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Fix the min/max optimizer so that it works when the FROM clause is a

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subquery.  Ticket #658. (CVS 1293)

FossilOrigin-Name: 31c94acc72d318b5dec0fef1485621943add45c8
This commit is contained in:
drh
2004-03-13 14:00:36 +00:00
parent 1a72d72a7f
commit 6e17529e97
5 changed files with 55 additions and 30 deletions
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46
src/select.c
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@@ -12,7 +12,7 @@
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.160 2004/03/02 18:37:41 drh Exp $
** $Id: select.c,v 1.161 2004/03/13 14:00:36 drh Exp $
*/
#include "sqliteInt.h"
@@ -1836,18 +1836,23 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
Vdbe *v;
int seekOp;
int cont;
ExprList eList;
ExprList *pEList, *pList, eList;
struct ExprList_item eListItem;
SrcList *pSrc;
/* Check to see if this query is a simple min() or max() query. Return
** zero if it is not.
*/
if( p->pGroupBy || p->pHaving || p->pWhere ) return 0;
if( p->pSrc->nSrc!=1 ) return 0;
if( p->pEList->nExpr!=1 ) return 0;
pExpr = p->pEList->a[0].pExpr;
pSrc = p->pSrc;
if( pSrc->nSrc!=1 ) return 0;
pEList = p->pEList;
if( pEList->nExpr!=1 ) return 0;
pExpr = pEList->a[0].pExpr;
if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
if( pExpr->pList==0 || pExpr->pList->nExpr!=1 ) return 0;
pList = pExpr->pList;
if( pList==0 || pList->nExpr!=1 ) return 0;
if( pExpr->token.n!=3 ) return 0;
if( sqliteStrNICmp(pExpr->token.z,"min",3)==0 ){
seekOp = OP_Rewind;
@@ -1856,10 +1861,10 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
}else{
return 0;
}
pExpr = pExpr->pList->a[0].pExpr;
pExpr = pList->a[0].pExpr;
if( pExpr->op!=TK_COLUMN ) return 0;
iCol = pExpr->iColumn;
pTab = p->pSrc->a[0].pTab;
pTab = pSrc->a[0].pTab;
/* If we get to here, it means the query is of the correct form.
** Check to make sure we have an index and make pIdx point to the
@@ -1899,10 +1904,12 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
** or last entry in the main table.
*/
sqliteCodeVerifySchema(pParse, pTab->iDb);
base = p->pSrc->a[0].iCursor;
base = pSrc->a[0].iCursor;
computeLimitRegisters(pParse, p);
sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
sqliteVdbeOp3(v, OP_OpenRead, base, pTab->tnum, pTab->zName, 0);
if( pSrc->a[0].pSelect==0 ){
sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
sqliteVdbeOp3(v, OP_OpenRead, base, pTab->tnum, pTab->zName, 0);
}
cont = sqliteVdbeMakeLabel(v);
if( pIdx==0 ){
sqliteVdbeAddOp(v, seekOp, base, 0);
@@ -1921,6 +1928,7 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
selectInnerLoop(pParse, p, &eList, 0, 0, 0, -1, eDest, iParm, cont, cont);
sqliteVdbeResolveLabel(v, cont);
sqliteVdbeAddOp(v, OP_Close, base, 0);
return 1;
}
@@ -2161,14 +2169,6 @@ int sqliteSelect(
generateColumnNames(pParse, pTabList, pEList);
}
/* Check for the special case of a min() or max() function by itself
** in the result set.
*/
if( simpleMinMaxQuery(pParse, p, eDest, iParm) ){
rc = 0;
goto select_end;
}
/* Generate code for all sub-queries in the FROM clause
*/
for(i=0; i<pTabList->nSrc; i++){
@@ -2198,6 +2198,14 @@ int sqliteSelect(
isDistinct = p->isDistinct;
}
/* Check for the special case of a min() or max() function by itself
** in the result set.
*/
if( simpleMinMaxQuery(pParse, p, eDest, iParm) ){
rc = 0;
goto select_end;
}
/* Check to see if this is a subquery that can be "flattened" into its parent.
** If flattening is a possiblity, do so and return immediately.
*/