Horton

Re: PG 18 release notes draft committed

Bruce Momjian <bruce@momjian.us>

View thread
From: Bruce Momjian <bruce@momjian.us>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: "David G. Johnston" <david.g.johnston@gmail.com>, PostgreSQL-development <pgsql-hackers@lists.postgresql.org>
Date: 2025-05-20T12:28:18Z
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

On Tue, May 13, 2025 at 08:05:24AM +0200, Laurenz Albe wrote:
> On Mon, 2025-05-12 at 20:27 -0700, David G. Johnston wrote:
> > Should all columns removed from system views and/or catalogs be listed in
> > “Migration” or is there some filtering criteria? There are at minimum quite
> > a few statistics related ones we’ve dropped that only appear in the Changes
> > section (e.g., pg_stat_io, pg_stat_wal).
> 
> I am not sure.
> 
> On the one hand, the catalogs don't promise to be a stable API, so there
> would be no need to enumerate such changes as compatibility breaks.
> The "Migration" section also doesn't list changes to the exported
> PostgreSQL functins, which has bitten me as extension developer several
> times.
> 
> On the other hand, the catalogs are described in the documentation, which
> gives them more exposure, and it doesn't seem unreasonable to document
> breaking changes as well.
> 
> Do you have an idea how many changes there are?  If there are not too many,
> and somebody is willing to do the work, I wouldn't be against it.

First, I apologize for the delay in my replying --- I was on vacation
last week.

Second, let me explain the criteria I use for table changes, and then we
can discuss if the criteria is correct, and whether I followed the
criteria accurately for PG 18.

So, there are system views and system tables.  Most system views are
important to users, because we created them mostly for user consumption,
while system tables might or might not hold useful information for
users.

Second, we have three possible changes --- column addition, column
renaming, and column removal.  And third, we can list the changes in the
incompatibility section, or in the main release notes.

So, for column additions, I would never list them in the incompatibility
section, though it could break SELECT *.  For renames and deletes, they
would normally appear in the incompatibility section, unless they are
system tables that do not normally hold user-helpful information, in
which case I might list it in the main section, or not at all.

I believe I followed that criteria for PG 18.  There might be a few
cases in PG 18 where columns used for monitoring were renamed or deleted
because they were replaced, and I felt it was too complex to list them
in the incompatibility section because there were new features mixed
into the process so I listed them in the main section.  I thought that
was the proper balance.

-- 
  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.