Re: Sending out a request for more buildfarm animals?

Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2014-05-25 01:02:25 +0200, Tomas Vondra wrote:
>> The cache invalidation bug was apparently fixed, but we're still getting
>> failures (see for example markhor):
>> http://www.pgbuildfarm.org/cgi-bin/show_history.pl?nm=markhor&br=HEAD
>> I see there's a transaction (COMMIT+BEGIN) - is this caused by the
>> extremely long runtimes?

> Yes, that's the reason. Normally the test doesn't trigger autovacuum at
> all, but if it's running for a *long* time it can. I haven't yet figured
> out a good way to deal with that.

Any way to make the test print only WAL entries arising from the
foreground transaction?

If an autovac run can trigger this failure, then I would think it would
happen sometimes, probabilistically, even when the test runtime wasn't
all that long. That would be very unhappy-making, eg for packagers
who would like build runs to reliably work the first time. So I think
this is important even without the desire to run CLOBBER_CACHE regression
tests.

Another idea is to provide a variant "expected" file, but that seems
a bit fragile: if you can get one extra transaction, why not two?

regards, tom lane