From: Tom Lane <tgl@sss.pgh.pa.us>
To: Simon Riggs <simon@2ndquadrant.com>
cc: pgsql-committers@lists.postgresql.org,
        Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
Subject: Re: pgsql: Allow HOT updates for some expression indexes
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Comments: In-reply-to Simon Riggs <simon@2ndquadrant.com>
	message dated "Tue, 27 Mar 2018 20:19:48 +0100"
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Date: Tue, 27 Mar 2018 17:07:15 -0400
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Simon Riggs <simon@2ndquadrant.com> writes:
> On 27 March 2018 at 20:11, Simon Riggs <simon@2ndquadrant.com> wrote:
>> Buildfarm failure seen, investigating

> Error on FreeBSD only , perhaps timing-related as a result of using
> pg_stat_get_xact_tuples_hot_updated()
> in tests.

It's by now obvious that it's not just "FreeBSD only".

The test script appears to imagine that pgstats outputs update
instantaneously.  I'm rather astonished that it passes anywhere,
much less that it seemingly passes reliably enough for you
to have not been noticed in precommit testing.

The existing "stats" test moves mountains to get repeatable results,
and is pretty slow in consequence, and even so it doesn't always succeed.
I think that rather than going down that path, you should drop this test
approach and think of some other way.

			regards, tom lane