Re: point in time recovery and moving datafiles online

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at>
Cc: "Marc Munro" <marc(at)bloodnok(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: point in time recovery and moving datafiles online
Date: 2002-02-22 14:32:20
Message-ID: 16520.1014388340@sss.pgh.pa.us
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"Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at> writes:
> Yes. But I think you might have to avoid "vacuum full" during data file backup.

Why? If vacuum is unsafe in this scenario, wouldn't it also be unsafe
in event of a system crash?

I do believe that vacuum should (but presently does not) emit a WAL
record showing its truncation of the file, so that the equivalent
truncation can be repeated during replay. However, this is needed
in any case --- point-in-time recovery simply means replaying WAL on
a slightly longer timescale than is usual for crash-recovery.

> And you need the whole WAL including the "page images".

Check, you can't compress out the page images.

regards, tom lane

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