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 c24df3f38c2bbf2e0becfe0394cb92fd6b6566d1..10386dadce5cbd6a7f8ce2e71e64a0406acf9f14 100644 (file)
--- 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 */