From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andreas Seltenreich <seltenreich@gmx.de>
Cc: pgsql-hackers@lists.postgresql.org, Tomas Vondra <tomas.vondra@postgresql.org>
Subject: Re: [sqlsmith] Crash in mcv_get_match_bitmap
Date: Wed, 10 Jul 2019 23:26:09 +0200
Message-ID: <20190710212609.5mrl7hltbozoxpq7@development> (raw)
In-Reply-To: <15097.1562792274@sss.pgh.pa.us>
References: <8736jdhbhc.fsf@ansel.ydns.eu>
<15097.1562792274@sss.pgh.pa.us>
On Wed, Jul 10, 2019 at 04:57:54PM -0400, Tom Lane wrote:
>Andreas Seltenreich <seltenreich@gmx.de> writes:
>> running sqlsmith on the regression database of REL_12_STABLE at
>> ff597b656f yielded a crash in mcv_get_match_bitmap. I can reproduce it
>> with the following query on the regression database:
>> select filler1 from mcv_lists where a is not null and (select 42) <= c;
>
>Seems to be the same problem I just complained of in the other
>thread: mcv_get_match_bitmap has an untenable assumption that
>"is a pseudoconstant" means "is a Const".
>
Yeah, that's a bug. Will fix (not sure how yet).
BTW which other thread? I don't see any other threads mentioning this
function.
>I notice it's also assuming that the Const must be non-null.
>It's not really easy to crash it that way, because if you just
>write "null <= c" that'll get reduced to constant-NULL earlier.
>But I bet there's a way.
>
Hmmm, I did not think of that.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: tomas.vondra@2ndquadrant.com, tgl@sss.pgh.pa.us, seltenreich@gmx.de, tomas.vondra@postgresql.org
Subject: Re: [sqlsmith] Crash in mcv_get_match_bitmap
In-Reply-To: <20190710212609.5mrl7hltbozoxpq7@development>
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