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From: David G. Johnston <[email protected]>
To: Tom Lane <[email protected]>
Cc: Michel SALAIS <[email protected]>
Cc: Pgsql-admin <[email protected]>
Subject: Re: "clearing" a relation file !
Date: Sat, 14 May 2022 14:06:56 -0700
Message-ID: <CAKFQuwYNSdvoa-Ygo2cL9QX4ZUGNQgB3xWj-Wrp_Q60tkFEoOw@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On Sat, May 14, 2022 at 1:46 PM Tom Lane <[email protected]> wrote:

> "Michel SALAIS" <[email protected]> writes:
> > \! dd if=/dev/zero of=$file_path bs=1024 count=100
>
> The other problem with this specific test is that an all-zero
> page is considered to be a valid state.  You may consider that
> a problem or not, but we're quite unlikely to change it, because
> doing so would create false failure reports.  See the mechanisms
> around file extension.
>
>
Should this detail be mentioned in the docs?

https://www.postgresql.org/docs/current/checksums.html

Namely (and not confirmed):

"A failure mode that produces empty pages will not be detected by this
mechanism during normal server operation, but the pg_checksums application
will since all normal usage of empty pages is restricted to runtime
transient state."

David J.


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