From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
---|---|
To: | Ronan Dunklau <ronan(dot)dunklau(at)aiven(dot)io> |
Cc: | PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
Subject: | Re: Add proper planner support for ORDER BY / DISTINCT aggregates |
Date: | 2021-07-17 02:36:09 |
Message-ID: | CAApHDvoi4mr1hq-WjTV=xmz_O-mjUox8CXEszNxJt+YVEcF44w@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Fri, 16 Jul 2021 at 22:00, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
>
> On Fri, 16 Jul 2021 at 18:04, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> > What we maybe could consider instead would be to pick the first Aggref
> > then look for the most sorted derivative of that then tally up the
> > number of Aggrefs that can be sorted using those pathkeys, then repeat
> > that process for the remaining Aggrefs that didn't have the same
> > prefix then use the pathkeys for the set with the most Aggrefs. We
> > could still tiebreak on the targetlist position so at least it's not
> > random which ones we pick. Now that we have a list of Aggrefs that are
> > deduplicated in the planner thanks to 0a2bc5d61e it should be fairly
> > easy to do that.
>
> I've attached a patch which does as I mention above.
Looks like I did a sloppy job of that. I messed up the condition in
standard_qp_callback() that sets the ORDER BY aggregate pathkeys so
that it accidentally set them when there was an unsortable GROUP BY
clause, as highlighted by the postgres_fdw tests failing. I've now
added a comment to explain why the condition is the way it is so that
I don't forget again.
Here's a cleaned-up version that passes make check-world.
David
Attachment | Content-Type | Size |
---|---|---|
v5-0001-Add-planner-support-for-ORDER-BY-aggregates.patch | application/octet-stream | 25.4 KB |
From | Date | Subject | |
---|---|---|---|
Next Message | Bharath Rupireddy | 2021-07-17 03:55:11 | Re: What are exactly bootstrap processes, auxiliary processes, standalone backends, normal backends(user sessions)? |
Previous Message | Justin Pryzby | 2021-07-17 01:02:59 | Re: CREATE TABLE .. PARTITION OF fails to preserve tgenabled for inherited row triggers |