Re: Strange coding in mvdistinct.c

On Mon, Apr 15, 2019 at 06:12:24PM -0400, Tom Lane wrote:
>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.)
>

Thanks. I noticed some of the bugs while investigating the recent MCV
serialization, and I plan to fix them soon. This week, hopefully.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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