Re: Eager aggregation, take 3

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?

> > I will continue to do benchmark on this feature.

Thanks again for running the benchmarks.

Thanks
Richard