From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andreas Seltenreich <seltenreich@gmx.de>
cc: pgsql-hackers@postgresql.org
Subject: Re: Failing assertions in indxpath.c, placeholder.c and brin_minmax.c
In-reply-to: <87k2tm2l3i.fsf@ex.ansel.ydns.eu>
References: <871tfv3wor.fsf@ex.ansel.ydns.eu> <15030.1437947313@sss.pgh.pa.us>
 <87k2tm2l3i.fsf@ex.ansel.ydns.eu>
Comments: In-reply-to Andreas Seltenreich <seltenreich@gmx.de>
 message dated "Mon, 27 Jul 2015 08:03:29 +0200"
Date: Mon, 27 Jul 2015 10:28:47 -0400
Message-ID: <25498.1438007327@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Andreas Seltenreich <seltenreich@gmx.de> writes:
> Tom Lane writes:
>> I've fixed the first two of these --- thanks for the report!

> I let sqlsmith run during the night, and it did no longer trigger the
> first two.  During roughly a million random queries it triggered the
> already mentioned brin one 10 times, but there was also one instance of
> this new one in the log:

Oh goody, more fun.  I'll take a look.

>> I'm a bit confused about this aspect of your report though, because in
>> my hands that example fails clear back to 9.2.  It doesn't seem to require
>> the predtest.c improvement to expose the fault.

> Hmm, I actually used a different, uglier query to trigger this assertion
> for the bisection run.

Ah, okay.  The triggering condition for both those cases is
provably-contradictory restriction clauses on an inheritance relation.
In what you showed yesterday, that was something like "x < x AND x IS
NULL", which the planner has been able to recognize as contradictory
for a long time because "<" is strict.  (It did not, and still doesn't,
notice that "x < x" all by itself is contradictory...).  But here it
looks like the trigger is

from public.b as rel4551420
where ( rel4551420.bb>rel4551420.bb ) and ( rel4551420.bb<rel4551420.bb )

It was the recent predtest improvements that allowed recognition that
bb < bb contradicts bb > bb.  So that's why this run started to fail
there, even though the bug it was tickling is much older.

			regards, tom lane


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