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Commit6d2bc0a

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Augment WAL records for btree delete with GetOldestXmin() to reduce
false positives during Hot Standby conflict processing. Simplepatch to enhance conflict processing, following previous discussions.Controlled by parameter minimize_standby_conflicts = on | off, withdefault off allows measurement of performance impact to see whetherit should be set on all the time.
1 parentd0cfc01 commit6d2bc0a

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6 files changed

+48
-12
lines changed

6 files changed

+48
-12
lines changed

‎doc/src/sgml/config.sgml

Lines changed: 17 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.246 2010/01/26 16:33:40 tgl Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.247 2010/01/29 18:39:05 sriggs Exp $ -->
22

33
<chapter Id="runtime-config">
44
<title>Server Configuration</title>
@@ -1840,6 +1840,22 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"' # Windows
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</listitem>
18411841
</varlistentry>
18421842

1843+
<varlistentry id="minimize-standby-conflicts" xreflabel="minimize_standby_conflicts">
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<term><varname>minimize_standby_conflicts</varname> (<type>boolean</type>)</term>
1845+
<indexterm>
1846+
<primary><varname>minimize_standby_conflicts</> configuration parameter</primary>
1847+
</indexterm>
1848+
<listitem>
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<para>
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Generates additional information to the transaction log (WAL) to minimize
1851+
the number of false positive cancelations caused by recovery conflicts on
1852+
a standby server that consumes WAL data from this server.
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There is additional performance cost to enabling this parameter.
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Parameter has no effect during recovery, only in normal running.
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</para>
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</listitem>
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</varlistentry>
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18431859
</variablelist>
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</sect2>
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</sect1>

‎src/backend/access/nbtree/nbtpage.c

Lines changed: 12 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
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*
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*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.115 2010/01/02 16:57:35 momjian Exp $
12+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.116 2010/01/29 18:39:05 sriggs Exp $
1313
*
1414
*NOTES
1515
* Postgres btree pages look like ordinary relation pages.The opaque
@@ -29,6 +29,7 @@
2929
#include"storage/freespace.h"
3030
#include"storage/indexfsm.h"
3131
#include"storage/lmgr.h"
32+
#include"storage/procarray.h"
3233
#include"utils/inval.h"
3334
#include"utils/snapmgr.h"
3435

@@ -671,9 +672,18 @@ _bt_delitems(Relation rel, Buffer buf,
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{
672673
Pagepage=BufferGetPage(buf);
673674
BTPageOpaqueopaque;
675+
TransactionIdlatestRemovedXid=InvalidTransactionId;
674676

675677
Assert(isVacuum||lastBlockVacuumed==0);
676678

679+
/*
680+
* If allowed, calculate an accurate latestRemovedXid, otherwise
681+
* pass InvalidTransactionId which can cause false positive
682+
* conflicts to be assessed when we replay this WAL record.
683+
*/
684+
if (!isVacuum&&XLogStandbyInfoActive()&&MinimizeStandbyConflicts)
685+
latestRemovedXid=GetOldestXmin(false, true);
686+
677687
/* No ereport(ERROR) until changes are logged */
678688
START_CRIT_SECTION();
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@@ -721,13 +731,7 @@ _bt_delitems(Relation rel, Buffer buf,
721731
xlrec_delete.node=rel->rd_node;
722732
xlrec_delete.block=BufferGetBlockNumber(buf);
723733

724-
/*
725-
* XXX: We would like to set an accurate latestRemovedXid, but
726-
* there is no easy way of obtaining a useful value. So we punt
727-
* and store InvalidTransactionId, which forces the standby to
728-
* wait for/cancel all currently running transactions.
729-
*/
730-
xlrec_delete.latestRemovedXid=InvalidTransactionId;
734+
xlrec_delete.latestRemovedXid=latestRemovedXid;
731735
rdata[0].data= (char*)&xlrec_delete;
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rdata[0].len=SizeOfBtreeDelete;
733737
}

‎src/backend/access/transam/xlog.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
10-
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.364 2010/01/28 19:17:22 heikki Exp $
10+
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.365 2010/01/29 18:39:05 sriggs Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -71,6 +71,7 @@ boolXLogArchiveMode = false;
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char*XLogArchiveCommand=NULL;
7272
boolXLogRequestRecoveryConnections= true;
7373
intMaxStandbyDelay=30;
74+
boolMinimizeStandbyConflicts= false;
7475
boolfullPageWrites= true;
7576
boollog_checkpoints= false;
7677
intsync_method=DEFAULT_SYNC_METHOD;

‎src/backend/utils/misc/guc.c

Lines changed: 12 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
* Written by Peter Eisentraut <peter_e@gmx.net>.
1111
*
1212
* IDENTIFICATION
13-
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.536 2010/01/26 16:33:40 tgl Exp $
13+
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.537 2010/01/29 18:39:05 sriggs Exp $
1414
*
1515
*--------------------------------------------------------------------
1616
*/
@@ -1222,6 +1222,17 @@ static struct config_bool ConfigureNamesBool[] =
12221222
true,NULL,NULL
12231223
},
12241224

1225+
{
1226+
{"minimize_standby_conflicts",PGC_POSTMASTER,WAL_SETTINGS,
1227+
gettext_noop("Additional information is added to WAL records to"
1228+
" minimize the number of false positive cancelations"
1229+
" caused by recovery conflicts on WAL standby nodes."),
1230+
NULL
1231+
},
1232+
&MinimizeStandbyConflicts,
1233+
false,NULL,NULL
1234+
},
1235+
12251236
{
12261237
{"allow_system_table_mods",PGC_POSTMASTER,DEVELOPER_OPTIONS,
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gettext_noop("Allows modifications of the structure of system tables."),

‎src/backend/utils/misc/postgresql.conf.sample

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -181,7 +181,10 @@
181181
#archive_timeout = 0# force a logfile segment switch after this
182182
# number of seconds; 0 disables
183183

184+
# - Hot Standby -
185+
184186
#recovery_connections = on# allows connections during recovery
187+
#minimize_standby_conflicts = on # additional WAL info to avoid conflicts
185188
#max_standby_delay = 30# max acceptable standby lag (s) to help queries
186189
# complete without conflict; -1 disables
187190

‎src/include/access/xlog.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
9-
* $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.99 2010/01/28 07:31:42 heikki Exp $
9+
* $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.100 2010/01/29 18:39:05 sriggs Exp $
1010
*/
1111
#ifndefXLOG_H
1212
#defineXLOG_H
@@ -183,6 +183,7 @@ extern intXLogArchiveTimeout;
183183
externboollog_checkpoints;
184184
externboolXLogRequestRecoveryConnections;
185185
externintMaxStandbyDelay;
186+
externboolMinimizeStandbyConflicts;
186187

187188
#defineXLogArchivingActive()(XLogArchiveMode)
188189
#defineXLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0')

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