| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "Todd A(dot) Cook" <tcook(at)blackducksoftware(dot)com>, pgsql-bugs(at)postgresql(dot)org |
| Subject: | Re: BUG #14932: SELECT DISTINCT val FROM table gets stuck in an infinite loop |
| Date: | 2018-01-26 23:47:41 |
| Message-ID: | 20180126234741.4wswfztzkuqrotnv@alap3.anarazel.de |
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| Lists: | pgsql-bugs |
On 2018-01-26 18:22:26 -0500, Tom Lane wrote:
> In any case, we still need a fix for the behavior that the hash table size
> is blown out by lots of collisions, because that can happen no matter what
> the hash function is. Andres seems to have dropped the ball on doing
> something about that.
Didn't have spare brain cycles :(, and the next backbranch release
wasn't yet close reducing immediate urgency a bit. As written nearby I
think we should make execGrouping.c users of hashtables use a more
random IV, and apply something similar to the growth limit patch from
Tomas.
Greetings,
Andres Freund
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