Horton

Re: PG 18 release notes draft committed

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: jian he <jian.universality@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@lists.postgresql.org>
Date: 2025-05-03T16:56:16Z
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. doc PG 18 relnotes: add AFTER trigger user change item

  2. doc PG 18 relnotes: modify async I/O item for other improvements

  3. doc PG 18 relnotes: split apart log_connections item

  4. doc PG 18 relnotes: move ANALYZE item,split ANALYZE/EXPLAIN item

  5. doc PG 18 relnotes: clarify multiplication item

  6. doc PG 18 relnotes: add removal details to MD5 item

  7. doc PG 18 relnotes: fix markup

  8. doc PG 18 relnotes: clarify btree skip-scan item

  9. doc PG 18 relnotes: update to current

  10. doc PG 18 relnotes: adjust CREATE SUBSCRIPTION attribution

  11. doc PG 18 relnotes: clarify btree skip scan item

  12. doc PG 18 relnotes: mv. hash joins and GROUP BY item to General

  13. Add support for runtime arguments in injection points

  14. doc PG 18 relnotes: fix missing parens for crc32c()

  15. PG 18 relnotes: adjust RETURNING new/old item

  16. doc PG 18 relnotes: adjust pg_log_backend_memory_contexts()

  17. doc PG 18 relnotes: add pg_log_backend_memory_contexts() mention

  18. doc PG 18 relnotes: adjust pgbench per-script reporting item

  19. doc PG 18 relnotes: mention GROUP SET fixes

  20. doc PG 18 relnotes: adjust partition planning item

  21. doc PG 18 relnotes: small adjustments regarding options

  22. doc PG 18 relnotes: move partition locking item to General Perf

  23. doc PG 18 relnotes: adjust partition items

  24. doc PG 18 relnotes: reword OAuth item

  25. doc PG 18 relnotes: add mention of pg_stat_reset_backend_stats()

  26. doc PG 18 relnotes: adjust hash item

  27. doc PG 18 relnotes: split partition optimizer item into two

  28. doc PG 18 relnotes: adjust COPY and REJECT_LIMIT items

  29. doc PG 18 relnotes: move and clarify constraint items

  30. doc PG 18 relnotes: add commit for cancel key and protocol neg.

  31. doc PG 18 relnotes: fix libpq wording

  32. doc PG 18 relnotes: add GROUP BY column elimination item

  33. doc PG 18 relnotes: move protocol version item to "server"

  34. doc PG 18 relnotes: adjust libpq trace & potocol version items

  35. doc PG 18 relnotes: reword and reorder items

  36. doc: Fix memory context level in pg_log_backend_memory_contexts() example.

  37. Make levels 1-based in pg_log_backend_memory_contexts()

  38. Introduce file_copy_method setting.

  39. libpq: Handle NegotiateProtocolVersion message differently

  40. Add timingsafe_bcmp(), for constant-time memory comparison

  41. Optimization for lower(), upper(), casefold() functions.

  42. Fix ALTER SUBSCRIPTION ... SET PUBLICATION ... command.

  43. Add connection establishment duration logging

  44. Modularize log_connections output

  45. Ensure that AFTER triggers run as the instigating user.

  46. Detect redundant GROUP BY columns using UNIQUE indexes

  47. Move cancel key generation to after forking the backend

Attachments

On Sat, May  3, 2025 at 11:04:45PM +0800, jian he wrote:
> On Fri, May 2, 2025 at 10:44 AM Bruce Momjian <bruce@momjian.us> wrote:
> >
> > I have committd the first draft of the PG 18 release notes.  The item
> > count looks strong:
> >         release-17:   182
> >         release-18:   209
> >
> > I will continue improving it until beta 1, and until the final release.
> > I will probably add markup in 1-3 weeks.  Let the feedback begin.  ;-)
> >
> > You can see the most current HTML-built version here:
> >
> >         https://momjian.us/pgsql_docs/release-18.html
> >
> 
> seems you missed this ([1]):
> 
> Detect redundant GROUP BY columns using UNIQUE indexes
> 
> d4c3a156c added support that when the GROUP BY contained all of the columns
> belonging to a relation's PRIMARY KEY, all other columns belonging to that
> relation would be removed from the GROUP BY clause. That's possible because all
> other columns are functionally dependent on the PRIMARY KEY and those columns
> alone ensure the groups are distinct.
> 
> [1] https://git.postgresql.org/cgit/postgresql.git/commit/?id=bd10ec529796a13670645e6acd640c6f290df020

We added this item to the PG 9.6 release notes:

	<!--
	2016-02-11 [d4c3a156c] Remove GROUP BY columns that are functionally dependent
	-->
	       <para>
	        Ignore <literal>GROUP BY</> columns that are
	        functionally dependent on other columns (David Rowley)
	       </para>
	
	       <para>
	        If a <literal>GROUP BY</> clause includes all columns of a
	        non-deferred primary key, as well as other columns of the same
	        table, those other columns are redundant and can be dropped
	        from the grouping.  This saves computation in many common cases.
	       </para>
	      </listitem>

Interestingly, the first paragraph suggests this optimization already
works for unique indexes, but the text below it states it only works for
primary keys.

As a nod to PG 9.6, which was released in 2016, I duplicated that item
and reworded it for this commit.  :-)  Patch attached.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Do not let urgent matters crowd out time for investment in the future.