Revert changes to CREATE TRIGGER and ALTER TABLE ADD FOREIGN KEY locking,

per request from Tom.

2 files changed, 9 insertions, 16 deletions

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 1a6c1f82625..7c19bcd3363 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.149 2005/03/23 07:44:57 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.150 2005/03/24 00:03:22 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3829,13 +3829,13 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 	Oid			constrOid;
 
 	/*
-	 * Grab a lock on the pk table, so that someone doesn't delete
-	 * rows out from under us. We will eventually need to add triggers
-	 * to the table, at which point we'll need to an ExclusiveLock --
-	 * therefore we grab an ExclusiveLock now to prevent possible
-	 * deadlock.
+	 * Grab an exclusive lock on the pk table, so that someone doesn't
+	 * delete rows out from under us. (Although a lesser lock would do for
+	 * that purpose, we'll need exclusive lock anyway to add triggers to
+	 * the pk table; trying to start with a lesser lock will just create a
+	 * risk of deadlock.)
 	 */
-	pkrel = heap_openrv(fkconstraint->pktable, ExclusiveLock);
+	pkrel = heap_openrv(fkconstraint->pktable, AccessExclusiveLock);
 
 	/*
 	 * Validity and permissions checks
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 55333e1f4f1..54e0eac2688 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 1.179 2005/03/23 07:44:57 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.180 2005/03/24 00:03:26 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -87,14 +87,7 @@ CreateTrigger(CreateTrigStmt *stmt, bool forConstraint)
 	ObjectAddress myself,
 				referenced;
 
-    /*
-     * We need to prevent concurrent CREATE TRIGGER commands, as well
-     * as concurrent table modifications (INSERT, DELETE, UPDATE), so
-     * acquire an ExclusiveLock -- it should be fine to allow SELECTs
-     * to proceed. We could perhaps acquire ShareRowExclusiveLock, but
-     * there seems little gain in allowing SELECT FOR UPDATE.
-     */
-	rel = heap_openrv(stmt->relation, ExclusiveLock);
+	rel = heap_openrv(stmt->relation, AccessExclusiveLock);
 
 	if (stmt->constrrel != NULL)
 		constrrelid = RangeVarGetRelid(stmt->constrrel, false);