From: | Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Samrat Revagade <revagade(dot)samrat(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Patch for fail-back without fresh backup |
Date: | 2013-11-02 15:25:33 |
Message-ID: | CAD21AoCoV_v3JVtV3RxL+ELcX5cf+3S-YU2y2ZLnL9H4oL3Opg@mail.gmail.com |
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Lists: | pgsql-hackers |
On Fri, Oct 25, 2013 at 8:08 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On 2013-10-24 13:51:52 -0700, Josh Berkus wrote:
>
> It entirely depends on your workload. If it happens to be something
> like:
> INSERT INTO table (lots_of_data);
> CHECKPOINT;
> SELECT * FROM TABLE;
>
> i.e. there's a checkpoint between loading the data and reading it - not
> exactly all that uncommon - we'll need to log something for every
> page. That can be rather noticeable. Especially as I think it will be
> rather hard to log anything but a real FPI.
>
> I really don't think everyone will want this. I am absolutely not
> against providing an option to log enough information to make pg_rewind
> work, but I think providing a command to do *safe* *planned* failover
> will help in many more.
>
I think it is better providing as option to log enough information
such as new wal_level.
If user doesn't realize until it's too late, such information is
contained in checkpoint record?
For example if checkpoint record contained information of wal_level
then we can inform to user
using by such information.
BTW this information is useful only for pg_rewind?
Is there for anything else?
(Sorry it might has already been discussed..)
Regards,
-------
Sawada Masahiko
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