| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Jeff Davis <jdavis(at)postgresql(dot)org> |
| Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: significant slowdown of HashAggregate between 9.6 and 10 |
| Date: | 2020-06-05 01:22:03 |
| Message-ID: | 267a8b8ea4c6610b8f6a4b23cdaa5e4e088f341a.camel@j-davis.com |
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| Lists: | pgsql-hackers |
On Thu, 2020-06-04 at 11:41 -0700, Andres Freund wrote:
> +/* minimum number of initial hash table buckets */
> +#define HASHAGG_MIN_BUCKETS 256
>
>
> I don't really see much explanation for that part in the commit,
> perhaps
> Jeff can chime in?
I did this in response to a review comment (point #5):
https://www.postgresql.org/message-id/20200219191636.gvdywx32kwbix6kd@development
Tomas suggested a min of 1024, and I thought I was being more
conservative choosing 256. Still too high, I guess?
I can lower it. What do you think is a reasonable minimum?
Regards,
Jeff Davis
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