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Re: Streaming replication, and walsender during recovery

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Streaming replication, and walsender during recovery
Date: 2010-01-29 08:41:19
Message-ID: 1264754479.24669.15374.camel@ebony (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, 2010-01-29 at 17:31 +0900, Fujii Masao wrote:
> On Fri, Jan 29, 2010 at 4:13 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> > Hmm, I'm sorry but that's bogus. Retaining so much WAL that we are
> > strongly in danger of blowing disk space is not what I would call a
> > safety feature. Since there is no way to control or restrain the number
> > of files for certain, that approach seems fatally flawed. Reducing
> > checkpoint_timeout is the opposite of what you would want to do for
> > performance.
> 
> Why do you worry about that only in the standby?

I don't. The "safety feature" we just added makes it much more likely
that this will happen on standby.

> To improve the situation, I think that we need to use
> checkpoint_segment/timeout as a trigger of restartpoint, regardless
> of the checkpoint record. Though I'm not sure that is possible and
> should be included in v9.0.

Yes, that is a simple change. I think it is needed now.

-- 
 Simon Riggs           www.2ndQuadrant.com


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