From 14ff44f80c09718d43d853363941457f5468cc03 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 22 Sep 2022 09:47:28 +0900
Subject: [PATCH] Used optimized linear search in more code paths
This commit updates two code paths to use pg_lfind32() introduced by
b6ef167 with TransactionId arrays:
- At the end of TransactionIdIsInProgress(), when checking for the case
of still running but overflowed subxids.
- XidIsConcurrent(), when checking for a serializable conflict.
These cases are less impactful than 37a6e5d, but a bit of
micro-benchmarking of this API shows that linear search speeds up by
~20% depending on the number of items involved (x86_64 and amd64 looked
at here).
Author: Nathan Bossart
Reviewed-by: Richard Guo, Michael Paquier
Discussion: https://postgr.es/m/20220901185153.GA783106@nathanxps13
---
src/backend/storage/ipc/procarray.c | 12 ++++--------
src/backend/storage/lmgr/predicate.c | 10 ++--------
2 files changed, 6 insertions(+), 16 deletions(-)
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 382f4cfb736..207c4b27fdf 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -58,6 +58,7 @@
#include "commands/dbcommands.h"
#include "miscadmin.h"
#include "pgstat.h"
+#include "port/pg_lfind.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/spin.h"
@@ -1586,14 +1587,9 @@ TransactionIdIsInProgress(TransactionId xid)
*/
topxid = SubTransGetTopmostTransaction(xid);
Assert(TransactionIdIsValid(topxid));
- if (!TransactionIdEquals(topxid, xid))
- {
- for (int i = 0; i < nxids; i++)
- {
- if (TransactionIdEquals(xids[i], topxid))
- return true;
- }
- }
+ if (!TransactionIdEquals(topxid, xid) &&
+ pg_lfind32(topxid, xids, nxids))
+ return true;
cachedXidIsNotInProgress = xid;
return false;
diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index 5f2a4805d82..e8120174d61 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -202,6 +202,7 @@
#include "access/xlog.h"
#include "miscadmin.h"
#include "pgstat.h"
+#include "port/pg_lfind.h"
#include "storage/bufmgr.h"
#include "storage/predicate.h"
#include "storage/predicate_internals.h"
@@ -4065,7 +4066,6 @@ static bool
XidIsConcurrent(TransactionId xid)
{
Snapshot snap;
- uint32 i;
Assert(TransactionIdIsValid(xid));
Assert(!TransactionIdEquals(xid, GetTopTransactionIdIfAny()));
@@ -4078,13 +4078,7 @@ XidIsConcurrent(TransactionId xid)
if (TransactionIdFollowsOrEquals(xid, snap->xmax))
return true;
- for (i = 0; i < snap->xcnt; i++)
- {
- if (xid == snap->xip[i])
- return true;
- }
-
- return false;
+ return pg_lfind32(xid, snap->xip, snap->xcnt);
}
bool