Make RecordTransactionCommit() respect wal_level.

Since the only purpose of WAL-loggin SharedInvalidationMessages is to support
Hot Standby operation, they needn't be included when wal_level < hot_standby.

Back-patch to 9.0.

Review by Heikki Linnakanagas and Fujii Masao.

src/backend/access/transam/xact.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.296 2010/08/12 23:24:53 rhaas Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.297 2010/08/13 15:42:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -915,13 +915,14 @@ RecordTransactionCommit(void)
 	bool		haveNonTemp;
 	int			nchildren;
 	TransactionId *children;
-	int			nmsgs;
+	int			nmsgs = 0;
 	SharedInvalidationMessage *invalMessages = NULL;
-	bool		RelcacheInitFileInval;
+	bool		RelcacheInitFileInval = false;
 
 	/* Get data needed for commit record */
 	nrels = smgrGetPendingDeletes(true, &rels, &haveNonTemp);
 	nchildren = xactGetCommittedChildren(&children);
+	if (XLogStandbyInfoActive())
 		nmsgs = xactGetCommittedInvalidationMessages(&invalMessages,
 													 &RelcacheInitFileInval);