From: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
---|---|
To: | Josh Kupershmidt <schmiddy(at)gmail(dot)com> |
Cc: | pgsql-docs <pgsql-docs(at)postgresql(dot)org> |
Subject: | Re: description of CHECKPOINT command confusing |
Date: | 2011-10-12 05:14:55 |
Message-ID: | CAHGQGwE0W8ptM6JMrpMfhMyhHhG3NavEQupBKe=UQVznsvFq-Q@mail.gmail.com |
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Lists: | pgsql-docs |
On Wed, Oct 12, 2011 at 12:02 PM, Josh Kupershmidt <schmiddy(at)gmail(dot)com> wrote:
> Basically, I think the page should be structured to emphasize
> 1.) what is a "checkpoint" to a user who is not familiar with the term, and
> 2.) why would a user want to use the CHECKPOINT command?
>
> To tackle 1.), I think a little bit of reorganization along with a
> link to the right spot, namely:
> http://www.postgresql.org/docs/current/static/wal-configuration.html
>
> will go a long way. I've attached an admittedly rough patch to try to
> address problem 1.).
+1
> As for 2.), there is no good answer on that page right now, other than
> "not intended for use during normal operation". Off the top of my
> head, the only suggested use I remember for CHECKPOINT is as a
> recommended step before pg_start_backup(); anyone know of other uses?
> And this bit:
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().
I'm not sure if there are other use cases during normal operation.
> | If executed during recovery, the CHECKPOINT command will
> | force a restartpoint rather than writing a new checkpoint.
>
> doesn't explain or link to what a "restartpoint" is, should it?
It's helpful to link to that. What a "restartpoint" is explained in also
http://www.postgresql.org/docs/current/static/wal-configuration.html
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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