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Commita255557

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Optimise btree delete processing when no active backends.
Clarify comments, downgrade a message to DEBUG and remove somedebug counters. Direct from ideas by Heikki Linnakangas.
1 parent781ec6b commita255557

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3 files changed

+22
-23
lines changed

3 files changed

+22
-23
lines changed

‎src/backend/access/nbtree/nbtxlog.c‎

Lines changed: 16 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.66 2010/04/19 17:54:48 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.67 2010/04/22 08:04:24 sriggs Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -578,9 +578,17 @@ btree_xlog_delete_get_latestRemovedXid(XLogRecord *record)
578578
OffsetNumberhoffnum;
579579
TransactionIdlatestRemovedXid=InvalidTransactionId;
580580
TransactionIdhtupxid=InvalidTransactionId;
581-
intnum_unused=0,num_redirect=0,num_dead=0;
582581
inti;
583582

583+
/*
584+
* If there's nothing running on the standby we don't need to derive
585+
* a full latestRemovedXid value, so use a fast path out of here.
586+
* That returns InvalidTransactionId, and so will conflict with
587+
* users, but since we just worked out that's zero people, its OK.
588+
*/
589+
if (CountDBBackends(InvalidOid)==0)
590+
returnlatestRemovedXid;
591+
584592
/*
585593
* Get index page
586594
*/
@@ -629,7 +637,6 @@ btree_xlog_delete_get_latestRemovedXid(XLogRecord *record)
629637
*/
630638
while (ItemIdIsRedirected(hitemid))
631639
{
632-
num_redirect++;
633640
hoffnum=ItemIdGetRedirect(hitemid);
634641
hitemid=PageGetItemId(hpage,hoffnum);
635642
CHECK_FOR_INTERRUPTS();
@@ -662,25 +669,23 @@ btree_xlog_delete_get_latestRemovedXid(XLogRecord *record)
662669
* marked on LP_NORMAL items. So we just ignore this item and move
663670
* onto the next, for the purposes of calculating latestRemovedxids.
664671
*/
665-
num_dead++;
666672
}
667673
else
668-
{
669674
Assert(!ItemIdIsUsed(hitemid));
670-
num_unused++;
671-
}
672675

673676
UnlockReleaseBuffer(hbuffer);
674677
}
675678

676679
UnlockReleaseBuffer(ibuffer);
677680

678-
Assert(num_unused==0);
679-
680681
/*
681682
* Note that if all heap tuples were LP_DEAD then we will be
682-
* returning InvalidTransactionId here. This seems very unlikely
683-
* in practice.
683+
* returning InvalidTransactionId here. That can happen if we are
684+
* re-replaying this record type, though that will be before the
685+
* consistency point and will not cause problems. It should
686+
* happen very rarely after the consistency point, though note
687+
* that we can't tell the difference between this and the fast
688+
* path exit above. May need to change that in future.
684689
*/
685690
returnlatestRemovedXid;
686691
}
@@ -963,13 +968,6 @@ btree_redo(XLogRecPtr lsn, XLogRecord *record)
963968
TransactionIdlatestRemovedXid=btree_xlog_delete_get_latestRemovedXid(record);
964969
xl_btree_delete*xlrec= (xl_btree_delete*)XLogRecGetData(record);
965970

966-
/*
967-
* XXX Currently we put everybody on death row, because
968-
* currently _bt_delitems() supplies InvalidTransactionId.
969-
* This can be fairly painful, so providing a better value
970-
* here is worth some thought and possibly some effort to
971-
* improve.
972-
*/
973971
ResolveRecoveryConflictWithSnapshot(latestRemovedXid,xlrec->node);
974972
}
975973
break;

‎src/backend/storage/ipc/procarray.c‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,7 @@
3737
*
3838
*
3939
* IDENTIFICATION
40-
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.65 2010/04/21 19:08:14 sriggs Exp $
40+
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.66 2010/04/2208:04:25 sriggs Exp $
4141
*
4242
*-------------------------------------------------------------------------
4343
*/
@@ -1839,7 +1839,8 @@ CountDBBackends(Oid databaseid)
18391839

18401840
if (proc->pid==0)
18411841
continue;/* do not count prepared xacts */
1842-
if (proc->databaseId==databaseid)
1842+
if (!OidIsValid(databaseid)||
1843+
proc->databaseId==databaseid)
18431844
count++;
18441845
}
18451846

‎src/backend/storage/ipc/standby.c‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
* Portions Copyright (c) 1994, Regents of the University of California
1212
*
1313
* IDENTIFICATION
14-
* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.17 2010/04/21 19:08:14 sriggs Exp $
14+
* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.18 2010/04/2208:04:25 sriggs Exp $
1515
*
1616
*-------------------------------------------------------------------------
1717
*/
@@ -248,15 +248,15 @@ ResolveRecoveryConflictWithSnapshot(TransactionId latestRemovedXid, RelFileNode
248248

249249
/*
250250
* If we get passed InvalidTransactionId then we are a little surprised,
251-
* but it is theoretically possible, so spit out aLOG message, but not
251+
* but it is theoretically possible, so spit out aDEBUG1 message, but not
252252
* one that needs translating.
253253
*
254254
* We grab latestCompletedXid instead because this is the very latest
255255
* value it could ever be.
256256
*/
257257
if (!TransactionIdIsValid(latestRemovedXid))
258258
{
259-
elog(LOG,"InvalidlatestRemovedXid reported, usinglatestCompletedXid instead");
259+
elog(DEBUG1,"InvalidlatestremovexXid reported, usinglatestcompletedxid instead");
260260

261261
LWLockAcquire(ProcArrayLock,LW_SHARED);
262262
latestRemovedXid=ShmemVariableCache->latestCompletedXid;

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