Horton

Re: PG 13 release notes, first draft

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Bruce Momjian <bruce@momjian.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2020-07-30T02:00:43Z
Lists: pgsql-hackers 
On Wed, Jul 29, 2020 at 6:30 PM Bruce Momjian <bruce@momjian.us> wrote:
> > There should be a note about this in the Postgres 13 release notes,
> > for the usual reasons. More importantly, the "Allow hash aggregation
> > to use disk storage for large aggregation result sets" feature should
> > reference the new GUC directly. Users should be advised that the GUC
> > may be useful in cases where they upgrade and experience a performance
> > regression linked to slower hash aggregation. Just including a
> > documentation link for the GUC would be very helpful.
>
> I came up with the attached patch.

I was thinking something along like the following (after the existing
sentence about avoiding hash aggs in the planner):

If you find that hash aggregation is slower than in previous major
releases of PostgreSQL, it may be useful to increase the value of
hash_mem_multiplier. This allows hash aggregation to use more memory
without affecting competing query operations that are generally less
likely to put any additional memory to good use.

-- 
Peter Geoghegan

Commits

  1. Doc: improve release notes' info about FROM UNPACKAGED feature removal.

  2. Doc: fix misstatement in v13 release notes.

  3. Doc: some more v13 release note tweaking.

  4. Doc: update v13 release notes through today, do a copy-editing pass.

  5. Doc: fill in "major enhancements" list in v13 release notes.

  6. doc: PG 13 relnotes: fix typos

  7. doc: PG 13 relnotes, update TOAST item to mention decompression

  8. pgbench: document that the default data loading is client-side

  9. psql \d: Display table where trigger is defined, if inherited

  10. Skip WAL for new relfilenodes, under wal_level=minimal.

  11. Introduce vacuum errcontext to display additional information.

  12. Fix lquery's behavior for consecutive '*' items.

  13. Improve the internal implementation of ereport().

  14. Add object names to partition integrity violations.

  15. Allow page lock to conflict among parallel group members.

  16. Allow relation extension lock to conflict among parallel group members.

  17. Introduce "anycompatible" family of polymorphic types.

  18. Improve checking of child pages in contrib/amcheck.

  19. doc: Add information about new SQL part SQL/MDA

  20. Added relation name in error messages for constraint checks.

  21. Avoid full scan of GIN indexes when possible

  22. Use carriage returns for data insertion logs in pgbench on terminal

  23. Use memcpy instead of a byte loop in pglz_decompress

  24. Add backtrace support for error reporting

  25. Improve pruning of a default partition

  26. Improve psql's \d output for partitioned indexes.

  27. initdb: Change authentication defaults