From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 6 Jan 2009 02:01:27 +0000 (+0000)
Subject: Add some comments about why function parameter default expressions are
X-Git-Tag: REL8_4_BETA1~470
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9f910a3b9aeab5a79142860eea53747c1f321aa3;p=postgresql

Add some comments about why function parameter default expressions are
restricted.
---

diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index 91b65b3a58..a813fd9a02 100644
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/functioncmds.c,v 1.106 2009/01/01 17:23:38 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/functioncmds.c,v 1.107 2009/01/06 02:01:27 tgl Exp $
  *
  * DESCRIPTION
  *	  These routines take the parse tree and pick out the
@@ -311,7 +311,15 @@ examine_parameter_list(List *parameters, Oid languageOid,
 						 errmsg("cannot use table references in parameter default value")));
 
 			/*
+			 * It can't return a set either --- but coerce_to_specific_type
+			 * already checked that for us.
+			 *
 			 * No subplans or aggregates, either...
+			 *
+			 * Note: the point of these restrictions is to ensure that an
+			 * expression that, on its face, hasn't got subplans, aggregates,
+			 * etc cannot suddenly have them after function default arguments
+			 * are inserted.
 			 */
 			if (pstate->p_hasSubLinks)
 				ereport(ERROR,