| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Jeff Davis <jdavis(at)postgresql(dot)org>, 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 01:57:58 |
| Message-ID: | 20200605015758.p64bz3srqi2a3pqr@alap3.anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers |
Hi,
On 2020-06-04 18:22:03 -0700, Jeff Davis wrote:
> 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?
I don't really see why there needs to be a minimum bigger than 1?
Greetings,
Andres Freund
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