Re: Strange coding in mvdistinct.c
От | Tomas Vondra |
---|---|
Тема | Re: Strange coding in mvdistinct.c |
Дата | |
Msg-id | 20190415223541.63ayu2aztt4qqh3l@development обсуждение исходный текст |
Ответ на | Re: Strange coding in mvdistinct.c (Tom Lane <tgl@sss.pgh.pa.us>) |
Список | pgsql-hackers |
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 PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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