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Commit3870609

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Add an optional parameter to pg_start_backup() that specifies whether to do
the checkpoint in immediate or lazy mode. This is to address complaintsthat pg_start_backup() takes a long time even when there's no need to minimizeits I/O consumption.
1 parent80df9c4 commit3870609

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6 files changed

+54
-27
lines changed

6 files changed

+54
-27
lines changed

‎doc/src/sgml/backup.sgml‎

Lines changed: 11 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.123 2009/03/05 19:50:03 tgl Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.124 2009/04/07 00:31:25 tgl Exp $ -->
22

33
<chapter id="backup">
44
<title>Backup and Restore</title>
@@ -730,19 +730,19 @@ SELECT pg_start_backup('label');
730730
</para>
731731

732732
<para>
733-
<function>pg_start_backup</> can take a long time to finish.
733+
By default,<function>pg_start_backup</> can take a long time to finish.
734734
This is because it performs a checkpoint, and the I/O
735-
required fora checkpoint will be spread out over a significant
735+
required forthe checkpoint will be spread out over a significant
736736
period of time, by default half your inter-checkpoint interval
737737
(see the configuration parameter
738738
<xref linkend="guc-checkpoint-completion-target">). Usually
739-
this is what you want because it minimizes the impact on query
739+
this is what you want, because it minimizes the impact on query
740740
processing. If you just want to start the backup as soon as
741-
possible,execute a <command>CHECKPOINT</> command
742-
(which performs a checkpoint as quickly as possible) and then
743-
immediately execute <function>pg_start_backup</>. Then there
744-
will be very little for <function>pg_start_backup</>'s checkpoint
745-
todo, and it won't take long.
741+
possible,use:
742+
<programlisting>
743+
SELECTpg_start_backup('label', true);
744+
</programlisting>
745+
This forces the checkpointtobe done as quickly as possible.
746746
</para>
747747
</listitem>
748748
<listitem>
@@ -769,9 +769,9 @@ SELECT pg_stop_backup();
769769
<para>
770770
Once the WAL segment files used during the backup are archived, you are
771771
done. The file identified by <function>pg_stop_backup</>'s result is
772-
the last segment that is required to form a complete set of backup files.
772+
the last segment that is required to form a complete set of backup files.
773773
<function>pg_stop_backup</> does not return until the last segment has
774-
been archived.
774+
been archived.
775775
Archiving of these files happens automatically since you have
776776
already configured <varname>archive_command</>. In most cases this
777777
happens quickly, but you are advised to monitor your archive

‎doc/src/sgml/func.sgml‎

Lines changed: 13 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.474 2009/04/01 03:32:29 tgl Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.475 2009/04/07 00:31:25 tgl Exp $ -->
22

33
<chapter id="functions">
44
<title>Functions and Operators</title>
@@ -12880,10 +12880,10 @@ SELECT set_config('log_statement_stats', 'off', false);
1288012880
<tbody>
1288112881
<row>
1288212882
<entry>
12883-
<literal><function>pg_start_backup</function>(<parameter>label</> <type>text</>)</literal>
12883+
<literal><function>pg_start_backup</function>(<parameter>label</> <type>text</> <optional>, <parameter>fast</> <type>boolean</> </optional>)</literal>
1288412884
</entry>
1288512885
<entry><type>text</type></entry>
12886-
<entry>Set up for performing on-line backup</entry>
12886+
<entry>Prepare for performing on-line backup</entry>
1288712887
</row>
1288812888
<row>
1288912889
<entry>
@@ -12932,20 +12932,25 @@ SELECT set_config('log_statement_stats', 'off', false);
1293212932
</table>
1293312933

1293412934
<para>
12935-
<function>pg_start_backup</> accepts asingle parameter which is an
12935+
<function>pg_start_backup</> accepts atext parameter which is an
1293612936
arbitrary user-defined label for the backup. (Typically this would be
1293712937
the name under which the backup dump file will be stored.) The function
1293812938
writes a backup label file into the database cluster's data directory,
12939-
and then returns the backup's starting transaction log location as text. The user
12940-
need not pay any attention to this result value, but it is provided in
12941-
case it is of use.
12939+
performs a checkpoint,
12940+
and then returns the backup's starting transaction log location as text.
12941+
The user need not pay any attention to this result value, but it is
12942+
provided in case it is of use.
1294212943
<programlisting>
1294312944
postgres=# select pg_start_backup('label_goes_here');
1294412945
pg_start_backup
1294512946
-----------------
1294612947
0/D4445B8
1294712948
(1 row)
1294812949
</programlisting>
12950+
There is an optional boolean second parameter. If <literal>true</>,
12951+
it specifies executing <function>pg_start_backup</> as quickly as
12952+
possible. This forces an immediate checkpoint which will cause a
12953+
spike in I/O operations, slowing any concurrently executing queries.
1294912954
</para>
1295012955

1295112956
<para>
@@ -12961,7 +12966,7 @@ postgres=# select pg_start_backup('label_goes_here');
1296112966
</para>
1296212967

1296312968
<para>
12964-
<function>pg_switch_xlog</> moves to the next transaction log file, allowing the
12969+
<function>pg_switch_xlog</> moves to the next transaction log file, allowing the
1296512970
current file to be archived (assuming you are using continuous archiving).
1296612971
The result is the ending transaction log location + 1 within the just-completed transaction log file.
1296712972
If there has been no transaction log activity since the last transaction log switch,

‎src/backend/access/transam/xlog.c‎

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2009, 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 1.334 2009/03/11 23:19:24 tgl Exp $
10+
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.335 2009/04/07 00:31:26 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -6914,6 +6914,7 @@ Datum
69146914
pg_start_backup(PG_FUNCTION_ARGS)
69156915
{
69166916
text*backupid=PG_GETARG_TEXT_P(0);
6917+
boolfast=PG_GETARG_BOOL(1);
69176918
char*backupidstr;
69186919
XLogRecPtrcheckpointloc;
69196920
XLogRecPtrstartpoint;
@@ -6983,9 +6984,11 @@ pg_start_backup(PG_FUNCTION_ARGS)
69836984
* have different checkpoint positions and hence different history
69846985
* file names, even if nothing happened in between.
69856986
*
6986-
* We don't use CHECKPOINT_IMMEDIATE, hence this can take awhile.
6987+
* We use CHECKPOINT_IMMEDIATE only if requested by user (via
6988+
* passing fast = true). Otherwise this can take awhile.
69876989
*/
6988-
RequestCheckpoint(CHECKPOINT_FORCE |CHECKPOINT_WAIT);
6990+
RequestCheckpoint(CHECKPOINT_FORCE |CHECKPOINT_WAIT |
6991+
(fast ?CHECKPOINT_IMMEDIATE :0));
69896992

69906993
/*
69916994
* Now we need to fetch the checkpoint record location, and also its

‎src/backend/catalog/system_views.sql‎

Lines changed: 20 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
*
44
* Copyright (c) 1996-2009, PostgreSQL Global Development Group
55
*
6-
* $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.59 2009/02/06 21:15:11 tgl Exp $
6+
* $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.60 2009/04/07 00:31:26 tgl Exp $
77
*/
88

99
CREATEVIEWpg_rolesAS
@@ -403,6 +403,12 @@ CREATE VIEW pg_user_mappings AS
403403

404404
REVOKE ALLon pg_user_mappingFROM public;
405405

406+
--
407+
-- We have a few function definitions in here, too.
408+
-- At some point there might be enough to justify breaking them out into
409+
-- a separate "system_functions.sql" file.
410+
--
411+
406412
-- Tsearch debug function. Defined here because it'd be pretty unwieldy
407413
-- to put it into pg_proc.h
408414

@@ -464,3 +470,16 @@ LANGUAGE SQL STRICT STABLE;
464470

465471
COMMENT ON FUNCTION ts_debug(text) IS
466472
'debug function for current text search configuration';
473+
474+
--
475+
-- Redeclare built-in functions that need default values attached to their
476+
-- arguments. It's impractical to set those up directly in pg_proc.h because
477+
-- of the complexity and platform-dependency of the expression tree
478+
-- representation. (Note that internal functions still have to have entries
479+
-- in pg_proc.h; we are merely causing their proargnames and proargdefaults
480+
-- to get filled in.)
481+
--
482+
483+
CREATEOR REPLACE FUNCTION
484+
pg_start_backup(labeltext, fastboolean DEFAULT false)
485+
RETURNStext STRICT VOLATILE LANGUAGE internalAS'pg_start_backup';

‎src/include/catalog/catversion.h‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,7 @@
3737
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
3838
* Portions Copyright (c) 1994, Regents of the University of California
3939
*
40-
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.528 2009/04/05 22:28:59 tgl Exp $
40+
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.529 2009/04/07 00:31:26 tgl Exp $
4141
*
4242
*-------------------------------------------------------------------------
4343
*/
@@ -53,6 +53,6 @@
5353
*/
5454

5555
/*yyyymmddN */
56-
#defineCATALOG_VERSION_NO200904051
56+
#defineCATALOG_VERSION_NO200904061
5757

5858
#endif

‎src/include/catalog/pg_proc.h‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.540 2009/04/05 22:28:59 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.541 2009/04/07 00:31:26 tgl Exp $
1111
*
1212
* NOTES
1313
* The script catalog/genbki.sh reads this file and generates .bki
@@ -3252,7 +3252,7 @@ DATA(insert OID = 2171 ( pg_cancel_backendPGNSP PGUID 12 1 0 0 f f f t f v 1 0
32523252
DESCR("cancel a server process' current query");
32533253
DATA(insertOID=2096 (pg_terminate_backendPGNSPPGUID12100ffftfv1016"23"_null__null__null__null_pg_terminate_backend_null__null__null_ ));
32543254
DESCR("terminate a server process");
3255-
DATA(insertOID=2172 (pg_start_backupPGNSPPGUID12100ffftfv1025"25"_null__null__null__null_pg_start_backup_null__null__null_ ));
3255+
DATA(insertOID=2172 (pg_start_backupPGNSPPGUID12100ffftfv2025"25 16"_null__null__null__null_pg_start_backup_null__null__null_ ));
32563256
DESCR("prepare for taking an online backup");
32573257
DATA(insertOID=2173 (pg_stop_backupPGNSPPGUID12100ffftfv0025""_null__null__null__null_pg_stop_backup_null__null__null_ ));
32583258
DESCR("finish taking an online backup");

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