Feedback-ID: i0fe9450f:Fastmail
Date: Tue, 31 May 2022 10:45:04 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Andres Freund <andres@anarazel.de>
Cc: Andrey Borodin <x4mmm@yandex-team.ru>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Robert Haas <robertmhaas@gmail.com>, Peter Geoghegan <pg@bowt.ie>,
	=?utf-8?B?0J/QtdGC0YrRgCDQodC70LDQstC+0LI=?= <pet.slavov@gmail.com>,
	PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17485: Records missing from Primary Key index when doing
 REINDEX INDEX CONCURRENTLY
Message-ID: <YpVzILvc0Uowuir8@paquier.xyz>
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On Mon, May 30, 2022 at 12:10:04PM -0700, Andres Freund wrote:
> I think it's ok if we have a heuristic test for this kind of thing. It
> sometimes can even be good, because it means we'll get different schedulings
> over time, hitting "unknown" bugs.

Yeah, the tricky part is how to parametize that to be cheap, still
useful.  Having a larger number of attributes makes the particular
problem of this thread easier to hit because it enlarges the
validation window in the concurrent build, and generating such dummy
data with a simple schema should be quick enough, but I would not
accept in the tree a test that takes ~5s to run without a rather good
hit rate.  For this particular issue, I would say that something able
to fail up to 20%~25% of the time for a short run-time would be quite
decent, actually, even if that sounds low in a single run because the
odds of detecting one failure increase a "lot" after a few repeated
runs.

On my own laptop, the original test of the reporter takes up to 3~4s
to reproduce the issue, for example, all the time, so that's good :)
--
Michael

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