From: Simon Riggs <simon@2ndQuadrant.com>
Date: Tue, 13 Nov 2012 19:00:19 +0000 (-0300)
Subject: Skip searching for subxact locks at commit.
X-Git-Tag: REL9_3_BETA1~718
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d9fad1076da4f3686b16e7c9f137118a3156a43a;p=thirdparty%2Fpostgresql.git

Skip searching for subxact locks at commit.
At commit all standby locks are released
for the top-level transaction, so searching
for locks for each subtransaction is both
pointless and costly (N^2) in the presence
of many AccessExclusiveLocks.
---

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index c24df3f38c2..10386dadce5 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -4609,9 +4609,11 @@ xact_redo_commit_internal(TransactionId xid, XLogRecPtr lsn,
 		/*
 		 * Release locks, if any. We do this for both two phase and normal one
 		 * phase transactions. In effect we are ignoring the prepare phase and
-		 * just going straight to lock release.
+		 * just going straight to lock release. At commit we release all locks
+		 * via their top-level xid only, so no need to provide subxact list,
+		 * which will save time when replaying commits.
 		 */
-		StandbyReleaseLockTree(xid, nsubxacts, sub_xids);
+		StandbyReleaseLockTree(xid, 0, NULL);
 	}
 
 	/* Make sure files supposed to be dropped are dropped */