Re: Parallel Query

Jeff Janes <[email protected]> Wed, 13 Nov 2019 17:21:26 -0500

Newsgroups	gmane.comp.db.postgresql.performance
Message-ID	<CAMkU=1wqPMzYoRo2zcqwqBkSd_AHnXjPWDmBRnTLFkpCwc7NXw@mail.gmail.com>

On Wed, Nov 13, 2019 at 4:01 PM Luís Roberto Weck <
[email protected]> wrote:

>
> Maybe PostgreSQL can't find a way to calculate having estimates?
>

I wasn't even thinking of the HAVING estimates I was thinking of just the
raw aggregates.  It can't implement the HAVING until has the raw aggregate
in hand. But, what is the actual row count without the HAVING?  Well, I
notice now this line:

Rows Removed by Filter: 6787359

So the row count of rows=86 is mostly due to the HAVING, not due to the raw
aggregation, a point I overlooked initially.  So the planner is not
mistaken in thinking that a huge number of rows need to be passed up--it is
correct in thinking that.

Cheers,

Jeff