Horton

Re: First draft of the PG 15 release notes (sorting)

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Bruce Momjian <bruce@momjian.us>, pgsql-hackers@postgresql.org
Date: 2022-05-11T02:38:19Z
Lists: pgsql-hackers 
On Wed, May 11, 2022 at 12:39:41PM +1200, David Rowley wrote:
> I think the sort improvements done in v15 are worth a mention under
> General Performance.  The commits for this were 91e9e89dc, 40af10b57
> and 697492434.  I've been running a few benchmarks between v14 and v15
> over the past few days and a fairly average case speedup is about 25%.
> but there are cases where I've seen up to 400%.  I think the increase
> is to an extent that we maybe should have considered making tweaks in
> cost_tuplesort(). I saw some plans that ran in about 60% of the time
> by disabling Hash Agg and allowing Sort / Group Agg to do the work.

Is there any reason not to consider it now ?  Either for v15 or v15+1.

I wonder if this is also relevant.

65014000b35 Replace polyphase merge algorithm with a simple balanced k-way merge.

-- 
Justin

Commits

  1. Doc: last minute adjustment to the release notes

  2. Doc: more tweaking of v15 release notes.

  3. Doc: further adjust notes about pg_upgrade_output.d.

  4. Doc: add list of major features to the v15 release notes.

  5. relnotes: update item about public schema permission change

  6. relnotes: update ordered partition scan item

  7. relnotes: add Heikki to UTF8 item

  8. relnotes: improve UTF8 text item in relation to ASCII

  9. relnotes: add null logical replication item

  10. relnotes: adjust several logical replication items and FK text

  11. relnotes: mention non-exclusive backup mode was deprecated

  12. relnotes: add author to in-memory sorts item

  13. relnotes: update for non-exclusive backup mode removal

  14. relnote: improve sorting entries

  15. relnotes: adjustments from Álvaro Herrera

  16. relnotes: update foreign key partition and add sort items

  17. relnotes: more adjustments

  18. relnotes: logical replication permissions checked by subscrib.

  19. relnotes: adjustments

  20. relnotes: remove sequence replication and update 'postgres -C'

  21. relnote: extensive updates

  22. relnotes: "training" -> "trailing"

  23. Standardize references to Zstandard as <productname>

  24. pgstat: Update docs to match the shared memory stats reality.

  25. Raise a WARNING for missing publications.

  26. Skip empty transactions for logical replication.

  27. Optionally disable subscriptions on error.

  28. Allow root-owned SSL private keys in libpq, not only the backend.

  29. Use COPY FREEZE in pgbench for faster benchmark table population.