Horton

Re: speeding up planning with partitions

Amit Langote <amitlangote09@gmail.com>

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From: Amit Langote <amitlangote09@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, David Rowley <david.rowley@2ndquadrant.com>, Imai Yoshikazu <yoshikazu_i443@live.jp>, "jesper.pedersen@redhat.com" <jesper.pedersen@redhat.com>, "Imai, Yoshikazu" <imai.yoshikazu@jp.fujitsu.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-03-30T16:06:26Z
Lists: pgsql-hackers 
On Sun, Mar 31, 2019 at 12:11 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Amit Langote <amitlangote09@gmail.com> writes:
> > I think the performance results did prove that degradation due to
> > those loops over part_rels becomes significant for very large
> > partition counts.  Is there a better solution than the bitmapset that
> > you have in mind?
>
> Hm, I didn't see much degradation in what you posted in
> <5c83dbca-12b5-1acf-0e85-58299e464a26@lab.ntt.co.jp>.

Sorry that I didn't mention the link to begin with, but I meant to
point to numbers that I reported on Monday this week.

https://www.postgresql.org/message-id/19f54c17-1619-b228-10e5-ca343be6a4e8%40lab.ntt.co.jp

You were complaining of the bitmapset being useless overhead for small
partition counts, but the numbers I get tend to suggest that any
degradation in performance is within noise range, whereas the
performance benefit from having them looks pretty significant for very
large partition counts.

> I am curious as to why there seems to be more degradation
> for hash cases, as per Yoshikazu-san's results in
> <0F97FA9ABBDBE54F91744A9B37151A512BAC60@g01jpexmbkw24>,
> but whatever's accounting for the difference probably
> is not that.

I suspected it may have been the lack of bitmapsets, but maybe only
Imai-san could've confirmed that by applying the live_parts patch too.

Thanks,
Amit

Commits

  1. Clean up handling of constraint_exclusion and enable_partition_pruning.

  2. Add test case exercising formerly-unreached code in inheritance_planner.

  3. Speed up planning when partitions can be pruned at plan time.

  4. Avoid crash in partitionwise join planning under GEQO.

  5. Avoid passing query tlist around separately from root->processed_tlist.

  6. Build "other rels" of appendrel baserels in a separate step.

  7. Get rid of duplicate child RTE for a partitioned table.

  8. Rearrange make_partitionedrel_pruneinfo to avoid work when we can't prune.

  9. Don't copy PartitionBoundInfo in set_relation_partition_info.

  10. Move building of child base quals out into a new function

  11. Reorganize planner code moved in b60c39759908

  12. Move inheritance expansion code into its own file

  13. Fix inherited UPDATE/DELETE with UNION ALL subqueries.

  14. Rearrange planner to save the whole PlannerInfo (subroot) for a subquery.