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Overview
| Comment: | An index might be useful for ORDER BY if any indexed column is in the ORDER BY clause, not just the first indexed column. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | nextgen-query-plan-exp |
| Files: | files | file ages | folders |
| SHA1: |
ade473b5ae3fe2162b0ec29731d8e864 |
| User & Date: | drh 2013-06-13 17:58:08 |
Context
|
2013-06-14
| ||
| 02:51 | Add a new ORDER BY optimization that bypasses ORDER BY terms that are constrained by == and IS NULL terms of the WHERE clause. check-in: b920bb70 user: drh tags: nextgen-query-plan-exp | |
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2013-06-13
| ||
| 17:58 | An index might be useful for ORDER BY if any indexed column is in the ORDER BY clause, not just the first indexed column. check-in: ade473b5 user: drh tags: nextgen-query-plan-exp | |
| 17:28 | Make sure that disabling the covering index scan optimization does not prevent a covering index from being used to satisfy an ORDER BY clause. check-in: e8b7ea82 user: drh tags: nextgen-query-plan-exp | |
Changes
Changes to src/where.c.
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*/
static int indexMightHelpWithOrderBy(
WhereLoopBuilder *pBuilder,
Index *pIndex,
int iCursor
){
ExprList *pOB;
int iCol;
int ii;
if( pIndex->bUnordered ) return 0;
if( (pOB = pBuilder->pWInfo->pOrderBy)==0 ) return 0;
iCol = pIndex->aiColumn[0];
for(ii=0; ii<pOB->nExpr; ii++){
Expr *pExpr = sqlite3ExprSkipCollate(pOB->a[ii].pExpr);
if( pExpr->op!=TK_COLUMN ) return 0;
if( pExpr->iTable==iCursor ){
if( pExpr->iColumn==iCol ) return 1;
return 0;
}
}
return 0;
}
/*
** Return a bitmask where 1s indicate that the corresponding column of
|
< | < | | > |
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*/
static int indexMightHelpWithOrderBy(
WhereLoopBuilder *pBuilder,
Index *pIndex,
int iCursor
){
ExprList *pOB;
int ii, jj;
if( pIndex->bUnordered ) return 0;
if( (pOB = pBuilder->pWInfo->pOrderBy)==0 ) return 0;
for(ii=0; ii<pOB->nExpr; ii++){
Expr *pExpr = sqlite3ExprSkipCollate(pOB->a[ii].pExpr);
if( pExpr->op!=TK_COLUMN ) return 0;
if( pExpr->iTable==iCursor ){
for(jj=0; jj<pIndex->nColumn; jj++){
if( pExpr->iColumn==pIndex->aiColumn[jj] ) return 1;
}
}
}
return 0;
}
/*
** Return a bitmask where 1s indicate that the corresponding column of
|