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Augment WAL records for btree delete with GetOldestXmin() to reduce
false positives during Hot Standby conflict processing. Simple patch to enhance conflict processing, following previous discussions. Controlled by parameter minimize_standby_conflicts = on | off, with default off allows measurement of performance impact to see whether it should be set on all the time.
This commit is contained in:
Simon Riggs
parent
d0cfc01823
commit
6d2bc0a6cf
@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.246 2010/01/26 16:33:40 tgl Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.247 2010/01/29 18:39:05 sriggs Exp $ -->
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<chapter Id="runtime-config">
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<title>Server Configuration</title>
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@ -1840,6 +1840,22 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"' # Windows
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</listitem>
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</varlistentry>
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<varlistentry id="minimize-standby-conflicts" xreflabel="minimize_standby_conflicts">
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<term><varname>minimize_standby_conflicts</varname> (<type>boolean</type>)</term>
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<indexterm>
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<primary><varname>minimize_standby_conflicts</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Generates additional information to the transaction log (WAL) to minimize
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the number of false positive cancelations caused by recovery conflicts on
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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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</variablelist>
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</sect2>
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</sect1>
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@ -9,7 +9,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.115 2010/01/02 16:57:35 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.116 2010/01/29 18:39:05 sriggs Exp $
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*
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* NOTES
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* Postgres btree pages look like ordinary relation pages. The opaque
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@ -29,6 +29,7 @@
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#include "storage/freespace.h"
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#include "storage/indexfsm.h"
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#include "storage/lmgr.h"
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#include "storage/procarray.h"
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#include "utils/inval.h"
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#include "utils/snapmgr.h"
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@ -671,9 +672,18 @@ _bt_delitems(Relation rel, Buffer buf,
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{
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Page page = BufferGetPage(buf);
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BTPageOpaque opaque;
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TransactionId latestRemovedXid = InvalidTransactionId;
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Assert(isVacuum || lastBlockVacuumed == 0);
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/*
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* If allowed, calculate an accurate latestRemovedXid, otherwise
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* pass InvalidTransactionId which can cause false positive
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* conflicts to be assessed when we replay this WAL record.
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*/
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if (!isVacuum && XLogStandbyInfoActive() && MinimizeStandbyConflicts)
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latestRemovedXid = GetOldestXmin(false, true);
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/* No ereport(ERROR) until changes are logged */
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START_CRIT_SECTION();
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@ -721,13 +731,7 @@ _bt_delitems(Relation rel, Buffer buf,
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xlrec_delete.node = rel->rd_node;
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xlrec_delete.block = BufferGetBlockNumber(buf);
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/*
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* XXX: We would like to set an accurate latestRemovedXid, but
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* there is no easy way of obtaining a useful value. So we punt
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* and store InvalidTransactionId, which forces the standby to
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* wait for/cancel all currently running transactions.
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*/
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xlrec_delete.latestRemovedXid = InvalidTransactionId;
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xlrec_delete.latestRemovedXid = latestRemovedXid;
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rdata[0].data = (char *) &xlrec_delete;
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rdata[0].len = SizeOfBtreeDelete;
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}
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@ -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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*
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.364 2010/01/28 19:17:22 heikki Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.365 2010/01/29 18:39:05 sriggs Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -71,6 +71,7 @@ bool XLogArchiveMode = false;
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char *XLogArchiveCommand = NULL;
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bool XLogRequestRecoveryConnections = true;
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int MaxStandbyDelay = 30;
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bool MinimizeStandbyConflicts = false;
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bool fullPageWrites = true;
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bool log_checkpoints = false;
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int sync_method = DEFAULT_SYNC_METHOD;
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@ -10,7 +10,7 @@
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* Written by Peter Eisentraut <peter_e@gmx.net>.
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.536 2010/01/26 16:33:40 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.537 2010/01/29 18:39:05 sriggs Exp $
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*
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*--------------------------------------------------------------------
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*/
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@ -1222,6 +1222,17 @@ static struct config_bool ConfigureNamesBool[] =
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true, NULL, NULL
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},
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{
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{"minimize_standby_conflicts", PGC_POSTMASTER, WAL_SETTINGS,
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gettext_noop("Additional information is added to WAL records to"
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" minimize the number of false positive cancelations"
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" caused by recovery conflicts on WAL standby nodes."),
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NULL
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},
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&MinimizeStandbyConflicts,
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false, NULL, NULL
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},
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{
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{"allow_system_table_mods", PGC_POSTMASTER, DEVELOPER_OPTIONS,
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gettext_noop("Allows modifications of the structure of system tables."),
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@ -181,7 +181,10 @@
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#archive_timeout = 0 # force a logfile segment switch after this
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# number of seconds; 0 disables
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# - Hot Standby -
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#recovery_connections = on # allows connections during recovery
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#minimize_standby_conflicts = on # additional WAL info to avoid conflicts
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#max_standby_delay = 30 # max acceptable standby lag (s) to help queries
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# complete without conflict; -1 disables
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@ -6,7 +6,7 @@
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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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*
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* $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.99 2010/01/28 07:31:42 heikki Exp $
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* $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.100 2010/01/29 18:39:05 sriggs Exp $
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*/
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#ifndef XLOG_H
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#define XLOG_H
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@ -183,6 +183,7 @@ extern int XLogArchiveTimeout;
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extern bool log_checkpoints;
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extern bool XLogRequestRecoveryConnections;
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extern int MaxStandbyDelay;
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extern bool MinimizeStandbyConflicts;
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#define XLogArchivingActive() (XLogArchiveMode)
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#define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0')
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