Overview
| Comment: | Additional comments to clarify the operation of the LIKE optimizer in where.c. (CVS 6731) |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: | cc9c12170c3f6f0f485977e47e7fbb75c50e82b1 |
| User & Date: | drh 2009-06-08 19:44:37 |
Context
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2009-06-09
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| 09:41 | Do not clear the MemPage.nFree variable when insertCell() adds an overflow cell to a page. Not doing this means balance_quick() can avoid a call to sqlite3BtreeInitPage(). (CVS 6732) check-in: 8f1c1f61 user: danielk1977 tags: trunk | |
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2009-06-08
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| 19:44 | Additional comments to clarify the operation of the LIKE optimizer in where.c. (CVS 6731) check-in: cc9c1217 user: drh tags: trunk | |
| 17:11 | Clarification of the operation of the OR-term optimizer in where.c. (CVS 6730) check-in: 6b42dc3d user: drh tags: trunk | |
Changes
Changes to src/where.c.
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** This module contains C code that generates VDBE code used to process ** the WHERE clause of SQL statements. This module is responsible 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 1.403 2009/06/08 17:11:08 drh Exp $ */ #include "sqliteInt.h" /* ** Trace output macros */ #if defined(SQLITE_TEST) || defined(SQLITE_DEBUG) ................................................................................ pLeft = pExpr->x.pList->a[1].pExpr; pRight = pExpr->x.pList->a[0].pExpr; pStr1 = sqlite3Expr(db, TK_STRING, pRight->u.zToken); if( pStr1 ) pStr1->u.zToken[nPattern] = 0; pStr2 = sqlite3ExprDup(db, pStr1, 0); if( !db->mallocFailed ){ u8 c, *pC; pC = (u8*)&pStr2->u.zToken[nPattern-1]; c = *pC; if( noCase ){ if( c=='@' ) isComplete = 0; c = sqlite3UpperToLower[c]; } *pC = c + 1; } pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft,0),pStr1,0); idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC); testcase( idxNew1==0 ); |
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** This module contains C code that generates VDBE code used to process ** the WHERE clause of SQL statements. This module is responsible 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 1.404 2009/06/08 19:44:37 drh Exp $ */ #include "sqliteInt.h" /* ** Trace output macros */ #if defined(SQLITE_TEST) || defined(SQLITE_DEBUG) ................................................................................ pLeft = pExpr->x.pList->a[1].pExpr; pRight = pExpr->x.pList->a[0].pExpr; pStr1 = sqlite3Expr(db, TK_STRING, pRight->u.zToken); if( pStr1 ) pStr1->u.zToken[nPattern] = 0; pStr2 = sqlite3ExprDup(db, pStr1, 0); if( !db->mallocFailed ){ u8 c, *pC; /* Last character before the first wildcard */ pC = (u8*)&pStr2->u.zToken[nPattern-1]; c = *pC; if( noCase ){ /* The point is to increment the last character before the first ** wildcard. But if we increment '@', that will push it into the ** alphabetic range where case conversions will mess up the ** inequality. To avoid this, make sure to also run the full ** LIKE on all candidate expressions by clearing the isComplete flag */ if( c=='A'-1 ) isComplete = 0; c = sqlite3UpperToLower[c]; } *pC = c + 1; } pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft,0),pStr1,0); idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC); testcase( idxNew1==0 ); |