From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Strange coding in mvdistinct.c
Date: Mon, 15 Apr 2019 18:12:24 -0400
Message-ID: <30400.1555366344@sss.pgh.pa.us> (raw)
In-Reply-To: <29785.1555365602@sss.pgh.pa.us>
References: <29785.1555365602@sss.pgh.pa.us>
Oh, and as I continue to grep, I found this in dependencies.c:
dependencies = (MVDependencies *) repalloc(dependencies,
offsetof(MVDependencies, deps)
+ dependencies->ndeps * sizeof(MVDependency));
I'm pretty sure this is an actual bug: the calculation should be
offsetof(MVDependencies, deps)
+ dependencies->ndeps * sizeof(MVDependency *));
because deps is an array of MVDependency* not MVDependency.
This would lead to an overallocation not underallocation, and it's
probably pretty harmless because ndeps can't get too large (I hope;
if it could, this would have O(N^2) performance problems). Still,
you oughta fix it.
(There's a similar calculation later in the file that gets it right.)
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, tomas.vondra@2ndquadrant.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Strange coding in mvdistinct.c
In-Reply-To: <30400.1555366344@sss.pgh.pa.us>
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