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

David Rowley <dgrowleyml@gmail.com>

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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: 2025-11-05T09:44:58Z

Lists: pgsql-hackers

Attachments

v1-0001-Fix-UNION-planner-estimate_num_groups-with-varno-.patch (application/octet-stream) patch v1-0001

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.

David

Commits

Fix UNION planner estimate_num_groups with varno==0
- eaa159632d03 19 (unreleased) landed
Fix possible usage of incorrect UPPERREL_SETOP RelOptInfo
- fdda78e361f1 19 (unreleased) landed
Teach planner to short-circuit EXCEPT/INTERSECT with dummy inputs
- 9c9d41af4db7 19 (unreleased) landed
Fix incorrect targetlist in dummy UNIONs
- 928df067d1e6 19 (unreleased) landed
Teach UNION planner to remove dummy inputs
- 03d40e4b523b 19 (unreleased) landed