0, pFirst->pEList);
2485: }
2486:
2487: /* Reassembly the compound query so that it will be freed correctly
2488: ** by the calling function */
2489: if( p->pPrior ){
2490: sqlite3SelectDelete(db, p->pPrior);
2491: }
2492: p->pPrior = pPrior;
2493:
2494: /*** TBD: Insert subroutine calls to close cursors on incomplete
2495: **** subqueries ****/
2496: explainComposite(pParse, p->op, iSub1, iSub2, 0);
2497: return SQLITE_OK;
2498: }
2499: #endif
2500:
2501: #if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
2502: /* Forward Declarations */
2503: static void substExprList(sqlite3*, ExprList*, int, ExprList*);
2504: static void substSelect(sqlite3*, Select *, int, ExprList *);
2505:
2506: /*
2507: ** Scan through the expression pExpr. Replace every reference to
2508: ** a column in table number iTable with a copy of the iColumn-th
2509: ** entry in pEList. (But leave references to the ROWID column
2510: ** unchanged.)
2511: **
2512: ** This routine is part of the flattening procedure. A subquery
2513: ** whose result set is defined by pEList appears as entry in the
2514: ** FROM clause of a SELECT such that the VDBE cursor assigned to that
2515: ** FORM clause entry is iTable. This routine make the necessary
2516: ** changes to pExpr so that it refers directly to the source table
2517: ** of the subquery rather the result set of the subquery.
2518: */
2519: static Expr *substExpr(
2520: sqlite3 *db, /* Report malloc errors to this connection */
2521: Expr *pExpr, /* Expr in which substitution occurs */
2522: int iTable, /* Table to be substituted */
2523: ExprList *pEList /* Substitute expressions */
2524: ){
2525: if( pExpr==0 ) return 0;
2526: if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable ){
2527: if( pExpr->iColumn<0 ){
2528: pExpr->op = TK_NULL;
2529: }else{
2530: Expr *pNew;
2531: assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
2532: assert( pExpr->pLeft==0 && pExpr->pRight==0 );
2533: pNew = sqlite3ExprDup(db, pEList->a[pExpr->iColumn].pExpr, 0);
2534: if( pNew && pExpr->pColl ){
2535: pNew->pColl = pExpr->pColl;
2536: }
2537: sqlite3ExprDelete(db, pExpr);
2538: pExpr = pNew;
2539: }
2540: }else{
2541: pExpr->pLeft = substExpr(db, pExpr->pLeft, iTable, pEList);
2542: pExpr->pRight = substExpr(db, pExpr->pRight, iTable, pEList);
2543: if( ExprHasProperty(pExpr, EP_xIsSelect) ){
2544: substSelect(db, pExpr->x.pSelect, iTable, pEList);
2545: }else{
2546: substExprList(db, pExpr->x.pList, iTable, pEList);
2547: }
2548: }
2549: return pExpr;
2550: }
2551: static void substExprList(
2552: sqlite3 *db, /* Report malloc errors here */
2553: ExprList *pList, /* List to scan and in which to make substitutes */
2554: int iTable, /* Table to be substituted */
2555: ExprList *pEList /* Substitute values */
2556: ){
2557: int i;
2558: if( pList==0 ) return;
2559: for(i=0; i<pList->nExpr; i++){
2560: pList->a[i].pExpr = substExpr(db, pList->a[i].pExpr, iTable, pEList);
2561: }
2562: }
2563: static void substSelect(
2564: sqlite3 *db, /* Report malloc errors here */
2565: Select *p, /* SELECT statement in which to make substitutions */
2566: int iTable, /* Table to be replaced */
2567: ExprList *pEList /* Substitute values */
2568: ){
2569: SrcList *pSrc;
2570: struct SrcList_item *pItem;
2571: int i;
2572: if( !p ) return;
2573: substExprList(db, p->pEList, iTable, pEList);
2574: substExprList(db, p->pGroupBy, iTable, pEList);
2575: substExprList(db, p->pOrderBy, iTable, pEList);
2576: p->pHaving = substExpr(db, p->pHaving, iTable, pEList);
2577: p->pWhere = substExpr(db, p->pWhere, iTable, pEList);
2578: substSelect(db, p->pPrior, iTable, pEList);
2579: pSrc = p->pSrc;
2580: assert( pSrc ); /* Even for (SELECT 1) we have: pSrc!=0 but pSrc->nSrc==0 */
2581: if( ALWAYS(pSrc) ){
2582: for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
2583: substSelect(db, pItem->pSelect, iTable, pEList);
2584: }
2585: }
2586: }
2587: #endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
2588:
2589: #if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
2590: /*
2591: ** This routine attempts to flatten subqueries as a performance optimization.
2592: ** This routine returns 1 if it makes changes and 0 if no flattening occurs.
2593: **
2594: ** To understand the concept of flattening, consider the following
2595: ** query:
2596: **
2597: ** SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
2598: **
2599: ** The default way of implementing this query is to execute the
2600: ** subquery first and store the results in a temporary table, then
2601: ** run the outer query on that temporary table. This requires two
2602: ** passes over the data. Furthermore, because the temporary table
2603: ** has no indices, the WHERE clause on the outer query cannot be
2604: ** optimized.
2605: **
2606: ** This routine attempts to rewrite queries such as the above into
2607: ** a single flat select, like this:
2608: **
2609: ** SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
2610: **
2611: ** The code generated for this simpification gives the same result
2612: ** but only has to scan the data once. And because indices might
2613: ** exist on the table t1, a complete scan of the data might be
2614: ** avoided.
2615: **
2616: ** Flattening is only attempted if all of the following are true:
2617: **
2618: ** (1) The subquery and the outer query do not both use aggregates.
2619: **
2620: ** (2) The subquery is not an aggregate or the outer query is not a join.
2621: **
2622: ** (3) The subquery is not the right operand of a left outer join
2623: ** (Originally ticket #306. Strengthened by ticket #3300)
2624: **
2625: ** (4) The subquery is not DISTINCT.
2626: **
2627: ** (**) At one point restrictions (4) and (5) defined a subset of DISTINCT
2628: ** sub-queries that were excluded from this optimization. Restriction
2629: ** (4) has since been expanded to exclude all DISTINCT subqueries.
2630: **
2631: ** (6) The subquery does not use aggregates or the outer query is not
2632: ** DISTINCT.
2633: **
2634: ** (7) The subquery has a FROM clause. TODO: For subqueries without
2635: ** A FROM clause, consider adding a FROM close with the special
2636: ** table sqlite_once that consists of a single row containing a
2637: ** single NULL.
2638: **
2639: ** (8) The subquery does not use LIMIT or the outer query is not a join.
2640: **
2641: ** (9) The subquery does not use LIMIT or the outer query does not use
2642: ** aggregates.
2643: **
2644: ** (10) The subquery does not use aggregates or the outer query does not
2645: ** use LIMIT.
2646: **
2647: ** (11) The subquery and the outer query do not both have ORDER BY clauses.
2648: **
2649: ** (**) Not implemented. Subsumed into restriction (3). Was previously
2650: ** a separate restriction deriving from ticket #350.
2651: **
2652: ** (13) The subquery and outer query do not both use LIMIT.
2653: **
2654: ** (14) The subquery does not use OFFSET.
2655: **
2656: ** (15) The outer query is not part of a compound select or the
2657: ** subquery does not have a LIMIT clause.
2658: ** (See ticket #2339 and ticket [02a8e81d44]).
2659: **
2660: ** (16) The outer query is not an aggregate or the subquery does
2661: ** not contain ORDER BY. (Ticket #2942) This used to not matter
2662: ** until we introduced the group_concat() function.
2663: **
2664: ** (17) The sub-query is not a compound select, or it is a UNION ALL
2665: ** compound clause made up entirely of non-aggregate queries, and
2666: ** the parent query:
2667: **
2668: ** * is not itself part of a compound select,
2669: ** * is not an aggregate or DISTINCT query, and
2670: ** * is not a join
2671: **
2672: ** The parent and sub-query may contain WHERE clauses. Subject to
2673: ** rules (11), (13) and (14), they may also contain ORDER BY,
2674: ** LIMIT and OFFSET clauses. The subquery cannot use any compound
2675: ** operator other than UNION ALL because all the other compound
2676: ** operators have an implied DISTINCT which is disallowed by
2677: ** restriction (4).
2678: **
2679: ** (18) If the sub-query is a compound select, then all terms of the
2680: ** ORDER by clause of the parent must be simple references to
2681: ** columns of the sub-query.
2682: **
2683: ** (19) The subquery does not use LIMIT or the outer query does not
2684: ** have a WHERE clause.
2685: **
2686: ** (20) If the sub-query is a compound select, then it must not use
2687: ** an ORDER BY clause. Ticket #3773. We could relax this constraint
2688: ** somewhat by saying that the terms of the ORDER BY clause must
2689: ** appear as unmodified result columns in the outer query. But we
2690: ** have other optimizations in mind to deal with that case.
2691: **
2692: ** (21) The subquery does not use LIMIT or the outer query is not
2693: ** DISTINCT. (See ticket [752e1646fc]).
2694: **
2695: ** In this routine, the "p" parameter is a pointer to the outer query.
2696: ** The subquery is p->pSrc->a[iFrom]. isAgg is true if the outer query
2697: ** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
2698: **
2699: ** If flattening is not attempted, this routine is a no-op and returns 0.
2700: ** If flattening is attempted this routine returns 1.
2701: **
2702: ** All of the expression analysis must occur on both the outer query and
2703: ** the subquery before this routine runs.
2704: */
2705: static int flattenSubquery(
2706: Parse *pParse, /* Parsing context */
2707: Select *p, /* The parent or outer SELECT statement */
2708: int iFrom, /* Index in p->pSrc->a[] of the inner subquery */
2709: int isAgg, /* True if outer SELECT uses aggregate functions */
2710: int subqueryIsAgg /* True if the subquery uses aggregate functions */
2711: ){
2712: const char *zSavedAuthContext = pParse->zAuthContext;
2713: Select *pParent;
2714: Select *pSub; /* The inner query or "subquery" */
2715: Select *pSub1; /* Pointer to the rightmost select in sub-query */
2716: SrcList *pSrc; /* The FROM clause of the outer query */
2717: SrcList *pSubSrc; /* The FROM clause of the subquery */
2718: ExprList *pList; /* The result set of the outer query */
2719: int iParent; /* VDBE cursor number of the pSub result set temp table */
2720: int i; /* Loop counter */
2721: Expr *pWhere; /* The WHERE clause */
2722: struct SrcList_item *pSubitem; /* The subquery */
2723: sqlite3 *db = pParse->db;
2724:
2725: /* Check to see if flattening is permitted. Return 0 if not.
2726: */
2727: assert( p!=0 );
2728: assert( p->pPrior==0 ); /* Unable to flatten compound queries */
2729: if( db->flags & SQLITE_QueryFlattener ) return 0;
2730: pSrc = p->pSrc;
2731: assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
2732: pSubitem = &pSrc->a[iFrom];
2733: iParent = pSubitem->iCursor;
2734: pSub = pSubitem->pSelect;
2735: assert( pSub!=0 );
2736: if( isAgg && subqueryIsAgg ) return 0; /* Restriction (1) */
2737: if( subqueryIsAgg && pSrc->nSrc>1 ) return 0; /* Restriction (2) */
2738: pSubSrc = pSub->pSrc;
2739: assert( pSubSrc );
2740: /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
2741: ** not arbitrary expresssions, we allowed some combining of LIMIT and OFFSET
2742: ** because they could be computed at compile-time. But when LIMIT and OFFSET
2743: ** became arbitrary expressions, we were forced to add restrictions (13)
2744: ** and (14). */
2745: if( pSub->pLimit && p->pLimit ) return 0; /* Restriction (13) */
2746: if( pSub->pOffset ) return 0; /* Restriction (14) */
2747: if( p->pRightmost && pSub->pLimit ){
2748: return 0; /* Restriction (15) */
2749: }
2750: if( pSubSrc->nSrc==0 ) return 0; /* Restriction (7) */
2751: if( pSub->selFlags & SF_Distinct ) return 0; /* Restriction (5) */
2752: if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
2753: return 0; /* Restrictions (8)(9) */
2754: }
2755: if( (p->selFlags & SF_Distinct)!=0 && subqueryIsAgg ){
2756: return 0; /* Restriction (6) */
2757: }
2758: if( p->pOrderBy && pSub->pOrderBy ){
2759: return 0; /* Restriction (11) */
2760: }
2761: if( isAgg && pSub->pOrderBy ) return 0; /* Restriction (16) */
2762: if( pSub->pLimit && p->pWhere ) return 0; /* Restriction (19) */
2763: if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
2764: return 0; /* Restriction (21) */
2765: }
2766:
2767: /* OBSOLETE COMMENT 1:
2768: ** Restriction 3: If the subquery is a join, make sure the subquery is
2769: ** not used as the right operand of an outer join. Examples of why this
2770: ** is not allowed:
2771: **
2772: ** t1 LEFT OUTER JOIN (t2 JOIN t3)
2773: **
2774: ** If we flatten the above, we would get
2775: **
2776: ** (t1 LEFT OUTER JOIN t2) JOIN t3
2777: **
2778: ** which is not at all the same thing.
2779: **
2780: ** OBSOLETE COMMENT 2:
2781: ** Restriction 12: If the subquery is the right operand of a left outer
2782: ** join, make sure the subquery has no WHERE clause.
2783: ** An examples of why this is not allowed:
2784: **
2785: ** t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
2786: **
2787: ** If we flatten the above, we would get
2788: **
2789: ** (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
2790: **
2791: ** But the t2.x>0 test will always fail on a NULL row of t2, which
2792: ** effectively converts the OUTER JOIN into an INNER JOIN.
2793: **
2794: ** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
2795: ** Ticket #3300 shows that flattening the right term of a LEFT JOIN
2796: ** is fraught with danger. Best to avoid the whole thing. If the
2797: ** subquery is the right term of a LEFT JOIN, then do not flatten.
2798: */
2799: if( (pSubitem->jointype & JT_OUTER)!=0 ){
2800: return 0;
2801: }
2802:
2803: /* Restriction 17: If the sub-query is a compound SELECT, then it must
2804: ** use only the UNION ALL operator. And none of the simple select queries
2805: ** that make up the compound SELECT are allowed to be aggregate or distinct
2806: ** queries.
2807: */
2808: if( pSub->pPrior ){
2809: if( pSub->pOrderBy ){
2810: return 0; /* Restriction 20 */
2811: }
2812: if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
2813: return 0;
2814: }
2815: for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
2816: testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
2817: testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
2818: assert( pSub->pSrc!=0 );
2819: if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0
2820: || (pSub1->pPrior && pSub1->op!=TK_ALL)
2821: || pSub1->pSrc->nSrc<1
2822: ){
2823: return 0;
2824: }
2825: testcase( pSub1->pSrc->nSrc>1 );
2826: }
2827:
2828: /* Restriction 18. */
2829: if( p->pOrderBy ){
2830: int ii;
2831: for(ii=0; ii<p->pOrderBy->nExpr; ii++){
2832: if( p->pOrderBy->a[ii].iOrderByCol==0 ) return 0;
2833: }
2834: }
2835: }
2836:
2837: /***** If we reach this point, flattening is permitted. *****/
2838:
2839: /* Authorize the subquery */
2840: pParse->zAuthContext = pSubitem->zName;
2841: sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);
2842: pParse->zAuthContext = zSavedAuthContext;
2843:
2844: /* If the sub-query is a compound SELECT statement, then (by restrictions
2845: ** 17 and 18 above) it must be a UNION ALL and the parent query must
2846: ** be of the form:
2847: **
2848: ** SELECT <expr-list> FROM (<sub-query>) <where-clause>
2849: **
2850: ** followed by any ORDER BY, LIMIT and/or OFFSET clauses. This block
2851: ** creates N-1 copies of the parent query without any ORDER BY, LIMIT or
2852: ** OFFSET clauses and joins them to the left-hand-side of the original
2853: ** using UNION ALL operators. In this case N is the number of simple
2854: ** select statements in the compound sub-query.
2855: **
2856: ** Example:
2857: **
2858: ** SELECT a+1 FROM (
2859: ** SELECT x FROM tab
2860: ** UNION ALL
2861: ** SELECT y FROM tab
2862: ** UNION ALL
2863: ** SELECT abs(z*2) FROM tab2
2864: ** ) WHERE a!=5 ORDER BY 1
2865: **
2866: ** Transformed into:
2867: **
2868: ** SELECT x+1 FROM tab WHERE x+1!=5
2869: ** UNION ALL
2870: ** SELECT y+1 FROM tab WHERE y+1!=5
2871: ** UNION ALL
2872: ** SELECT abs(z*2)+1 FROM tab2 WHERE abs(z*2)+1!=5
2873: ** ORDER BY 1
2874: **
2875: ** We call this the "compound-subquery flattening".
2876: */
2877: for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
2878: Select *pNew;
2879: ExprList *pOrderBy = p->pOrderBy;
2880: Expr *pLimit = p->pLimit;
2881: Select *pPrior = p->pPrior;
2882: p->pOrderBy = 0;
2883: p->pSrc = 0;
2884: p->pPrior = 0;
2885: p->pLimit = 0;
2886: pNew = sqlite3SelectDup(db, p, 0);
2887: p->pLimit = pLimit;
2888: p->pOrderBy = pOrderBy;
2889: p->pSrc = pSrc;
2890: p->op = TK_ALL;
2891: p->pRightmost = 0;
2892: if( pNew==0 ){
2893: pNew = pPrior;
2894: }else{
2895: pNew->pPrior = pPrior;
2896: pNew->pRightmost = 0;
2897: }
2898: p->pPrior = pNew;
2899: if( db->mallocFailed ) return 1;
2900: }
2901:
2902: /* Begin flattening the iFrom-th entry of the FROM clause
2903: ** in the outer query.
2904: */
2905: pSub = pSub1 = pSubitem->pSelect;
2906:
2907: /* Delete the transient table structure associated with the
2908: ** subquery
2909: */
2910: sqlite3DbFree(db, pSubitem->zDatabase);
2911: sqlite3DbFree(db, pSubitem->zName);
2912: sqlite3DbFree(db, pSubitem->zAlias);
2913: pSubitem->zDatabase = 0;
2914: pSubitem->zName = 0;
2915: pSubitem->zAlias = 0;
2916: pSubitem->pSelect = 0;
2917:
2918: /* Defer deleting the Table object associated with the
2919: ** subquery until code generation is
2920: ** complete, since there may still exist Expr.pTab entries that
2921: ** refer to the subquery even after flattening. Ticket #3346.
2922: **
2923: ** pSubitem->pTab is always non-NULL by test restrictions and tests above.
2924: */
2925: if( ALWAYS(pSubitem->pTab!=0) ){
2926: Table *pTabToDel = pSubitem->pTab;
2927: if( pTabToDel->nRef==1 ){
2928: Parse *pToplevel = sqlite3ParseToplevel(pParse);
2929: pTabToDel->pNextZombie = pToplevel->pZombieTab;
2930: pToplevel->pZombieTab = pTabToDel;
2931: }else{
2932: pTabToDel->nRef--;
2933: }
2934: pSubitem->pTab = 0;
2935: }
2936:
2937: /* The following loop runs once for each term in a compound-subquery
2938: ** flattening (as described above). If we are doing a different kind
2939: ** of flattening - a flattening other than a compound-subquery flattening -
2940: ** then this loop only runs once.
2941: **
2942: ** This loop moves all of the FROM elements of the subquery into the
2943: ** the FROM clause of the outer query. Before doing this, remember
2944: ** the cursor number for the original outer query FROM element in
2945: ** iParent. The iParent cursor will never be used. Subsequent code
2946: ** will scan expressions looking for iParent references and replace
2947: ** those references with expressions that resolve to the subquery FROM
2948: ** elements we are now copying in.
2949: */
2950: for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
2951: int nSubSrc;
2952: u8 jointype = 0;
2953: pSubSrc = pSub->pSrc; /* FROM clause of subquery */
2954: nSubSrc = pSubSrc->nSrc; /* Number of terms in subquery FROM clause */
2955: pSrc = pParent->pSrc; /* FROM clause of the outer query */
2956:
2957: if( pSrc ){
2958: assert( pParent==p ); /* First time through the loop */
2959: jointype = pSubitem->jointype;
2960: }else{
2961: assert( pParent!=p ); /* 2nd and subsequent times through the loop */
2962: pSrc = pParent->pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
2963: if( pSrc==0 ){
2964: assert( db->mallocFailed );
2965: break;
2966: }
2967: }
2968:
2969: /* The subquery uses a single slot of the FROM clause of the outer
2970: ** query. If the subquery has more than one element in its FROM clause,
2971: ** then expand the outer query to make space for it to hold all elements
2972: ** of the subquery.
2973: **
2974: ** Example:
2975: **
2976: ** SELECT * FROM tabA, (SELECT * FROM sub1, sub2), tabB;
2977: **
2978: ** The outer query has 3 slots in its FROM clause. One slot of the
2979: ** outer query (the middle slot) is used by the subquery. The next
2980: ** block of code will expand the out query to 4 slots. The middle
2981: ** slot is expanded to two slots in order to make space for the
2982: ** two elements in the FROM clause of the subquery.
2983: */
2984: if( nSubSrc>1 ){
2985: pParent->pSrc = pSrc = sqlite3SrcListEnlarge(db, pSrc, nSubSrc-1,iFrom+1);
2986: if( db->mallocFailed ){
2987: break;
2988: }
2989: }
2990:
2991: /* Transfer the FROM clause terms from the subquery into the
2992: ** outer query.
2993: */
2994: for(i=0; i<nSubSrc; i++){
2995: sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
2996: pSrc->a[i+iFrom] = pSubSrc->a[i];
2997: memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
2998: }
2999: pSrc->a[iFrom].jointype = jointype;
3000:
3001: /* Now begin substituting subquery result set expressions for
3002: ** references to the iParent in the outer query.
3003: **
3004: ** Example:
3005: **
3006: ** SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
3007: ** \ \_____________ subquery __________/ /
3008: ** \_____________________ outer query ______________________________/
3009: **
3010: ** We look at every expression in the outer query and every place we see
3011: ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
3012: */
3013: pList = pParent->pEList;
3014: for(i=0; i<pList->nExpr; i++){
3015: if( pList->a[i].zName==0 ){
3016: const char *zSpan = pList->a[i].zSpan;
3017: if( ALWAYS(zSpan) ){
3018: pList->a[i].zName = sqlite3DbStrDup(db, zSpan);
3019: }
3020: }
3021: }
3022: substExprList(db, pParent->pEList, iParent, pSub->pEList);
3023: if( isAgg ){
3024: substExprList(db, pParent->pGroupBy, iParent, pSub->pEList);
3025: pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
3026: }
3027: if( pSub->pOrderBy ){
3028: assert( pParent->pOrderBy==0 );
3029: pParent->pOrderBy = pSub->pOrderBy;
3030: pSub->pOrderBy = 0;
3031: }else if( pParent->pOrderBy ){
3032: substExprList(db, pParent->pOrderBy, iParent, pSub->pEList);
3033: }
3034: if( pSub->pWhere ){
3035: pWhere = sqlite3ExprDup(db, pSub->pWhere, 0);
3036: }else{
3037: pWhere = 0;
3038: }
3039: if( subqueryIsAgg ){
3040: assert( pParent->pHaving==0 );
3041: pParent->pHaving = pParent->pWhere;
3042: pParent->pWhere = pWhere;
3043: pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
3044: pParent->pHaving = sqlite3ExprAnd(db, pParent->pHaving,
3045: sqlite3ExprDup(db, pSub->pHaving, 0));
3046: assert( pParent->pGroupBy==0 );
3047: pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy, 0);
3048: }else{
3049: pParent->pWhere = substExpr(db, pParent->pWhere, iParent, pSub->pEList);
3050: pParent->pWhere = sqlite3ExprAnd(db, pParent->pWhere, pWhere);
3051: }
3052:
3053: /* The flattened query is distinct if either the inner or the
3054: ** outer query is distinct.
3055: */
3056: pParent->selFlags |= pSub->selFlags & SF_Distinct;
3057:
3058: /*
3059: ** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
3060: **
3061: ** One is tempted to try to add a and b to combine the limits. But this
3062: ** does not work if either limit is negative.
3063: */
3064: if( pSub->pLimit ){
3065: pParent->pLimit = pSub->pLimit;
3066: pSub->pLimit = 0;
3067: }
3068: }
3069:
3070: /* Finially, delete what is left of the subquery and return
3071: ** success.
3072: */
3073: sqlite3SelectDelete(db, pSub1);
3074:
3075: return 1;
3076: }
3077: #endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
3078:
3079: /*
3080: ** Analyze the SELECT statement passed as an argument to see if it
3081: ** is a min() or max() query. Return WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX if
3082: ** it is, or 0 otherwise. At present, a query is considered to be
3083: ** a min()/max() query if:
3084: **
3085: ** 1. There is a single object in the FROM clause.
3086: **
3087: ** 2. There is a single expression in the result set, and it is
3088: ** either min(x) or max(x), where x is a column reference.
3089: */
3090: static u8 minMaxQuery(Select *p){
3091: Expr *pExpr;
3092: ExprList *pEList = p->pEList;
3093:
3094: if( pEList->nExpr!=1 ) return WHERE_ORDERBY_NORMAL;
3095: pExpr = pEList->a[0].pExpr;
3096: if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
3097: if( NEVER(ExprHasProperty(pExpr, EP_xIsSelect)) ) return 0;
3098: pEList = pExpr->x.pList;
3099: if( pEList==0 || pEList->nExpr!=1 ) return 0;
3100: if( pEList->a[0].pExpr->op!=TK_AGG_COLUMN ) return WHERE_ORDERBY_NORMAL;
3101: assert( !ExprHasProperty(pExpr, EP_IntValue) );
3102: if( sqlite3StrICmp(pExpr->u.zToken,"min")==0 ){
3103: return WHERE_ORDERBY_MIN;
3104: }else if( sqlite3StrICmp(pExpr->u.zToken,"max")==0 ){
3105: return WHERE_ORDERBY_MAX;
3106: }
3107: return WHERE_ORDERBY_NORMAL;
3108: }
3109:
3110: /*
3111: ** The select statement passed as the first argument is an aggregate query.
3112: ** The second argment is the associated aggregate-info object. This
3113: ** function tests if the SELECT is of the form:
3114: **
3115: ** SELECT count(*) FROM <tbl>
3116: **
3117: ** where table is a database table, not a sub-select or view. If the query
3118: ** does match this pattern, then a pointer to the Table object representing
3119: ** <tbl> is returned. Otherwise, 0 is returned.
3120: */
3121: static Table *isSimpleCount(Select *p, AggInfo *pAggInfo){
3122: Table *pTab;
3123: Expr *pExpr;
3124:
3125: assert( !p->pGroupBy );
3126:
3127: if( p->pWhere || p->pEList->nExpr!=1
3128: || p->pSrc->nSrc!=1 || p->pSrc->a[0].pSelect
3129: ){
3130: return 0;
3131: }
3132: pTab = p->pSrc->a[0].pTab;
3133: pExpr = p->pEList->a[0].pExpr;
3134: assert( pTab && !pTab->pSelect && pExpr );
3135:
3136: if( IsVirtual(pTab) ) return 0;
3137: if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
3138: if( (pAggInfo->aFunc[0].pFunc->flags&SQLITE_FUNC_COUNT)==0 ) return 0;
3139: if( pExpr->flags&EP_Distinct ) return 0;
3140:
3141: return pTab;
3142: }
3143:
3144: /*
3145: ** If the source-list item passed as an argument was augmented with an
3146: ** INDEXED BY clause, then try to locate the specified index. If there
3147: ** was such a clause and the named index cannot be found, return
3148: ** SQLITE_ERROR and leave an error in pParse. Otherwise, populate
3149: ** pFrom->pIndex and return SQLITE_OK.
3150: */
3151: int sqlite3IndexedByLookup(Parse *pParse, struct SrcList_item *pFrom){
3152: if( pFrom->pTab && pFrom->zIndex ){
3153: Table *pTab = pFrom->pTab;
3154: char *zIndex = pFrom->zIndex;
3155: Index *pIdx;
3156: for(pIdx=pTab->pIndex;
3157: pIdx && sqlite3StrICmp(pIdx->zName, zIndex);
3158: pIdx=pIdx->pNext
3159: );
3160: if( !pIdx ){
3161: sqlite3ErrorMsg(pParse, "no such index: %s", zIndex, 0);
3162: pParse->checkSchema = 1;
3163: return SQLITE_ERROR;
3164: }
3165: pFrom->pIndex = pIdx;
3166: }
3167: return SQLITE_OK;
3168: }
3169:
3170: /*
3171: ** This routine is a Walker callback for "expanding" a SELECT statement.
3172: ** "Expanding" means to do the following:
3173: **
3174: ** (1) Make sure VDBE cursor numbers have been assigned to every
3175: ** element of the FROM clause.
3176: **
3177: ** (2) Fill in the pTabList->a[].pTab fields in the SrcList that
3178: ** defines FROM clause. When views appear in the FROM clause,
3179: ** fill pTabList->a[].pSelect with a copy of the SELECT statement
3180: ** that implements the view. A copy is made of the view's SELECT
3181: ** statement so that we can freely modify or delete that statement
3182: ** without worrying about messing up the presistent representation
3183: ** of the view.
3184: **
3185: ** (3) Add terms to the WHERE clause to accomodate the NATURAL keyword
3186: ** on joins and the ON and USING clause of joins.
3187: **
3188: ** (4) Scan the list of columns in the result set (pEList) looking
3189: ** for instances of the "*" operator or the TABLE.* operator.
3190: ** If found, expand each "*" to be every column in every table
3191: ** and TABLE.* to be every column in TABLE.
3192: **
3193: */
3194: static int selectExpander(Walker *pWalker, Select *p){
3195: Parse *pParse = pWalker->pParse;
3196: int i, j, k;
3197: SrcList *pTabList;
3198: ExprList *pEList;
3199: struct SrcList_item *pFrom;
3200: sqlite3 *db = pParse->db;
3201:
3202: if( db->mallocFailed ){
3203: return WRC_Abort;
3204: }
3205: if( NEVER(p->pSrc==0) || (p->selFlags & SF_Expanded)!=0 ){
3206: return WRC_Prune;
3207: }
3208: p->selFlags |= SF_Expanded;
3209: pTabList = p->pSrc;
3210: pEList = p->pEList;
3211:
3212: /* Make sure cursor numbers have been assigned to all entries in
3213: ** the FROM clause of the SELECT statement.
3214: */
3215: sqlite3SrcListAssignCursors(pParse, pTabList);
3216:
3217: /* Look up every table named in the FROM clause of the select. If
3218: ** an entry of the FROM clause is a subquery instead of a table or view,
3219: ** then create a transient table structure to describe the subquery.
3220: */
3221: for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
3222: Table *pTab;
3223: if( pFrom->pTab!=0 ){
3224: /* This statement has already been prepared. There is no need
3225: ** to go further. */
3226: assert( i==0 );
3227: return WRC_Prune;
3228: }
3229: if( pFrom->zName==0 ){
3230: #ifndef SQLITE_OMIT_SUBQUERY
3231: Select *pSel = pFrom->pSelect;
3232: /* A sub-query in the FROM clause of a SELECT */
3233: assert( pSel!=0 );
3234: assert( pFrom->pTab==0 );
3235: sqlite3WalkSelect(pWalker, pSel);
3236: pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
3237: if( pTab==0 ) return WRC_Abort;
3238: pTab->nRef = 1;
3239: pTab->zName = sqlite3MPrintf(db, "sqlite_subquery_%p_", (void*)pTab);
3240: while( pSel->pPrior ){ pSel = pSel->pPrior; }
3241: selectColumnsFromExprList(pParse, pSel->pEList, &pTab->nCol, &pTab->aCol);
3242: pTab->iPKey = -1;
3243: pTab->nRowEst = 1000000;
3244: pTab->tabFlags |= TF_Ephemeral;
3245: #endif
3246: }else{
3247: /* An ordinary table or view name in the FROM clause */
3248: assert( pFrom->pTab==0 );
3249: pFrom->pTab = pTab =
3250: sqlite3LocateTable(pParse,0,pFrom->zName,pFrom->zDatabase);
3251: if( pTab==0 ) return WRC_Abort;
3252: pTab->nRef++;
3253: #if !defined(SQLITE_OMIT_VIEW) || !defined (SQLITE_OMIT_VIRTUALTABLE)
3254: if( pTab->pSelect || IsVirtual(pTab) ){
3255: /* We reach here if the named table is a really a view */
3256: if( sqlite3ViewGetColumnNames(pParse, pTab) ) return WRC_Abort;
3257: assert( pFrom->pSelect==0 );
3258: pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect, 0);
3259: sqlite3WalkSelect(pWalker, pFrom->pSelect);
3260: }
3261: #endif
3262: }
3263:
3264: /* Locate the index named by the INDEXED BY clause, if any. */
3265: if( sqlite3IndexedByLookup(pParse, pFrom) ){
3266: return WRC_Abort;
3267: }
3268: }
3269:
3270: /* Process NATURAL keywords, and ON and USING clauses of joins.
3271: */
3272: if( db->mallocFailed || sqliteProcessJoin(pParse, p) ){
3273: return WRC_Abort;
3274: }
3275:
3276: /* For every "*" that occurs in the column list, insert the names of
3277: ** all columns in all tables. And for every TABLE.* insert the names
3278: ** of all columns in TABLE. The parser inserted a special expression
3279: ** with the TK_ALL operator for each "*" that it found in the column list.
3280: ** The following code just has to locate the TK_ALL expressions and expand
3281: ** each one to the list of all columns in all tables.
3282: **
3283: ** The first loop just checks to see if there are any "*" operators
3284: ** that need expanding.
3285: */
3286: for(k=0; k<pEList->nExpr; k++){
3287: Expr *pE = pEList->a[k].pExpr;
3288: if( pE->op==TK_ALL ) break;
3289: assert( pE->op!=TK_DOT || pE->pRight!=0 );
3290: assert( pE->op!=TK_DOT || (pE->pLeft!=0 && pE->pLeft->op==TK_ID) );
3291: if( pE->op==TK_DOT && pE->pRight->op==TK_ALL ) break;
3292: }
3293: if( k<pEList->nExpr ){
3294: /*
3295: ** If we get here it means the result set contains one or more "*"
3296: ** operators that need to be expanded. Loop through each expression
3297: ** in the result set and expand them one by one.
3298: */
3299: struct ExprList_item *a = pEList->a;
3300: ExprList *pNew = 0;
3301: int flags = pParse->db->flags;
3302: int longNames = (flags & SQLITE_FullColNames)!=0
3303: && (flags & SQLITE_ShortColNames)==0;
3304:
3305: for(k=0; k<pEList->nExpr; k++){
3306: Expr *pE = a[k].pExpr;
3307: assert( pE->op!=TK_DOT || pE->pRight!=0 );
3308: if( pE->op!=TK_ALL && (pE->op!=TK_DOT || pE->pRight->op!=TK_ALL) ){
3309: /* This particular expression does not need to be expanded.
3310: */
3311: pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr);
3312: if( pNew ){
3313: pNew->a[pNew->nExpr-1].zName = a[k].zName;
3314: pNew->a[pNew->nExpr-1].zSpan = a[k].zSpan;
3315: a[k].zName = 0;
3316: a[k].zSpan = 0;
3317: }
3318: a[k].pExpr = 0;
3319: }else{
3320: /* This expression is a "*" or a "TABLE.*" and needs to be
3321: ** expanded. */
3322: int tableSeen = 0; /* Set to 1 when TABLE matches */
3323: char *zTName; /* text of name of TABLE */
3324: if( pE->op==TK_DOT ){
3325: assert( pE->pLeft!=0 );
3326: assert( !ExprHasProperty(pE->pLeft, EP_IntValue) );
3327: zTName = pE->pLeft->u.zToken;
3328: }else{
3329: zTName = 0;
3330: }
3331: for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
3332: Table *pTab = pFrom->pTab;
3333: char *zTabName = pFrom->zAlias;
3334: if( zTabName==0 ){
3335: zTabName = pTab->zName;
3336: }
3337: if( db->mallocFailed ) break;
3338: if( zTName && sqlite3StrICmp(zTName, zTabName)!=0 ){
3339: continue;
3340: }
3341: tableSeen = 1;
3342: for(j=0; j<pTab->nCol; j++){
3343: Expr *pExpr, *pRight;
3344: char *zName = pTab->aCol[j].zName;
3345: char *zColname; /* The computed column name */
3346: char *zToFree; /* Malloced string that needs to be freed */
3347: Token sColname; /* Computed column name as a token */
3348:
3349: /* If a column is marked as 'hidden' (currently only possible
3350: ** for virtual tables), do not include it in the expanded
3351: ** result-set list.
3352: */
3353: if( IsHiddenColumn(&pTab->aCol[j]) ){
3354: assert(IsVirtual(pTab));
3355: continue;
3356: }
3357:
3358: if( i>0 && zTName==0 ){
3359: if( (pFrom->jointype & JT_NATURAL)!=0
3360: && tableAndColumnIndex(pTabList, i, zName, 0, 0)
3361: ){
3362: /* In a NATURAL join, omit the join columns from the
3363: ** table to the right of the join */
3364: continue;
3365: }
3366: if( sqlite3IdListIndex(pFrom->pUsing, zName)>=0 ){
3367: /* In a join with a USING clause, omit columns in the
3368: ** using clause from the table on the right. */
3369: continue;
3370: }
3371: }
3372: pRight = sqlite3Expr(db, TK_ID, zName);
3373: zColname = zName;
3374: zToFree = 0;
3375: if( longNames || pTabList->nSrc>1 ){
3376: Expr *pLeft;
3377: pLeft = sqlite3Expr(db, TK_ID, zTabName);
3378: pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight, 0);
3379: if( longNames ){
3380: zColname = sqlite3MPrintf(db, "%s.%s", zTabName, zName);
3381: zToFree = zColname;
3382: }
3383: }else{
3384: pExpr = pRight;
3385: }
3386: pNew = sqlite3ExprListAppend(pParse, pNew, pExpr);
3387: sColname.z = zColname;
3388: sColname.n = sqlite3Strlen30(zColname);
3389: sqlite3ExprListSetName(pParse, pNew, &sColname, 0);
3390: sqlite3DbFree(db, zToFree);
3391: }
3392: }
3393: if( !tableSeen ){
3394: if( zTName ){
3395: sqlite3ErrorMsg(pParse, "no such table: %s", zTName);
3396: }else{
3397: sqlite3ErrorMsg(pParse, "no tables specified");
3398: }
3399: }
3400: }
3401: }
3402: sqlite3ExprListDelete(db, pEList);
3403: p->pEList = pNew;
3404: }
3405: #if SQLITE_MAX_COLUMN
3406: if( p->pEList && p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
3407: sqlite3ErrorMsg(pParse, "too many columns in result set");
3408: }
3409: #endif
3410: return WRC_Continue;
3411: }
3412:
3413: /*
3414: ** No-op routine for the parse-tree walker.
3415: **
3416: ** When this routine is the Walker.xExprCallback then expression trees
3417: ** are walked without any actions being taken at each node. Presumably,
3418: ** when this routine is used for Walker.xExprCallback then
3419: ** Walker.xSelectCallback is set to do something useful for every
3420: ** subquery in the parser tree.
3421: */
3422: static int exprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
3423: UNUSED_PARAMETER2(NotUsed, NotUsed2);
3424: return WRC_Continue;
3425: }
3426:
3427: /*
3428: ** This routine "expands" a SELECT statement and all of its subqueries.
3429: ** For additional information on what it means to "expand" a SELECT
3430: ** statement, see the comment on the selectExpand worker callback above.
3431: **
3432: ** Expanding a SELECT statement is the first step in processing a
3433: ** SELECT statement. The SELECT statement must be expanded before
3434: ** name resolution is performed.
3435: **
3436: ** If anything goes wrong, an error message is written into pParse.
3437: ** The calling function can detect the problem by looking at pParse->nErr
3438: ** and/or pParse->db->mallocFailed.
3439: */
3440: static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
3441: Walker w;
3442: w.xSelectCallback = selectExpander;
3443: w.xExprCallback = exprWalkNoop;
3444: w.pParse = pParse;
3445: sqlite3WalkSelect(&w, pSelect);
3446: }
3447:
3448:
3449: #ifndef SQLITE_OMIT_SUBQUERY
3450: /*
3451: ** This is a Walker.xSelectCallback callback for the sqlite3SelectTypeInfo()
3452: ** interface.
3453: **
3454: ** For each FROM-clause subquery, add Column.zType and Column.zColl
3455: ** information to the Table structure that represents the result set
3456: ** of that subquery.
3457: **
3458: ** The Table structure that represents the result set was constructed
3459: ** by selectExpander() but the type and collation information was omitted
3460: ** at that point because identifiers had not yet been resolved. This
3461: ** routine is called after identifier resolution.
3462: */
3463: static int selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
3464: Parse *pParse;
3465: int i;
3466: SrcList *pTabList;
3467: struct SrcList_item *pFrom;
3468:
3469: assert( p->selFlags & SF_Resolved );
3470: if( (p->selFlags & SF_HasTypeInfo)==0 ){
3471: p->selFlags |= SF_HasTypeInfo;
3472: pParse = pWalker->pParse;
3473: pTabList = p->pSrc;
3474: for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
3475: Table *pTab = pFrom->pTab;
3476: if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
3477: /* A sub-query in the FROM clause of a SELECT */
3478: Select *pSel = pFrom->pSelect;
3479: assert( pSel );
3480: while( pSel->pPrior ) pSel = pSel->pPrior;
3481: selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
3482: }
3483: }
3484: }
3485: return WRC_Continue;
3486: }
3487: #endif
3488:
3489:
3490: /*
3491: ** This routine adds datatype and collating sequence information to
3492: ** the Table structures of all FROM-clause subqueries in a
3493: ** SELECT statement.
3494: **
3495: ** Use this routine after name resolution.
3496: */
3497: static void sqlite3SelectAddTypeInfo(Parse *pParse, Select *pSelect){
3498: #ifndef SQLITE_OMIT_SUBQUERY
3499: Walker w;
3500: w.xSelectCallback = selectAddSubqueryTypeInfo;
3501: w.xExprCallback = exprWalkNoop;
3502: w.pParse = pParse;
3503: sqlite3WalkSelect(&w, pSelect);
3504: #endif
3505: }
3506:
3507:
3508: /*
3509: ** This routine sets of a SELECT statement for processing. The
3510: ** following is accomplished:
3511: **
3512: ** * VDBE Cursor numbers are assigned to all FROM-clause terms.
3513: ** * Ephemeral Table objects are created for all FROM-clause subqueries.
3514: ** * ON and USING clauses are shifted into WHERE statements
3515: ** * Wildcards "*" and "TABLE.*" in result sets are expanded.
3516: ** * Identifiers in expression are matched to tables.
3517: **
3518: ** This routine acts recursively on all subqueries within the SELECT.
3519: */
3520: void sqlite3SelectPrep(
3521: Parse *pParse, /* The parser context */
3522: Select *p, /* The SELECT statement being coded. */
3523: NameContext *pOuterNC /* Name context for container */
3524: ){
3525: sqlite3 *db;
3526: if( NEVER(p==0) ) return;
3527: db = pParse->db;
3528: if( p->selFlags & SF_HasTypeInfo ) return;
3529: sqlite3SelectExpand(pParse, p);
3530: if( pParse->nErr || db->mallocFailed ) return;
3531: sqlite3ResolveSelectNames(pParse, p, pOuterNC);
3532: if( pParse->nErr || db->mallocFailed ) return;
3533: sqlite3SelectAddTypeInfo(pParse, p);
3534: }
3535:
3536: /*
3537: ** Reset the aggregate accumulator.
3538: **
3539: ** The aggregate accumulator is a set of memory cells that hold
3540: ** intermediate results while calculating an aggregate. This
3541: ** routine simply stores NULLs in all of those memory cells.
3542: */
3543: static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
3544: Vdbe *v = pParse->pVdbe;
3545: int i;
3546: struct AggInfo_func *pFunc;
3547: if( pAggInfo->nFunc+pAggInfo->nColumn==0 ){
3548: return;
3549: }
3550: for(i=0; i<pAggInfo->nColumn; i++){
3551: sqlite3VdbeAddOp2(v, OP_Null, 0, pAggInfo->aCol[i].iMem);
3552: }
3553: for(pFunc=pAggInfo->aFunc, i=0; i<pAggInfo->nFunc; i++, pFunc++){
3554: sqlite3VdbeAddOp2(v, OP_Null, 0, pFunc->iMem);
3555: if( pFunc->iDistinct>=0 ){
3556: Expr *pE = pFunc->pExpr;
3557: assert( !ExprHasProperty(pE, EP_xIsSelect) );
3558: if( pE->x.pList==0 || pE->x.pList->nExpr!=1 ){
3559: sqlite3ErrorMsg(pParse, "DISTINCT aggregates must have exactly one "
3560: "argument");
3561: pFunc->iDistinct = -1;
3562: }else{
3563: KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->x.pList);
3564: sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pFunc->iDistinct, 0, 0,
3565: (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
3566: }
3567: }
3568: }
3569: }
3570:
3571: /*
3572: ** Invoke the OP_AggFinalize opcode for every aggregate function
3573: ** in the AggInfo structure.
3574: */
3575: static void finalizeAggFunctions(Parse *pParse, AggInfo *pAggInfo){
3576: Vdbe *v = pParse->pVdbe;
3577: int i;
3578: struct AggInfo_func *pF;
3579: for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
3580: ExprList *pList = pF->pExpr->x.pList;
3581: assert( !ExprHasProperty(pF->pExpr, EP_xIsSelect) );
3582: sqlite3VdbeAddOp4(v, OP_AggFinal, pF->iMem, pList ? pList->nExpr : 0, 0,
3583: (void*)pF->pFunc, P4_FUNCDEF);
3584: }
3585: }
3586:
3587: /*
3588: ** Update the accumulator memory cells for an aggregate based on
3589: ** the current cursor position.
3590: */
3591: static void updateAccumulator(Parse *pParse, AggInfo *pAggInfo){
3592: Vdbe *v = pParse->pVdbe;
3593: int i;
3594: struct AggInfo_func *pF;
3595: struct AggInfo_col *pC;
3596:
3597: pAggInfo->directMode = 1;
3598: sqlite3ExprCacheClear(pParse);
3599: for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
3600: int nArg;
3601: int addrNext = 0;
3602: int regAgg;
3603: ExprList *pList = pF->pExpr->x.pList;
3604: assert( !ExprHasProperty(pF->pExpr, EP_xIsSelect) );
3605: if( pList ){
3606: nArg = pList->nExpr;
3607: regAgg = sqlite3GetTempRange(pParse, nArg);
3608: sqlite3ExprCodeExprList(pParse, pList, regAgg, 1);
3609: }else{
3610: nArg = 0;
3611: regAgg = 0;
3612: }
3613: if( pF->iDistinct>=0 ){
3614: addrNext = sqlite3VdbeMakeLabel(v);
3615: assert( nArg==1 );
3616: codeDistinct(pParse, pF->iDistinct, addrNext, 1, regAgg);
3617: }
3618: if( pF->pFunc->flags & SQLITE_FUNC_NEEDCOLL ){
3619: CollSeq *pColl = 0;
3620: struct ExprList_item *pItem;
3621: int j;
3622: assert( pList!=0 ); /* pList!=0 if pF->pFunc has NEEDCOLL */
3623: for(j=0, pItem=pList->a; !pColl && j<nArg; j++, pItem++){
3624: pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
3625: }
3626: if( !pColl ){
3627: pColl = pParse->db->pDfltColl;
3628: }
3629: sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
3630: }
3631: sqlite3VdbeAddOp4(v, OP_AggStep, 0, regAgg, pF->iMem,
3632: (void*)pF->pFunc, P4_FUNCDEF);
3633: sqlite3VdbeChangeP5(v, (u8)nArg);
3634: sqlite3ExprCacheAffinityChange(pParse, regAgg, nArg);
3635: sqlite3ReleaseTempRange(pParse, regAgg, nArg);
3636: if( addrNext ){
3637: sqlite3VdbeResolveLabel(v, addrNext);
3638: sqlite3ExprCacheClear(pParse);
3639: }
3640: }
3641:
3642: /* Before populating the accumulator registers, clear the column cache.
3643: ** Otherwise, if any of the required column values are already present
3644: ** in registers, sqlite3ExprCode() may use OP_SCopy to copy the value
3645: ** to pC->iMem. But by the time the value is used, the original register
3646: ** may have been used, invalidating the underlying buffer holding the
3647: ** text or blob value. See ticket [883034dcb5].
3648: **
3649: ** Another solution would be to change the OP_SCopy used to copy cached
3650: ** values to an OP_Copy.
3651: */
3652: sqlite3ExprCacheClear(pParse);
3653: for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
3654: sqlite3ExprCode(pParse, pC->pExpr, pC->iMem);
3655: }
3656: pAggInfo->directMode = 0;
3657: sqlite3ExprCacheClear(pParse);
3658: }
3659:
3660: /*
3661: ** Add a single OP_Explain instruction to the VDBE to explain a simple
3662: ** count(*) query ("SELECT count(*) FROM pTab").
3663: */
3664: #ifndef SQLITE_OMIT_EXPLAIN
3665: static void explainSimpleCount(
3666: Parse *pParse, /* Parse context */
3667: Table *pTab, /* Table being queried */
3668: Index *pIdx /* Index used to optimize scan, or NULL */
3669: ){
3670: if( pParse->explain==2 ){
3671: char *zEqp = sqlite3MPrintf(pParse->db, "SCAN TABLE %s %s%s(~%d rows)",
3672: pTab->zName,
3673: pIdx ? "USING COVERING INDEX " : "",
3674: pIdx ? pIdx->zName : "",
3675: pTab->nRowEst
3676: );
3677: sqlite3VdbeAddOp4(
3678: pParse->pVdbe, OP_Explain, pParse->iSelectId, 0, 0, zEqp, P4_DYNAMIC
3679: );
3680: }
3681: }
3682: #else
3683: # define explainSimpleCount(a,b,c)
3684: #endif
3685:
3686: /*
3687: ** Generate code for the SELECT statement given in the p argument.
3688: **
3689: ** The results are distributed in various ways depending on the
3690: ** contents of the SelectDest structure pointed to by argument pDest
3691: ** as follows:
3692: **
3693: ** pDest->eDest Result
3694: ** ------------ -------------------------------------------
3695: ** SRT_Output Generate a row of output (using the OP_ResultRow
3696: ** opcode) for each row in the result set.
3697: **
3698: ** SRT_Mem Only valid if the result is a single column.
3699: ** Store the first column of the first result row
3700: ** in register pDest->iParm then abandon the rest
3701: ** of the query. This destination implies "LIMIT 1".
3702: **
3703: ** SRT_Set The result must be a single column. Store each
3704: ** row of result as the key in table pDest->iParm.
3705: ** Apply the affinity pDest->affinity before storing
3706: ** results. Used to implement "IN (SELECT ...)".
3707: **
3708: ** SRT_Union Store results as a key in a temporary table pDest->iParm.
3709: **
3710: ** SRT_Except Remove results from the temporary table pDest->iParm.
3711: **
3712: ** SRT_Table Store results in temporary table pDest->iParm.
3713: ** This is like SRT_EphemTab except that the table
3714: ** is assumed to already be open.
3715: **
3716: ** SRT_EphemTab Create an temporary table pDest->iParm and store
3717: ** the result there. The cursor is left open after
3718: ** returning. This is like SRT_Table except that
3719: ** this destination uses OP_OpenEphemeral to create
3720: ** the table first.
3721: **
3722: ** SRT_Coroutine Generate a co-routine that returns a new row of
3723: ** results each time it is invoked. The entry point
3724: ** of the co-routine is stored in register pDest->iParm.
3725: **
3726: ** SRT_Exists Store a 1 in memory cell pDest->iParm if the result
3727: ** set is not empty.
3728: **
3729: ** SRT_Discard Throw the results away. This is used by SELECT
3730: ** statements within triggers whose only purpose is
3731: ** the side-effects of functions.
3732: **
3733: ** This routine returns the number of errors. If any errors are
3734: ** encountered, then an appropriate error message is left in
3735: ** pParse->zErrMsg.
3736: **
3737: ** This routine does NOT free the Select structure passed in. The
3738: ** calling function needs to do that.
3739: */
3740: int sqlite3Select(
3741: Parse *pParse, /* The parser context */
3742: Select *p, /* The SELECT statement being coded. */
3743: SelectDest *pDest /* What to do with the query results */
3744: ){
3745: int i, j; /* Loop counters */
3746: WhereInfo *pWInfo; /* Return from sqlite3WhereBegin() */
3747: Vdbe *v; /* The virtual machine under construction */
3748: int isAgg; /* True for select lists like "count(*)" */
3749: ExprList *pEList; /* List of columns to extract. */
3750: SrcList *pTabList; /* List of tables to select from */
3751: Expr *pWhere; /* The WHERE clause. May be NULL */
3752: ExprList *pOrderBy; /* The ORDER BY clause. May be NULL */
3753: ExprList *pGroupBy; /* The GROUP BY clause. May be NULL */
3754: Expr *pHaving; /* The HAVING clause. May be NULL */
3755: int isDistinct; /* True if the DISTINCT keyword is present */
3756: int distinct; /* Table to use for the distinct set */
3757: int rc = 1; /* Value to return from this function */
3758: int addrSortIndex; /* Address of an OP_OpenEphemeral instruction */
3759: int addrDistinctIndex; /* Address of an OP_OpenEphemeral instruction */
3760: AggInfo sAggInfo; /* Information used by aggregate queries */
3761: int iEnd; /* Address of the end of the query */
3762: sqlite3 *db; /* The database connection */
3763:
3764: #ifndef SQLITE_OMIT_EXPLAIN
3765: int iRestoreSelectId = pParse->iSelectId;
3766: pParse->iSelectId = pParse->iNextSelectId++;
3767: #endif
3768:
3769: db = pParse->db;
3770: if( p==0 || db->mallocFailed || pParse->nErr ){
3771: return 1;
3772: }
3773: if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
3774: memset(&sAggInfo, 0, sizeof(sAggInfo));
3775:
3776: if( IgnorableOrderby(pDest) ){
3777: assert(pDest->eDest==SRT_Exists || pDest->eDest==SRT_Union ||
3778: pDest->eDest==SRT_Except || pDest->eDest==SRT_Discard);
3779: /* If ORDER BY makes no difference in the output then neither does
3780: ** DISTINCT so it can be removed too. */
3781: sqlite3ExprListDelete(db, p->pOrderBy);
3782: p->pOrderBy = 0;
3783: p->selFlags &= ~SF_Distinct;
3784: }
3785: sqlite3SelectPrep(pParse, p, 0);
3786: pOrderBy = p->pOrderBy;
3787: pTabList = p->pSrc;
3788: pEList = p->pEList;
3789: if( pParse->nErr || db->mallocFailed ){
3790: goto select_end;
3791: }
3792: isAgg = (p->selFlags & SF_Aggregate)!=0;
3793: assert( pEList!=0 );
3794:
3795: /* Begin generating code.
3796: */
3797: v = sqlite3GetVdbe(pParse);
3798: if( v==0 ) goto select_end;
3799:
3800: /* If writing to memory or generating a set
3801: ** only a single column may be output.
3802: */
3803: #ifndef SQLITE_OMIT_SUBQUERY
3804: if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
3805: goto select_end;
3806: }
3807: #endif
3808:
3809: /* Generate code for all sub-queries in the FROM clause
3810: */
3811: #if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
3812: for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
3813: struct SrcList_item *pItem = &pTabList->a[i];
3814: SelectDest dest;
3815: Select *pSub = pItem->pSelect;
3816: int isAggSub;
3817:
3818: if( pSub==0 ) continue;
3819: if( pItem->addrFillSub ){
3820: sqlite3VdbeAddOp2(v, OP_Gosub, pItem->regReturn, pItem->addrFillSub);
3821: continue;
3822: }
3823:
3824: /* Increment Parse.nHeight by the height of the largest expression
3825: ** tree refered to by this, the parent select. The child select
3826: ** may contain expression trees of at most
3827: ** (SQLITE_MAX_EXPR_DEPTH-Parse.nHeight) height. This is a bit
3828: ** more conservative than necessary, but much easier than enforcing
3829: ** an exact limit.
3830: */
3831: pParse->nHeight += sqlite3SelectExprHeight(p);
3832:
3833: isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
3834: if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
3835: /* This subquery can be absorbed into its parent. */
3836: if( isAggSub ){
3837: isAgg = 1;
3838: p->selFlags |= SF_Aggregate;
3839: }
3840: i = -1;
3841: }else{
3842: /* Generate a subroutine that will fill an ephemeral table with
3843: ** the content of this subquery. pItem->addrFillSub will point
3844: ** to the address of the generated subroutine. pItem->regReturn
3845: ** is a register allocated to hold the subroutine return address
3846: */
3847: int topAddr;
3848: int onceAddr = 0;
3849: int retAddr;
3850: assert( pItem->addrFillSub==0 );
3851: pItem->regReturn = ++pParse->nMem;
3852: topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
3853: pItem->addrFillSub = topAddr+1;
3854: VdbeNoopComment((v, "materialize %s", pItem->pTab->zName));
3855: if( pItem->isCorrelated==0 ){
3856: /* If the subquery is no correlated and if we are not inside of
3857: ** a trigger, then we only need to compute the value of the subquery
3858: ** once. */
3859: onceAddr = sqlite3CodeOnce(pParse);
3860: }
3861: sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
3862: explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
3863: sqlite3Select(pParse, pSub, &dest);
3864: pItem->pTab->nRowEst = (unsigned)pSub->nSelectRow;
3865: if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
3866: retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);
3867: VdbeComment((v, "end %s", pItem->pTab->zName));
3868: sqlite3VdbeChangeP1(v, topAddr, retAddr);
3869: sqlite3ClearTempRegCache(pParse);
3870: }
3871: if( /*pParse->nErr ||*/ db->mallocFailed ){
3872: goto select_end;
3873: }
3874: pParse->nHeight -= sqlite3SelectExprHeight(p);
3875: pTabList = p->pSrc;
3876: if( !IgnorableOrderby(pDest) ){
3877: pOrderBy = p->pOrderBy;
3878: }
3879: }
3880: pEList = p->pEList;
3881: #endif
3882: pWhere = p->pWhere;
3883: pGroupBy = p->pGroupBy;
3884: pHaving = p->pHaving;
3885: isDistinct = (p->selFlags & SF_Distinct)!=0;
3886:
3887: #ifndef SQLITE_OMIT_COMPOUND_SELECT
3888: /* If there is are a sequence of queries, do the earlier ones first.
3889: */
3890: if( p->pPrior ){
3891: if( p->pRightmost==0 ){
3892: Select *pLoop, *pRight = 0;
3893: int cnt = 0;
3894: int mxSelect;
3895: for(pLoop=p; pLoop; pLoop=pLoop->pPrior, cnt++){
3896: pLoop->pRightmost = p;
3897: pLoop->pNext = pRight;
3898: pRight = pLoop;
3899: }
3900: mxSelect = db->aLimit[SQLITE_LIMIT_COMPOUND_SELECT];
3901: if( mxSelect && cnt>mxSelect ){
3902: sqlite3ErrorMsg(pParse, "too many terms in compound SELECT");
3903: goto select_end;
3904: }
3905: }
3906: rc = multiSelect(pParse, p, pDest);
3907: explainSetInteger(pParse->iSelectId, iRestoreSelectId);
3908: return rc;
3909: }
3910: #endif
3911:
3912: /* If there is both a GROUP BY and an ORDER BY clause and they are
3913: ** identical, then disable the ORDER BY clause since the GROUP BY
3914: ** will cause elements to come out in the correct order. This is
3915: ** an optimization - the correct answer should result regardless.
3916: ** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER
3917: ** to disable this optimization for testing purposes.
3918: */
3919: if( sqlite3ExprListCompare(p->pGroupBy, pOrderBy)==0
3920: && (db->flags & SQLITE_GroupByOrder)==0 ){
3921: pOrderBy = 0;
3922: }
3923:
3924: /* If the query is DISTINCT with an ORDER BY but is not an aggregate, and
3925: ** if the select-list is the same as the ORDER BY list, then this query
3926: ** can be rewritten as a GROUP BY. In other words, this:
3927: **
3928: ** SELECT DISTINCT xyz FROM ... ORDER BY xyz
3929: **
3930: ** is transformed to:
3931: **
3932: ** SELECT xyz FROM ... GROUP BY xyz
3933: **
3934: ** The second form is preferred as a single index (or temp-table) may be
3935: ** used for both the ORDER BY and DISTINCT processing. As originally
3936: ** written the query must use a temp-table for at least one of the ORDER
3937: ** BY and DISTINCT, and an index or separate temp-table for the other.
3938: */
3939: if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct
3940: && sqlite3ExprListCompare(pOrderBy, p->pEList)==0
3941: ){
3942: p->selFlags &= ~SF_Distinct;
3943: p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
3944: pGroupBy = p->pGroupBy;
3945: pOrderBy = 0;
3946: }
3947:
3948: /* If there is an ORDER BY clause, then this sorting
3949: ** index might end up being unused if the data can be
3950: ** extracted in pre-sorted order. If that is the case, then the
3951: ** OP_OpenEphemeral instruction will be changed to an OP_Noop once
3952: ** we figure out that the sorting index is not needed. The addrSortIndex
3953: ** variable is used to facilitate that change.
3954: */
3955: if( pOrderBy ){
3956: KeyInfo *pKeyInfo;
3957: pKeyInfo = keyInfoFromExprList(pParse, pOrderBy);
3958: pOrderBy->iECursor = pParse->nTab++;
3959: p->addrOpenEphm[2] = addrSortIndex =
3960: sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
3961: pOrderBy->iECursor, pOrderBy->nExpr+2, 0,
3962: (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
3963: }else{
3964: addrSortIndex = -1;
3965: }
3966:
3967: /* If the output is destined for a temporary table, open that table.
3968: */
3969: if( pDest->eDest==SRT_EphemTab ){
3970: sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pDest->iParm, pEList->nExpr);
3971: }
3972:
3973: /* Set the limiter.
3974: */
3975: iEnd = sqlite3VdbeMakeLabel(v);
3976: p->nSelectRow = (double)LARGEST_INT64;
3977: computeLimitRegisters(pParse, p, iEnd);
3978: if( p->iLimit==0 && addrSortIndex>=0 ){
3979: sqlite3VdbeGetOp(v, addrSortIndex)->opcode = OP_SorterOpen;
3980: p->selFlags |= SF_UseSorter;
3981: }
3982:
3983: /* Open a virtual index to use for the distinct set.
3984: */
3985: if( p->selFlags & SF_Distinct ){
3986: KeyInfo *pKeyInfo;
3987: distinct = pParse->nTab++;
3988: pKeyInfo = keyInfoFromExprList(pParse, p->pEList);
3989: addrDistinctIndex = sqlite3VdbeAddOp4(v, OP_OpenEphemeral, distinct, 0, 0,
3990: (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
3991: sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
3992: }else{
3993: distinct = addrDistinctIndex = -1;
3994: }
3995:
3996: /* Aggregate and non-aggregate queries are handled differently */
3997: if( !isAgg && pGroupBy==0 ){
3998: ExprList *pDist = (isDistinct ? p->pEList : 0);
3999:
4000: /* Begin the database scan. */
4001: pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, pDist, 0);
4002: if( pWInfo==0 ) goto select_end;
4003: if( pWInfo->nRowOut < p->nSelectRow ) p->nSelectRow = pWInfo->nRowOut;
4004:
4005: /* If sorting index that was created by a prior OP_OpenEphemeral
4006: ** instruction ended up not being needed, then change the OP_OpenEphemeral
4007: ** into an OP_Noop.
4008: */
4009: if( addrSortIndex>=0 && pOrderBy==0 ){
4010: sqlite3VdbeChangeToNoop(v, addrSortIndex);
4011: p->addrOpenEphm[2] = -1;
4012: }
4013:
4014: if( pWInfo->eDistinct ){
4015: VdbeOp *pOp; /* No longer required OpenEphemeral instr. */
4016:
4017: assert( addrDistinctIndex>=0 );
4018: pOp = sqlite3VdbeGetOp(v, addrDistinctIndex);
4019:
4020: assert( isDistinct );
4021: assert( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED
4022: || pWInfo->eDistinct==WHERE_DISTINCT_UNIQUE
4023: );
4024: distinct = -1;
4025: if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED ){
4026: int iJump;
4027: int iExpr;
4028: int iFlag = ++pParse->nMem;
4029: int iBase = pParse->nMem+1;
4030: int iBase2 = iBase + pEList->nExpr;
4031: pParse->nMem += (pEList->nExpr*2);
4032:
4033: /* Change the OP_OpenEphemeral coded earlier to an OP_Integer. The
4034: ** OP_Integer initializes the "first row" flag. */
4035: pOp->opcode = OP_Integer;
4036: pOp->p1 = 1;
4037: pOp->p2 = iFlag;
4038:
4039: sqlite3ExprCodeExprList(pParse, pEList, iBase, 1);
4040: iJump = sqlite3VdbeCurrentAddr(v) + 1 + pEList->nExpr + 1 + 1;
4041: sqlite3VdbeAddOp2(v, OP_If, iFlag, iJump-1);
4042: for(iExpr=0; iExpr<pEList->nExpr; iExpr++){
4043: CollSeq *pColl = sqlite3ExprCollSeq(pParse, pEList->a[iExpr].pExpr);
4044: sqlite3VdbeAddOp3(v, OP_Ne, iBase+iExpr, iJump, iBase2+iExpr);
4045: sqlite3VdbeChangeP4(v, -1, (const char *)pColl, P4_COLLSEQ);
4046: sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
4047: }
4048: sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iContinue);
4049:
4050: sqlite3VdbeAddOp2(v, OP_Integer, 0, iFlag);
4051: assert( sqlite3VdbeCurrentAddr(v)==iJump );
4052: sqlite3VdbeAddOp3(v, OP_Move, iBase, iBase2, pEList->nExpr);
4053: }else{
4054: pOp->opcode = OP_Noop;
4055: }
4056: }
4057:
4058: /* Use the standard inner loop. */
4059: selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, distinct, pDest,
4060: pWInfo->iContinue, pWInfo->iBreak);
4061:
4062: /* End the database scan loop.
4063: */
4064: sqlite3WhereEnd(pWInfo);
4065: }else{
4066: /* This is the processing for aggregate queries */
4067: NameContext sNC; /* Name context for processing aggregate information */
4068: int iAMem; /* First Mem address for storing current GROUP BY */
4069: int iBMem; /* First Mem address for previous GROUP BY */
4070: int iUseFlag; /* Mem address holding flag indicating that at least
4071: ** one row of the input to the aggregator has been
4072: ** processed */
4073: int iAbortFlag; /* Mem address which causes query abort if positive */
4074: int groupBySort; /* Rows come from source in GROUP BY order */
4075: int addrEnd; /* End of processing for this SELECT */
4076: int sortPTab = 0; /* Pseudotable used to decode sorting results */
4077: int sortOut = 0; /* Output register from the sorter */
4078:
4079: /* Remove any and all aliases between the result set and the
4080: ** GROUP BY clause.
4081: */
4082: if( pGroupBy ){
4083: int k; /* Loop counter */
4084: struct ExprList_item *pItem; /* For looping over expression in a list */
4085:
4086: for(k=p->pEList->nExpr, pItem=p->pEList->a; k>0; k--, pItem++){
4087: pItem->iAlias = 0;
4088: }
4089: for(k=pGroupBy->nExpr, pItem=pGroupBy->a; k>0; k--, pItem++){
4090: pItem->iAlias = 0;
4091: }
4092: if( p->nSelectRow>(double)100 ) p->nSelectRow = (double)100;
4093: }else{
4094: p->nSelectRow = (double)1;
4095: }
4096:
4097:
4098: /* Create a label to jump to when we want to abort the query */
4099: addrEnd = sqlite3VdbeMakeLabel(v);
4100:
4101: /* Convert TK_COLUMN nodes into TK_AGG_COLUMN and make entries in
4102: ** sAggInfo for all TK_AGG_FUNCTION nodes in expressions of the
4103: ** SELECT statement.
4104: */
4105: memset(&sNC, 0, sizeof(sNC));
4106: sNC.pParse = pParse;
4107: sNC.pSrcList = pTabList;
4108: sNC.pAggInfo = &sAggInfo;
4109: sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr+1 : 0;
4110: sAggInfo.pGroupBy = pGroupBy;
4111: sqlite3ExprAnalyzeAggList(&sNC, pEList);
4112: sqlite3ExprAnalyzeAggList(&sNC, pOrderBy);
4113: if( pHaving ){
4114: sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
4115: }
4116: sAggInfo.nAccumulator = sAggInfo.nColumn;
4117: for(i=0; i<sAggInfo.nFunc; i++){
4118: assert( !ExprHasProperty(sAggInfo.aFunc[i].pExpr, EP_xIsSelect) );
4119: sqlite3ExprAnalyzeAggList(&sNC, sAggInfo.aFunc[i].pExpr->x.pList);
4120: }
4121: if( db->mallocFailed ) goto select_end;
4122:
4123: /* Processing for aggregates with GROUP BY is very different and
4124: ** much more complex than aggregates without a GROUP BY.
4125: */
4126: if( pGroupBy ){
4127: KeyInfo *pKeyInfo; /* Keying information for the group by clause */
4128: int j1; /* A-vs-B comparision jump */
4129: int addrOutputRow; /* Start of subroutine that outputs a result row */
4130: int regOutputRow; /* Return address register for output subroutine */
4131: int addrSetAbort; /* Set the abort flag and return */
4132: int addrTopOfLoop; /* Top of the input loop */
4133: int addrSortingIdx; /* The OP_OpenEphemeral for the sorting index */
4134: int addrReset; /* Subroutine for resetting the accumulator */
4135: int regReset; /* Return address register for reset subroutine */
4136:
4137: /* If there is a GROUP BY clause we might need a sorting index to
4138: ** implement it. Allocate that sorting index now. If it turns out
4139: ** that we do not need it after all, the OP_SorterOpen instruction
4140: ** will be converted into a Noop.
4141: */
4142: sAggInfo.sortingIdx = pParse->nTab++;
4143: pKeyInfo = keyInfoFromExprList(pParse, pGroupBy);
4144: addrSortingIdx = sqlite3VdbeAddOp4(v, OP_SorterOpen,
4145: sAggInfo.sortingIdx, sAggInfo.nSortingColumn,
4146: 0, (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
4147:
4148: /* Initialize memory locations used by GROUP BY aggregate processing
4149: */
4150: iUseFlag = ++pParse->nMem;
4151: iAbortFlag = ++pParse->nMem;
4152: regOutputRow = ++pParse->nMem;
4153: addrOutputRow = sqlite3VdbeMakeLabel(v);
4154: regReset = ++pParse->nMem;
4155: addrReset = sqlite3VdbeMakeLabel(v);
4156: iAMem = pParse->nMem + 1;
4157: pParse->nMem += pGroupBy->nExpr;
4158: iBMem = pParse->nMem + 1;
4159: pParse->nMem += pGroupBy->nExpr;
4160: sqlite3VdbeAddOp2(v, OP_Integer, 0, iAbortFlag);
4161: VdbeComment((v, "clear abort flag"));
4162: sqlite3VdbeAddOp2(v, OP_Integer, 0, iUseFlag);
4163: VdbeComment((v, "indicate accumulator empty"));
4164: sqlite3VdbeAddOp3(v, OP_Null, 0, iAMem, iAMem+pGroupBy->nExpr-1);
4165:
4166: /* Begin a loop that will extract all source rows in GROUP BY order.
4167: ** This might involve two separate loops with an OP_Sort in between, or
4168: ** it might be a single loop that uses an index to extract information
4169: ** in the right order to begin with.
4170: */
4171: sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
4172: pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0, 0);
4173: if( pWInfo==0 ) goto select_end;
4174: if( pGroupBy==0 ){
4175: /* The optimizer is able to deliver rows in group by order so
4176: ** we do not have to sort. The OP_OpenEphemeral table will be
4177: ** cancelled later because we still need to use the pKeyInfo
4178: */
4179: pGroupBy = p->pGroupBy;
4180: groupBySort = 0;
4181: }else{
4182: /* Rows are coming out in undetermined order. We have to push
4183: ** each row into a sorting index, terminate the first loop,
4184: ** then loop over the sorting index in order to get the output
4185: ** in sorted order
4186: */
4187: int regBase;
4188: int regRecord;
4189: int nCol;
4190: int nGroupBy;
4191:
4192: explainTempTable(pParse,
4193: isDistinct && !(p->selFlags&SF_Distinct)?"DISTINCT":"GROUP BY");
4194:
4195: groupBySort = 1;
4196: nGroupBy = pGroupBy->nExpr;
4197: nCol = nGroupBy + 1;
4198: j = nGroupBy+1;
4199: for(i=0; i<sAggInfo.nColumn; i++){
4200: if( sAggInfo.aCol[i].iSorterColumn>=j ){
4201: nCol++;
4202: j++;
4203: }
4204: }
4205: regBase = sqlite3GetTempRange(pParse, nCol);
4206: sqlite3ExprCacheClear(pParse);
4207: sqlite3ExprCodeExprList(pParse, pGroupBy, regBase, 0);
4208: sqlite3VdbeAddOp2(v, OP_Sequence, sAggInfo.sortingIdx,regBase+nGroupBy);
4209: j = nGroupBy+1;
4210: for(i=0; i<sAggInfo.nColumn; i++){
4211: struct AggInfo_col *pCol = &sAggInfo.aCol[i];
4212: if( pCol->iSorterColumn>=j ){
4213: int r1 = j + regBase;
4214: int r2;
4215:
4216: r2 = sqlite3ExprCodeGetColumn(pParse,
4217: pCol->pTab, pCol->iColumn, pCol->iTable, r1);
4218: if( r1!=r2 ){
4219: sqlite3VdbeAddOp2(v, OP_SCopy, r2, r1);
4220: }
4221: j++;
4222: }
4223: }
4224: regRecord = sqlite3GetTempReg(pParse);
4225: sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
4226: sqlite3VdbeAddOp2(v, OP_SorterInsert, sAggInfo.sortingIdx, regRecord);
4227: sqlite3ReleaseTempReg(pParse, regRecord);
4228: sqlite3ReleaseTempRange(pParse, regBase, nCol);
4229: sqlite3WhereEnd(pWInfo);
4230: sAggInfo.sortingIdxPTab = sortPTab = pParse->nTab++;
4231: sortOut = sqlite3GetTempReg(pParse);
4232: sqlite3VdbeAddOp3(v, OP_OpenPseudo, sortPTab, sortOut, nCol);
4233: sqlite3VdbeAddOp2(v, OP_SorterSort, sAggInfo.sortingIdx, addrEnd);
4234: VdbeComment((v, "GROUP BY sort"));
4235: sAggInfo.useSortingIdx = 1;
4236: sqlite3ExprCacheClear(pParse);
4237: }
4238:
4239: /* Evaluate the current GROUP BY terms and store in b0, b1, b2...
4240: ** (b0 is memory location iBMem+0, b1 is iBMem+1, and so forth)
4241: ** Then compare the current GROUP BY terms against the GROUP BY terms
4242: ** from the previous row currently stored in a0, a1, a2...
4243: */
4244: addrTopOfLoop = sqlite3VdbeCurrentAddr(v);
4245: sqlite3ExprCacheClear(pParse);
4246: if( groupBySort ){
4247: sqlite3VdbeAddOp2(v, OP_SorterData, sAggInfo.sortingIdx, sortOut);
4248: }
4249: for(j=0; j<pGroupBy->nExpr; j++){
4250: if( groupBySort ){
4251: sqlite3VdbeAddOp3(v, OP_Column, sortPTab, j, iBMem+j);
4252: if( j==0 ) sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
4253: }else{
4254: sAggInfo.directMode = 1;
4255: sqlite3ExprCode(pParse, pGroupBy->a[j].pExpr, iBMem+j);
4256: }
4257: }
4258: sqlite3VdbeAddOp4(v, OP_Compare, iAMem, iBMem, pGroupBy->nExpr,
4259: (char*)pKeyInfo, P4_KEYINFO);
4260: j1 = sqlite3VdbeCurrentAddr(v);
4261: sqlite3VdbeAddOp3(v, OP_Jump, j1+1, 0, j1+1);
4262:
4263: /* Generate code that runs whenever the GROUP BY changes.
4264: ** Changes in the GROUP BY are detected by the previous code
4265: ** block. If there were no changes, this block is skipped.
4266: **
4267: ** This code copies current group by terms in b0,b1,b2,...
4268: ** over to a0,a1,a2. It then calls the output subroutine
4269: ** and resets the aggregate accumulator registers in preparation
4270: ** for the next GROUP BY batch.
4271: */
4272: sqlite3ExprCodeMove(pParse, iBMem, iAMem, pGroupBy->nExpr);
4273: sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
4274: VdbeComment((v, "output one row"));
4275: sqlite3VdbeAddOp2(v, OP_IfPos, iAbortFlag, addrEnd);
4276: VdbeComment((v, "check abort flag"));
4277: sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
4278: VdbeComment((v, "reset accumulator"));
4279:
4280: /* Update the aggregate accumulators based on the content of
4281: ** the current row
4282: */
4283: sqlite3VdbeJumpHere(v, j1);
4284: updateAccumulator(pParse, &sAggInfo);
4285: sqlite3VdbeAddOp2(v, OP_Integer, 1, iUseFlag);
4286: VdbeComment((v, "indicate data in accumulator"));
4287:
4288: /* End of the loop
4289: */
4290: if( groupBySort ){
4291: sqlite3VdbeAddOp2(v, OP_SorterNext, sAggInfo.sortingIdx, addrTopOfLoop);
4292: }else{
4293: sqlite3WhereEnd(pWInfo);
4294: sqlite3VdbeChangeToNoop(v, addrSortingIdx);
4295: }
4296:
4297: /* Output the final row of result
4298: */
4299: sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
4300: VdbeComment((v, "output final row"));
4301:
4302: /* Jump over the subroutines
4303: */
4304: sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEnd);
4305:
4306: /* Generate a subroutine that outputs a single row of the result
4307: ** set. This subroutine first looks at the iUseFlag. If iUseFlag
4308: ** is less than or equal to zero, the subroutine is a no-op. If
4309: ** the processing calls for the query to abort, this subroutine
4310: ** increments the iAbortFlag memory location before returning in
4311: ** order to signal the caller to abort.
4312: */
4313: addrSetAbort = sqlite3VdbeCurrentAddr(v);
4314: sqlite3VdbeAddOp2(v, OP_Integer, 1, iAbortFlag);
4315: VdbeComment((v, "set abort flag"));
4316: sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
4317: sqlite3VdbeResolveLabel(v, addrOutputRow);
4318: addrOutputRow = sqlite3VdbeCurrentAddr(v);
4319: sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
4320: VdbeComment((v, "Groupby result generator entry point"));
4321: sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
4322: finalizeAggFunctions(pParse, &sAggInfo);
4323: sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
4324: selectInnerLoop(pParse, p, p->pEList, 0, 0, pOrderBy,
4325: distinct, pDest,
4326: addrOutputRow+1, addrSetAbort);
4327: sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
4328: VdbeComment((v, "end groupby result generator"));
4329:
4330: /* Generate a subroutine that will reset the group-by accumulator
4331: */
4332: sqlite3VdbeResolveLabel(v, addrReset);
4333: resetAccumulator(pParse, &sAggInfo);
4334: sqlite3VdbeAddOp1(v, OP_Return, regReset);
4335:
4336: } /* endif pGroupBy. Begin aggregate queries without GROUP BY: */
4337: else {
4338: ExprList *pDel = 0;
4339: #ifndef SQLITE_OMIT_BTREECOUNT
4340: Table *pTab;
4341: if( (pTab = isSimpleCount(p, &sAggInfo))!=0 ){
4342: /* If isSimpleCount() returns a pointer to a Table structure, then
4343: ** the SQL statement is of the form:
4344: **
4345: ** SELECT count(*) FROM <tbl>
4346: **
4347: ** where the Table structure returned represents table <tbl>.
4348: **
4349: ** This statement is so common that it is optimized specially. The
4350: ** OP_Count instruction is executed either on the intkey table that
4351: ** contains the data for table <tbl> or on one of its indexes. It
4352: ** is better to execute the op on an index, as indexes are almost
4353: ** always spread across less pages than their corresponding tables.
4354: */
4355: const int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
4356: const int iCsr = pParse->nTab++; /* Cursor to scan b-tree */
4357: Index *pIdx; /* Iterator variable */
4358: KeyInfo *pKeyInfo = 0; /* Keyinfo for scanned index */
4359: Index *pBest = 0; /* Best index found so far */
4360: int iRoot = pTab->tnum; /* Root page of scanned b-tree */
4361:
4362: sqlite3CodeVerifySchema(pParse, iDb);
4363: sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
4364:
4365: /* Search for the index that has the least amount of columns. If
4366: ** there is such an index, and it has less columns than the table
4367: ** does, then we can assume that it consumes less space on disk and
4368: ** will therefore be cheaper to scan to determine the query result.
4369: ** In this case set iRoot to the root page number of the index b-tree
4370: ** and pKeyInfo to the KeyInfo structure required to navigate the
4371: ** index.
4372: **
4373: ** (2011-04-15) Do not do a full scan of an unordered index.
4374: **
4375: ** In practice the KeyInfo structure will not be used. It is only
4376: ** passed to keep OP_OpenRead happy.
4377: */
4378: for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
4379: if( pIdx->bUnordered==0 && (!pBest || pIdx->nColumn<pBest->nColumn) ){
4380: pBest = pIdx;
4381: }
4382: }
4383: if( pBest && pBest->nColumn<pTab->nCol ){
4384: iRoot = pBest->tnum;
4385: pKeyInfo = sqlite3IndexKeyinfo(pParse, pBest);
4386: }
4387:
4388: /* Open a read-only cursor, execute the OP_Count, close the cursor. */
4389: sqlite3VdbeAddOp3(v, OP_OpenRead, iCsr, iRoot, iDb);
4390: if( pKeyInfo ){
4391: sqlite3VdbeChangeP4(v, -1, (char *)pKeyInfo, P4_KEYINFO_HANDOFF);
4392: }
4393: sqlite3VdbeAddOp2(v, OP_Count, iCsr, sAggInfo.aFunc[0].iMem);
4394: sqlite3VdbeAddOp1(v, OP_Close, iCsr);
4395: explainSimpleCount(pParse, pTab, pBest);
4396: }else
4397: #endif /* SQLITE_OMIT_BTREECOUNT */
4398: {
4399: /* Check if the query is of one of the following forms:
4400: **
4401: ** SELECT min(x) FROM ...
4402: ** SELECT max(x) FROM ...
4403: **
4404: ** If it is, then ask the code in where.c to attempt to sort results
4405: ** as if there was an "ORDER ON x" or "ORDER ON x DESC" clause.
4406: ** If where.c is able to produce results sorted in this order, then
4407: ** add vdbe code to break out of the processing loop after the
4408: ** first iteration (since the first iteration of the loop is
4409: ** guaranteed to operate on the row with the minimum or maximum
4410: ** value of x, the only row required).
4411: **
4412: ** A special flag must be passed to sqlite3WhereBegin() to slightly
4413: ** modify behaviour as follows:
4414: **
4415: ** + If the query is a "SELECT min(x)", then the loop coded by
4416: ** where.c should not iterate over any values with a NULL value
4417: ** for x.
4418: **
4419: ** + The optimizer code in where.c (the thing that decides which
4420: ** index or indices to use) should place a different priority on
4421: ** satisfying the 'ORDER BY' clause than it does in other cases.
4422: ** Refer to code and comments in where.c for details.
4423: */
4424: ExprList *pMinMax = 0;
4425: u8 flag = minMaxQuery(p);
4426: if( flag ){
4427: assert( !ExprHasProperty(p->pEList->a[0].pExpr, EP_xIsSelect) );
4428: pMinMax = sqlite3ExprListDup(db, p->pEList->a[0].pExpr->x.pList,0);
4429: pDel = pMinMax;
4430: if( pMinMax && !db->mallocFailed ){
4431: pMinMax->a[0].sortOrder = flag!=WHERE_ORDERBY_MIN ?1:0;
4432: pMinMax->a[0].pExpr->op = TK_COLUMN;
4433: }
4434: }
4435:
4436: /* This case runs if the aggregate has no GROUP BY clause. The
4437: ** processing is much simpler since there is only a single row
4438: ** of output.
4439: */
4440: resetAccumulator(pParse, &sAggInfo);
4441: pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, 0, flag);
4442: if( pWInfo==0 ){
4443: sqlite3ExprListDelete(db, pDel);
4444: goto select_end;
4445: }
4446: updateAccumulator(pParse, &sAggInfo);
4447: if( !pMinMax && flag ){
4448: sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iBreak);
4449: VdbeComment((v, "%s() by index",
4450: (flag==WHERE_ORDERBY_MIN?"min":"max")));
4451: }
4452: sqlite3WhereEnd(pWInfo);
4453: finalizeAggFunctions(pParse, &sAggInfo);
4454: }
4455:
4456: pOrderBy = 0;
4457: sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
4458: selectInnerLoop(pParse, p, p->pEList, 0, 0, 0, -1,
4459: pDest, addrEnd, addrEnd);
4460: sqlite3ExprListDelete(db, pDel);
4461: }
4462: sqlite3VdbeResolveLabel(v, addrEnd);
4463:
4464: } /* endif aggregate query */
4465:
4466: if( distinct>=0 ){
4467: explainTempTable(pParse, "DISTINCT");
4468: }
4469:
4470: /* If there is an ORDER BY clause, then we need to sort the results
4471: ** and send them to the callback one by one.
4472: */
4473: if( pOrderBy ){
4474: explainTempTable(pParse, "ORDER BY");
4475: generateSortTail(pParse, p, v, pEList->nExpr, pDest);
4476: }
4477:
4478: /* Jump here to skip this query
4479: */
4480: sqlite3VdbeResolveLabel(v, iEnd);
4481:
4482: /* The SELECT was successfully coded. Set the return code to 0
4483: ** to indicate no errors.
4484: */
4485: rc = 0;
4486:
4487: /* Control jumps to here if an error is encountered above, or upon
4488: ** successful coding of the SELECT.
4489: */
4490: select_end:
4491: explainSetInteger(pParse->iSelectId, iRestoreSelectId);
4492:
4493: /* Identify column names if results of the SELECT are to be output.
4494: */
4495: if( rc==SQLITE_OK && pDest->eDest==SRT_Output ){
4496: generateColumnNames(pParse, pTabList, pEList);
4497: }
4498:
4499: sqlite3DbFree(db, sAggInfo.aCol);
4500: sqlite3DbFree(db, sAggInfo.aFunc);
4501: return rc;
4502: }
4503:
4504: #if defined(SQLITE_ENABLE_TREE_EXPLAIN)
4505: /*
4506: ** Generate a human-readable description of a the Select object.
4507: */
4508: static void explainOneSelect(Vdbe *pVdbe, Select *p){
4509: sqlite3ExplainPrintf(pVdbe, "SELECT ");
4510: if( p->selFlags & (SF_Distinct|SF_Aggregate) ){
4511: if( p->selFlags & SF_Distinct ){
4512: sqlite3ExplainPrintf(pVdbe, "DISTINCT ");
4513: }
4514: if( p->selFlags & SF_Aggregate ){
4515: sqlite3ExplainPrintf(pVdbe, "agg_flag ");
4516: }
4517: sqlite3ExplainNL(pVdbe);
4518: sqlite3ExplainPrintf(pVdbe, " ");
4519: }
4520: sqlite3ExplainExprList(pVdbe, p->pEList);
4521: sqlite3ExplainNL(pVdbe);
4522: if( p->pSrc && p->pSrc->nSrc ){
4523: int i;
4524: sqlite3ExplainPrintf(pVdbe, "FROM ");
4525: sqlite3ExplainPush(pVdbe);
4526: for(i=0; i<p->pSrc->nSrc; i++){
4527: struct SrcList_item *pItem = &p->pSrc->a[i];
4528: sqlite3ExplainPrintf(pVdbe, "{%d,*} = ", pItem->iCursor);
4529: if( pItem->pSelect ){
4530: sqlite3ExplainSelect(pVdbe, pItem->pSelect);
4531: if( pItem->pTab ){
4532: sqlite3ExplainPrintf(pVdbe, " (tabname=%s)", pItem->pTab->zName);
4533: }
4534: }else if( pItem->zName ){
4535: sqlite3ExplainPrintf(pVdbe, "%s", pItem->zName);
4536: }
4537: if( pItem->zAlias ){
4538: sqlite3ExplainPrintf(pVdbe, " (AS %s)", pItem->zAlias);
4539: }
4540: if( pItem->jointype & JT_LEFT ){
4541: sqlite3ExplainPrintf(pVdbe, " LEFT-JOIN");
4542: }
4543: sqlite3ExplainNL(pVdbe);
4544: }
4545: sqlite3ExplainPop(pVdbe);
4546: }
4547: if( p->pWhere ){
4548: sqlite3ExplainPrintf(pVdbe, "WHERE ");
4549: sqlite3ExplainExpr(pVdbe, p->pWhere);
4550: sqlite3ExplainNL(pVdbe);
4551: }
4552: if( p->pGroupBy ){
4553: sqlite3ExplainPrintf(pVdbe, "GROUPBY ");
4554: sqlite3ExplainExprList(pVdbe, p->pGroupBy);
4555: sqlite3ExplainNL(pVdbe);
4556: }
4557: if( p->pHaving ){
4558: sqlite3ExplainPrintf(pVdbe, "HAVING ");
4559: sqlite3ExplainExpr(pVdbe, p->pHaving);
4560: sqlite3ExplainNL(pVdbe);
4561: }
4562: if( p->pOrderBy ){
4563: sqlite3ExplainPrintf(pVdbe, "ORDERBY ");
4564: sqlite3ExplainExprList(pVdbe, p->pOrderBy);
4565: sqlite3ExplainNL(pVdbe);
4566: }
4567: if( p->pLimit ){
4568: sqlite3ExplainPrintf(pVdbe, "LIMIT ");
4569: sqlite3ExplainExpr(pVdbe, p->pLimit);
4570: sqlite3ExplainNL(pVdbe);
4571: }
4572: if( p->pOffset ){
4573: sqlite3ExplainPrintf(pVdbe, "OFFSET ");
4574: sqlite3ExplainExpr(pVdbe, p->pOffset);
4575: sqlite3ExplainNL(pVdbe);
4576: }
4577: }
4578: void sqlite3ExplainSelect(Vdbe *pVdbe, Select *p){
4579: if( p==0 ){
4580: sqlite3ExplainPrintf(pVdbe, "(null-select)");
4581: return;
4582: }
4583: while( p->pPrior ) p = p->pPrior;
4584: sqlite3ExplainPush(pVdbe);
4585: while( p ){
4586: explainOneSelect(pVdbe, p);
4587: p = p->pNext;
4588: if( p==0 ) break;
4589: sqlite3ExplainNL(pVdbe);
4590: sqlite3ExplainPrintf(pVdbe, "%s\n", selectOpName(p->op));
4591: }
4592: sqlite3ExplainPrintf(pVdbe, "END");
4593: sqlite3ExplainPop(pVdbe);
4594: }
4595:
4596: /* End of the structure debug printing code
4597: *****************************************************************************/
4598: #endif /* defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
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