Horton

Re: POC: GROUP BY optimization

Alexander Korotkov <aekorotkov@gmail.com>

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From: Alexander Korotkov <aekorotkov@gmail.com>
To: Andrei Lepikhov <a.lepikhov@postgrespro.ru>
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>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2024-01-19T14:21:48Z
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

Hi!

I've applied your changes with minor editing, thank you.

On Thu, Jan 18, 2024 at 11:49 AM Andrei Lepikhov
<a.lepikhov@postgrespro.ru> wrote:
> >> * Part of the work performed in this patch overlaps with that of
> >> preprocess_groupclause.  They are both trying to adjust the ordering of
> >> the GROUP BY keys to match ORDER BY.  I wonder if it would be better to
> >> perform this work only once.
> >
> > Andrei, could you take a look.
> As I see, the PathKeyInfo list often contains duplicated pathkeys,
> coming from either sort_pathkeys or path->pathkeys orderings. So, I can
> propose to check duplicates each time (see step2.txt in attachment).

Actually I asked to recheck if we can cut some part of
preprocess_groupclause() given that we're reordering the pathkeys
later.  It seems that we can remove everything except the work with a
grouping set.  I've done this in the revised patchset.

I'm going to push this if there are no objections.

------
Regards,
Alexander Korotkov