Optimization: Convert an ORDER BY clause into a no-op if the query also
contains a GROUP BY clause that will force the same output order.
FossilOrigin-Name: ca9d86baf70f210d331ce93102177c8005c494cb
diff --git a/src/expr.c b/src/expr.c
index 034088f..70526ae 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -3440,7 +3440,6 @@
** 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 @@
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 @@
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