From: | Michael Banck <michael(dot)banck(at)credativ(dot)de> |
---|---|
To: | Daniel Gustafsson <daniel(at)yesql(dot)se> |
Cc: | PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: clarify "rewritten" in pg_checksums docs |
Date: | 2020-09-01 13:34:11 |
Message-ID: | f1fd7a65dd48cf381b751e8183eab49f090b64d3.camel@credativ.de |
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Thread: | |
Lists: | pgsql-hackers |
Hi,
Am Dienstag, den 01.09.2020, 15:29 +0200 schrieb Daniel Gustafsson:
> > On 1 Sep 2020, at 15:13, Michael Banck <michael(dot)banck(at)credativ(dot)de> wrote:
> > the pg_checksums docs mention that "When enabling checksums, every file
> > in the cluster is rewritten".
> >
> > From IRC discussions, "rewritten" seems ambiguous, it could mean that a
> > second copy of the file is written and then switched over, implying
> > increased storage demand during the operation.
>
> Makes sense, I can see that confusion.
>
> > So maybe "rewritten in-place" is better, as per the attached?
>
> Isn't "modified in-place" a more accurate description of the process?
AIUI we do rewrite the whole file (block by block, after updating the
page header with the checksum), so yeah, I though about using modified
instead but then decided rewritten is pretty (or even more) accurate.
Michael
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