Implement subselects in target lists. Also, relax requirement that

subselects can only appear on the righthand side of a binary operator.
That's still true for quantified predicates like x = ANY (SELECT ...),
but a subselect that delivers a single result can now appear anywhere
in an expression.  This is implemented by changing EXPR_SUBLINK sublinks
to represent just the (SELECT ...) expression, without any 'left hand
side' or combining operator --- so they're now more like EXISTS_SUBLINK.
To handle the case of '(x, y, z) = (SELECT ...)', I added a new sublink
type MULTIEXPR_SUBLINK, which acts just like EXPR_SUBLINK used to.
But the grammar will only generate one for a multiple-left-hand-side
row expression.

1 files changed, 22 insertions, 8 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 22f904b60d5..89febb159b9 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -3,7 +3,7 @@
  *			  out of it's tuple
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.30 1999/11/07 23:08:24 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.31 1999/11/15 02:00:05 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -1681,15 +1681,17 @@ get_sublink_expr(Node *node, deparse_context *context)
 	StringInfo	buf = context->buf;
 	SubLink    *sublink = (SubLink *) node;
 	Query	   *query = (Query *) (sublink->subselect);
-	Oper	   *oper;
 	List	   *l;
 	char	   *sep;
+	Oper	   *oper;
+	bool		need_paren;
 
 	appendStringInfo(buf, "(");
 
-	if (sublink->lefthand != NULL)
+	if (sublink->lefthand != NIL)
 	{
-		if (length(sublink->lefthand) > 1)
+		need_paren = (length(sublink->lefthand) > 1);
+		if (need_paren)
 			appendStringInfo(buf, "(");
 
 		sep = "";
@@ -1700,12 +1702,14 @@ get_sublink_expr(Node *node, deparse_context *context)
 			get_rule_expr((Node *) lfirst(l), context);
 		}
 
-		if (length(sublink->lefthand) > 1)
+		if (need_paren)
 			appendStringInfo(buf, ") ");
 		else
 			appendStringInfo(buf, " ");
 	}
 
+	need_paren = true;
+
 	switch (sublink->subLinkType)
 	{
 		case EXISTS_SUBLINK:
@@ -1722,20 +1726,30 @@ get_sublink_expr(Node *node, deparse_context *context)
 			appendStringInfo(buf, "%s ALL ", get_opname(oper->opno));
 			break;
 
-		case EXPR_SUBLINK:
+		case MULTIEXPR_SUBLINK:
 			oper = (Oper *) lfirst(sublink->oper);
 			appendStringInfo(buf, "%s ", get_opname(oper->opno));
 			break;
 
+		case EXPR_SUBLINK:
+			need_paren = false;
+			break;
+
 		default:
 			elog(ERROR, "get_sublink_expr: unsupported sublink type %d",
 				 sublink->subLinkType);
 			break;
 	}
 
-	appendStringInfo(buf, "(");
+	if (need_paren)
+		appendStringInfo(buf, "(");
+
 	get_query_def(query, buf, context->rangetables);
-	appendStringInfo(buf, "))");
+
+	if (need_paren)
+		appendStringInfo(buf, "))");
+	else
+		appendStringInfo(buf, ")");
 }
 
 /* ----------