Fill out an initial implementation of the sqlite3ExprImpliesExpr() function.
FossilOrigin-Name: 8e07aa2ad5579aeb82174ce5bd432ddb9c058bc1
diff --git a/src/expr.c b/src/expr.c
index 96c05dc..6fa3444 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -3798,6 +3798,9 @@
** by a COLLATE operator at the top level. Return 2 if there are differences
** other than the top-level COLLATE operator.
**
+** If any subelement of pB has Expr.iTable==(-1) then it is allowed
+** to compare equal to an equivalent element in pA with Expr.iTable==iTab.
+**
** Sometimes this routine will return 2 even if the two expressions
** really are equivalent. If we cannot prove that the expressions are
** identical, we return 2 just to be safe. So if this routine
@@ -3808,7 +3811,7 @@
** just might result in some slightly slower code. But returning
** an incorrect 0 or 1 could lead to a malfunction.
*/
-int sqlite3ExprCompare(Expr *pA, Expr *pB){
+int sqlite3ExprCompare(Expr *pA, Expr *pB, int iTab){
if( pA==0||pB==0 ){
return pB==pA ? 0 : 2;
}
@@ -3819,18 +3822,19 @@
}
if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;
if( pA->op!=pB->op ){
- if( pA->op==TK_COLLATE && sqlite3ExprCompare(pA->pLeft, pB)<2 ){
+ if( pA->op==TK_COLLATE && sqlite3ExprCompare(pA->pLeft, pB, iTab)<2 ){
return 1;
}
- if( pB->op==TK_COLLATE && sqlite3ExprCompare(pA, pB->pLeft)<2 ){
+ if( pB->op==TK_COLLATE && sqlite3ExprCompare(pA, pB->pLeft, iTab)<2 ){
return 1;
}
return 2;
}
- if( sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 2;
- if( sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 2;
- if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList) ) return 2;
- if( pA->iTable!=pB->iTable || pA->iColumn!=pB->iColumn ) return 2;
+ if( sqlite3ExprCompare(pA->pLeft, pB->pLeft, iTab) ) return 2;
+ if( sqlite3ExprCompare(pA->pRight, pB->pRight, iTab) ) return 2;
+ if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList, iTab) ) return 2;
+ if( pA->iColumn!=pB->iColumn ) return 2;
+ if( pA->iTable!=pB->iTable && (pA->iTable!=iTab || pB->iTable>=0) ) return 2;
if( ExprHasProperty(pA, EP_IntValue) ){
if( !ExprHasProperty(pB, EP_IntValue) || pA->u.iValue!=pB->u.iValue ){
return 2;
@@ -3848,6 +3852,9 @@
** Compare two ExprList objects. Return 0 if they are identical and
** non-zero if they differ in any way.
**
+** If any subelement of pB has Expr.iTable==(-1) then it is allowed
+** to compare equal to an equivalent element in pA with Expr.iTable==iTab.
+**
** 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
@@ -3856,7 +3863,7 @@
** 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 sqlite3ExprListCompare(ExprList *pA, ExprList *pB, int iTab){
int i;
if( pA==0 && pB==0 ) return 0;
if( pA==0 || pB==0 ) return 1;
@@ -3865,7 +3872,7 @@
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;
+ if( sqlite3ExprCompare(pExprA, pExprB, iTab) ) return 1;
}
return 0;
}
@@ -3875,9 +3882,13 @@
** true. Return false if we cannot complete the proof or if pE2 might
** be false. Examples:
**
-** pE1: x==5 pE2: x>0 Result: true
-** pE1: x>0 pE2: x==5 Result: false
-** pE1: x!=123 pE2: x IS NOT NULL Result: true
+** pE1: x==5 pE2: x==5 Result: true
+** pE1: x>0 pE2: x==5 Result: false
+** pE1: x=21 pE2: x=21 OR y=43 Result: true
+** pE1: x!=123 pE2: x IS NOT NULL Result: true
+** pE1: x!=?1 pE2: x IS NOT NULL Result: true
+** pE1: x IS NULL pE2: x IS NOT NULL Result: false
+** pE1: x IS ?2 pE2: x IS NOT NULL Reuslt: false
**
** When comparing TK_COLUMN nodes between pE1 and pE2, if pE2 has
** Expr.iTable<0 then assume a table number given by iTab.
@@ -3887,7 +3898,22 @@
** it will always give the correct answer and is hence always safe.
*/
int sqlite3ExprImpliesExpr(Expr *pE1, Expr *pE2, int iTab){
- return 0; /* FIXME: this needs to be worked out */
+ if( sqlite3ExprCompare(pE1, pE2, iTab)==0 ){
+ return 1;
+ }
+ if( pE2->op==TK_OR
+ && (sqlite3ExprImpliesExpr(pE1, pE2->pLeft, iTab)
+ || sqlite3ExprImpliesExpr(pE1, pE2->pRight, iTab) )
+ ){
+ return 1;
+ }
+ if( pE2->op==TK_NOTNULL
+ && sqlite3ExprCompare(pE1->pLeft, pE2->pLeft, iTab)==0
+ && (pE1->op!=TK_ISNULL && pE1->op!=TK_IS)
+ ){
+ return 1;
+ }
+ return 0;
}
/*
@@ -4070,7 +4096,7 @@
*/
struct AggInfo_func *pItem = pAggInfo->aFunc;
for(i=0; i<pAggInfo->nFunc; i++, pItem++){
- if( sqlite3ExprCompare(pItem->pExpr, pExpr)==0 ){
+ if( sqlite3ExprCompare(pItem->pExpr, pExpr, -1)==0 ){
break;
}
}