Re: Recovery inconsistencies, standby much larger than primary

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <stark(at)mit(dot)edu>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Andres Freund <andres(at)2ndquadrant(dot)com>
Subject: Re: Recovery inconsistencies, standby much larger than primary
Date: 2014-02-12 19:55:17
Message-ID: 18168.1392234917@sss.pgh.pa.us
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Greg Stark <stark(at)mit(dot)edu> writes:
> On Wed, Feb 12, 2014 at 6:55 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Greg Stark <stark(at)mit(dot)edu> writes:
>>> This does possibly allocate an extra block past the target block. I'm
>>> not sure how surprising that would be for the rest of the code.

>> Should be fine; we could end up with an extra block after a failed
>> extension operation in any case.

> I know it's fine on the active database, I'm not so clear whether it's
> compatible with the xlog records from the primary. I suppose it'll
> just see an Initialize Page record and happily see the nul block and
> initialize it. It's still a bit scary.

Well, we can easily find uninitialized extra pages on the primary too,
so if WAL replay were unable to cope with that, it would be a bug
regardless.

>> Huh? Bug in wal-e? What bug?

> WAL-E actually didn't restore a whole 1GB file due to a transient S3
> problem, in fact a bunch of them.

Hah. Okay, I think we can write this issue off as closed then.

regards, tom lane

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