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Enhancements to sqlite3ExprImpliesExpr() so that it realizes that

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"iif(A,B)" implies "A".

FossilOrigin-Name: d96ecbee59b50eca25447456dfff2c168e8eade7a68e542932d5829f97debb31
This commit is contained in:
drh
2024-11-28 00:34:20 +00:00
parent 0bce1d6c9f
commit 60ad526639
4 changed files with 83 additions and 29 deletions
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90
src/expr.c
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@@ -6180,16 +6180,20 @@ void sqlite3ExprIfFalseDup(Parse *pParse, Expr *pExpr, int dest,int jumpIfNull){
** same as that currently bound to variable pVar, non-zero is returned.
** Otherwise, if the values are not the same or if pExpr is not a simple
** SQL value, zero is returned.
**
** If the SQLITE_EnableQPSG flag is set on the database connection, then
** this routine always returns false.
*/
static int exprCompareVariable(
static SQLITE_NOINLINE int exprCompareVariable(
const Parse *pParse,
const Expr *pVar,
const Expr *pExpr
){
int res = 0;
int res = 2;
int iVar;
sqlite3_value *pL, *pR = 0;
if( (pParse->db->flags & SQLITE_EnableQPSG)!=0 ) return 2;
sqlite3ValueFromExpr(pParse->db, pExpr, SQLITE_UTF8, SQLITE_AFF_BLOB, &pR);
if( pR ){
iVar = pVar->iColumn;
@@ -6199,12 +6203,11 @@ static int exprCompareVariable(
if( sqlite3_value_type(pL)==SQLITE_TEXT ){
sqlite3_value_text(pL); /* Make sure the encoding is UTF-8 */
}
res = 0==sqlite3MemCompare(pL, pR, 0);
res = sqlite3MemCompare(pL, pR, 0) ? 2 : 0;
}
sqlite3ValueFree(pR);
sqlite3ValueFree(pL);
}
return res;
}
@@ -6230,12 +6233,10 @@ static int exprCompareVariable(
** just might result in some slightly slower code. But returning
** an incorrect 0 or 1 could lead to a malfunction.
**
** If pParse is not NULL then TK_VARIABLE terms in pA with bindings in
** pParse->pReprepare can be matched against literals in pB. The
** pParse->pVdbe->expmask bitmask is updated for each variable referenced.
** If pParse is NULL (the normal case) then any TK_VARIABLE term in
** Argument pParse should normally be NULL. If it is not NULL and pA or
** pB causes a return value of 2.
** If pParse is not NULL and SQLITE_EnableQPSG is off then TK_VARIABLE
** terms in pA with bindings in pParse->pReprepare can be matched against
** literals in pB. The pParse->pVdbe->expmask bitmask is updated for
** each variable referenced.
*/
int sqlite3ExprCompare(
const Parse *pParse,
@@ -6247,8 +6248,8 @@ int sqlite3ExprCompare(
if( pA==0 || pB==0 ){
return pB==pA ? 0 : 2;
}
if( pParse && pA->op==TK_VARIABLE && exprCompareVariable(pParse, pA, pB) ){
return 0;
if( pParse && pA->op==TK_VARIABLE ){
return exprCompareVariable(pParse, pA, pB);
}
combinedFlags = pA->flags | pB->flags;
if( combinedFlags & EP_IntValue ){
@@ -6443,18 +6444,66 @@ static int exprImpliesNotNull(
return 0;
}
/*
** Return true if the boolean value of the expression is always either
** FALSE or NULL.
*/
static int sqlite3ExprIsNotTrue(Expr *pExpr){
int v;
if( pExpr->op==TK_NULL ) return 1;
if( pExpr->op==TK_TRUEFALSE && sqlite3ExprTruthValue(pExpr)==0 ) return 1;
v = 1;
if( sqlite3ExprIsInteger(pExpr, &v, 0) && v==0 ) return 1;
return 0;
}
/*
** Return true if the expression is one of the following:
**
** CASE WHEN x THEN y END
** CASE WHEN x THEN y ELSE NULL END
** CASE WHEN x THEN y ELSE false END
** iif(x,y)
** iif(x,y,NULL)
** iif(x,y,false)
*/
static int sqlite3ExprIsIIF(sqlite3 *db, const Expr *pExpr){
ExprList *pList;
if( pExpr->op==TK_FUNCTION ){
const char *z = pExpr->u.zToken;
FuncDef *pDef;
if( (z[0]!='i' && z[0]!='I') ) return 0;
if( pExpr->x.pList==0 ) return 0;
pDef = sqlite3FindFunction(db, z, pExpr->x.pList->nExpr, ENC(db), 0);
if( pDef==0 ) return 0;
if( (pDef->funcFlags & SQLITE_FUNC_INLINE)==0 ) return 0;
if( SQLITE_PTR_TO_INT(pDef->pUserData)!=INLINEFUNC_iif ) return 0;
}else if( pExpr->op==TK_CASE ){
if( pExpr->pLeft!=0 ) return 0;
}else{
return 0;
}
pList = pExpr->x.pList;
assert( pList!=0 );
if( pList->nExpr==2 ) return 1;
if( pList->nExpr==3 && sqlite3ExprIsNotTrue(pList->a[2].pExpr) ) return 1;
return 0;
}
/*
** Return true if we can prove the pE2 will always be true if pE1 is
** true. Return false if we cannot complete the proof or if pE2 might
** be false. Examples:
**
** 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 Result: false
** 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 Result: false
** pE1: iif(x,y) pE2: x Result: true
** PE1: iif(x,y,0) pE2: x Result: true
**
** When comparing TK_COLUMN nodes between pE1 and pE2, if pE2 has
** Expr.iTable<0 then assume a table number given by iTab.
@@ -6488,6 +6537,9 @@ int sqlite3ExprImpliesExpr(
){
return 1;
}
if( sqlite3ExprIsIIF(pParse->db, pE1) ){
return sqlite3ExprImpliesExpr(pParse,pE1->x.pList->a[0].pExpr,pE2,iTab);
}
return 0;
}