From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 10 Apr 2005 20:57:45 +0000 (+0000)
Subject: Make constant-folding produce sane output for COALESCE(NULL,NULL),
X-Git-Tag: REL8_0_3~48
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=88b229d9076748e09124c3ffae2987cf4ecd9ca3;p=thirdparty%2Fpostgresql.git

Make constant-folding produce sane output for COALESCE(NULL,NULL),
that is a plain NULL and not a COALESCE with no inputs.  Fixes crash
reported by Michael Williamson.
---

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index c6057687b8f..a43256cc1f2 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.186.4.2 2005/02/02 21:49:43 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.186.4.3 2005/04/10 20:57:45 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -1771,6 +1771,10 @@ eval_const_expressions_mutator(Node *node,
 			newargs = lappend(newargs, e);
 		}
 
+		/* If all the arguments were constant null, the result is just null */
+		if (newargs == NIL)
+			return (Node *) makeNullConst(coalesceexpr->coalescetype);
+
 		newcoalesce = makeNode(CoalesceExpr);
 		newcoalesce->coalescetype = coalesceexpr->coalescetype;
 		newcoalesce->args = newargs;