From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Andreas Seltenreich <seltenreich(at)gmx(dot)de>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Tomas Vondra <tomas(dot)vondra(at)postgresql(dot)org> |
Subject: | Re: [sqlsmith] Crash in mcv_get_match_bitmap |
Date: | 2019-07-10 21:26:09 |
Message-ID: | 20190710212609.5mrl7hltbozoxpq7@development |
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Lists: | pgsql-hackers |
On Wed, Jul 10, 2019 at 04:57:54PM -0400, Tom Lane wrote:
>Andreas Seltenreich <seltenreich(at)gmx(dot)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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