| From: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
|---|---|
| To: | Alena Rybakina <a(dot)rybakina(at)postgrespro(dot)ru> |
| Cc: | Andrei Lepikhov <lepihov(at)gmail(dot)com>, Richard Guo <guofenglinux(at)gmail(dot)com>, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alexander Lakhin <exclusion(at)gmail(dot)com>, "Gregory Stark (as CFM)" <stark(dot)cfm(at)gmail(dot)com>, Michał Kłeczek <michal(at)kleczek(dot)org>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
| Subject: | Re: Removing unneeded self joins |
| Date: | 2025-04-26 20:05:27 |
| Message-ID: | CAPpHfds_s7PvwpUAjzhTy730cR3duvVYG2Asy85mzMvTyqtErA@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Sat, Apr 26, 2025 at 11:04 PM Alexander Korotkov
<aekorotkov(at)gmail(dot)com> wrote:
> On Sun, Apr 6, 2025 at 12:02 AM Alena Rybakina
> <a(dot)rybakina(at)postgrespro(dot)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
| Attachment | Content-Type | Size |
|---|---|---|
| v3-0001-Disallow-removing-placeholders-during-Self-Join-E.patch | application/octet-stream | 6.8 KB |
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tomas Vondra | 2025-04-26 20:44:00 | Re: Get rid of integer divide in FAST_PATH_REL_GROUP() macro |
| Previous Message | Alexander Korotkov | 2025-04-26 20:04:22 | Re: Removing unneeded self joins |