Re: Offline enabling/disabling of data checksums

From: Michael Banck <michael(dot)banck(at)credativ(dot)de>
To: Magnus Hagander <magnus(at)hagander(dot)net>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Sergei Kornilov <sk(at)zsrv(dot)org>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Offline enabling/disabling of data checksums
Date: 2019-03-13 11:09:24
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Am Mittwoch, den 13.03.2019, 11:47 +0100 schrieb Magnus Hagander:
> On Wed, Mar 13, 2019 at 11:41 AM Michael Banck <michael(dot)banck(at)credativ(dot)de> wrote:
> > I propose we re-read the control file for the enable case after we
> > finished operating on all files and (i) check the instance is still
> > offline and (ii) update the checksums version from there. That should be
> > a small but worthwhile change that could be done anyway.
> In (i) you need to also check that is' not offline *again*. Somebody
> could start *and* stop the database while pg_checksums is running. But
> that should hopefully be enough to check the time field?

Good point.

> > Also, I suggest to maybe add a notice in verbose mode that we are
> > syncing the data directory - otherwise the user might wonder what's
> > going on at 100% done, though I haven't seen a large delay in my tests
> > so far.
> Seems like a good idea -- there certainly could be a substantial delay
> there depending on data size and underlying storage.

The attached patch should do the above, on top of Michael's last


Michael Banck
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Attachment Content-Type Size
0001-Guard-against-concurrent-cluster-changes-when-enabli.patch text/x-patch 3.2 KB

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