From db2687d1f3787aa8113b3dbb358153feee30c64c Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Mon, 11 Nov 2019 16:34:01 +1300 Subject: [PATCH] Optimize PredicateLockTuple(). PredicateLockTuple() has a fast exit if tuple was written by the current transaction, as in that case it already has a lock. This check can be performed using TransactionIdIsCurrentTransactionId() instead of SubTransGetTopmostTransaction(), to avoid any chance of having to hit the disk. Author: Ashwin Agrawal, based on a suggestion from Andres Freund Reviewed-by: Thomas Munro Discussion: https://postgr.es/m/CALfoeiv0k3hkEb3Oqk%3DziWqtyk2Jys1UOK5hwRBNeANT_yX%2Bng%40mail.gmail.com --- src/backend/storage/lmgr/predicate.c | 22 +++------------------- 1 file changed, 3 insertions(+), 19 deletions(-) diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c index 78fb90fb1b..86b46d68b9 100644 --- a/src/backend/storage/lmgr/predicate.c +++ b/src/backend/storage/lmgr/predicate.c @@ -2549,7 +2549,6 @@ PredicateLockTuple(Relation relation, HeapTuple tuple, Snapshot snapshot) { PREDICATELOCKTARGETTAG tag; ItemPointer tid; - TransactionId targetxmin; if (!SerializationNeededForRead(relation, snapshot)) return; @@ -2559,24 +2558,9 @@ PredicateLockTuple(Relation relation, HeapTuple tuple, Snapshot snapshot) */ if (relation->rd_index == NULL) { - TransactionId myxid; - - targetxmin = HeapTupleHeaderGetXmin(tuple->t_data); - - myxid = GetTopTransactionIdIfAny(); - if (TransactionIdIsValid(myxid)) - { - if (TransactionIdFollowsOrEquals(targetxmin, TransactionXmin)) - { - TransactionId xid = SubTransGetTopmostTransaction(targetxmin); - - if (TransactionIdEquals(xid, myxid)) - { - /* We wrote it; we already have a write lock. */ - return; - } - } - } + /* If we wrote it; we already have a write lock. */ + if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetXmin(tuple->t_data))) + return; } /*