Re: [PATCH] Remove redundant ORDER BY from COUNT aggregates - Mailing list pgsql-hackers

On Wed, Aug 12, 2026 at 11:01 AM Haibo Yan <tristan.yim@gmail.com> wrote:
> I’d like to propose a small optimization for aggregate-local ORDER BY in COUNT.
> Currently, for example:
>
>     SELECT count(a ORDER BY b) FROM t;
>
> is planned as an ordered aggregate, even though the ordering cannot affect the
> result of COUNT.  This may require a Sort, but the impact is broader than just
> the extra sort: having aggorder also prevents partial aggregation and hash
> aggregation, and prevents the aggregate from sharing state with an otherwise
> identical count(a).

The question that comes to mind is, why would someone (or a program
for that matter) write it this way? Self-join elimination cited ORMs
as a motivation, what is it for this case?

--
John Naylor
Amazon Web Services