Re: Removing unneeded self joins

Alexander Korotkov <aekorotkov@gmail.com>

From: Alexander Korotkov <aekorotkov@gmail.com>

To: Alena Rybakina <a.rybakina@postgrespro.ru>

Cc: Andrei Lepikhov <lepihov@gmail.com>, Richard Guo <guofenglinux@gmail.com>, Ranier Vilela <ranier.vf@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, Alexander Lakhin <exclusion@gmail.com>, "Gregory Stark (as CFM)" <stark.cfm@gmail.com>, Michał Kłeczek <michal@kleczek.org>, Dean Rasheed <dean.a.rasheed@gmail.com>

Date: 2025-04-26T20:05:27Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Remove GUC_NOT_IN_SAMPLE from enable_self_join_elimination
- 717d0e8dd945 18.0 landed
Put enable_self_join_elimination into postgresql.conf.sample
- c2d329260cd8 18.0 landed
Get rid of ojrelid local variable in remove_rel_from_query()
- e167191dc146 18.0 landed
Implement Self-Join Elimination
- fc069a3a6319 18.0 cited
Revert: Remove useless self-joins
- d1d286d83c0e 17.0 landed
Replace lateral references to removed rels in subqueries
- 466979ef031a 17.0 landed
Replace relids in lateral subquery parse tree during SJE
- 489072ab7a9e 17.0 landed
Forbid SJE with result relation
- 8c441c082797 17.0 landed
Fix misuse of RelOptInfo.unique_for_rels cache by SJE
- 30b4955a4668 17.0 landed
Replace the relid in some missing fields during SJE
- a7928a57b9f0 17.0 landed
Revert 56-bit relfilenode change and follow-up commits.
- a448e49bcbe4 16.0 cited
Stabilize timetz test across DST transitions.
- 4a071afbd056 14.0 cited
Speed up finding EquivalenceClasses for a given set of rels
- 3373c7155350 13.0 cited
Fix mark-and-restore-skipping test case to not be a self-join.
- 24d08f3c0a1f 12.0 landed

Attachments

v3-0001-Disallow-removing-placeholders-during-Self-Join-E.patch (application/octet-stream) patch v3-0001

On Sat, Apr 26, 2025 at 11:04 PM Alexander Korotkov
<aekorotkov@gmail.com> wrote:
> On Sun, Apr 6, 2025 at 12:02 AM Alena Rybakina
> <a.rybakina@postgrespro.ru> wrote:
> > Should we add more regression tests covering these cases?
> >
> > I experimented with some examples like this and noticed that it does affect cardinality estimation, though I'm not sure the impact is significant.
> > I used the tables from the regression tests, so if they’re appropriate for reproducing this case, it should be straightforward to add them.
>
> Thank you for your feedback.  I've check the cases you've provided.  I
> found that the differences here are related to the SJE itself, not to
> changes regarding PHVs handling.  I think it generally OK that
> estimates are somewhat changed due to such significant query
> transformation.  Hopefully they should be improved in the majority of
> cases.
>
> I did some improvements to PHVs patch: revised comments and commit
> message.  I'm going to push it if no objections.

Uh, v2 was there already.  That should be v3.

------
Regards,
Alexander Korotkov
Supabase