Re: PITR potentially broken in 9.2

From: Tatsuo Ishii <ishii(at)postgresql(dot)org>
To: tgl(at)sss(dot)pgh(dot)pa(dot)us
Cc: andres(at)2ndquadrant(dot)com, jeff(dot)janes(at)gmail(dot)com, hlinnakangas(at)vmware(dot)com, noah(at)leadboat(dot)com, pgsql-bugs(at)postgresql(dot)org
Subject: Re: PITR potentially broken in 9.2
Date: 2012-12-05 10:06:55
Message-ID: 20121205.190655.2190182738409340212.t-ishii@sraoss.co.jp
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So what status are we on? Are we going to release 9.2.2 as it is?
Or withdraw current 9.2.2?
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
>> On 2012-12-04 21:27:34 -0500, Tom Lane wrote:
>>> So the upshot is that I propose a patch more like the attached.
>
>> Without having run anything so far it looks good to me.
>
> BTW, while on the theme of the pause feature being several bricks shy of
> a load, it looks to me like the place that it was added to the replay
> loop was less than sane as well. Presumably the purpose of a pause is
> to let you stop application of the WAL at exactly the current spot;
> but you can *not* do that midway through application of the record,
> and where it is is effectively that. As soon as we've updated
> xlogctl->replayEndRecPtr, we're committed to replay the record,
> because we can't guarantee that the controlfile minRecoveryPoint
> doesn't get pushed up to that point by buffer flush activity.
> So an abort here could leave the database in an unrestartable condition.
>
> I guess the idea of putting it there was to save one spinlock acquire,
> but I'm having a bit of a hard time believing that one spinlock acquire
> per WAL record means much. Still we could possibly preserve that
> attribute by moving the pause down to just after the update of
> xlogctl->recoveryLastRecPtr.
>
> Thoughts?
>
> regards, tom lane
>
>
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