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: recoveryinfrav9~126
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=ab5aad3c30585ae3ce773e989a85d38d9c50047a;p=users%2Fsimon%2Fpostgres.git

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 91a3cd8e73..c0542ef3d6 100644
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -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,