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Improve the bytecode generated for comparisons so that if one operand is

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a subquery and the other operand evaluates to NULL, the subquery operand
is not even computed.  This fixes 5 of the 12 slow queries described
in [forum:/forumpost/52651713ac|forum post 52651713ac].

FossilOrigin-Name: f147bc04776ac0056412f69dfc518016c0d5b4e9d964664e3d88f595fb29dbe0
This commit is contained in:
drh
2025-06-28 17:59:15 +00:00
parent c52e9d97d4
commit 311d73efc2
3 changed files with 50 additions and 8 deletions
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41
src/expr.c
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@@ -6088,10 +6088,48 @@ void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
case TK_GE:
case TK_NE:
case TK_EQ: {
int r2Done = 0;
int addrBypass = 0;
if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
testcase( jumpIfNull==0 );
/*
** If the left operand is a (possibly expensive) subquery and the
** right operand is not and the right operation might be NULL and
** the operator is not IS or IS NOT, then compute the right operand
** first and skip the computation of the left operand if the right
** operand is NULL.
*/
if( jumpIfNull!=SQLITE_NULLEQ
&& ExprHasProperty(pExpr->pLeft, EP_Subquery)
&& !ExprHasProperty(pExpr->pRight, EP_Subquery)
&& sqlite3ExprCanBeNull(pExpr->pRight)
){
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
addrBypass = sqlite3VdbeAddOp2(v, OP_IsNull, r2, dest);
VdbeCoverageIf(v, jumpIfNull==SQLITE_JUMPIFNULL);
VdbeCoverageIf(v, jumpIfNull!=SQLITE_JUMPIFNULL);
if( jumpIfNull==SQLITE_JUMPIFNULL ) addrBypass = 0;
r2Done = 1;
}
r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
if( !r2Done ){
/*
** If the right operand is a subquery and the left operand is not
** and the left operand might be NULL and the comparison operator
** is not IS or IS NOT, then check the left operand to see if it is
** NULL and skip the computation of the right operand if it is.
*/
if( jumpIfNull!=SQLITE_NULLEQ
&& ExprHasProperty(pExpr->pRight, EP_Subquery)
&& sqlite3ExprCanBeNull(pExpr->pLeft)
){
addrBypass = sqlite3VdbeAddOp2(v, OP_IsNull, r1, dest);
VdbeCoverageIf(v, jumpIfNull==SQLITE_JUMPIFNULL);
VdbeCoverageIf(v, jumpIfNull!=SQLITE_JUMPIFNULL);
if( jumpIfNull==SQLITE_JUMPIFNULL ) addrBypass = 0;
}
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
}
codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
r1, r2, dest, jumpIfNull,ExprHasProperty(pExpr,EP_Commuted));
assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
@@ -6106,6 +6144,7 @@ void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
VdbeCoverageIf(v, op==OP_Ne && jumpIfNull==SQLITE_NULLEQ);
testcase( regFree1==0 );
testcase( regFree2==0 );
if( addrBypass ) sqlite3VdbeJumpHere(v, addrBypass);
break;
}
case TK_ISNULL: