On Wed, Oct 12, 2011 at 1:14 AM, Fujii Masao <masao.fu...@gmail.com> wrote:
> On Wed, Oct 12, 2011 at 12:02 PM, Josh Kupershmidt <schmi...@gmail.com> wrote:
> It's for preventing pg_start_backup() from taking lots of time? If so,
> you're right in 8.3 and before. In 8.4 and later, instead, you can specify
> whether pg_start_backup() performs smoothed checkpoint or immediate
> one, by using the second argument of pg_start_backup().
Neat, I hadn't seen that change to pg_start_backup().
> I'm not sure if there are other use cases during normal operation.
If there's no real use-case for the command, I think the existing text
of "not intended for use during normal operation" is fine.
> It's helpful to link to that. What a "restartpoint" is explained in also
> http://www.postgresql.org/docs/current/static/wal-configuration.html
I wonder if it'd be helpful to break up that page into sub-sections,
it is quite a large single section now. That might make it easier to
link into that page for explaining restartpoint.
Slightly updated patch attached.
Josh
diff --git a/doc/src/sgml/ref/checkpoint.sgml b/doc/src/sgml/ref/checkpoint.sgml
index 7ffd40a..e70b8c8 100644
*** a/doc/src/sgml/ref/checkpoint.sgml
--- b/doc/src/sgml/ref/checkpoint.sgml
*************** CHECKPOINT
*** 26,55 ****
<title>Description</title>
<para>
- Write-Ahead Logging (WAL) puts a checkpoint in the transaction log
- every so often. (To adjust the automatic checkpoint interval, see
- the run-time configuration options <xref linkend="guc-checkpoint-segments">
- and <xref linkend="guc-checkpoint-timeout">.) The
- <command>CHECKPOINT</command> command forces an immediate
- checkpoint when the command is issued, without waiting for a
- scheduled checkpoint.
- </para>
-
- <para>
A checkpoint is a point in the transaction log sequence at which
all data files have been updated to reflect the information in the
log. All data files will be flushed to disk. Refer to
! <xref linkend="wal"> for more information about the WAL system.
</para>
<para>
If executed during recovery, the <command>CHECKPOINT</command> command
! will force a restartpoint rather than writing a new checkpoint.
</para>
<para>
! Only superusers can call <command>CHECKPOINT</command>. The command is
! not intended for use during normal operation.
</para>
</refsect1>
--- 26,55 ----
<title>Description</title>
<para>
A checkpoint is a point in the transaction log sequence at which
all data files have been updated to reflect the information in the
log. All data files will be flushed to disk. Refer to
! <xref linkend="wal-configuration"> for more details about what happens
! during a checkpoint.
! </para>
!
! <para>
! The <command>CHECKPOINT</command> command forces an immediate
! checkpoint when the command is issued, without waiting for a
! regular checkpoint scheduled by the system (controlled by the settings in
! <xref linkend="runtime-config-wal-checkpoints">).
! <command>CHECKPOINT</command> is not intended for use during normal
! operation.
</para>
<para>
If executed during recovery, the <command>CHECKPOINT</command> command
! will force a restartpoint (see <xref linkend="wal-configuration">)
! rather than writing a new checkpoint.
</para>
<para>
! Only superusers can call <command>CHECKPOINT</command>.
</para>
</refsect1>
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