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Query optimizer enhancement: In "FROM a,b,c left join d" allow the C table

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to be reordered with A and B.  This used to be the case but the capability
was removed by (3203) and (3052) in response to ticket #1652.  This change
restores the capability. (CVS 3529)

FossilOrigin-Name: 7393c81b8cb9d4344ae744de9eabcb3af64f1db8
This commit is contained in:
drh
2006-12-16 16:25:15 +00:00
parent f0fa1c1b9f
commit 61dfc31d80
9 changed files with 212 additions and 86 deletions
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35
src/expr.c
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@@ -12,7 +12,7 @@
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.269 2006/11/23 11:59:13 drh Exp $
** $Id: expr.c,v 1.270 2006/12/16 16:25:15 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
@@ -891,22 +891,23 @@ static int lookupName(
pExpr->iColumn = j==pTab->iPKey ? -1 : j;
pExpr->affinity = pTab->aCol[j].affinity;
pExpr->pColl = sqlite3FindCollSeq(db, ENC(db), zColl,-1, 0);
if( pItem->jointype & JT_NATURAL ){
/* If this match occurred in the left table of a natural join,
** then skip the right table to avoid a duplicate match */
pItem++;
i++;
}
if( (pUsing = pItem->pUsing)!=0 ){
/* If this match occurs on a column that is in the USING clause
** of a join, skip the search of the right table of the join
** to avoid a duplicate match there. */
int k;
for(k=0; k<pUsing->nId; k++){
if( sqlite3StrICmp(pUsing->a[k].zName, zCol)==0 ){
pItem++;
i++;
break;
if( i<pSrcList->nSrc-1 ){
if( pItem[1].jointype & JT_NATURAL ){
/* If this match occurred in the left table of a natural join,
** then skip the right table to avoid a duplicate match */
pItem++;
i++;
}else if( (pUsing = pItem[1].pUsing)!=0 ){
/* If this match occurs on a column that is in the USING clause
** of a join, skip the search of the right table of the join
** to avoid a duplicate match there. */
int k;
for(k=0; k<pUsing->nId; k++){
if( sqlite3StrICmp(pUsing->a[k].zName, zCol)==0 ){
pItem++;
i++;
break;
}
}
}
}