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From: Richard Guo <guofenglinux@gmail.com>
Date: Thu, 29 Aug 2024 10:45:58 +0800
Message-ID: <CAMbWs4-Q-CHadH1ub_oAv3sJ_NHt0GUO4nce3LBhpPmp1v6Z_Q@mail.gmail.com>
Subject: Re: Eager aggregation, take 3
To: Robert Haas <robertmhaas@gmail.com>
Cc: Tender Wang <tndrwang@gmail.com>, Paul George <p.a.george19@gmail.com>, 
	Andy Fan <zhihuifan1213@163.com>, 
	PostgreSQL-development <pgsql-hackers@postgresql.org>, pgsql-hackers@lists.postgresql.org
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On Wed, Aug 28, 2024 at 9:01=E2=80=AFPM Robert Haas <robertmhaas@gmail.com>=
 wrote:
> On Tue, Aug 27, 2024 at 11:57=E2=80=AFPM Tender Wang <tndrwang@gmail.com>=
 wrote:
> > I haven't look all of them. I just pick few simple plan test(e.g. 19.sq=
l, 45.sql).
> > For example, 19.sql, eager agg pushdown doesn't get large gain, but a l=
ittle
> > 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 will continue to do benchmark on this feature.

Thanks again for running the benchmarks.

Thanks
Richard