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Optimization: Convert an ORDER BY clause into a no-op if the query also

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contains a GROUP BY clause that will force the same output order.

FossilOrigin-Name: ca9d86baf70f210d331ce93102177c8005c494cb
This commit is contained in:
drh
2010-04-26 19:17:26 +00:00
parent 93791ea0ba
commit 8c6f666b26
5 changed files with 53 additions and 26 deletions
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39
src/expr.c
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@@ -3440,7 +3440,6 @@ void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
** an incorrect 0 or 1 could lead to a malfunction.
*/
int sqlite3ExprCompare(Expr *pA, Expr *pB){
int i;
if( pA==0||pB==0 ){
return pB==pA ? 0 : 2;
}
@@ -3453,18 +3452,7 @@ int sqlite3ExprCompare(Expr *pA, Expr *pB){
if( pA->op!=pB->op ) return 2;
if( sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 2;
if( sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 2;
if( pA->x.pList && pB->x.pList ){
if( pA->x.pList->nExpr!=pB->x.pList->nExpr ) return 2;
for(i=0; i<pA->x.pList->nExpr; i++){
Expr *pExprA = pA->x.pList->a[i].pExpr;
Expr *pExprB = pB->x.pList->a[i].pExpr;
if( sqlite3ExprCompare(pExprA, pExprB) ) return 2;
}
}else if( pA->x.pList || pB->x.pList ){
return 2;
}
if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList) ) return 2;
if( pA->iTable!=pB->iTable || pA->iColumn!=pB->iColumn ) return 2;
if( ExprHasProperty(pA, EP_IntValue) ){
if( !ExprHasProperty(pB, EP_IntValue) || pA->u.iValue!=pB->u.iValue ){
@@ -3481,6 +3469,31 @@ int sqlite3ExprCompare(Expr *pA, Expr *pB){
return 0;
}
/*
** Compare two ExprList objects. Return 0 if they are identical and
** non-zero if they differ in any way.
**
** This routine might return non-zero for equivalent ExprLists. The
** only consequence will be disabled optimizations. But this routine
** must never return 0 if the two ExprList objects are different, or
** a malfunction will result.
**
** Two NULL pointers are considered to be the same. But a NULL pointer
** always differs from a non-NULL pointer.
*/
int sqlite3ExprListCompare(ExprList *pA, ExprList *pB){
int i;
if( pA==0 && pB==0 ) return 0;
if( pA==0 || pB==0 ) return 1;
if( pA->nExpr!=pB->nExpr ) return 1;
for(i=0; i<pA->nExpr; i++){
Expr *pExprA = pA->a[i].pExpr;
Expr *pExprB = pB->a[i].pExpr;
if( pA->a[i].sortOrder!=pB->a[i].sortOrder ) return 1;
if( sqlite3ExprCompare(pExprA, pExprB) ) return 1;
}
return 0;
}
/*
** Add a new element to the pAggInfo->aCol[] array. Return the index of