From fe546f3da6a5ff1d879f587728f74ec457f0ee5f Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Tue, 17 Apr 2012 16:28:31 +0300
Subject: [PATCH] Don't wait for the commit record to be replicated if we wrote
 no WAL.

When using synchronous replication, we waited for the commit record to be
replicated, but if we our transaction didn't write any other WAL records,
that's not required because we don't even flush the WAL locally to disk in
that case. This lead to long waits when committing a transaction that only
modified a temporary table. Bug spotted by Thom Brown.
---
 src/backend/access/transam/xact.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e22bdacbba2..d8523f37b2f 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1168,7 +1168,8 @@ RecordTransactionCommit(void)
 	 * Note that at this stage we have marked clog, but still show as running
 	 * in the procarray and continue to hold locks.
 	 */
-	SyncRepWaitForLSN(XactLastRecEnd);
+	if (wrote_xlog)
+		SyncRepWaitForLSN(XactLastRecEnd);
 
 	/* Reset XactLastRecEnd until the next transaction writes something */
 	XactLastRecEnd.xrecoff = 0;
-- 
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