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Commit0cb91cc

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Remove the logId/logSeg fields from pg_control, because they are not needed
in normal operation, and we can avoid rewriting pg_control at every logsegment switch if we don't insist that these values be valid. Reducingthe number of pg_control updates is a good idea for both performance andreliability. It does make pg_resetxlog's life a bit harder, but that seemsa good tradeoff; and anyway the change to pg_resetxlog amounts to automatingsomething people formerly needed to do by hand, namely look at the existingpg_xlog files to make sure the new WAL start point was past them.In passing, change the wording of xlog.c's "database system was interrupted"messages: describe the pg_control timestamp as "last known up at" rather thanimplying it is the exact time of service interruption. With this change thetimestamp will generally be the time of the last checkpoint, which could bemany minutes before the failure; and we've already seen indications thatpeople tend to misinterpret the old wording.initdb forced due to change in pg_control layout. Simon Riggs and Tom Lane
1 parent98cacd1 commit0cb91cc

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5 files changed

+172
-99
lines changed

5 files changed

+172
-99
lines changed

‎doc/src/sgml/ref/pg_resetxlog.sgml

Lines changed: 15 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$PostgreSQL: pgsql/doc/src/sgml/ref/pg_resetxlog.sgml,v 1.18 2006/09/16 00:30:19 momjian Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/ref/pg_resetxlog.sgml,v 1.19 2006/12/08 19:50:52 tgl Exp $
33
PostgreSQL documentation
44
-->
55

@@ -72,7 +72,7 @@ PostgreSQL documentation
7272
<literal>-f</> can still be used, but
7373
the recovered database must be treated with even more suspicion than
7474
usual: an immediate dump and reload is imperative. <emphasis>Do not</>
75-
execute any data-modifying operations in the database before you dump;
75+
execute any data-modifying operations in the database before you dump,
7676
as any such action is likely to make the corruption worse.
7777
</para>
7878

@@ -127,7 +127,7 @@ PostgreSQL documentation
127127
<listitem>
128128
<para>
129129
The WAL starting address (<literal>-l</>) should be
130-
larger than any file name currently existing in
130+
larger than anyWAL segmentfile name currently existing in
131131
the directory <filename>pg_xlog</> under the data directory.
132132
These names are also in hexadecimal and have three parts. The first
133133
part is the <quote>timeline ID</> and should usually be kept the same.
@@ -139,6 +139,18 @@ PostgreSQL documentation
139139
<filename>000000010000003A000000FF</>, choose <literal>-l 0x1,0x3B,0x0</>
140140
or more.
141141
</para>
142+
143+
<note>
144+
<para>
145+
<command>pg_resetxlog</command> itself looks at the files in
146+
<filename>pg_xlog</> and chooses a default <literal>-l</> setting
147+
beyond the last existing file name. Therefore, manual adjustment of
148+
<literal>-l</> should only be needed if you are aware of WAL segment
149+
files that are not currently present in <filename>pg_xlog</>, such as
150+
entries in an offline archive; or if the contents of
151+
<filename>pg_xlog</> have been lost entirely.
152+
</para>
153+
</note>
142154
</listitem>
143155

144156
<listitem>

‎src/backend/access/transam/xlog.c

Lines changed: 42 additions & 58 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.258 2006/11/30 18:29:11 tgl Exp $
10+
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.259 2006/12/08 19:50:53 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -1538,54 +1538,6 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch)
15381538
openLogFile=XLogFileInit(openLogId,openLogSeg,
15391539
&use_existent, true);
15401540
openLogOff=0;
1541-
1542-
/* update pg_control, unless someone else already did */
1543-
LWLockAcquire(ControlFileLock,LW_EXCLUSIVE);
1544-
if (ControlFile->logId<openLogId||
1545-
(ControlFile->logId==openLogId&&
1546-
ControlFile->logSeg<openLogSeg+1))
1547-
{
1548-
ControlFile->logId=openLogId;
1549-
ControlFile->logSeg=openLogSeg+1;
1550-
ControlFile->time=time(NULL);
1551-
UpdateControlFile();
1552-
1553-
/*
1554-
* Signal bgwriter to start a checkpoint if it's been too long
1555-
* since the last one.(We look at local copy of RedoRecPtr
1556-
* which might be a little out of date, but should be close
1557-
* enough for this purpose.)
1558-
*
1559-
* A straight computation of segment number could overflow 32
1560-
* bits. Rather than assuming we have working 64-bit
1561-
* arithmetic, we compare the highest-order bits separately,
1562-
* and force a checkpoint immediately when they change.
1563-
*/
1564-
if (IsUnderPostmaster)
1565-
{
1566-
uint32old_segno,
1567-
new_segno;
1568-
uint32old_highbits,
1569-
new_highbits;
1570-
1571-
old_segno= (RedoRecPtr.xlogid %XLogSegSize)*XLogSegsPerFile+
1572-
(RedoRecPtr.xrecoff /XLogSegSize);
1573-
old_highbits=RedoRecPtr.xlogid /XLogSegSize;
1574-
new_segno= (openLogId %XLogSegSize)*XLogSegsPerFile+
1575-
openLogSeg;
1576-
new_highbits=openLogId /XLogSegSize;
1577-
if (new_highbits!=old_highbits||
1578-
new_segno >=old_segno+ (uint32)CheckPointSegments)
1579-
{
1580-
#ifdefWAL_DEBUG
1581-
if (XLOG_DEBUG)
1582-
elog(LOG,"time for a checkpoint, signaling bgwriter");
1583-
#endif
1584-
RequestCheckpoint(false, true);
1585-
}
1586-
}
1587-
}
1588-
LWLockRelease(ControlFileLock);
15891541
}
15901542

15911543
/* Make sure we have the current logfile open */
@@ -1669,7 +1621,9 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch)
16691621
*
16701622
* This is also the right place to notify the Archiver that the
16711623
* segment is ready to copy to archival storage, and to update the
1672-
* timer for archive_timeout.
1624+
* timer for archive_timeout, and to signal for a checkpoint if
1625+
* too many logfile segments have been used since the last
1626+
* checkpoint.
16731627
*/
16741628
if (finishing_seg|| (xlog_switch&&last_iteration))
16751629
{
@@ -1680,6 +1634,41 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch)
16801634
XLogArchiveNotifySeg(openLogId,openLogSeg);
16811635

16821636
Write->lastSegSwitchTime=time(NULL);
1637+
1638+
/*
1639+
* Signal bgwriter to start a checkpoint if it's been too long
1640+
* since the last one.(We look at local copy of RedoRecPtr
1641+
* which might be a little out of date, but should be close
1642+
* enough for this purpose.)
1643+
*
1644+
* A straight computation of segment number could overflow 32
1645+
* bits. Rather than assuming we have working 64-bit
1646+
* arithmetic, we compare the highest-order bits separately,
1647+
* and force a checkpoint immediately when they change.
1648+
*/
1649+
if (IsUnderPostmaster)
1650+
{
1651+
uint32old_segno,
1652+
new_segno;
1653+
uint32old_highbits,
1654+
new_highbits;
1655+
1656+
old_segno= (RedoRecPtr.xlogid %XLogSegSize)*XLogSegsPerFile+
1657+
(RedoRecPtr.xrecoff /XLogSegSize);
1658+
old_highbits=RedoRecPtr.xlogid /XLogSegSize;
1659+
new_segno= (openLogId %XLogSegSize)*XLogSegsPerFile+
1660+
openLogSeg;
1661+
new_highbits=openLogId /XLogSegSize;
1662+
if (new_highbits!=old_highbits||
1663+
new_segno >=old_segno+ (uint32) (CheckPointSegments-1))
1664+
{
1665+
#ifdefWAL_DEBUG
1666+
if (XLOG_DEBUG)
1667+
elog(LOG,"time for a checkpoint, signaling bgwriter");
1668+
#endif
1669+
RequestCheckpoint(false, true);
1670+
}
1671+
}
16831672
}
16841673
}
16851674

@@ -4199,8 +4188,6 @@ BootStrapXLOG(void)
41994188
ControlFile->system_identifier=sysidentifier;
42004189
ControlFile->state=DB_SHUTDOWNED;
42014190
ControlFile->time=checkPoint.time;
4202-
ControlFile->logId=0;
4203-
ControlFile->logSeg=1;
42044191
ControlFile->checkPoint=checkPoint.redo;
42054192
ControlFile->checkPointCopy=checkPoint;
42064193
/* some additional ControlFile fields are set in WriteControlFile() */
@@ -4659,8 +4646,7 @@ StartupXLOG(void)
46594646
*/
46604647
ReadControlFile();
46614648

4662-
if (ControlFile->logSeg==0||
4663-
ControlFile->state<DB_SHUTDOWNED||
4649+
if (ControlFile->state<DB_SHUTDOWNED||
46644650
ControlFile->state>DB_IN_PRODUCTION||
46654651
!XRecOffIsValid(ControlFile->checkPoint.xrecoff))
46664652
ereport(FATAL,
@@ -4672,7 +4658,7 @@ StartupXLOG(void)
46724658
str_time(ControlFile->time))));
46734659
elseif (ControlFile->state==DB_SHUTDOWNING)
46744660
ereport(LOG,
4675-
(errmsg("database system shutdown was interrupted at %s",
4661+
(errmsg("database system shutdown was interrupted; last known up at %s",
46764662
str_time(ControlFile->time))));
46774663
elseif (ControlFile->state==DB_IN_CRASH_RECOVERY)
46784664
ereport(LOG,
@@ -4688,7 +4674,7 @@ StartupXLOG(void)
46884674
" and you may need to choose an earlier recovery target.")));
46894675
elseif (ControlFile->state==DB_IN_PRODUCTION)
46904676
ereport(LOG,
4691-
(errmsg("database system was interrupted at %s",
4677+
(errmsg("database system was interrupted; last known up at %s",
46924678
str_time(ControlFile->time))));
46934679

46944680
/* This is just to allow attaching to startup process with a debugger */
@@ -5064,8 +5050,6 @@ StartupXLOG(void)
50645050
openLogSeg=endLogSeg;
50655051
openLogFile=XLogFileOpen(openLogId,openLogSeg);
50665052
openLogOff=0;
5067-
ControlFile->logId=openLogId;
5068-
ControlFile->logSeg=openLogSeg+1;
50695053
Insert=&XLogCtl->Insert;
50705054
Insert->PrevRecord=LastRec;
50715055
XLogCtl->xlblocks[0].xlogid=openLogId;

‎src/bin/pg_controldata/pg_controldata.c

Lines changed: 1 addition & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* copyright (c) Oliver Elphick <olly@lfix.co.uk>, 2001;
77
* licence: BSD
88
*
9-
* $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.31 2006/08/21 16:16:31 tgl Exp $
9+
* $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.32 2006/12/08 19:50:53 tgl Exp $
1010
*/
1111
#include"postgres.h"
1212

@@ -159,10 +159,6 @@ main(int argc, char *argv[])
159159
dbState(ControlFile.state));
160160
printf(_("pg_control last modified: %s\n"),
161161
pgctime_str);
162-
printf(_("Current log file ID: %u\n"),
163-
ControlFile.logId);
164-
printf(_("Next log file segment: %u\n"),
165-
ControlFile.logSeg);
166162
printf(_("Latest checkpoint location: %X/%X\n"),
167163
ControlFile.checkPoint.xlogid,
168164
ControlFile.checkPoint.xrecoff);

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