Horton

Re: POC: GROUP BY optimization

Andrei Lepikhov <a.lepikhov@postgrespro.ru>

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From: Andrei Lepikhov <a.lepikhov@postgrespro.ru>
To: Tom Lane <tgl@sss.pgh.pa.us>, Alexander Korotkov <aekorotkov@gmail.com>
Cc: Richard Guo <guofenglinux@gmail.com>, Pavel Borisov <pashkin.elfe@gmail.com>, vignesh C <vignesh21@gmail.com>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Teodor Sigaev <teodor@sigaev.ru>, David Rowley <dgrowleyml@gmail.com>, "a.rybakina" <a.rybakina@postgrespro.ru>
Date: 2024-02-02T03:42:45Z
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 →

  1. Restore preprocess_groupclause()

  2. Rename PathKeyInfo to GroupByOrdering

  3. Add invariants check to get_useful_group_keys_orderings()

  4. Fix asymmetry in setting EquivalenceClass.ec_sortref

  5. Multiple revisions to the GROUP BY reordering tests

  6. Get rid of pg_class usage in SJE regression tests

  7. Rename index "abc" in aggregates.sql

  8. Explore alternative orderings of group-by pathkeys during optimization.

  9. Generalize the common code of adding sort before processing of grouping

  10. Fix out-dated comment in preprocess_groupclause()

  11. Force parallelism in partition_aggregate

  12. Optimize order of GROUP BY keys

Attachments

On 2/2/2024 09:02, Tom Lane wrote:
> Alexander Korotkov <aekorotkov@gmail.com> writes:
>> I'm going to push this if there are no objections.
> 
> One of the test cases added by this commit has not been very
> stable in the buildfarm.  Latest example is here:
> 
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=prion&dt=2024-02-01%2021%3A28%3A04
> 
> and I've seen similar failures intermittently on other machines.
> 
> I'd suggest building this test atop a table that is more stable
> than pg_class.  You're just waving a red flag in front of a bull
> if you expect stable statistics from that during a regression run.
> Nor do I see any particular reason for pg_class to be especially
> suited to the test.
Yeah, It is my fault. Please, see in the attachment the patch fixing that.
-- 
regards,
Andrei Lepikhov
Postgres Professional