Horton

Re: Teaching planner to short-circuit empty UNION/EXCEPT/INTERSECT inputs

David Rowley <dgrowleyml@gmail.com>

View thread View on postgr.es
From: David Rowley <dgrowleyml@gmail.com>
To: Alexander Lakhin <exclusion@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2025-11-06T03:35:43Z
Lists: pgsql-hackers 
On Wed, 5 Nov 2025 at 22:44, David Rowley <dgrowleyml@gmail.com> wrote:
>
> On Wed, 5 Nov 2025 at 18:26, David Rowley <dgrowleyml@gmail.com> wrote:
> > I'm considering restricting that code Path to where the
> > path->parent->reloptkind != RELOPT_UPPER_REL.
>
> I couldn't think of anything better, so here's a patch to that effect.

I've pushed this.

David

Commits

  1. Fix UNION planner estimate_num_groups with varno==0

  2. Fix possible usage of incorrect UPPERREL_SETOP RelOptInfo

  3. Teach planner to short-circuit EXCEPT/INTERSECT with dummy inputs

  4. Fix incorrect targetlist in dummy UNIONs

  5. Teach UNION planner to remove dummy inputs