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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 |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
cc9c12170c3f6f0f485977e47e7fbb75 |
| User & Date: | drh 2009-06-08 19:44:37.000 |
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: 8f1c1f61f7 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: cc9c12170c user: drh tags: trunk) | |
| 17:11 | Clarification of the operation of the OR-term optimizer in where.c. (CVS 6730) (check-in: 6b42dc3d04 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 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". ** | | | 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 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) |
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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 ){
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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 );
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