| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | "Todd A(dot) Cook" <tcook(at)blackducksoftware(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, PostgreSQL Bugs <pgsql-bugs(at)postgresql(dot)org> |
| Subject: | Re: BUG #14932: SELECT DISTINCT val FROM table gets stuck in an infinite loop |
| Date: | 2017-12-06 21:40:03 |
| Message-ID: | 20171206214003.lvz3q5coaewxr7vp@alap3.anarazel.de |
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| Lists: | pgsql-bugs |
On 2017-12-06 16:38:18 -0500, Todd A. Cook wrote:
> On 12/06/17 16:12, Andres Freund wrote:
> >
> > > The datasets I shared are somewhat extreme in the sense that there are
> > > many contiguous sequences of hash values, but it only takes one such
> > > sequence with at least SH_GROW_MAX_MOVE values to trigger the issue. So
> > > the hash table may still be perfectly fine for most keys, and only
> > > slightly slower for the keys in the sequence.
> >
> > Meh, we're talking about adversarial attacks here.
>
> Hmmmmm...
>
> I found this problem when I dropped 10.1 into a test environment to see
> what would happen. There was no deliberate attempt to break anything.
Read Thomas' message at: http://archives.postgresql.org/message-id/263b03b1-3e1c-49ca-165a-8ac6751419c4%402ndquadrant.com
Greetings,
Andres Freund
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