From d474e7b41298944e43bb9141eb33adbdd9ea1098 Mon Sep 17 00:00:00 2001
From: Laurenz Albe <laurenz.albe@cybertec.at>
Date: Tue, 22 May 2018 18:13:31 +0200
Subject: [PATCH] Don't log locks on unlogged tables

---
 src/backend/storage/lmgr/lock.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c
index dc3d8d9817..70cac47ab3 100644
--- a/src/backend/storage/lmgr/lock.c
+++ b/src/backend/storage/lmgr/lock.c
@@ -37,6 +37,7 @@
 #include "access/twophase_rmgr.h"
 #include "access/xact.h"
 #include "access/xlog.h"
+#include "catalog/pg_class.h"
 #include "miscadmin.h"
 #include "pg_trace.h"
 #include "pgstat.h"
@@ -47,6 +48,7 @@
 #include "storage/standby.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
+#include "utils/rel.h"
 #include "utils/resowner_private.h"
 
 
@@ -1041,13 +1043,25 @@ LockAcquireExtended(const LOCKTAG *locktag,
 	 */
 	if (log_lock)
 	{
-		/*
-		 * Decode the locktag back to the original values, to avoid sending
-		 * lots of empty bytes with every message.  See lock.h to check how a
-		 * locktag is defined for LOCKTAG_RELATION
-		 */
-		LogAccessExclusiveLock(locktag->locktag_field1,
-							   locktag->locktag_field2);
+		bool unlogged_rel = false;
+
+		if (locktag->locktag_type == LOCKTAG_RELATION)
+		{
+			Relation r = RelationIdGetRelation(locktag->locktag_field2);
+			unlogged_rel = r->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED;
+			RelationClose(r);
+		}
+
+		if (!unlogged_rel)
+		{
+			/*
+			 * Decode the locktag back to the original values, to avoid sending
+			 * lots of empty bytes with every message.  See lock.h to check how a
+			 * locktag is defined for LOCKTAG_RELATION
+			 */
+			LogAccessExclusiveLock(locktag->locktag_field1,
+								   locktag->locktag_field2);
+		}
 	}
 
 	return LOCKACQUIRE_OK;
-- 
2.14.3