Re: Forcing wal rotation

From: "Florian G(dot) Pflug" <fgp(at)phlo(dot)org>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Postgresql-General <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Forcing wal rotation
Date: 2006-07-14 23:55:27
Message-ID: 44B82EEF.7060808@phlo.org
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Simon Riggs wrote:
> On Fri, 2006-07-14 at 12:09 -0400, Tom Lane wrote:
>> "Florian G. Pflug" <fgp(at)phlo(dot)org> writes:
>>> I've now thought about how to fix that without doing that rather crude rsync-pg_xlog-hack.
>>> I've read through the code, and learned that wal-segments are expected to have a specific size -
>>> thus rotating them "early" is not that easy.
>> Simon was working on a patch for this at the code sprint; I think it's
>> submitted to -patches already.
>
> Slightly different patch. I'm working on this one still.
Cool - what are the chances of this being included in 8.2?

>> Explicitly filling the segment as you
>> propose would be really bad for performance.
>
> Yes, current approach I am taking is better than that.
Well, my proposal wasn't really a long-term solution - I was thinking about I quick fix
that I could implement for 8.1, basically to let my warm-standby-setup feel less like
as "house of cards" as someone put it ;-)
I didn't care too much about the performance hit - I don't expect the database I indent
to use it for to have much load, otherwise the wal segments are rotated quite often anyway.
But I agree that for a general solution, my approach is not really ideal ;-)

Since we just ported the application in question to 8.1, I'm not sure that we will switch
to 8.2 when it is released - so I'm still interested in finding a solution for 8.1

Do you think I could backport your patch to 8.1 - or does it depend on some other new features
of 8.2?

greetings, Florian Pflug

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