Re: Eager aggregation, take 3

Richard Guo <guofenglinux(at)gmail(dot)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(at)gmail(dot)com> wrote:
> > On Tue, Aug 27, 2024 at 11:57 PM Tender Wang <tndrwang(at)gmail(dot)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?
>
> I upload EXPLAIN(COSTS ON, ANALYZE) test to [1].
I ran the same query three times, and I chose the third time result.
You can check 19_off_explain.out and 19_on_explain.out.

[1] https://github.com/tenderwg/eager_agg

--
Tender Wang