diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 09cc7860e0c73b1b61d94915c16d86e6c4fb46ee..699493c3350e07f9100cadbed6d4223932286ec0 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.244 2009/01/21 09:28:26 mha Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.245 2009/01/22 19:16:31 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -992,12 +992,14 @@ renametrig(Oid relid,
 /*
  * EnableDisableTrigger()
  *
- *	Called by ALTER TABLE ENABLE/DISABLE TRIGGER
+ *	Called by ALTER TABLE ENABLE/DISABLE [ REPLICA | ALWAYS ] TRIGGER
  *	to change 'tgenabled' field for the specified trigger(s)
  *
  * rel: relation to process (caller must hold suitable lock on it)
  * tgname: trigger to process, or NULL to scan all triggers
- * enable: new value for tgenabled field
+ * fires_when: new value for tgenabled field. In addition to generic
+ *			   enablement/disablement, this also defines when the trigger
+ *			   should be fired in session replication roles.
  * skip_system: if true, skip "system" triggers (constraint triggers)
  *
  * Caller should have checked permissions for the table; here we also
diff --git a/src/include/commands/trigger.h b/src/include/commands/trigger.h
index 50f11078a5066b916bb393d23a994eaecfad97b1..0b0c6c22323265b3b4d9b6de653d00332bdbd531 100644
--- a/src/include/commands/trigger.h
+++ b/src/include/commands/trigger.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/trigger.h,v 1.70 2009/01/01 17:23:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/commands/trigger.h,v 1.71 2009/01/22 19:16:31 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -95,6 +95,10 @@ typedef struct TriggerData
 #define SESSION_REPLICATION_ROLE_LOCAL		2
 extern PGDLLIMPORT int	SessionReplicationRole;
 
+/*
+ * States at which a trigger can be fired. These are the
+ * possible values for pg_trigger.tgenabled.
+ */
 #define TRIGGER_FIRES_ON_ORIGIN				'O'
 #define TRIGGER_FIRES_ALWAYS				'A'
 #define TRIGGER_FIRES_ON_REPLICA			'R'