From a58843b49afdc15c3e319072916a4d9390cf70b1 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 19 Apr 1999 04:17:11 +0000
Subject: [PATCH] Fix problems seen when result of a subselect was used in an
expression context (ie, not at the top level of a WHERE clause). Examples
like this one work now: SELECT name, value FROM t1 as touter WHERE
(value/(SELECT AVG(value) FROM t1 WHERE name = touter.name)) > 0.75;
---
src/backend/executor/nodeSubplan.c | 55 +++++++++++++++++++++++-------
src/backend/parser/parse_expr.c | 25 ++++++++------
2 files changed, 57 insertions(+), 23 deletions(-)
diff --git a/src/backend/executor/nodeSubplan.c b/src/backend/executor/nodeSubplan.c
index 9f872c60682..2eebbf1f1e2 100644
--- a/src/backend/executor/nodeSubplan.c
+++ b/src/backend/executor/nodeSubplan.c
@@ -29,10 +29,11 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
{
Plan *plan = node->plan;
SubLink *sublink = node->sublink;
+ SubLinkType subLinkType = sublink->subLinkType;
TupleTableSlot *slot;
List *lst;
- bool result = false;
- bool found = false;
+ Datum result = (Datum) false;
+ bool found = false; /* TRUE if got at least one subplan tuple */
if (node->setParam != NULL)
elog(ERROR, "ExecSubPlan: can't set parent params from subquery");
@@ -56,6 +57,18 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
ExecReScan(plan, (ExprContext *) NULL, plan);
+ /*
+ * For all sublink types except EXPR_SUBLINK, the result type is boolean,
+ * and we have a fairly clear idea of how to combine multiple subitems
+ * and deal with NULL values or an empty subplan result.
+ *
+ * For EXPR_SUBLINK, the result type is whatever the combining operator
+ * returns. We have no way to deal with more than one column in the
+ * subplan result --- hopefully the parser forbids that. More seriously,
+ * it's unclear what to do with NULL values or an empty subplan result.
+ * For now, we error out, but should something else happen?
+ */
+
for (slot = ExecProcNode(plan, plan);
!TupIsNull(slot);
slot = ExecProcNode(plan, plan))
@@ -64,13 +77,13 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
TupleDesc tdesc = slot->ttc_tupleDescriptor;
int i = 1;
- if (sublink->subLinkType == EXPR_SUBLINK && found)
+ if (subLinkType == EXPR_SUBLINK && found)
{
elog(ERROR, "ExecSubPlan: more than one tuple returned by expression subselect");
return (Datum) false;
}
- if (sublink->subLinkType == EXISTS_SUBLINK)
+ if (subLinkType == EXISTS_SUBLINK)
return (Datum) true;
found = true;
@@ -82,23 +95,39 @@ ExecSubPlan(SubPlan *node, List *pvar, ExprContext *econtext)
bool isnull;
con->constvalue = heap_getattr(tup, i, tdesc, &(con->constisnull));
- result = (bool) ExecEvalExpr((Node *) expr, econtext, &isnull, (bool *) NULL);
+ result = ExecEvalExpr((Node *) expr, econtext, &isnull, (bool *) NULL);
if (isnull)
- result = false;
- if ((!result && !(sublink->useor)) || (result && sublink->useor))
- break;
+ {
+ if (subLinkType == EXPR_SUBLINK)
+ elog(ERROR, "ExecSubPlan: null value returned by expression subselect");
+ else
+ result = (Datum) false;
+ }
+ if (subLinkType != EXPR_SUBLINK)
+ {
+ if ((! (bool) result && !(sublink->useor)) ||
+ ((bool) result && sublink->useor))
+ break;
+ }
i++;
}
- if ((!result && sublink->subLinkType == ALL_SUBLINK) ||
- (result && sublink->subLinkType == ANY_SUBLINK))
+ if (subLinkType == ALL_SUBLINK && ! (bool) result)
+ break;
+ if (subLinkType == ANY_SUBLINK && (bool) result)
break;
}
- if (!found && sublink->subLinkType == ALL_SUBLINK)
- return (Datum) true;
+ if (!found)
+ {
+ /* deal with empty subplan result. Note default result is 'false' */
+ if (subLinkType == ALL_SUBLINK)
+ result = (Datum) true;
+ else if (subLinkType == EXPR_SUBLINK)
+ elog(ERROR, "ExecSubPlan: no tuples returned by expression subselect");
+ }
- return (Datum) result;
+ return result;
}
/* ----------------------------------------------------------------
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index d23d7214a34..f18fbd46eed 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.41 1999/04/18 17:35:51 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.42 1999/04/19 04:17:11 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -312,14 +312,6 @@ transformExpr(ParseState *pstate, Node *expr, int precedence)
op_expr = make_op(op, lexpr, tent->expr);
- /*
- * HACK! Second IF is more valid but currently we
- * don't support EXPR subqueries inside
- * expressions generally, only in WHERE clauses.
- * After fixing this, first IF must be removed.
- */
- if (op_expr->typeOid != BOOLOID)
- elog(ERROR, "parser: '%s' must return 'bool' to be used with subquery", op);
if (op_expr->typeOid != BOOLOID &&
sublink->subLinkType != EXPR_SUBLINK)
elog(ERROR, "parser: '%s' must return 'bool' to be used with quantified predicate subquery", op);
@@ -598,7 +590,20 @@ exprType(Node *expr)
type = ((Param *) expr)->paramtype;
break;
case T_SubLink:
- type = BOOLOID;
+ {
+ SubLink *sublink = (SubLink *) expr;
+ if (sublink->subLinkType == EXPR_SUBLINK)
+ {
+ /* return the result type of the combining operator */
+ Expr *op_expr = (Expr *) lfirst(sublink->oper);
+ type = op_expr->typeOid;
+ }
+ else
+ {
+ /* for all other sublink types, result is boolean */
+ type = BOOLOID;
+ }
+ }
break;
case T_CaseExpr:
type = ((CaseExpr *) expr)->casetype;
--
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