| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | "Todd A(dot) Cook" <tcook(at)blackducksoftware(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(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: | 2017-11-28 18:14:59 |
| Message-ID: | 20171128181459.d4pqmum2tjtrdwdd@alap3.anarazel.de |
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| Lists: | pgsql-bugs |
On 2017-11-28 09:55:13 -0500, Todd A. Cook wrote:
> On 11/27/17 23:03, Tom Lane wrote:
> >
> > Note that the sample data has a lot of collisions:
> >
> > regression=# select hashint8(val), count(*) from reproducer group by 1 order by 2 desc;
> > hashint8 | count
> > -------------+-------
> > 441526644 | 2337
> > -1117776826 | 1221
> > -1202007016 | 935
> > -2068831050 | 620
> > 1156644653 | 538
> > 553783815 | 510
> > 259780770 | 444
> > 371047036 | 394
> > 915722575 | 359
> > ... etc etc ...
>
> In case it matters, the complete data set will have some outlier values with 10k to 100k
> collisions in this column.
To make sure we're on the same page, this is data intentionally created
to have a lot of hash collisions, is that right?
Greetings,
Andres Freund
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