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Overview
Comment: | Update comments in where.c. No code changes. (CVS 2727) |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
bb84d27eda64479d65b13fbbcaeef6a0 |
User & Date: | drh 2005-09-20 08:47:20.000 |
Context
2005-09-20
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13:12 | NULLs compare equal to each other when computing GROUP BY categories. (CVS 2728) (check-in: d9b0c97053 user: drh tags: trunk) | |
08:47 | Update comments in where.c. No code changes. (CVS 2727) (check-in: bb84d27eda user: drh tags: trunk) | |
01:36 | Documentation updates. (CVS 2726) (check-in: 6ec8883c36 user: drh tags: trunk) | |
Changes
Changes to src/where.c.
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12 13 14 15 16 17 18 | ** This module contains C code that generates VDBE code used to process ** the WHERE clause of SQL statements. This module is reponsible for ** generating the code that loops through a table looking for applicable ** rows. Indices are selected and used to speed the search when doing ** so is applicable. Because this module is responsible for selecting ** indices, you might also think of this module as the "query optimizer". ** | | | 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | ** This module contains C code that generates VDBE code used to process ** the WHERE clause of SQL statements. This module is reponsible for ** generating the code that loops through a table looking for applicable ** rows. Indices are selected and used to speed the search when doing ** so is applicable. Because this module is responsible for selecting ** indices, you might also think of this module as the "query optimizer". ** ** $Id: where.c,v 1.178 2005/09/20 08:47:20 drh Exp $ */ #include "sqliteInt.h" /* ** The number of bits in a Bitmask. "BMS" means "BitMask Size". */ #define BMS (sizeof(Bitmask)*8) |
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228 229 230 231 232 233 234 | pTerm->pWC = pWC; pTerm->iParent = -1; return idx; } /* ** This routine identifies subexpressions in the WHERE clause where | | | 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 | pTerm->pWC = pWC; pTerm->iParent = -1; return idx; } /* ** This routine identifies subexpressions in the WHERE clause where ** each subexpression is separated by the AND operator or some other ** operator specified in the op parameter. The WhereClause structure ** is filled with pointers to subexpressions. For example: ** ** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22) ** \________/ \_______________/ \________________/ ** slot[0] slot[1] slot[2] ** |
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277 278 279 280 281 282 283 | } /* ** Create a new mask for cursor iCursor. ** ** There is one cursor per table in the FROM clause. The number of ** tables in the FROM clause is limited by a test early in the | | | 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 | } /* ** Create a new mask for cursor iCursor. ** ** There is one cursor per table in the FROM clause. The number of ** tables in the FROM clause is limited by a test early in the ** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[] ** array will never overflow. */ static void createMask(ExprMaskSet *pMaskSet, int iCursor){ assert( pMaskSet->n < ARRAYSIZE(pMaskSet->ix) ); pMaskSet->ix[pMaskSet->n++] = iCursor; } |
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528 529 530 531 532 533 534 | ** subexpression and populate all the other fields of the WhereTerm ** structure. ** ** If the expression is of the form "<expr> <op> X" it gets commuted ** to the standard form of "X <op> <expr>". If the expression is of ** the form "X <op> Y" where both X and Y are columns, then the original ** expression is unchanged and a new virtual expression of the form | | | 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 | ** subexpression and populate all the other fields of the WhereTerm ** structure. ** ** If the expression is of the form "<expr> <op> X" it gets commuted ** to the standard form of "X <op> <expr>". If the expression is of ** the form "X <op> Y" where both X and Y are columns, then the original ** expression is unchanged and a new virtual expression of the form ** "Y <op> X" is added to the WHERE clause and analyzed separately. */ static void exprAnalyze( SrcList *pSrc, /* the FROM clause */ ExprMaskSet *pMaskSet, /* table masks */ WhereClause *pWC, /* the WHERE clause */ int idxTerm /* Index of the term to be analyzed */ ){ |
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843 844 845 846 847 848 849 | *pbRev = pOrderBy->a[0].sortOrder; return 1; } return 0; } /* | | | 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 | *pbRev = pOrderBy->a[0].sortOrder; return 1; } return 0; } /* ** Prepare a crude estimate of the logarithm of the input value. ** The results need not be exact. This is only used for estimating ** the total cost of performing operatings with O(logN) or O(NlogN) ** complexity. Because N is just a guess, it is no great tragedy if ** logN is a little off. */ static double estLog(double N){ double logN = 1.0; |
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1102 1103 1104 1105 1106 1107 1108 | ** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok' ** ** The t2.z='ok' is disabled in the in (2) because it originates ** in the ON clause. The term is disabled in (3) because it is not part ** of a LEFT OUTER JOIN. In (1), the term is not disabled. ** ** Disabling a term causes that term to not be tested in the inner loop | | > | | | | | 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 | ** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok' ** ** The t2.z='ok' is disabled in the in (2) because it originates ** in the ON clause. The term is disabled in (3) because it is not part ** of a LEFT OUTER JOIN. In (1), the term is not disabled. ** ** Disabling a term causes that term to not be tested in the inner loop ** of the join. Disabling is an optimization. When terms are satisfied ** by indices, we disable them to prevent redundant tests in the inner ** loop. We would get the correct results if nothing were ever disabled, ** but joins might run a little slower. The trick is to disable as much ** as we can without disabling too much. If we disabled in (1), we'd get ** the wrong answer. See ticket #813. */ static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){ if( pTerm && (pTerm->flags & TERM_CODED)==0 && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin)) ){ pTerm->flags |= TERM_CODED; |
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1421 1422 1423 1424 1425 1426 1427 | sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1); pWhere = 0; } /* Analyze all of the subexpressions. Note that exprAnalyze() might ** add new virtual terms onto the end of the WHERE clause. We do not ** want to analyze these virtual terms, so start analyzing at the end | | | 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 | sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1); pWhere = 0; } /* Analyze all of the subexpressions. Note that exprAnalyze() might ** add new virtual terms onto the end of the WHERE clause. We do not ** want to analyze these virtual terms, so start analyzing at the end ** and work forward so that the added virtual terms are never processed. */ for(i=0; i<pTabList->nSrc; i++){ createMask(&maskSet, pTabList->a[i].iCursor); } exprAnalyzeAll(pTabList, &maskSet, &wc); if( sqlite3_malloc_failed ){ goto whereBeginNoMem; |
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