From: Simon Riggs <simon@2ndQuadrant.com>
Date: Tue, 13 Nov 2012 19:12:20 +0000 (-0300)
Subject: Skip searching for subxact locks at commit.
X-Git-Tag: REL9_2_2~37
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=31541778b612fd59257a2bf571229f400d35ecf0;p=postgresql

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 5f85fe2011..58bb28177d 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -4629,9 +4629,11 @@ 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 */