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Commita58843b

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Fix problems seen when result of a subselect was used in an
expression context (ie, not at the top level of a WHERE clause). Exampleslike this one work now:SELECT name, value FROM t1 as touter WHERE(value/(SELECT AVG(value) FROM t1 WHERE name = touter.name)) > 0.75;
1 parent4438b70 commita58843b

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2 files changed

+57
-23
lines changed

2 files changed

+57
-23
lines changed

‎src/backend/executor/nodeSubplan.c

Lines changed: 42 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -29,10 +29,11 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
2929
{
3030
Plan*plan=node->plan;
3131
SubLink*sublink=node->sublink;
32+
SubLinkTypesubLinkType=sublink->subLinkType;
3233
TupleTableSlot*slot;
3334
List*lst;
34-
boolresult= false;
35-
boolfound= false;
35+
Datumresult= (Datum) false;
36+
boolfound= false;/* TRUE if got at least one subplan tuple */
3637

3738
if (node->setParam!=NULL)
3839
elog(ERROR,"ExecSubPlan: can't set parent params from subquery");
@@ -56,6 +57,18 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
5657

5758
ExecReScan(plan, (ExprContext*)NULL,plan);
5859

60+
/*
61+
* For all sublink types except EXPR_SUBLINK, the result type is boolean,
62+
* and we have a fairly clear idea of how to combine multiple subitems
63+
* and deal with NULL values or an empty subplan result.
64+
*
65+
* For EXPR_SUBLINK, the result type is whatever the combining operator
66+
* returns. We have no way to deal with more than one column in the
67+
* subplan result --- hopefully the parser forbids that. More seriously,
68+
* it's unclear what to do with NULL values or an empty subplan result.
69+
* For now, we error out, but should something else happen?
70+
*/
71+
5972
for (slot=ExecProcNode(plan,plan);
6073
!TupIsNull(slot);
6174
slot=ExecProcNode(plan,plan))
@@ -64,13 +77,13 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
6477
TupleDesctdesc=slot->ttc_tupleDescriptor;
6578
inti=1;
6679

67-
if (sublink->subLinkType==EXPR_SUBLINK&&found)
80+
if (subLinkType==EXPR_SUBLINK&&found)
6881
{
6982
elog(ERROR,"ExecSubPlan: more than one tuple returned by expression subselect");
7083
return (Datum) false;
7184
}
7285

73-
if (sublink->subLinkType==EXISTS_SUBLINK)
86+
if (subLinkType==EXISTS_SUBLINK)
7487
return (Datum) true;
7588

7689
found= true;
@@ -82,23 +95,39 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
8295
boolisnull;
8396

8497
con->constvalue=heap_getattr(tup,i,tdesc,&(con->constisnull));
85-
result=(bool)ExecEvalExpr((Node*)expr,econtext,&isnull, (bool*)NULL);
98+
result=ExecEvalExpr((Node*)expr,econtext,&isnull, (bool*)NULL);
8699
if (isnull)
87-
result= false;
88-
if ((!result&& !(sublink->useor))|| (result&&sublink->useor))
89-
break;
100+
{
101+
if (subLinkType==EXPR_SUBLINK)
102+
elog(ERROR,"ExecSubPlan: null value returned by expression subselect");
103+
else
104+
result= (Datum) false;
105+
}
106+
if (subLinkType!=EXPR_SUBLINK)
107+
{
108+
if ((! (bool)result&& !(sublink->useor))||
109+
((bool)result&&sublink->useor))
110+
break;
111+
}
90112
i++;
91113
}
92114

93-
if ((!result&&sublink->subLinkType==ALL_SUBLINK)||
94-
(result&&sublink->subLinkType==ANY_SUBLINK))
115+
if (subLinkType==ALL_SUBLINK&& ! (bool)result)
116+
break;
117+
if (subLinkType==ANY_SUBLINK&& (bool)result)
95118
break;
96119
}
97120

98-
if (!found&&sublink->subLinkType==ALL_SUBLINK)
99-
return (Datum) true;
121+
if (!found)
122+
{
123+
/* deal with empty subplan result. Note default result is 'false' */
124+
if (subLinkType==ALL_SUBLINK)
125+
result= (Datum) true;
126+
elseif (subLinkType==EXPR_SUBLINK)
127+
elog(ERROR,"ExecSubPlan: no tuples returned by expression subselect");
128+
}
100129

101-
return(Datum)result;
130+
returnresult;
102131
}
103132

104133
/* ----------------------------------------------------------------

‎src/backend/parser/parse_expr.c

Lines changed: 15 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.41 1999/04/1817:35:51 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.42 1999/04/19 04:17:11 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -312,14 +312,6 @@ transformExpr(ParseState *pstate, Node *expr, int precedence)
312312

313313
op_expr=make_op(op,lexpr,tent->expr);
314314

315-
/*
316-
* HACK! Second IF is more valid but currently we
317-
* don't support EXPR subqueries inside
318-
* expressions generally, only in WHERE clauses.
319-
* After fixing this, first IF must be removed.
320-
*/
321-
if (op_expr->typeOid!=BOOLOID)
322-
elog(ERROR,"parser: '%s' must return 'bool' to be used with subquery",op);
323315
if (op_expr->typeOid!=BOOLOID&&
324316
sublink->subLinkType!=EXPR_SUBLINK)
325317
elog(ERROR,"parser: '%s' must return 'bool' to be used with quantified predicate subquery",op);
@@ -598,7 +590,20 @@ exprType(Node *expr)
598590
type= ((Param*)expr)->paramtype;
599591
break;
600592
caseT_SubLink:
601-
type=BOOLOID;
593+
{
594+
SubLink*sublink= (SubLink*)expr;
595+
if (sublink->subLinkType==EXPR_SUBLINK)
596+
{
597+
/* return the result type of the combining operator */
598+
Expr*op_expr= (Expr*)lfirst(sublink->oper);
599+
type=op_expr->typeOid;
600+
}
601+
else
602+
{
603+
/* for all other sublink types, result is boolean */
604+
type=BOOLOID;
605+
}
606+
}
602607
break;
603608
caseT_CaseExpr:
604609
type= ((CaseExpr*)expr)->casetype;

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