Re: Should we optimize the `ORDER BY random() LIMIT x` case?

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Aleksander Alekseev <aleksander@timescale.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andrei Lepikhov <lepihov@gmail.com>, wenhui qiu <qiuwenhuifx@gmail.com>
Date: 2025-05-16T13:01:50Z
Lists: pgsql-hackers
Aleksander Alekseev <aleksander@timescale.com> writes:
> If I'm right about the limitations of aggregate functions and SRFs
> this leaves us the following options:

> 1. Changing the constraints of aggregate functions or SRFs. However I
> don't think we want to do it for such a single niche scenario.
> 2. Custom syntax and a custom node.
> 3. To give up

Seems to me the obvious answer is to extend TABLESAMPLE (or at least, some
of the tablesample methods) to allow it to work on a subquery.

			regards, tom lane