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Used optimized linear search in more code paths

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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
This commit is contained in:
Michael Paquier 2022-09-22 09:47:28 +09:00
parent 9a6915257d
commit 14ff44f80c
2 changed files with 6 additions and 16 deletions
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12
src/backend/storage/ipc/procarray.c
View File

@ -58,6 +58,7 @@
#include "commands/dbcommands.h" #include "commands/dbcommands.h"
#include "miscadmin.h" #include "miscadmin.h"
#include "pgstat.h" #include "pgstat.h"
#include "port/pg_lfind.h"
#include "storage/proc.h" #include "storage/proc.h"
#include "storage/procarray.h" #include "storage/procarray.h"
#include "storage/spin.h" #include "storage/spin.h"
@ -1586,14 +1587,9 @@ TransactionIdIsInProgress(TransactionId xid)
*/ */
topxid = SubTransGetTopmostTransaction(xid); topxid = SubTransGetTopmostTransaction(xid);
Assert(TransactionIdIsValid(topxid)); Assert(TransactionIdIsValid(topxid));
if (!TransactionIdEquals(topxid, xid)) if (!TransactionIdEquals(topxid, xid) &&
{ pg_lfind32(topxid, xids, nxids))
for (int i = 0; i < nxids; i++) return true;
{
if (TransactionIdEquals(xids[i], topxid))
return true;
}
}
cachedXidIsNotInProgress = xid; cachedXidIsNotInProgress = xid;
return false; return false;

10
src/backend/storage/lmgr/predicate.c
View File

@ -202,6 +202,7 @@
#include "access/xlog.h" #include "access/xlog.h"
#include "miscadmin.h" #include "miscadmin.h"
#include "pgstat.h" #include "pgstat.h"
#include "port/pg_lfind.h"
#include "storage/bufmgr.h" #include "storage/bufmgr.h"
#include "storage/predicate.h" #include "storage/predicate.h"
#include "storage/predicate_internals.h" #include "storage/predicate_internals.h"
@ -4065,7 +4066,6 @@ static bool
XidIsConcurrent(TransactionId xid) XidIsConcurrent(TransactionId xid)
{ {
Snapshot snap; Snapshot snap;
uint32 i;
Assert(TransactionIdIsValid(xid)); Assert(TransactionIdIsValid(xid));
Assert(!TransactionIdEquals(xid, GetTopTransactionIdIfAny())); Assert(!TransactionIdEquals(xid, GetTopTransactionIdIfAny()));
@ -4078,13 +4078,7 @@ XidIsConcurrent(TransactionId xid)
if (TransactionIdFollowsOrEquals(xid, snap->xmax)) if (TransactionIdFollowsOrEquals(xid, snap->xmax))
return true; return true;
for (i = 0; i < snap->xcnt; i++) return pg_lfind32(xid, snap->xip, snap->xcnt);
{
if (xid == snap->xip[i])
return true;
}
return false;
} }
bool bool