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Basic Recovery Control functions for use in Hot Standby. Pause, Resume,

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Status check functions only. Also, new recovery.conf parameter to
pause_at_recovery_target, default on.

Simon Riggs, reviewed by Fujii Masao
This commit is contained in:
Simon Riggs
2011-02-08 18:30:22 +00:00
parent f9f9d696a9
commit 8c6e3adbf7
5 changed files with 230 additions and 0 deletions
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58
doc/src/sgml/func.sgml
View File

@ -14173,6 +14173,64 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
</tgroup>
</table>
<para>
The functions shown in <xref
linkend="functions-recovery-control-table"> control the progress of recovery.
These functions may be executed only during recovery.
</para>
<table id="functions-recovery-control-table">
<title>Recovery Control Functions</title>
<tgroup cols="3">
<thead>
<row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>
<literal><function>pg_is_xlog_replay_paused()</function></literal>
</entry>
<entry><type>bool</type></entry>
<entry>True if recovery is paused.
</entry>
</row>
<row>
<entry>
<literal><function>pg_xlog_replay_pause()</function></literal>
</entry>
<entry><type>void</type></entry>
<entry>Pauses recovery immediately.
</entry>
</row>
<row>
<entry>
<literal><function>pg_xlog_replay_resume()</function></literal>
</entry>
<entry><type>void</type></entry>
<entry>Restarts recovery if it was paused.
</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
While recovery is paused no further database changes are applied.
If in hot standby, all new queries will see the same consistent snapshot
of the database, and no further query conflicts will be generated until
recovery is resumed.
</para>
<para>
If streaming replication is disabled, the paused state may continue
indefinitely without problem. While streaming replication is in
progress WAL records will continue to be received, which will
eventually fill available disk space, depending upon the duration of
the pause, the rate of WAL generation and available disk space.
</para>
<para>
The functions shown in <xref linkend="functions-admin-dbsize"> calculate
the disk space usage of database objects.

25
doc/src/sgml/recovery-config.sgml
View File

@ -227,6 +227,31 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
</listitem>
</varlistentry>
<varlistentry id="pause-at-recovery-target"
xreflabel="pause_at_recovery_target">
<term><varname>pause_at_recovery_target</varname>
(<type>boolean</type>)
</term>
<indexterm>
<primary><varname>pause_at_recovery_target</> recovery parameter</primary>
</indexterm>
<listitem>
<para>
Specifies whether recovery should pause when the recovery target
is reached. The default is true, if a recovery target is set.
This is intended to allow queries to be executed against the
database to check if this recovery target is the most desirable
point for recovery. The paused state can be resumed by using
<function>pg_xlog_replay_resume()</> (See
<xref linkend="functions-recovery-control-table">), which then
causes recovery to end. If this recovery target is not the
desired stopping point, then shutdown the server, change the
recovery target settings to a later target and restart to
continue recovery.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>