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Generalize pushdown to allow any uncorrelated subquery to be pushed down.

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FossilOrigin-Name: 87c45fb0d5f5ca5d6d1ad27bef83f294231d17d94299e1997364a7975b423e38
This commit is contained in:
drh
2024-04-06 12:19:50 +00:00
parent 743ae4c68b
commit de6a4be9b5
6 changed files with 21 additions and 46 deletions
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32
src/expr.c
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@@ -2550,38 +2550,17 @@ static int sqlite3ExprIsConstantNotJoin(Parse *pParse, Expr *p){
/*
** This routine examines sub-SELECT statements as an expression is being
** walked as part of sqlite3ExprIsTableConstant() (hereafter IsTabConst()).
** Most SELECT statements will cause IsTabConst() to return false. However,
** if:
**
** (1) The SELECT is the right-hand side of an IN operator, and
** (2) Nothing in the SELECT refers to anything other than itself
**
** Then this routine causes the sub-SELECT to be bypassed, so that if
** nothing else is amiss the IsTabConst() routine can return true.
** walked as part of sqlite3ExprIsTableConstant(). Sub-SELECTs are considered
** constant as long as they are uncorrelated - meaning that they do not
** contain any terms from outer contexts.
*/
static int exprSelectWalkTableConstant(Walker *pWalker, Select *pSelect){
int savedCursor;
assert( pSelect!=0 );
assert( pWalker->eCode==3 || pWalker->eCode==0 );
if( (pSelect->selFlags & SF_RhsOfIN)==0 ){
if( (pSelect->selFlags & SF_Correlated)!=0 ){
pWalker->eCode = 0;
return WRC_Abort;
}
assert( pSelect->pSrc!=0 );
assert( pSelect->pSrc->nSrc==1 );
assert( pSelect->pWhere==0 );
assert( pSelect->pGroupBy==0 );
assert( pSelect->pHaving==0 );
assert( pSelect->pOrderBy==0 );
assert( pSelect->pPrior==0 );
assert( pSelect->pNext==0 );
assert( pSelect->pLimit==0 );
assert( pSelect->pWith==0 );
savedCursor = pWalker->u.iCur;
pWalker->u.iCur = pSelect->pSrc->a[0].iCursor;
sqlite3WalkExprList(pWalker, pSelect->pEList);
pWalker->u.iCur = savedCursor;
return WRC_Prune;
}
@@ -2591,8 +2570,7 @@ static int exprSelectWalkTableConstant(Walker *pWalker, Select *pSelect){
** expression must not refer to any non-deterministic function nor any
** table other than iCur.
**
** 2024-04-05: Operators of the form "expr IN table" are now allowed, where
** "table" is the name of a table.
** Enhanced on 2024-04-06: Allow pExpr to contain uncorrelated subqueries.
*/
static int sqlite3ExprIsTableConstant(Expr *p, int iCur){
Walker w;