From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 10 Apr 2005 20:58:03 +0000 (+0000)
Subject: Make constant-folding produce sane output for COALESCE(NULL,NULL),
X-Git-Tag: REL7_4_8~22
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=29028762a96741647681495fc16ede97d743107c;p=postgresql

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 d8809a5252..ae0c387e69 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.154.2.2 2004/01/28 00:05:25 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.154.2.3 2005/04/10 20:58:03 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -1553,6 +1553,10 @@ eval_const_expressions_mutator(Node *node, List *active_fns)
 			FastAppend(&newargs, e);
 		}
 
+		/* If all the arguments were constant null, the result is just null */
+		if (FastListValue(&newargs) == NIL)
+			return (Node *) makeNullConst(coalesceexpr->coalescetype);
+
 		newcoalesce = makeNode(CoalesceExpr);
 		newcoalesce->coalescetype = coalesceexpr->coalescetype;
 		newcoalesce->args = FastListValue(&newargs);