Horton

Re: snapbuild woes

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Noah Misch <noah@leadboat.com>, Petr Jelinek <petr.jelinek@2ndquadrant.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Erik Rijkers <er@xs4all.nl>, David Steele <david@pgmasters.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Robert Haas <robertmhaas@gmail.com>, Craig Ringer <craig@2ndquadrant.com>, pgsql-hackers-owner@postgresql.org
Date: 2017-05-01T16:09:18Z
Lists: pgsql-hackers 
On 2017-05-01 08:46:47 -0400, Tom Lane wrote:
> Noah Misch <noah@leadboat.com> writes:
> > On Fri, Apr 21, 2017 at 10:34:58PM -0700, Andres Freund wrote:
> >> ... I was wondering about adding
> >> a loop that simply runs for like 30s and then quits or such, but who
> >> knows.
> 
> > If the probabilistic test catches the bug even 5% of the time in typical
> > configurations, the buildfarm will rapidly identify any regression.  I'd
> > choose a 7s test that detects the bug 5% of the time over a 30s test that
> > detects it 99% of the time.  (When I wrote src/bin/pgbench/t/001_pgbench.pl
> > for a probabilistic bug, I sized that test to finish in 1s and catch its bug
> > half the time.  In its case, only two buildfarm members were able to
> > demonstrate the original bug, so 5% detection would have been too low.)
> 
> 30sec is kind of a big lump from a buildfarm standpoint, especially if
> you mean "it runs for 30s on my honkin' fast workstation".  I'm fine
> with individual tests that run for ~ 1sec.

I was more thinking of pgench -T$XX, rather than constant number of
iterations.  I currently can reproduce the issues within like 3-4
minutes, so 5s is probably not quite sufficient to get decent coverage.


- Andres

Commits

  1. Fix thinko introduced in 2bef06d516460 et al.

  2. Avoid superfluous work for commits during logical slot creation.

  3. Fix race condition leading to hanging logical slot creation.

  4. Don't use on-disk snapshots for exported logical decoding snapshot.

  5. Preserve required !catalog tuples while computing initial decoding snapshot.