| From: | "Todd A(dot) Cook" <tcook(at)blackducksoftware(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | 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 21:38:18 |
| Message-ID: | 21d507d9-9024-33a8-37c8-b472b3dce7df@blackducksoftware.com |
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| Lists: | pgsql-bugs |
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.
-- todd
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