From 6942097a6406bca2c52851bbad40e5f679cc18ef Mon Sep 17 00:00:00 2001 From: Nathan Bossart Date: Wed, 3 Aug 2022 09:59:28 -0700 Subject: [PATCH v9 2/2] Optimize linear searches in XidInMVCCSnapshot(). This change makes use of the recently-introduced optimized linear search routine to speed up searches through the [sub]xip arrays when possible, which should improve performance significantly when the arrays are large. Author: Nathan Bossart Reviewed by: Andres Freund, John Naylor Discussion: https://postgr.es/m/20220713170950.GA3116318%40nathanxps13 --- src/backend/utils/time/snapmgr.c | 28 +++++++--------------------- 1 file changed, 7 insertions(+), 21 deletions(-) diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c index 5bc2a15160..9b504c9745 100644 --- a/src/backend/utils/time/snapmgr.c +++ b/src/backend/utils/time/snapmgr.c @@ -56,6 +56,7 @@ #include "datatype/timestamp.h" #include "lib/pairingheap.h" #include "miscadmin.h" +#include "port/pg_lfind.h" #include "storage/predicate.h" #include "storage/proc.h" #include "storage/procarray.h" @@ -2284,8 +2285,6 @@ RestoreTransactionSnapshot(Snapshot snapshot, void *source_pgproc) bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot) { - uint32 i; - /* * Make a quick range check to eliminate most XIDs without looking at the * xip arrays. Note that this is OK even if we convert a subxact XID to @@ -2317,13 +2316,8 @@ XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot) if (!snapshot->suboverflowed) { /* we have full data, so search subxip */ - int32 j; - - for (j = 0; j < snapshot->subxcnt; j++) - { - if (TransactionIdEquals(xid, snapshot->subxip[j])) - return true; - } + if (pg_lfind32(xid, snapshot->subxip, snapshot->subxcnt)) + return true; /* not there, fall through to search xip[] */ } @@ -2344,16 +2338,11 @@ XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot) return false; } - for (i = 0; i < snapshot->xcnt; i++) - { - if (TransactionIdEquals(xid, snapshot->xip[i])) - return true; - } + if (pg_lfind32(xid, snapshot->xip, snapshot->xcnt)) + return true; } else { - int32 j; - /* * In recovery we store all xids in the subxact array because it is by * far the bigger array, and we mostly don't know which xids are @@ -2383,11 +2372,8 @@ XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot) * indeterminate xid. We don't know whether it's top level or subxact * but it doesn't matter. If it's present, the xid is visible. */ - for (j = 0; j < snapshot->subxcnt; j++) - { - if (TransactionIdEquals(xid, snapshot->subxip[j])) - return true; - } + if (pg_lfind32(xid, snapshot->subxip, snapshot->subxcnt)) + return true; } return false; -- 2.25.1