Re: Eager aggregation, take 3
| От | Tender Wang |
|---|---|
| Тема | Re: Eager aggregation, take 3 |
| Дата | |
| Msg-id | CAHewXNn8zB5vH7r6bASznviYY-oJL_pxJyo=s6fPA+NV1_hv2g@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Eager aggregation, take 3 (Richard Guo <guofenglinux@gmail.com>) |
| Список | pgsql-hackers |
Richard Guo <guofenglinux@gmail.com> 于2024年8月29日周四 10:46写道：
On Wed, Aug 28, 2024 at 9:01 PM Robert Haas <robertmhaas@gmail.com> wrote:
> On Tue, Aug 27, 2024 at 11:57 PM Tender Wang <tndrwang@gmail.com> wrote:
> > I haven't look all of them. I just pick few simple plan test(e.g. 19.sql, 45.sql).
> > For example, 19.sql, eager agg pushdown doesn't get large gain, but a little
> > performance regress.
>
> Yeah, this is one of the things I was worried about in my previous
> reply to Richard. It would be worth Richard, or someone, probing into
> exactly why that's happening. My fear is that we just don't have good
> enough estimates to make good decisions, but there might well be
> another explanation.
It's great that we have a query to probe into. Your guess is likely
correct: it may be caused by poor estimates.
Tender, would you please help provide the outputs of
EXPLAIN (COSTS ON, ANALYZE)
on 19.sql with and without eager aggregation?
Yeah, in [1], 19_off.out and 19_on.out are the output of explain(costs off, analyze).
I will do EXPLAIN(COSTS ON, ANALYZE) tests and upload them later today.
Tender Wang
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