Implement COMMIT_SIBLINGS parameter to allow pre-commit delay to occur
only if at least N other backends currently have open transactions. This is not a great deal of intelligence about whether a delay might be profitable ... but it beats no intelligence at all. Note that the default COMMIT_DELAY is still zero --- this new code does nothing unless that setting is changed. Also, mark ENABLEFSYNC as a system-wide setting. It's no longer safe to allow that to be set per-backend, since we may be relying on some other backend's fsync to have synced the WAL log.
This commit is contained in:
Tom Lane
parent
60774e8210
commit
9c9936587c
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@ -1,4 +1,4 @@
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<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.2 2001/02/18 04:50:43 tgl Exp $ -->
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<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.3 2001/02/26 00:50:07 tgl Exp $ -->
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<chapter id="wal">
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<title>Write-Ahead Logging (<acronym>WAL</acronym>)</title>
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@ -295,10 +295,13 @@
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record to the log with <function>LogInsert</function> but before
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performing a <function>LogFlush</function>. This delay allows other
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backends to add their commit records to the log so as to have all
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of them flushed with a single log sync. Unfortunately, this
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mechanism is not fully implemented at release 7.1, so there is at
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present usually no benefit to be gained from increasing this parameter
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above its default value of zero.
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of them flushed with a single log sync. No sleep will occur if fsync
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is not enabled or if fewer than <varname>COMMIT_SIBLINGS</varname>
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other backends are not currently in active transactions; this avoids
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sleeping when it's unlikely that any other backend will commit soon.
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Note that on most platforms, the resolution of a sleep request is
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ten milliseconds, so that any nonzero <varname>COMMIT_DELAY</varname>
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setting between 1 and 10000 microseconds will have the same effect.
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</para>
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</sect1>
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</chapter>
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.97 2001/02/18 04:50:43 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.98 2001/02/26 00:50:07 tgl Exp $
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*
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* NOTES
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* Transaction aborts can now occur two ways:
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@ -157,6 +157,7 @@
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#include <sys/time.h>
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#include "access/nbtree.h"
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#include "access/xact.h"
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#include "catalog/heap.h"
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#include "catalog/index.h"
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#include "commands/async.h"
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@ -177,8 +178,6 @@
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extern bool SharedBufferChanged;
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void RecordTransactionCommit(void);
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static void AbortTransaction(void);
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static void AtAbort_Cache(void);
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static void AtAbort_Locks(void);
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@ -216,12 +215,14 @@ TransactionStateData CurrentTransactionStateData = {
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TransactionState CurrentTransactionState = &CurrentTransactionStateData;
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/*
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* User-tweakable parameters
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*/
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int DefaultXactIsoLevel = XACT_READ_COMMITTED;
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int XactIsoLevel;
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#include "access/xlogutils.h"
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int CommitDelay = 0; /* in microseconds */
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int CommitDelay = 0; /* precommit delay in microseconds */
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int CommitSiblings = 5; /* number of concurrent xacts needed to sleep */
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static void (*_RollbackFunc)(void*) = NULL;
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static void *_RollbackData = NULL;
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@ -687,10 +688,15 @@ RecordTransactionCommit()
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* Sleep before commit! So we can flush more than one
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* commit records per single fsync. (The idea is some other
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* backend may do the XLogFlush while we're sleeping. This
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* needs work however, because on most Unixen, the minimum
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* needs work still, because on most Unixen, the minimum
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* select() delay is 10msec or more, which is way too long.)
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*
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* We do not sleep if enableFsync is not turned on, nor if there
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* are fewer than CommitSiblings other backends with active
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* transactions.
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*/
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if (CommitDelay > 0)
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if (CommitDelay > 0 && enableFsync &&
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CountActiveBackends() >= CommitSiblings)
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{
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struct timeval delay;
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@ -6,7 +6,7 @@
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* Portions Copyright (c) 1996-2001, 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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* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.54 2001/02/18 04:39:42 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.55 2001/02/26 00:50:07 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -2096,8 +2096,6 @@ ShutdownXLOG()
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elog(LOG, "database system is shut down");
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}
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extern XLogRecPtr GetUndoRecPtr(void);
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void
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CreateCheckPoint(bool shutdown)
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{
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@ -8,16 +8,14 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.25 2001/01/24 19:43:07 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.26 2001/02/26 00:50:07 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/* #define INVALIDDEBUG 1 */
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#include "postgres.h"
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#include <sys/types.h>
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#include "postgres.h"
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#include "storage/backendid.h"
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#include "storage/proc.h"
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#include "storage/sinval.h"
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@ -347,11 +345,54 @@ GetSnapshotData(bool serializable)
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return snapshot;
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}
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/*
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* CountActiveBackends --- count backends (other than myself) that are in
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* active transactions. This is used as a heuristic to decide if
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* a pre-XLOG-flush delay is worthwhile during commit.
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*
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* An active transaction is something that has written at least one XLOG
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* record; read-only transactions don't count. Also, do not count backends
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* that are blocked waiting for locks, since they are not going to get to
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* run until someone else commits.
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*/
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int
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CountActiveBackends(void)
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{
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SISeg *segP = shmInvalBuffer;
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ProcState *stateP = segP->procState;
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int count = 0;
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int index;
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/*
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* Note: for speed, we don't acquire SInvalLock. This is a little bit
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* bogus, but since we are only testing xrecoff for zero or nonzero,
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* it should be OK. The result is only used for heuristic purposes
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* anyway...
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*/
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for (index = 0; index < segP->lastBackend; index++)
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{
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SHMEM_OFFSET pOffset = stateP[index].procStruct;
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if (pOffset != INVALID_OFFSET)
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{
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PROC *proc = (PROC *) MAKE_PTR(pOffset);
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if (proc == MyProc)
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continue; /* do not count myself */
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if (proc->logRec.xrecoff == 0)
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continue; /* do not count if not in a transaction */
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if (proc->waitLock != NULL)
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continue; /* do not count if blocked on a lock */
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count++;
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}
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}
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return count;
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}
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/*
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* GetUndoRecPtr -- returns oldest PROC->logRec.
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*/
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XLogRecPtr GetUndoRecPtr(void);
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XLogRecPtr
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GetUndoRecPtr(void)
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{
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@ -4,7 +4,7 @@
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* Support for grand unified configuration scheme, including SET
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* command, configuration file, and command line options.
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*
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* $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.30 2001/02/18 04:50:43 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.31 2001/02/26 00:50:07 tgl Exp $
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*
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* Copyright 2000 by PostgreSQL Global Development Group
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* Written by Peter Eisentraut <peter_e@gmx.net>.
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@ -41,6 +41,7 @@ extern int XLOGbuffers;
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extern int XLOGfiles;
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extern int XLOG_DEBUG;
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extern int CommitDelay;
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extern int CommitSiblings;
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extern bool FixBTree;
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@ -181,7 +182,7 @@ ConfigureNamesBool[] =
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{"tcpip_socket", PGC_POSTMASTER, &NetServer, false},
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{"ssl", PGC_POSTMASTER, &EnableSSL, false},
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{"fsync", PGC_USERSET, &enableFsync, true},
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{"fsync", PGC_SIGHUP, &enableFsync, true},
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{"silent_mode", PGC_POSTMASTER, &SilentMode, false},
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{"log_connections", PGC_SIGHUP, &Log_connections, false},
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@ -279,7 +280,7 @@ ConfigureNamesInt[] =
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0777, 0000, 0777},
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{"checkpoint_timeout", PGC_POSTMASTER, &CheckPointTimeout,
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300, 30, 1800},
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300, 30, 3600},
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{"wal_buffers", PGC_POSTMASTER, &XLOGbuffers,
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8, 4, INT_MAX},
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{"commit_delay", PGC_USERSET, &CommitDelay,
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0, 0, 100000},
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{"commit_siblings", PGC_USERSET, &CommitSiblings,
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5, 1, 1000},
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{NULL, 0, NULL, 0, 0, 0}
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};
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@ -109,7 +109,8 @@
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#wal_files = 0 # range 0-64
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#wal_debug = 0 # range 0-16
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#commit_delay = 0 # range 0-100000
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#checkpoint_timeout = 300 # range 30-1800
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#commit_siblings = 5 # range 1-1000
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#checkpoint_timeout = 300 # in seconds, range 30-3600
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#
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@ -3,7 +3,7 @@
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*
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* Copyright 2000 by PostgreSQL Global Development Group
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*
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* $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.26 2001/02/10 02:31:28 tgl Exp $
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* $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.27 2001/02/26 00:50:07 tgl Exp $
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*/
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/*----------------------------------------------------------------------
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@ -241,6 +241,7 @@ psql_completion(char *text, int start, int end)
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"debug_level",
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"max_expr_depth",
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"commit_delay",
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"commit_siblings",
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"effective_cache_size",
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"random_page_cost",
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@ -3,7 +3,7 @@
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*
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* PostgreSQL transaction log manager
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*
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* $Header: /cvsroot/pgsql/src/include/access/xlog.h,v 1.17 2001/01/14 05:08:16 tgl Exp $
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* $Header: /cvsroot/pgsql/src/include/access/xlog.h,v 1.18 2001/02/26 00:50:07 tgl Exp $
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*/
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#ifndef XLOG_H
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#define XLOG_H
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@ -146,4 +146,9 @@ extern void ShutdownXLOG(void);
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extern void CreateCheckPoint(bool shutdown);
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extern void SetThisStartUpID(void);
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/* in storage/ipc/sinval.c, but don't want to declare in sinval.h because
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* we'd have to include xlog.h into that ...
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*/
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extern XLogRecPtr GetUndoRecPtr(void);
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#endif /* XLOG_H */
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2001, 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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* $Id: proc.h,v 1.39 2001/01/25 03:31:16 tgl Exp $
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* $Id: proc.h,v 1.40 2001/02/26 00:50:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -50,6 +50,10 @@ struct proc
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* were starting our xact: vacuum must not
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* remove tuples deleted by xid >= xmin ! */
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/* XLOG location of first XLOG record written by this backend's current
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* transaction. If backend is not in a transaction or hasn't yet modified
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* anything, logRec.xrecoff is zero.
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*/
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XLogRecPtr logRec;
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/* Info about lock the process is currently waiting for, if any. */
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2001, 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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* $Id: sinval.h,v 1.17 2001/01/24 19:43:28 momjian Exp $
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* $Id: sinval.h,v 1.18 2001/02/26 00:50:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -30,6 +30,6 @@ extern void InvalidateSharedInvalid(void (*invalFunction) (),
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extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
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extern bool TransactionIdIsInProgress(TransactionId xid);
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extern void GetXmaxRecent(TransactionId *XmaxRecent);
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extern int CountActiveBackends(void);
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#endif /* SINVAL_H */
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