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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Josh berkus <josh@agliodbs.com>
Cc: Peter Geoghegan <pg@heroku.com>
Cc: Jeff Janes <jeff.janes@gmail.com>
Cc: Joe Conway <mail@joeconway.com>
Cc: Victor Yegorov <vyegorov@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Reviewing freeze map code
Date: Wed, 18 May 2016 18:42:16 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2016-05-18 18:25:39 -0400, Tom Lane wrote:
>> Yes, I've been wondering that too.  VACUUM is not meant as a corruption
>> checker, and should not be made into one, so what is the point of this
>> flag exactly?

> Well, so far a VACUUM FREEZE (or just setting vacuum_freeze_table_age =
> 0) verified the correctness of the visibility map; and that found a
> number of bugs.  Now visibilitymap grew additional responsibilities,
> with a noticeable risk of data eating bugs, and there's no way to verify
> whether visibilitymap's frozen bits are set correctly.

Meh.  I'm not sure we should grow a rather half-baked feature we'll never
be able to remove as a substitute for a separate sanity checker.  The
latter is really the right place for this kind of thing.

			regards, tom lane


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