Horton

Re: POC: GROUP BY optimization

Pavel Borisov <pashkin.elfe@gmail.com>

View thread
From: Pavel Borisov <pashkin.elfe@gmail.com>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Teodor Sigaev <teodor@sigaev.ru>, Gavin Flower <GavinFlower@archidevsys.co.nz>, Andres Freund <andres@anarazel.de>, Michael Paquier <michael@paquier.xyz>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2020-10-26T09:28:59Z
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

> Thanks for your interest! FYI there is a new thread about this topic [1]
> with the next version of the patch and more commentaries (I've created
> it for visibility purposes, but probably it also created some confusion,
> sorry for that).
>
> Thanks!

I made a very quick look at your updates and noticed that it is intended to
be simple and some parts of the code are removed as they have little test
coverage. I'd propose vice versa to increase test coverage to enjoy more
precise cost calculation and probably partial grouping.

Or maybe it's worth to benchmark both patches and then re-decide what we
want more to have a more complicated or a simpler version.

Good to know that this feature is not stuck anymore and we have more than
one proposal.
Thanks!

-- 
Best regards,
Pavel Borisov

Postgres Professional: http://postgrespro.com <http://www.postgrespro.com>