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  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

  1. PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-02T02:44:50Z

    I have committd the first draft of the PG 18 release notes.  The item
count looks strong:

	release-7.4:  263
	release-8.0:  230
	release-8.1:  174
	release-8.2:  215
	release-8.3:  214
	release-8.4:  314
	release-9.0:  237
	release-9.1:  203
	release-9.2:  238
	release-9.3:  177
	release-9.4:  211
	release-9.5:  193
	release-9.6:  214
	release-10:   189
	release-11:   170
	release-12:   180
	release-13:   178
	release-14:   220
	release-15:   184
	release-16:   206
	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

-- 
  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.

  2. Re: PG 18 release notes draft committed

    amit <amitlangote09@gmail.com> — 2025-05-02T04:00:57Z

    Hi Bruce,

On Fri, May 2, 2025 at 11:44 AM Bruce Momjian <bruce@momjian.us> wrote:
> I have committd the first draft of the PG 18 release notes.
>
> 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.  ;-)

Thanks as always for working on this.

I noticed the release notes currently combine several
partition-related commits under one item:

+<!--
+Author: Amit Langote <amitlan@postgresql.org>
+2025-01-30 [bb3ec16e1] Move PartitionPruneInfo out of plan nodes into PlannedSt
+Author: Amit Langote <amitlan@postgresql.org>
+2025-01-31 [d47cbf474] Perform runtime initial pruning outside ExecInitNode()
+Author: Amit Langote <amitlan@postgresql.org>
+2025-02-07 [cbc127917] Track unpruned relids to avoid processing pruned relatio
+Author: Amit Langote <amitlan@postgresql.org>
+2025-02-20 [525392d57] Don't lock partitions pruned by initial pruning
+Author: Amit Langote <amitlan@postgresql.org>
+2025-04-04 [88f55bc97] Make derived clause lookup in EquivalenceClass more effi
+Author: David Rowley <drowley@postgresql.org>
+2025-04-08 [d69d45a5a] Speedup child EquivalenceMember lookup in planner
+-->
+<listitem>
+<para>
+Allow partitions to be pruned earlier and quicker, and skipped in
more places (Amit Langote, Ashutosh Bapat, Yuya Watari, David Rowley)
+<ulink url="&commit_baseurl;bb3ec16e1">&sect;</ulink>
+<ulink url="&commit_baseurl;d47cbf474">&sect;</ulink>
+<ulink url="&commit_baseurl;cbc127917">&sect;</ulink>
+<ulink url="&commit_baseurl;525392d57">&sect;</ulink>
+<ulink url="&commit_baseurl;88f55bc97">&sect;</ulink>
+<ulink url="&commit_baseurl;d69d45a5a">&sect;</ulink>
+</para>
+</listitem>

But I think these really fall into three separate improvements:

1. Speed up execution of cached plans by deferring locks on partitions
subject to pruning (Amit Langote)
(bb3ec16e1, d47cbf474, cbc127917, 525392d57)

2. Speed up child EquivalenceMember lookup in planner (Yuya Watari,
David Rowley)
(d69d45a5a)

3. Speed up derived clause lookup in EquivalenceClass (Ashutosh Bapat)
(88f55bc97)

Alternatively, 2 and 3 can be combined as:

2. Speed up partition planning by improving EquivalenceClass lookups
(Yuya Watari, David Rowley, Ashutosh Bapat)

I think 1 should go under Partitioning, which I see is currently missing.

Any thoughts, David?

Can work on a patch if you'd like.

-- 
Thanks, Amit Langote

  3. Re: PG 18 release notes draft committed

    Jacob Champion <jacob.champion@enterprisedb.com> — 2025-05-02T15:24:42Z

    On Thu, May 1, 2025 at 7:44 PM Bruce Momjian <bruce@momjian.us> wrote:
> I will probably add markup in 1-3 weeks.  Let the feedback begin.  ;-)

Thanks!

>    <para>
>     Version 18 contains a number of changes that may affect compatibility
>     with previous releases.  Observe the following incompatibilities:
>    </para>
>    [...]
> Rename server variable ssl_ecdh_curve to ssl_groups and allow multiple colon-separated ECDH curves to be specified (Erica Zhang, Daniel Gustafsson)

The previous setting name should continue to function correctly, since
it's mapped as an alias, so this can probably be moved into the
"standard" config features rather than a compatibility change.

--Jacob

  4. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-02T15:38:35Z

    On Fri, May  2, 2025 at 08:24:42AM -0700, Jacob Champion wrote:
> On Thu, May 1, 2025 at 7:44 PM Bruce Momjian <bruce@momjian.us> wrote:
> > I will probably add markup in 1-3 weeks.  Let the feedback begin.  ;-)
> 
> Thanks!
> 
> >    <para>
> >     Version 18 contains a number of changes that may affect compatibility
> >     with previous releases.  Observe the following incompatibilities:
> >    </para>
> >    [...]
> > Rename server variable ssl_ecdh_curve to ssl_groups and allow multiple colon-separated ECDH curves to be specified (Erica Zhang, Daniel Gustafsson)
> 
> The previous setting name should continue to function correctly, since
> it's mapped as an alias, so this can probably be moved into the
> "standard" config features rather than a compatibility change.

Thanks, done.  The commit message didn't indicate the old name would
still work, and I didn't review the patch for that.

-- 
  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.

  5. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-02T16:18:06Z

    On Fri, May  2, 2025 at 01:00:57PM +0900, Amit Langote wrote:
> 1. Speed up execution of cached plans by deferring locks on partitions
> subject to pruning (Amit Langote)
> (bb3ec16e1, d47cbf474, cbc127917, 525392d57)
> 
> 2. Speed up child EquivalenceMember lookup in planner (Yuya Watari,
> David Rowley)
> (d69d45a5a)
> 
> 3. Speed up derived clause lookup in EquivalenceClass (Ashutosh Bapat)
> (88f55bc97)
> 
> Alternatively, 2 and 3 can be combined as:
> 
> 2. Speed up partition planning by improving EquivalenceClass lookups
> (Yuya Watari, David Rowley, Ashutosh Bapat)
> 
> I think 1 should go under Partitioning, which I see is currently missing.
> 
> Any thoughts, David?
> 
> Can work on a patch if you'd like.

So, a few things.  First, these set of commits was in a group of 10 that
I added since there have been complaints in the past that optimizer
improvements were not listed and therefore patch authors were not given
sufficient credit.  That means the 209 item count for PG 18 is 10 higher
than my normal filtering would produce.

Second, looking at the items, these are a case of "X is faster", which
we don't normally mention in the release notes.  We normally mention
"faster" when it is so much faster that use cases which were not
possible before might be possible now, so it is recommended to retest.
That is what I saw this grouped item as, whereas I don't think the
individual items meet that criteria.

Also, I didn't see enough partition items to warrant a separate
partition section, and we didn't have one in PG 17 either.  We could
pull all the partition items from the sections they are already in, but
they seem more natural in the sections they are in.

I don't think most people would know what EquivalenceMember is, and even
if they did, would they be able to connect it to an SQL query?

Finally, I see the big increases in this release as being the optimizer,
monitoring, and constraints.

-- 
  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.

  6. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-02T16:25:07Z

    On Fri, May  2, 2025 at 12:18:06PM -0400, Bruce Momjian wrote:
> Finally, I see the big increases in this release as being the optimizer,
> monitoring, and constraints.

Also, and I am loving the chapter markers linking to gitweb.

-- 
  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.

  7. Re: PG 18 release notes draft committed

    Jelte Fennema-Nio <postgres@jeltef.nl> — 2025-05-02T23:46:29Z

    On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
>
> I have committd the first draft of the PG 18 release notes.  The item
> count looks strong:

Thanks for all the work. Some notes:

1. There's currently no mention that protocol version 3.2 was
introduced in this release. I'm not sure where/how this should be
mentioned, but I definitely think it should be somewhere. It's a
pretty major change. One option is to replace/amend the "Make cancel
request keys 256 bits" item. Maybe replace that with something like:
"Postgres 18 introduces protocol version 3.2. This is the first new
protocol version since 3.0, which was introduced in Postgres 7.4. This
new protocol version 3.2 allows a server to use longer cancel request
keys. When the client advertises support for protocol version 3.2 (or
higher) Postgres 18 will use a cancel key size of 256 bits."
2. Obviously biased since it's my contribution, but I think d38bab5
might deserve a mention.
3. The "Add PQtrace() output..." commitlist should also contain 7adec2d5fc

  8. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-03T00:06:41Z

    On Sat, May  3, 2025 at 01:46:29AM +0200, Jelte Fennema-Nio wrote:
> On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
> >
> > I have committd the first draft of the PG 18 release notes.  The item
> > count looks strong:
> 
> Thanks for all the work. Some notes:
> 
> 1. There's currently no mention that protocol version 3.2 was
> introduced in this release. I'm not sure where/how this should be
> mentioned, but I definitely think it should be somewhere. It's a
> pretty major change. One option is to replace/amend the "Make cancel
> request keys 256 bits" item. Maybe replace that with something like:
> "Postgres 18 introduces protocol version 3.2. This is the first new
> protocol version since 3.0, which was introduced in Postgres 7.4. This
> new protocol version 3.2 allows a server to use longer cancel request
> keys. When the client advertises support for protocol version 3.2 (or
> higher) Postgres 18 will use a cancel key size of 256 bits."

Okay, I added a mention next to the libpq version function entries.

> 2. Obviously biased since it's my contribution, but I think d38bab5
> might deserve a mention.

I disagree.  pgbench limits like this are not something we give much
detail around error avoidance to in the release notes.

> 3. The "Add PQtrace() output..." commitlist should also contain 7adec2d5fc

Added.  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.

  9. Re: PG 18 release notes draft committed

    Jelte Fennema-Nio <postgres@jeltef.nl> — 2025-05-03T11:16:24Z

    On Sat, 3 May 2025 at 02:06, Bruce Momjian <bruce@momjian.us> wrote:
>
> On Sat, May  3, 2025 at 01:46:29AM +0200, Jelte Fennema-Nio wrote:
> > On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
> > >
> > > I have committd the first draft of the PG 18 release notes.  The item
> > > count looks strong:
> >
> > Thanks for all the work. Some notes:
> >
> > 1. There's currently no mention that protocol version 3.2 was
> > introduced in this release. I'm not sure where/how this should be
> > mentioned, but I definitely think it should be somewhere. It's a
> > pretty major change. One option is to replace/amend the "Make cancel
> > request keys 256 bits" item. Maybe replace that with something like:
> > "Postgres 18 introduces protocol version 3.2. This is the first new
> > protocol version since 3.0, which was introduced in Postgres 7.4. This
> > new protocol version 3.2 allows a server to use longer cancel request
> > keys. When the client advertises support for protocol version 3.2 (or
> > higher) Postgres 18 will use a cancel key size of 256 bits."
>
> Okay, I added a mention next to the libpq version function entries.

I think it should be mentioned in the server section. How about we
replace: "This is enabled when the libpq client and server are
Postgres 18 or later. ", with the following:

This is only enabled when the client supports the wire protocol
version 3.2 (or up), Wire protocol version 3.2 is introduced in this
release. For libpq based clients that means that libpq needs to be of
version 18 or higher.

That also makes it clear that for non-libpq based clients people
should check if their client supports it.

  10. Re: PG 18 release notes draft committed

    jian he <jian.universality@gmail.com> — 2025-05-03T15:04:45Z

    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

  11. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-03T16:19:54Z

    On Sat, May  3, 2025 at 01:16:24PM +0200, Jelte Fennema-Nio wrote:
> On Sat, 3 May 2025 at 02:06, Bruce Momjian <bruce@momjian.us> wrote:
> >
> > On Sat, May  3, 2025 at 01:46:29AM +0200, Jelte Fennema-Nio wrote:
> > > On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
> > > >
> > > > I have committd the first draft of the PG 18 release notes.  The item
> > > > count looks strong:
> > >
> > > Thanks for all the work. Some notes:
> > >
> > > 1. There's currently no mention that protocol version 3.2 was
> > > introduced in this release. I'm not sure where/how this should be
> > > mentioned, but I definitely think it should be somewhere. It's a
> > > pretty major change. One option is to replace/amend the "Make cancel
> > > request keys 256 bits" item. Maybe replace that with something like:
> > > "Postgres 18 introduces protocol version 3.2. This is the first new
> > > protocol version since 3.0, which was introduced in Postgres 7.4. This
> > > new protocol version 3.2 allows a server to use longer cancel request
> > > keys. When the client advertises support for protocol version 3.2 (or
> > > higher) Postgres 18 will use a cancel key size of 256 bits."
> >
> > Okay, I added a mention next to the libpq version function entries.
> 
> I think it should be mentioned in the server section. How about we
> replace: "This is enabled when the libpq client and server are
> Postgres 18 or later. ", with the following:
> 
> This is only enabled when the client supports the wire protocol
> version 3.2 (or up), Wire protocol version 3.2 is introduced in this
> release. For libpq based clients that means that libpq needs to be of
> version 18 or higher.
> 
> That also makes it clear that for non-libpq based clients people
> should check if their client supports it.

I moved the item and added some text, 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.

  12. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-03T16:56:16Z

    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.

  13. Re: PG 18 release notes draft committed

    Jelte Fennema-Nio <postgres@jeltef.nl> — 2025-05-03T19:40:47Z

    On Sat, 3 May 2025 at 18:19, Bruce Momjian <bruce@momjian.us> wrote:
> I moved the item and added some text, patch attached.

LGTM, apart from the typo in the word "client' (it's spelled as
"cliient" in the diff).

Noticed a few other small things when rereading:

1. "Add libpq functions and environment..." should be "Add libpq
connection parameters and environment
2. "Allow the specification of non-overlapping PRIMARY KEY and UNIQUE
constraints" has no commit attached to it. I noticed this because it
wasn't fully clear to me what this feature entailed, so I wanted to
look at it in more detail.
3. "Report search_path changes to the client." is currently in the
libpq section, but this is a server-only change. So that seems a bit
strange. Not sure where to put it though.

  14. Re: PG 18 release notes draft committed

    Alexander Borisov <lex.borisov@gmail.com> — 2025-05-03T22:31:51Z

    Hi hackers,

> 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
> 


I'm not sure, but I'll ask.

I have significantly improved the handling of Unicode Case in
PostgreSQL.
The improvements affect important functions such as lower(), upper(),
casefold().
Specifically, the patch has significantly reduced the size of Unicode
Case tables (and consequently the size of the object file).
We got a significant speed gain:
ASCII by ≈10%
Cyrillic by ≈80%
Unicode in general by ≈30%

But, unfortunately, I didn't see any mention of this improvement in the
release notes.
Hence the question to the community - are such improvements worth
mentioning?

I'm just new to the community, and want to understand.

Commit: 
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=27bdec06841d1bb004ca7627eac97808b08a7ac7

I am now actively working on a major improvement to Unicode
Normalization Forms.

Thanks!


-- 
Regards,
Alexander Borisov

  15. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-03T22:47:24Z

    On Sun, May  4, 2025 at 01:31:51AM +0300, Alexander Borisov wrote:
> Hi hackers,
> 
> > 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
> > 
> 
> 
> I'm not sure, but I'll ask.
> 
> I have significantly improved the handling of Unicode Case in
> PostgreSQL.
> The improvements affect important functions such as lower(), upper(),
> casefold().
> Specifically, the patch has significantly reduced the size of Unicode
> Case tables (and consequently the size of the object file).
> We got a significant speed gain:
> ASCII by ≈10%
> Cyrillic by ≈80%
> Unicode in general by ≈30%
> 
> But, unfortunately, I didn't see any mention of this improvement in the
> release notes.
> Hence the question to the community - are such improvements worth
> mentioning?
> 
> I'm just new to the community, and want to understand.
> 
> Commit: https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=27bdec06841d1bb004ca7627eac97808b08a7ac7
> 
> I am now actively working on a major improvement to Unicode
> Normalization Forms.

Given the performance numbers above, which were not in the commit, maybe
I should add it to the case folding item, and add his name as a
co-author.

-- 
  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.

  16. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-03T22:50:33Z

    On Sat, May  3, 2025 at 09:40:47PM +0200, Jelte Fennema-Nio wrote:
> On Sat, 3 May 2025 at 18:19, Bruce Momjian <bruce@momjian.us> wrote:
> > I moved the item and added some text, patch attached.
> 
> LGTM, apart from the typo in the word "client' (it's spelled as
> "cliient" in the diff).

Thanks, fixed.

> Noticed a few other small things when rereading:
> 
> 1. "Add libpq functions and environment..." should be "Add libpq
> connection parameters and environment

Fixed.

> 2. "Allow the specification of non-overlapping PRIMARY KEY and UNIQUE
> constraints" has no commit attached to it. I noticed this because it
> wasn't fully clear to me what this feature entailed, so I wanted to
> look at it in more detail.

Fixed.

> 3. "Report search_path changes to the client." is currently in the
> libpq section, but this is a server-only change. So that seems a bit
> strange. Not sure where to put it though.

Not sure.  The only idea I had was server configuration, which doesn't
match well.

-- 
  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.

  17. Re: PG 18 release notes draft committed

    Alexander Borisov <lex.borisov@gmail.com> — 2025-05-03T23:24:16Z

    04.05.2025 01:47, Bruce Momjian wrote:

[...]

> Given the performance numbers above, which were not in the commit, maybe
> I should add it to the case folding item, and add his name as a
> co-author.
> 

I'm not a co-author, I'm the author of my own algorithm that
significantly improves PostgreSQL code.
The author of casefold() is Jeff Davis (and in general, as I understand,
Jeff is responsible for Unicode in Postgres).
I only suggested how to significantly improve the storage of Unicode
Case data and provide fast access to this data.
In other words, I improved, accelerated the algorithms.

Because of which the functions lower(), upper(), casefold() got a
significant boost.

-- 
Regards,
Alexander Borisov

  18. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-03T23:28:43Z

    On Sun, May  4, 2025 at 02:24:16AM +0300, Alexander Borisov wrote:
> 04.05.2025 01:47, Bruce Momjian wrote:
> 
> [...]
> 
> > Given the performance numbers above, which were not in the commit, maybe
> > I should add it to the case folding item, and add his name as a
> > co-author.
> > 
> 
> I'm not a co-author, I'm the author of my own algorithm that
> significantly improves PostgreSQL code.
> The author of casefold() is Jeff Davis (and in general, as I understand,
> Jeff is responsible for Unicode in Postgres).
> I only suggested how to significantly improve the storage of Unicode
> Case data and provide fast access to this data.
> In other words, I improved, accelerated the algorithms.
> 
> Because of which the functions lower(), upper(), casefold() got a
> significant boost.

It doesn't warrant its own item because it is not user-facing work.  The
best we can do is add the commit to an existing item and add you as a
co-author on an existing item.  You will see several items that are that
way already.

-- 
  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.

  19. Re: PG 18 release notes draft committed

    Alexander Borisov <lex.borisov@gmail.com> — 2025-05-03T23:48:31Z

    04.05.2025 02:28, Bruce Momjian wrote:


> It doesn't warrant its own item because it is not user-facing work.  The
> best we can do is add the commit to an existing item and add you as a
> co-author on an existing item.  You will see several items that are that
> way already.
> 

Thank you for clarifying!
Users are not interested in performance gains.
Then it's not worth considering. Sorry to interrupt.

-- 
Regards,
Alexander Borisov

  20. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-04T01:21:24Z

    On Sun, May  4, 2025 at 02:48:31AM +0300, Alexander Borisov wrote:
> 04.05.2025 02:28, Bruce Momjian wrote:
> 
> 
> > It doesn't warrant its own item because it is not user-facing work.  The
> > best we can do is add the commit to an existing item and add you as a
> > co-author on an existing item.  You will see several items that are that
> > way already.
> > 
> 
> Thank you for clarifying!
> Users are not interested in performance gains.
> Then it's not worth considering. Sorry to interrupt.

So the logic is something I posted to this thread already:

	So, a few things.  First, these set of commits was in a group of 10 that
	I added since there have been complaints in the past that optimizer
	improvements were not listed and therefore patch authors were not given
	sufficient credit.  That means the 209 item count for PG 18 is 10 higher
	than my normal filtering would produce.
	
	Second, looking at the items, these are a case of "X is faster", which
	we don't normally mention in the release notes.  We normally mention
	"faster" when it is so much faster that use cases which were not
	possible before might be possible now, so it is recommended to retest.
	That is what I saw this grouped item as, whereas I don't think the
	individual items meet that criteria.

So, users are interested in performance in the sense it makes use cases
possible, and if your commit is making the case folding useful, we
should mention it in the release notes.  I don't think making it
separate would fit though.

-- 
  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.

  21. Re: PG 18 release notes draft committed

    Jelte Fennema-Nio <postgres@jeltef.nl> — 2025-05-04T09:19:36Z

    On Sun, 4 May 2025 at 03:21, Bruce Momjian <bruce@momjian.us> wrote:
> So the logic is something I posted to this thread already:
>
>         So, a few things.  First, these set of commits was in a group of 10 that
>         I added since there have been complaints in the past that optimizer
>         improvements were not listed and therefore patch authors were not given
>         sufficient credit.  That means the 209 item count for PG 18 is 10 higher
>         than my normal filtering would produce.
>
>         Second, looking at the items, these are a case of "X is faster", which
>         we don't normally mention in the release notes.  We normally mention
>         "faster" when it is so much faster that use cases which were not
>         possible before might be possible now, so it is recommended to retest.
>         That is what I saw this grouped item as, whereas I don't think the
>         individual items meet that criteria.

Let me start off the yearly thread of people saying they disagree with
this filtering logic. I think there's an important utility of the
Release Notes that these logic is not covering well:

Many people read the release notes to see if upgrading is worth the
hassle & risk for them specifically. The aggregate of some small
performance improvements that apply to their queries could very well
push them over the edge. These performance improvements don't need to
"allow any new use cases" for that to be the case.

The filtering that you currently do makes the release notes much less
useful for people using the release notes for this purpose. Users
might very well care more about ~10% perf improvement for a feature
they use heavily, than all of the newly added SQL syntax combined.

> So, users are interested in performance in the sense it makes use cases
> possible, and if your commit is making the case folding useful, we
> should mention it in the release notes.  I don't think making it
> separate would fit though.

For this specific commit, I think if it had only changed the
performance of casefold(), then I'd agree that it should be grouped
with the casefold addition in the release notes. My reasoning would be
that there's no "diff" in performance since the previous release,
because the function did not exist in the previous release. So the
perf improvements are simply part of the "initial implementation" of
casefold from a user perspective.

However since this commit also impacts the very commonly used lower()
and upper() functions, I think that it would make sense if it got its
own entry. It's neither clear for me from the commit message nor the
skimming the original thread, whether the perf improvement numbers
listed by Alexander also apply to lower() and upper(), or if they only
apply to casefold():

On Sun, 4 May 2025 at 00:32, Alexander Borisov <lex.borisov@gmail.com> wrote:
> ASCII by ≈10%
> Cyrillic by ≈80%
> Unicode in general by ≈30%

If they apply the lower() and upper() I definitely think this patch
deserves a place in "General Performance".

  22. Re: PG 18 release notes draft committed

    Jelte Fennema-Nio <postgres@jeltef.nl> — 2025-05-04T09:49:47Z

    On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
> I have committd the first draft of the PG 18 release notes.

Some suggestions for additional commits to list for the items in the changelog:
1. I think 5070349102af12832c8528651c8ed18b16346323 should be listed
as a commit for "Add libpq connection parameters and environment
variables...". This commit contains a major part of the change that
allows supporting multiple protocol versions client side.
2. I think 9d9b9d46f3c509c722ebbf2a1e7dc6296a6c711d &
09be39112654c3f158098fdb5f820143c0330763 should be listed as a commits
for "Make cancel request keys 256 bits". These commits contain crucial
parts of that change. This would also put me in there as one of the
co-authors for this item.

  23. Re: PG 18 release notes draft committed

    Álvaro Herrera <alvherre@kurilemu.de> — 2025-05-04T11:35:30Z

    Regarding these items

* Allow ALTER TABLE to set the NOT VALID attribute of NOT NULL constraints
  (Rushabh Lathia, Jian He)

* Allow NOT VALID foreign key constraints on partitioned tables (Amul Sul)

* Allow modification of the inheritability of constraints (Suraj Kharage, Álvaro Herrera)

  The syntax is ALTER TABLE ... ALTER CONSTRAINT ... [NO] INHERIT.

* Store column NOT NULL specifications in pg_constraint (Álvaro Herrera, Bernd Helmle)

  This allows names to be specified for NOT NULL constraint. This also adds NOT
  NULL constraints to foreign tables and NOT NULL inheritance control to local
  tables.


I think the wording and order of them is a bit unclear.  I would put the
last item first, immediately followed by the other two; alternatively we
could merge them all into a single one:

* Store NOT NULL constraints in pg_constraint for better preservability
  (Álvaro, Bernd, Suraj, Rushabh, Jian)

  The constraint names are well defined and are preserved across
  dump/restore.  Also, the NOT VALID and NO INHERIT properties work
  as expected and can be modified by users via ALTER TABLE.

Or something along those lines.

This one in particular:
  Allow modification of the inheritability of constraints (Suraj Kharage, Álvaro Herrera)

  The syntax is ALTER TABLE ... ALTER CONSTRAINT ... [NO] INHERIT.

only works with not-null constraints, which is why I suggest to merge
together with the above item.  Ideally, on the next release somebody
would work to make that feature more general (work with other types of
constraints).


I think this item
  Allow CHECK and foreign key constraints to be specified as NOT ENFORCED
  (Amul Sul)

  This also adds column pg_constraint.conenforced.

should come second or maybe even first in that section, as it is I think
the most user-visible.


These two items
  Allow NOT VALID foreign key constraints on partitioned tables (Amul Sul)

  Allow dropping of constraints ONLY on partitioned tables (Álvaro Herrera)

  This was previously erroneously prohibited.

can mostly be considered bug-fixes, so they should be last in the
section; they aren't new features, just making existing features work
correctly.  The one I have second is I think of lesser importance.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"I'm impressed how quickly you are fixing this obscure issue. I came from 
MS SQL and it would be hard for me to put into words how much of a better job
you all are doing on [PostgreSQL]."
 Steve Midgley, http://archives.postgresql.org/pgsql-sql/2008-08/msg00000.php

  24. Re: PG 18 release notes draft committed

    Atsushi Torikoshi <torikoshia.tech@gmail.com> — 2025-05-04T13:41:30Z

    Hi,

On Fri, May 2, 2025 at 11:44 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-7.4:  263
>         release-8.0:  230
>         release-8.1:  174
>         release-8.2:  215
>         release-8.3:  214
>         release-8.4:  314
>         release-9.0:  237
>         release-9.1:  203
>         release-9.2:  238
>         release-9.3:  177
>         release-9.4:  211
>         release-9.5:  193
>         release-9.6:  214
>         release-10:   189
>         release-11:   170
>         release-12:   180
>         release-13:   178
>         release-14:   220
>         release-15:   184
>         release-16:   206
>         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.  ;-)

Thanks for your work!

> Add REJECT_LIMIT to control the number of invalid rows COPY IN can ignore (Atsushi Torikoshi)

Since REJECT_LIMIT cannot be used with COPY IN but can be used with
COPY FROM, I think "IN" should be "FROM".

  =# COPY t1 TO '/tmp/a' WITH (REJECT_LIMIT 3);
  ERROR:  COPY REJECT_LIMIT requires ON_ERROR to be set to IGNORE
  =# COPY t1 TO '/tmp/a' WITH ( ON_ERROR ignore, REJECT_LIMIT 3);
  ERROR:  COPY ON_ERROR cannot be used with COPY TO
  LINE 1: COPY t1 to '/tmp/a' WITH (ON_ERROR ignore, REJECT_LIMIT 3);


> This is active when ON_ERROR = 'ignore'.

As a non-native English speaker, I may be misunderstanding this, but
the word "active" might suggest that REJECT_LIMIT always takes effect
by default, causing the COPY operation to stop after a certain number
of errors.
However, in reality, REJECT_LIMIT does not have any effect by default
— unless explicitly set, there is no limit on the number of rows that
can be skipped when ON_ERROR is set to ignore.
To avoid this potential confusion, a phrasing like:

  This option must be used with ON_ERROR ignore.

might be clearer.

Also, in the v17 release notes, COPY option values are not enclosed in
single quotes but written in <literal> tag.
For consistency, it might be better to follow the same style in the
v18 notes as well.

  -- https://www.postgresql.org/docs/current/release-17.html
  Add new COPY option ON_ERROR ignore to discard error rows
  The default behavior is ON_ERROR stop


> Add COPY log_verbosity level "silent" to suppress all log output (Atsushi Torikoshi)

Similarly, in the v17 release notes, the log_verbosity option was
written in uppercase (LOG_VERBOSITY).
For consistency, it may be preferable to use the same case formatting
in this entry as well.

  -- https://www.postgresql.org/docs/current/release-17.html
  Add new COPY option LOG_VERBOSITY which reports COPY FROM ignored error rows

Also, the phrase "suppress all log output" may be slightly misleading.
Even with log_verbosity = 'silent', COPY still outputs logs — it only
suppresses log messages related to skipped rows when ON_ERROR ignore
is used.
It might help to clarify this nuance to avoid confusion.
For example, how about "Add COPY LOG_VERBOSITY silent to suppress logs
related to skipped rows"?


> Add on_error and log_verbosity options to file_fdw (Atsushi Torikoshi)
> Add REJECT_LIMIT to control the number of invalid rows file_fdw can ignore (Atsushi Torikoshi)
> This is active when ON_ERROR = 'ignore'.

The case of option names for file_fdw is inconsistent — some are
lowercase (on_error, log_verbosity), while others use uppercase
(REJECT_LIMIT, ON_ERROR).
For consistency, it might be better to standardize the option names
throughout the release notes.
Since the file_fdw documentation consistently uses lowercase for all
options, using lowercase in the release notes as well might feel more
natural.


--
Regards,
Atsushi Torikoshi

  25. Re: PG 18 release notes draft committed

    Alexander Borisov <lex.borisov@gmail.com> — 2025-05-04T20:28:44Z

    04.05.2025 12:19, Jelte Fennema-Nio wrote:
> On Sun, 4 May 2025 at 03:21, Bruce Momjian <bruce@momjian.us> wrote:
>> So the logic is something I posted to this thread already:
>>
>>          So, a few things.  First, these set of commits was in a group of 10 that
>>          I added since there have been complaints in the past that optimizer
>>          improvements were not listed and therefore patch authors were not given
>>          sufficient credit.  That means the 209 item count for PG 18 is 10 higher
>>          than my normal filtering would produce.
>>
>>          Second, looking at the items, these are a case of "X is faster", which
>>          we don't normally mention in the release notes.  We normally mention
>>          "faster" when it is so much faster that use cases which were not
>>          possible before might be possible now, so it is recommended to retest.
>>          That is what I saw this grouped item as, whereas I don't think the
>>          individual items meet that criteria.
> 
> Let me start off the yearly thread of people saying they disagree with
> this filtering logic. I think there's an important utility of the
> Release Notes that these logic is not covering well:
> 
> Many people read the release notes to see if upgrading is worth the
> hassle & risk for them specifically. The aggregate of some small
> performance improvements that apply to their queries could very well
> push them over the edge. These performance improvements don't need to
> "allow any new use cases" for that to be the case.
> 
> The filtering that you currently do makes the release notes much less
> useful for people using the release notes for this purpose. Users
> might very well care more about ~10% perf improvement for a feature
> they use heavily, than all of the newly added SQL syntax combined.
> 
>> So, users are interested in performance in the sense it makes use cases
>> possible, and if your commit is making the case folding useful, we
>> should mention it in the release notes.  I don't think making it
>> separate would fit though.
> 
> For this specific commit, I think if it had only changed the
> performance of casefold(), then I'd agree that it should be grouped
> with the casefold addition in the release notes. My reasoning would be
> that there's no "diff" in performance since the previous release,
> because the function did not exist in the previous release. So the
> perf improvements are simply part of the "initial implementation" of
> casefold from a user perspective.
> 
> However since this commit also impacts the very commonly used lower()
> and upper() functions, I think that it would make sense if it got its
> own entry. It's neither clear for me from the commit message nor the
> skimming the original thread, whether the perf improvement numbers
> listed by Alexander also apply to lower() and upper(), or if they only
> apply to casefold():
> 
> On Sun, 4 May 2025 at 00:32, Alexander Borisov <lex.borisov@gmail.com> wrote:
>> ASCII by ≈10%
>> Cyrillic by ≈80%
>> Unicode in general by ≈30%
> 
> If they apply the lower() and upper() I definitely think this patch
> deserves a place in "General Performance".

I'm actually a bit confused, and didn't expect such a heated discussion
about creating an entry about my patch in Release Notes.

I thought I had made significant Unicode improvements to Postgres.
Namely, significantly reduce the object file size for Unicode Case, and
most importantly increased performance.
Thanks to my approach/algorithm, all Unicode Case related functions got
a significant boost.
Namely: lower(), upper(), casefold(). I have already given the figures.
Why casefold() is the one that got caught here is not clear to me, I
have nothing to do with the implementation of this function.
I improved the overall Unicode Case algorithm, which caused a boost in
all of the listed functions.

I thought it would be useful for users to know that Postgres is
improving in the performance direction, especially in such functions
that are very often used by users to compare text by bringing it to a
certain case.

The discussion made me realize that it's not that important.
I'm not insisting. If it really doesn't matter to users, then it's not
worth discussing.


Thank you for your attention.
I will continue to improve Postgres.

-- 
Regards,
Alexander Borisov

  26. Re: PG 18 release notes draft committed

    Jonathan S. Katz <jkatz@postgresql.org> — 2025-05-04T20:43:16Z

    
On 5/3/25 7:48 PM, Alexander Borisov wrote:
> 04.05.2025 02:28, Bruce Momjian wrote:
> 
> 
>> It doesn't warrant its own item because it is not user-facing work.  The
>> best we can do is add the commit to an existing item and add you as a
>> co-author on an existing item.  You will see several items that are that
>> way already.
>>
> 
> Thank you for clarifying!
> Users are not interested in performance gains.
> Then it's not worth considering. Sorry to interrupt.

I do know that users are interested in performance gains - and it is 
definitely user facing - and as such I try to include these things in 
the release announcement (which I'm currently drafting) as part of 
making the release available. Similarly, we do need to use discretion 
with how we discuss performance enhancements in the release announcement 
to ensure we make directionally accurate claims and look towards broad 
impact.

I've noted the claims on upper/lower; we'll see if it makes the cut in 
the release announcement.

Thanks,

Jonathan

  27. Re: PG 18 release notes draft committed

    Jelte Fennema-Nio <postgres@jeltef.nl> — 2025-05-05T00:22:53Z

    On Sun, 4 May 2025 at 22:28, Alexander Borisov <lex.borisov@gmail.com> wrote:
> I'm actually a bit confused, and didn't expect such a heated discussion
> about creating an entry about my patch in Release Notes.

I definitely understand this. And to make my own opinion on this
matter extremely clear: I *do* think it's important to users, and it
should be included in the release notes.

I think there are a few things at play here why that did not happen in
Bruce his initial draft:
1. I personally think the requirement that Bruce uses for perf
improvements to make it into the changelog is too strict (see my
previous email for details)
2. Bruce is only a single person, and as such cannot read all emails
on pgsql-hackers, so he relies only on commit messages to determine
impact for release notes. The commit message for your change did not
include any details on the perf improvements that could be expected.
3. After skimming the email thread[1], it's hard for me to understand
where these perf numbers came from. And the first few results only
mention casefold performance i.e. they call the results: "casefold()
test." So, it's unclear what perf gains are expected for the other
functions mentioned in the email subject.

As for how to improve these:
1 is discussed/complained about basically every year whenever release
notes are created. I don't think we can do any better than having
those discussions. Unless someone else wants to start owning writing
the release notes, or we somehow share the burden, e.g. by having the
person that commits also write a release note entry.
2 can be improved by people including perf numbers in their commit
messages. The second way to improve is by sending feedback on the
release notes if things are missed, like you did.
3 is something you could help with I think. It would have been helpful
if you had shared the script/commands you used to get these
performance numbers. That way I could reproduce them myself. Also if
you had included some perf numbers for lower() and upper() that would
have been great too, as those are (currently) much more commonly used
than casefold(). NOTE: I might have missed the script or be wrong
about this some other way, since Jeff did not require this for
committing it. If so, please disregard.

[1]: https://www.postgresql.org/message-id/flat/7cac7e66-9a3b-4e3f-a997-42aa0c401f80%40gmail.com

> I will continue to improve Postgres.

Please do, your work is very much appreciated!

  28. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T01:42:32Z

    On Sun, May  4, 2025 at 11:49:47AM +0200, Jelte Fennema-Nio wrote:
> On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
> > I have committd the first draft of the PG 18 release notes.
> 
> Some suggestions for additional commits to list for the items in the changelog:
> 1. I think 5070349102af12832c8528651c8ed18b16346323 should be listed
> as a commit for "Add libpq connection parameters and environment
> variables...". This commit contains a major part of the change that
> allows supporting multiple protocol versions client side.

Added.

> 2. I think 9d9b9d46f3c509c722ebbf2a1e7dc6296a6c711d &
> 09be39112654c3f158098fdb5f820143c0330763 should be listed as a commits
> for "Make cancel request keys 256 bits". These commits contain crucial
> parts of that change. This would also put me in there as one of the
> co-authors for this item.

I added the first commit but the second one is:

	commit 09be3911265
	Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
	Date:   Wed Apr 2 15:32:40 2025 +0300
	
	    Add timingsafe_bcmp(), for constant-time memory comparison
	
	    timingsafe_bcmp() should be used instead of memcmp() or a naive
	    for-loop, when comparing passwords or secret tokens, to avoid leaking
	    information about the secret token by timing. This commit just
	    introduces the function but does not change any existing code to use
	    it yet.
	
	    Co-authored-by: Jelte Fennema-Nio <github-tech@jeltef.nl>
	    Discussion: https://www.postgresql.org/message-id/7b86da3b-9356-4e50-aa1b-56570825e234@iki.fi

which is either the wrong commit hash or too far away from the item
description to be added.

-- 
  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.

  29. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T02:06:38Z

    On Sun, May  4, 2025 at 01:35:30PM +0200, Álvaro Herrera wrote:
> Regarding these items
> 
> * Allow ALTER TABLE to set the NOT VALID attribute of NOT NULL constraints
>   (Rushabh Lathia, Jian He)
> 
> * Allow NOT VALID foreign key constraints on partitioned tables (Amul Sul)
> 
> * Allow modification of the inheritability of constraints (Suraj Kharage, Álvaro Herrera)
> 
>   The syntax is ALTER TABLE ... ALTER CONSTRAINT ... [NO] INHERIT.
> 
> * Store column NOT NULL specifications in pg_constraint (Álvaro Herrera, Bernd Helmle)
> 
>   This allows names to be specified for NOT NULL constraint. This also adds NOT
>   NULL constraints to foreign tables and NOT NULL inheritance control to local
>   tables.
> 
> 
> I think the wording and order of them is a bit unclear.  I would put the
> last item first, immediately followed by the other two; alternatively we
> could merge them all into a single one:

I moved the last item to first in the group.

> * Store NOT NULL constraints in pg_constraint for better preservability
>   (Álvaro, Bernd, Suraj, Rushabh, Jian)
> 
>   The constraint names are well defined and are preserved across
>   dump/restore.  Also, the NOT VALID and NO INHERIT properties work
>   as expected and can be modified by users via ALTER TABLE.
> 
> Or something along those lines.

I think the merged text is too confusing.

> This one in particular:
>   Allow modification of the inheritability of constraints (Suraj Kharage, Álvaro Herrera)
> 
>   The syntax is ALTER TABLE ... ALTER CONSTRAINT ... [NO] INHERIT.
> 
> only works with not-null constraints, which is why I suggest to merge
> together with the above item.  Ideally, on the next release somebody
> would work to make that feature more general (work with other types of
> constraints).

Yes, I see that detail in the docs of the first commit, and in the second commit
text.  I modified to say NOT NULL.

> 
> I think this item
>   Allow CHECK and foreign key constraints to be specified as NOT ENFORCED
>   (Amul Sul)
> 
>   This also adds column pg_constraint.conenforced.
> 
> should come second or maybe even first in that section, as it is I think
> the most user-visible.

I made it second.

> These two items
>   Allow NOT VALID foreign key constraints on partitioned tables (Amul Sul)
> 
>   Allow dropping of constraints ONLY on partitioned tables (Álvaro Herrera)
> 
>   This was previously erroneously prohibited.
> 
> can mostly be considered bug-fixes, so they should be last in the
> section; they aren't new features, just making existing features work
> correctly.  The one I have second is I think of lesser importance.

Agreed, moved as you suggested.  I have trouble figuring out the
importance sometimes, and this section is very large.

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.

  30. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T02:36:33Z

    On Sun, May  4, 2025 at 10:41:30PM +0900, Atsushi Torikoshi wrote:
> > 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.  ;-)
> 
> Thanks for your work!
> 
> > Add REJECT_LIMIT to control the number of invalid rows COPY IN can ignore (Atsushi Torikoshi)
> 
> Since REJECT_LIMIT cannot be used with COPY IN but can be used with
> COPY FROM, I think "IN" should be "FROM".
> 
>   =# COPY t1 TO '/tmp/a' WITH (REJECT_LIMIT 3);
>   ERROR:  COPY REJECT_LIMIT requires ON_ERROR to be set to IGNORE
>   =# COPY t1 TO '/tmp/a' WITH ( ON_ERROR ignore, REJECT_LIMIT 3);
>   ERROR:  COPY ON_ERROR cannot be used with COPY TO
>   LINE 1: COPY t1 to '/tmp/a' WITH (ON_ERROR ignore, REJECT_LIMIT 3);

Agreed.  A PG 18 commit had "COPY IN" and I ended up using that, even
though we have no COPY IN but only COPY FROM.  Fixed in all placed.

> > This is active when ON_ERROR = 'ignore'.
> 
> As a non-native English speaker, I may be misunderstanding this, but
> the word "active" might suggest that REJECT_LIMIT always takes effect
> by default, causing the COPY operation to stop after a certain number
> of errors.
> However, in reality, REJECT_LIMIT does not have any effect by default
> — unless explicitly set, there is no limit on the number of rows that
> can be skipped when ON_ERROR is set to ignore.
> To avoid this potential confusion, a phrasing like:
> 
>   This option must be used with ON_ERROR ignore.
> 
> might be clearer.

Uh, that might suggest you have to use REJECT_LIMIT with ON_ERROR, which
is untrue.  I used:

	This is available when ON_ERROR = 'ignore'.

> Also, in the v17 release notes, COPY option values are not enclosed in
> single quotes but written in <literal> tag.
> For consistency, it might be better to follow the same style in the
> v18 notes as well.
> 
>   -- https://www.postgresql.org/docs/current/release-17.html
>   Add new COPY option ON_ERROR ignore to discard error rows
>   The default behavior is ON_ERROR stop

The quotes will be removed when I add XML markup in 1-3 weeks.

> > Add COPY log_verbosity level "silent" to suppress all log output (Atsushi Torikoshi)
> 
> Similarly, in the v17 release notes, the log_verbosity option was
> written in uppercase (LOG_VERBOSITY).
>
> For consistency, it may be preferable to use the same case formatting
> in this entry as well.
> 
>   -- https://www.postgresql.org/docs/current/release-17.html
>   Add new COPY option LOG_VERBOSITY which reports COPY FROM ignored error rows

Same.

> Also, the phrase "suppress all log output" may be slightly misleading.
> Even with log_verbosity = 'silent', COPY still outputs logs — it only
> suppresses log messages related to skipped rows when ON_ERROR ignore
> is used.
> It might help to clarify this nuance to avoid confusion.
> For example, how about "Add COPY LOG_VERBOSITY silent to suppress logs
> related to skipped rows"?

I went with:

	Add COPY LOG_VERBOSITY level "silent" to suppress log output of ignored rows

because the docs call them "ignored" rows rather than "skipped" rows. 

> > Add on_error and log_verbosity options to file_fdw (Atsushi Torikoshi)
> > Add REJECT_LIMIT to control the number of invalid rows file_fdw can ignore (Atsushi Torikoshi)
> > This is active when ON_ERROR = 'ignore'.
> 
> The case of option names for file_fdw is inconsistent — some are
> lowercase (on_error, log_verbosity), while others use uppercase
> (REJECT_LIMIT, ON_ERROR).
> For consistency, it might be better to standardize the option names
> throughout the release notes.
> Since the file_fdw documentation consistently uses lowercase for all
> options, using lowercase in the release notes as well might feel more
> natural.

Case changed.  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.

  31. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-05T09:42:10Z

    On Fri, 2 May 2025 at 16:01, Amit Langote <amitlangote09@gmail.com> wrote:
> +Allow partitions to be pruned earlier and quicker, and skipped in
> more places (Amit Langote, Ashutosh Bapat, Yuya Watari, David Rowley)
>
> Alternatively, 2 and 3 can be combined as:

> 2. Speed up partition planning by improving EquivalenceClass lookups
> (Yuya Watari, David Rowley, Ashutosh Bapat)

> Any thoughts, David?

I agree that 88f55bc97 and d69d45a5a should be in their own item.
Likely no need to go into detail about the speed up being about
"EquivalenceClass lookups". I imagine something like "Reduce planner
overheads when planning queries to partitioned and inheritance parent
tables"

Then for bb3ec16e1, d47cbf474, cbc127917 and 525392d57, something like
"Defer locking of partitions during execution until after partition
elimination".  The release notes for 11.0 called it "partition
elimination", so I went with that naming.

David

  32. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-05T10:14:22Z

    On Fri, 2 May 2025 at 14:44, Bruce Momjian <bruce@momjian.us> wrote:
> You can see the most current HTML-built version here:
>
>         https://momjian.us/pgsql_docs/release-18.html

Thanks for working on these.

For "Improve the performance of hash joins (David Rowley)", 0f5738202
did the same thing for GROUP BY and hashed subplans too. It might be
worth adjusting this to some more generic text which covers all of
these. Something like "Speed up hash value generation in Hash Join,
GROUP BY, hashed Subplan and hashed set operations</p><p>This change
also allows JIT compilation for obtaining hash values for these
operations". The set operations I likely should have mentioned in the
commit message.

There's also Jeff's work in cc721c459, 4d143509c, a0942f441, 626df47ad
which does work to reduce the memory overheads of hashed GROUP BY,
hashed Subplans and hashed set operations. I think Jeff might have
understated the possible performance gains from these commits. I very
much think this is worth something like "Reduce memory overheads for
hashed GROUP BY, subplans and set operation processing (Jeff Davis)".

A quick test with: explain analyze select a from
generate_series(1,1000000) a group by a;

v17: Batches: 1  Memory Usage: 90145kB
v18: Batches: 1  Memory Usage: 57385kB

A 37% reduction for this case. Not insignificant.

David

  33. Re: PG 18 release notes draft committed

    Bertrand Drouvot <bertranddrouvot.pg@gmail.com> — 2025-05-05T14:09:26Z

    Hi,

On Thu, May 01, 2025 at 10:44:50PM -0400, Bruce Momjian wrote:
> I have committd the first draft of the PG 18 release notes. 

Thanks for working on this!

> You can see the most current HTML-built version here:
> 
> 	https://momjian.us/pgsql_docs/release-18.html


I have one comment related to "per backend" statistics.

We have this:

"
Add per-backend I/O statistics reporting (Bertrand Drouvot)

The statistics are accessed via pg_stat_get_backend_io(). Per-backend statistics can be cleared via pg_stat_reset_backend_stats(). 
"

and

"
Add function pg_stat_get_backend_wal() to return per-backend WAL statistics (Bertrand Drouvot) 
"

I think that we could mention pg_stat_reset_backend_stats() in both case, something
like:

A.

"Per-backend I/O statistics can be cleared via pg_stat_reset_backend_stats()"

and

"Per-backend WAL statistics can be cleared via pg_stat_reset_backend_stats()"

for consitency.

Or:

B.  mention pg_stat_reset_backend_stats() "separately" just saying:

"
Per-backend statistics can be cleared via pg_stat_reset_backend_stats()
"

and get rid of the mention in "per-backend I/O statistics".

I'd be tempted to vote for B (so that pg_stat_reset_backend_stats() is introduced
separately): thoughts?

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

  34. Re: PG 18 release notes draft committed

    Daniel Westermann (DWE) <daniel.westermann@dbi-services.com> — 2025-05-05T14:56:12Z

    On Thu, May 01, 2025 at 10:44:50PM -0400, Bruce Momjian wrote:
> I have committd the first draft of the PG 18 release notes.

I don't think pg_buffercache_numa does exist.

Regards
Daniel

  35. Re: PG 18 release notes draft committed

    Daniel Westermann (DWE) <daniel.westermann@dbi-services.com> — 2025-05-05T14:59:01Z

    >On Thu, May 01, 2025 at 10:44:50PM -0400, Bruce Momjian wrote:
>> I have committd the first draft of the PG 18 release notes.

>I don't think pg_buffercache_numa does exist.

Please ignore

Regards
Daniel

  36. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T15:59:16Z

    On Mon, May  5, 2025 at 09:42:10PM +1200, David Rowley wrote:
> On Fri, 2 May 2025 at 16:01, Amit Langote <amitlangote09@gmail.com> wrote:
> > +Allow partitions to be pruned earlier and quicker, and skipped in
> > more places (Amit Langote, Ashutosh Bapat, Yuya Watari, David Rowley)
> >
> > Alternatively, 2 and 3 can be combined as:
> 
> > 2. Speed up partition planning by improving EquivalenceClass lookups
> > (Yuya Watari, David Rowley, Ashutosh Bapat)
> 
> > Any thoughts, David?
> 
> I agree that 88f55bc97 and d69d45a5a should be in their own item.
> Likely no need to go into detail about the speed up being about
> "EquivalenceClass lookups". I imagine something like "Reduce planner
> overheads when planning queries to partitioned and inheritance parent
> tables"
> 
> Then for bb3ec16e1, d47cbf474, cbc127917 and 525392d57, something like
> "Defer locking of partitions during execution until after partition
> elimination".  The release notes for 11.0 called it "partition
> elimination", so I went with that naming.

Okay, I split them up and went with the attached patch.

-- 
  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.

  37. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T16:31:28Z

    On Mon, May  5, 2025 at 10:14:22PM +1200, David Rowley wrote:
> On Fri, 2 May 2025 at 14:44, Bruce Momjian <bruce@momjian.us> wrote:
> > You can see the most current HTML-built version here:
> >
> >         https://momjian.us/pgsql_docs/release-18.html
> 
> Thanks for working on these.
> 
> For "Improve the performance of hash joins (David Rowley)", 0f5738202
> did the same thing for GROUP BY and hashed subplans too. It might be
> worth adjusting this to some more generic text which covers all of
> these. Something like "Speed up hash value generation in Hash Join,
> GROUP BY, hashed Subplan and hashed set operations</p><p>This change
> also allows JIT compilation for obtaining hash values for these
> operations". The set operations I likely should have mentioned in the
> commit message.

Okay, text added.

> There's also Jeff's work in cc721c459, 4d143509c, a0942f441, 626df47ad
> which does work to reduce the memory overheads of hashed GROUP BY,
> hashed Subplans and hashed set operations. I think Jeff might have
> understated the possible performance gains from these commits. I very
> much think this is worth something like "Reduce memory overheads for
> hashed GROUP BY, subplans and set operation processing (Jeff Davis)".
> 
> A quick test with: explain analyze select a from
> generate_series(1,1000000) a group by a;
> 
> v17: Batches: 1  Memory Usage: 90145kB
> v18: Batches: 1  Memory Usage: 57385kB
> 
> A 37% reduction for this case. Not insignificant.

Commits added and Jeff's name added, 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.

  38. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T18:57:21Z

    On Mon, May  5, 2025 at 02:09:26PM +0000, Bertrand Drouvot wrote:
> A.
> 
> "Per-backend I/O statistics can be cleared via pg_stat_reset_backend_stats()"
> 
> and
> 
> "Per-backend WAL statistics can be cleared via pg_stat_reset_backend_stats()"
> 
> for consitency.
> 
> Or:

I went with the A option, 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.

  39. Re: PG 18 release notes draft committed

    Jacob Champion <jacob.champion@enterprisedb.com> — 2025-05-05T19:20:15Z

    On Thu, May 1, 2025 at 7:44 PM Bruce Momjian <bruce@momjian.us> wrote:
>         https://momjian.us/pgsql_docs/release-18.html

> +Add support for the "oauth" authentication (Jacob Champion, Daniel Gustafsson, Thomas Munro)

Should be either 'support for "oauth" authentication' or 'support for
the "oauth" authentication method', I think.

> +This adds an "oauth" authentication method to pg_hba.conf, a server variable oauth_validator_libraries to specify OAUTH libraries, a configure flag --with-libcurl to add the required
> +compile-time libraries, and libpq OAUTH options.

Maybe the description of oauth_validator_libraries could be something
like "to load token validation modules"?

Also, "OAUTH" should just be "OAuth". We should probably lock in the
capitalization:

- "OAuth" is the name of the framework we're using
- "oauth" is the HBA method name in the configs
- "OAUTHBEARER" is the internal name of the SASL method, which most
users don't care about and should only rarely appear in the docs

Thanks!
--Jacob

  40. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T19:42:50Z

    On Mon, May  5, 2025 at 12:20:15PM -0700, Jacob Champion wrote:
> On Thu, May 1, 2025 at 7:44 PM Bruce Momjian <bruce@momjian.us> wrote:
> >         https://momjian.us/pgsql_docs/release-18.html
> 
> > +Add support for the "oauth" authentication (Jacob Champion, Daniel Gustafsson, Thomas Munro)
> 
> Should be either 'support for "oauth" authentication' or 'support for
> the "oauth" authentication method', I think.
Okay.

 
> > +This adds an "oauth" authentication method to pg_hba.conf, a server variable oauth_validator_libraries to specify OAUTH libraries, a configure flag --with-libcurl to add the required
> > +compile-time libraries, and libpq OAUTH options.
> 
> Maybe the description of oauth_validator_libraries could be something
> like "to load token validation modules"?

Done.

> Also, "OAUTH" should just be "OAuth". We should probably lock in the
> capitalization:
> 
> - "OAuth" is the name of the framework we're using
> - "oauth" is the HBA method name in the configs
> - "OAUTHBEARER" is the internal name of the SASL method, which most
> users don't care about and should only rarely appear in the docs

Capitalization changed, 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.

  41. Re: PG 18 release notes draft committed

    Alexander Borisov <lex.borisov@gmail.com> — 2025-05-05T19:43:37Z

    05.05.2025 03:22, Jelte Fennema-Nio wrote:

[...]

> 
> I think there are a few things at play here why that did not happen in
> Bruce his initial draft:
> 1. I personally think the requirement that Bruce uses for perf
> improvements to make it into the changelog is too strict (see my
> previous email for details)
> 2. Bruce is only a single person, and as such cannot read all emails
> on pgsql-hackers, so he relies only on commit messages to determine
> impact for release notes. The commit message for your change did not
> include any details on the perf improvements that could be expected.
> 3. After skimming the email thread[1], it's hard for me to understand
> where these perf numbers came from. And the first few results only
> mention casefold performance i.e. they call the results: "casefold()
> test." So, it's unclear what perf gains are expected for the other
> functions mentioned in the email subject.

I totally agree with you, it's hard to keep track of everything. It's
also a lot of work to read every commit and understand its essence.

I have no complaints, I'm just trying to understand the rules of getting
into Release Notes.
The rules, as it turns out, are not simple. But they are rules, even
though I don't agree with them, I accept them.

> 
> As for how to improve these:
> 1 is discussed/complained about basically every year whenever release
> notes are created. I don't think we can do any better than having
> those discussions. Unless someone else wants to start owning writing
> the release notes, or we somehow share the burden, e.g. by having the
> person that commits also write a release note entry.
> 2 can be improved by people including perf numbers in their commit
> messages. The second way to improve is by sending feedback on the
> release notes if things are missed, like you did.
> 3 is something you could help with I think. It would have been helpful
> if you had shared the script/commands you used to get these
> performance numbers. That way I could reproduce them myself. Also if
> you had included some perf numbers for lower() and upper() that would
> have been great too, as those are (currently) much more commonly used
> than casefold(). NOTE: I might have missed the script or be wrong
> about this some other way, since Jeff did not require this for
> committing it. If so, please disregard.
> 
> [1]: https://www.postgresql.org/message-id/flat/7cac7e66-9a3b-4e3f-a997-42aa0c401f80%40gmail.com

A bit about what those numbers are, in the discussion for the patch I
described how I got those numbers.

The point is that functions lower(), upper(), casefold() have one common
algorithm, the difference is in what table for mapping we pass to this
algorithm.
Therefore, there is no sense to measure the performance of each function
separately. Any of these functions will show the performance of the
algorithm of getting codepoints from tables in the same way.

Therefore, we can take lower() or upper() or casefold() and get the
result of Unicode table mapping algorithm (that's where I changed the
code, the algorithm).
I can measure everything, but there is no sense in it.
Here are the measurements made at the moment of patch discussion:

For each test, a sql file was created for pgbench. The data description
is present.

casefold() test.

ASCII:
Repeated characters (700kb) in the range from 0x20 to 0x7E.
Patch: tps = 278.449809
Without: tps = 266.526168

Cyrillic:
Repeated characters (1MB) in the range from 0x0410 to 0x042F.
Patch: tps = 86.740680
Without: tps = 49.373695

Unicode:
A query consisting of all Unicode characters from 0xA0 to 0x2FA1D
(excluding 0xD800..0xDFFF).
Patch: tps = 102.221092
Without: tps = 92.477798

* Ubuntu 24.04.1 (Intel(R) Xeon(R) Gold 6140) (gcc version 13.3.0)

ASCII:
Repeated characters (700kb) in the range from 0x20 to 0x7E.
Patch: tps = 146.712371
Without: tps = 120.794307

Cyrillic:
Repeated characters (1MB) in the range from 0x0410 to 0x042F.
Patch: tps = 44.499567
Without: tps = 24.237999

Unicode:
A query consisting of all Unicode characters from 0xA0 to 0x2FA1D
(excluding 0xD800..0xDFFF).
Patch: tps = 54.354833
Without: tps = 46.556531

> 
>> I will continue to improve Postgres.
> 
> Please do, your work is very much appreciated!

I thought it was worthy of a separate line in the Release Notes.
As I think, it is not so easy to increase the performance for Unicode.
So many users use lower() and upper(), and it would be nice to know that
work is being done to improve performance in this area.
But again, I'm new to the Postgres community and I'm getting to know
what's going on here and how it works.

Thank you for paying attention to it!

-- 
Regards,
Alexander Borisov

  42. Re: PG 18 release notes draft committed

    Tom Lane <tgl@sss.pgh.pa.us> — 2025-05-05T20:12:16Z

    Bruce Momjian <bruce@momjian.us> writes:
> Capitalization changed, patch attached.

I need to start wrapping the tarballs soon ... are you done
with the release notes for today?

			regards, tom lane

  43. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-05T20:15:36Z

    On Mon, May  5, 2025 at 04:12:16PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Capitalization changed, patch attached.
> 
> I need to start wrapping the tarballs soon ... are you done
> with the release notes for today?

Yes, I am, thanks for asking.  I was waiting for the case folding thread
to conclude, but I think it is still being discussed so let's not wait
for it.

-- 
  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.

  44. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-06T03:14:56Z

    On Tue, 6 May 2025 at 03:59, Bruce Momjian <bruce@momjian.us> wrote:
>
> On Mon, May  5, 2025 at 09:42:10PM +1200, David Rowley wrote:
> > I agree that 88f55bc97 and d69d45a5a should be in their own item.
> > Likely no need to go into detail about the speed up being about
> > "EquivalenceClass lookups". I imagine something like "Reduce planner
> > overheads when planning queries to partitioned and inheritance parent
> > tables"
> >
> > Then for bb3ec16e1, d47cbf474, cbc127917 and 525392d57, something like
> > "Defer locking of partitions during execution until after partition
> > elimination".  The release notes for 11.0 called it "partition
> > elimination", so I went with that naming.
>
> Okay, I split them up and went with the attached patch.


> +Allow partitions to be pruned more efficienty (Ashutosh Bapat, Yuya Watari, David Rowley)

I think you've misunderstood what's been changed here. Unfortunately,
it's not even true with a bit of eye squinting as these changes have
nothing to do with partition pruning. I think it would be much more
informative to state it as I suggested. Also, the spelling of
"efficiently" needs adjusted.

> +Avoid the locking of pruned partitions during planning (Amit Langote)

At the very least, you'd need to swap "planning" for "execution" as
the above statement isn't true.

David

  45. Re: PG 18 release notes draft committed

    amit <amitlangote09@gmail.com> — 2025-05-06T06:08:13Z

    On Sat, May 3, 2025 at 1:18 AM Bruce Momjian <bruce@momjian.us> wrote:
> On Fri, May  2, 2025 at 01:00:57PM +0900, Amit Langote wrote:
> > 1. Speed up execution of cached plans by deferring locks on partitions
> > subject to pruning (Amit Langote)
> > (bb3ec16e1, d47cbf474, cbc127917, 525392d57)
> >
> > 2. Speed up child EquivalenceMember lookup in planner (Yuya Watari,
> > David Rowley)
> > (d69d45a5a)
> >
> > 3. Speed up derived clause lookup in EquivalenceClass (Ashutosh Bapat)
> > (88f55bc97)
> >
> > Alternatively, 2 and 3 can be combined as:
> >
> > 2. Speed up partition planning by improving EquivalenceClass lookups
> > (Yuya Watari, David Rowley, Ashutosh Bapat)
> >
> > I think 1 should go under Partitioning, which I see is currently missing.
> >
> > Any thoughts, David?
> >
> > Can work on a patch if you'd like.
>
> So, a few things.  First, these set of commits was in a group of 10 that
> I added since there have been complaints in the past that optimizer
> improvements were not listed and therefore patch authors were not given
> sufficient credit.  That means the 209 item count for PG 18 is 10 higher
> than my normal filtering would produce.
>
> Second, looking at the items, these are a case of "X is faster", which
> we don't normally mention in the release notes.  We normally mention
> "faster" when it is so much faster that use cases which were not
> possible before might be possible now, so it is recommended to retest.
> That is what I saw this grouped item as, whereas I don't think the
> individual items meet that criteria.
>
> Also, I didn't see enough partition items to warrant a separate
> partition section, and we didn't have one in PG 17 either.  We could
> pull all the partition items from the sections they are already in, but
> they seem more natural in the sections they are in.
>
> I don't think most people would know what EquivalenceMember is, and even
> if they did, would they be able to connect it to an SQL query?

Thanks for splitting these (cf847d634). I think the text for the
locking item should mention “during execution,” as David also
suggested. Again, I don’t think this change belongs under Optimizer
since it doesn’t really affect the planner -- it’s mainly an executor
improvement. Maybe the General Performance section is a better fit.

Also, just to clarify why the individual items are meaningful
performance improvements:

* Locking change: Executing cached plans involving hundreds or
thousands of partitions was bottlenecked by locking; with this change,
execution is now roughly 20x faster with 1000 partitions.

* Planning time improvements: Planning certain commonly used queries
against partitioned tables when they don’t use partition pruning is
now roughly 20x faster with 1000 partitions.

-- 
Thanks, Amit Langote

  46. Re: PG 18 release notes draft committed

    jian he <jian.universality@gmail.com> — 2025-05-06T14:13:36Z

    On Fri, May 2, 2025 at 10:44 AM Bruce Momjian <bruce@momjian.us> wrote:
>
>         release-16:   206
>         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
>


```
Add pg_dump options --with-schema, --with-data, and --with_statistics
(Jeff Davis) §
The negative versions of these options already existed.

Add pg_dump option --sequence-data to dump sequence data that would
normally be excluded (Nathan Bossart) §

Add pg_dump, pg_dumpall, and pg_restore options --statistics-only,
--no-statistics, --no-data, and --no-schema (Corey Huinker, Jeff
Davis) §
````

in pg17, we only have "--schema-only", "--data-only",
so description "The negative versions of these options already
existed." is wrong?
you can also see the above third item conflict with it.

``--with_statistics`` should be ``--with-statistics``.



Add option --no-policies to pg_dump, pg_dumpall, pg_restore to avoid
policy specification (Nikolay Samokhvalov) §
This is useful for migrating to systems with different policies.

generally, we should say "row level security policy" instead of "policy"?
I think this sentence ( Add --no-policies option to control row level
security policy handling
in dump and restore operations.) in the commit message is good.
maybe we can change it to
( Add --no-policies option to control row level security policy
handling in pg_dump, pg_dumpall, pg_restore)



Allow jsonb NULL values to be cast to scalar types as NULL (Tom Lane) §
Previously such casts generated an error.

here should be "jsonb null values", since we can not do ``select
'NULL'::jsonb;``

  47. Re: PG 18 release notes draft committed

    jian he <jian.universality@gmail.com> — 2025-05-06T14:18:27Z

    Allow partitions to be pruned more efficienty (Ashutosh Bapat, Yuya
Watari, David Rowley) § §
typo, "efficienty" should be "efficiently"?

  48. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-06T19:44:16Z

    On Tue, May  6, 2025 at 03:14:56PM +1200, David Rowley wrote:
> On Tue, 6 May 2025 at 03:59, Bruce Momjian <bruce@momjian.us> wrote:
> >
> > On Mon, May  5, 2025 at 09:42:10PM +1200, David Rowley wrote:
> > > I agree that 88f55bc97 and d69d45a5a should be in their own item.
> > > Likely no need to go into detail about the speed up being about
> > > "EquivalenceClass lookups". I imagine something like "Reduce planner
> > > overheads when planning queries to partitioned and inheritance parent
> > > tables"
> > >
> > > Then for bb3ec16e1, d47cbf474, cbc127917 and 525392d57, something like
> > > "Defer locking of partitions during execution until after partition
> > > elimination".  The release notes for 11.0 called it "partition
> > > elimination", so I went with that naming.
> >
> > Okay, I split them up and went with the attached patch.
> 
> 
> > +Allow partitions to be pruned more efficienty (Ashutosh Bapat, Yuya Watari, David Rowley)
> 
> I think you've misunderstood what's been changed here. Unfortunately,
> it's not even true with a bit of eye squinting as these changes have
> nothing to do with partition pruning. I think it would be much more

I think what you are saying is that this has to do with partition
processing of joins, but not the pruning process.  I don't think a
non-partition joins are likely to hit 32 EquivalenceClasses.

> informative to state it as I suggested. Also, the spelling of
> "efficiently" needs adjusted.

Fixed.  My spell check filter was wrong.

> > +Avoid the locking of pruned partitions during planning (Amit Langote)
> 
> At the very least, you'd need to swap "planning" for "execution" as
> the above statement isn't true.

I went with the attached patch.

-- 
  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.

  49. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-06T20:07:24Z

    On Tue, May  6, 2025 at 03:08:13PM +0900, Amit Langote wrote:
> > I don't think most people would know what EquivalenceMember is, and even
> > if they did, would they be able to connect it to an SQL query?
> 
> Thanks for splitting these (cf847d634). I think the text for the
> locking item should mention “during execution,” as David also
> suggested. Again, I don’t think this change belongs under Optimizer
> since it doesn’t really affect the planner -- it’s mainly an executor
> improvement. Maybe the General Performance section is a better fit.

Yes, good idea, done.

> Also, just to clarify why the individual items are meaningful
> performance improvements:
> 
> * Locking change: Executing cached plans involving hundreds or
> thousands of partitions was bottlenecked by locking; with this change,
> execution is now roughly 20x faster with 1000 partitions.
> 
> * Planning time improvements: Planning certain commonly used queries
> against partitioned tables when they don’t use partition pruning is
> now roughly 20x faster with 1000 partitions.

That's impressive!

-- 
  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.

  50. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-06T20:27:38Z

    On Tue, May  6, 2025 at 10:18:27PM +0800, jian he wrote:
> Allow partitions to be pruned more efficienty (Ashutosh Bapat, Yuya
> Watari, David Rowley) § §
> typo, "efficienty" should be "efficiently"?

Yes, fixed from other email report.  My spellcheck filter was broken.

-- 
  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.

  51. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-06T21:17:05Z

    On Tue, May  6, 2025 at 10:13:36PM +0800, jian he wrote:
> Add pg_dump options --with-schema, --with-data, and --with_statistics
> (Jeff Davis) §
> The negative versions of these options already existed.
> 
> Add pg_dump option --sequence-data to dump sequence data that would
> normally be excluded (Nathan Bossart) §
> 
> Add pg_dump, pg_dumpall, and pg_restore options --statistics-only,
> --no-statistics, --no-data, and --no-schema (Corey Huinker, Jeff
> Davis) §
> ````
> 
> in pg17, we only have "--schema-only", "--data-only",
> so description "The negative versions of these options already
> existed." is wrong?
> you can also see the above third item conflict with it.
> 
> ``--with_statistics`` should be ``--with-statistics``.
> 
> 
> 
> Add option --no-policies to pg_dump, pg_dumpall, pg_restore to avoid
> policy specification (Nikolay Samokhvalov) §
> This is useful for migrating to systems with different policies.
> 
> generally, we should say "row level security policy" instead of "policy"?
> I think this sentence ( Add --no-policies option to control row level
> security policy handling
> in dump and restore operations.) in the commit message is good.
> maybe we can change it to
> ( Add --no-policies option to control row level security policy
> handling in pg_dump, pg_dumpall, pg_restore)
> 
> 
> 
> Allow jsonb NULL values to be cast to scalar types as NULL (Tom Lane) §
> Previously such casts generated an error.
> 
> here should be "jsonb null values", since we can not do ``select
> 'NULL'::jsonb;``

All fixed in the attached applied patch.

-- 
  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.

  52. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-06T21:27:14Z

    On Wed, 7 May 2025 at 07:44, Bruce Momjian <bruce@momjian.us> wrote:
> I think what you are saying is that this has to do with partition
> processing of joins, but not the pruning process.  I don't think a
> non-partition joins are likely to hit 32 EquivalenceClasses.

A query such as: SELECT * FROM table_with_lots_of_partitions ORDER BY
col; will plan much faster now. No joins there.

David

  53. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-07T01:17:15Z

    On Wed, May  7, 2025 at 09:27:14AM +1200, David Rowley wrote:
> On Wed, 7 May 2025 at 07:44, Bruce Momjian <bruce@momjian.us> wrote:
> > I think what you are saying is that this has to do with partition
> > processing of joins, but not the pruning process.  I don't think a
> > non-partition joins are likely to hit 32 EquivalenceClasses.
> 
> A query such as: SELECT * FROM table_with_lots_of_partitions ORDER BY
> col; will plan much faster now. No joins there.

Ah, interesting.  I am guessing the ORDER BY requires the
EquivalenceClasses items.  Applied patch attached.  I don't think we can
make more precise wording for this item.

-- 
  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.

  54. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-07T01:34:23Z

    On Wed, 7 May 2025 at 13:17, Bruce Momjian <bruce@momjian.us> wrote:
>
> On Wed, May  7, 2025 at 09:27:14AM +1200, David Rowley wrote:
> > On Wed, 7 May 2025 at 07:44, Bruce Momjian <bruce@momjian.us> wrote:
> > A query such as: SELECT * FROM table_with_lots_of_partitions ORDER BY
> > col; will plan much faster now. No joins there.
>
> Ah, interesting.  I am guessing the ORDER BY requires the
> EquivalenceClasses items.  Applied patch attached.  I don't think we can
> make more precise wording for this item.

The new wording looks good to me.

David

  55. Re: PG 18 release notes draft committed

    Richard Guo <guofenglinux@gmail.com> — 2025-05-07T06:03:32Z

    On Fri, May 2, 2025 at 11:44 AM Bruce Momjian <bruce@momjian.us> wrote:
>
> I have committd the first draft of the PG 18 release notes.

> 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.  ;-)

Thanks for working on these.

I'm wondering if we should consider mentioning that several
long-standing issues related to grouping sets have been fixed starting
from PostgreSQL v18.  I understand that we typically don't include bug
fixes in the release notes, but these particular issues have been
present since grouping sets were first introduced, and currently they
still exist in the back branches (yeah, for some reason we do not have
back-branch fixes; we only fix them in v18 and going forward).

There have been complaints from users about grouping sets giving
incorrect results in certain cases, which has made them hesitant to
use PostgreSQL for analytical workloads.  Since these issues are fixed
in v18, it might be worthwhile to point this out — if only to reassure
users that these issues are no longer a concern going forward.

(FWIW, the related commits are 247dea89f, f5050f795, and cc5d98525).

Thanks
Richard

  56. Re: PG 18 release notes draft committed

    Yugo Nagata <nagata@sraoss.co.jp> — 2025-05-07T10:59:41Z

    On Thu, 1 May 2025 22:44:50 -0400
Bruce Momjian <bruce@momjian.us> wrote:

> I have committd the first draft of the PG 18 release notes.  The item
> count looks strong:

Thank you for working on this.

>  Have pgbench report the number of failed transactions (Yugo Nagata) 

I think that should be

"Have pgbench report the number of failed, retried, or skipped transactions
in per-script reports"

because the number of failed, retried, or skip transactions was already reported
in the main report, but these are now reported in per-script reports.

Regards,
Yugo Nagata


-- 
Yugo Nagata <nagata@sraoss.co.jp>

  57. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-07T20:41:20Z

    On Wed, May  7, 2025 at 03:03:32PM +0900, Richard Guo wrote:
> On Fri, May 2, 2025 at 11:44 AM Bruce Momjian <bruce@momjian.us> wrote:
> >
> > I have committd the first draft of the PG 18 release notes.
> 
> > 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.  ;-)
> 
> Thanks for working on these.
> 
> I'm wondering if we should consider mentioning that several
> long-standing issues related to grouping sets have been fixed starting
> from PostgreSQL v18.  I understand that we typically don't include bug
> fixes in the release notes, but these particular issues have been
> present since grouping sets were first introduced, and currently they
> still exist in the back branches (yeah, for some reason we do not have
> back-branch fixes; we only fix them in v18 and going forward).
> 
> There have been complaints from users about grouping sets giving
> incorrect results in certain cases, which has made them hesitant to
> use PostgreSQL for analytical workloads.  Since these issues are fixed
> in v18, it might be worthwhile to point this out — if only to reassure
> users that these issues are no longer a concern going forward.
> 
> (FWIW, the related commits are 247dea89f, f5050f795, and cc5d98525).

Agreed, any fix that commonly used to return wrong results should be
mentioned.  Applied 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.

  58. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-07T20:56:43Z

    On Wed, May  7, 2025 at 07:59:41PM +0900, Yugo Nagata wrote:
> On Thu, 1 May 2025 22:44:50 -0400
> Bruce Momjian <bruce@momjian.us> wrote:
> 
> > I have committd the first draft of the PG 18 release notes.  The item
> > count looks strong:
> 
> Thank you for working on this.
> 
> >  Have pgbench report the number of failed transactions (Yugo Nagata) 
> 
> I think that should be
> 
> "Have pgbench report the number of failed, retried, or skipped transactions
> in per-script reports"
> 
> because the number of failed, retried, or skip transactions was already reported
> in the main report, but these are now reported in per-script reports.

Good point, applied 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.

  59. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-07T21:33:49Z

    On Fri, 2 May 2025 at 14:44, Bruce Momjian <bruce@momjian.us> wrote:
> You can see the most current HTML-built version here:
>
>         https://momjian.us/pgsql_docs/release-18.html

You might have left it out on purpose as the output isn't likely to be
read by a machine, but for "Change pg_backend_memory_contexts.level to
be one-based", d9e03864b applied the same change to
pg_log_backend_memory_contexts().

David

  60. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-08T00:36:08Z

    On Thu, May  8, 2025 at 09:33:49AM +1200, David Rowley wrote:
> On Fri, 2 May 2025 at 14:44, Bruce Momjian <bruce@momjian.us> wrote:
> > You can see the most current HTML-built version here:
> >
> >         https://momjian.us/pgsql_docs/release-18.html
> 
> You might have left it out on purpose as the output isn't likely to be
> read by a machine, but for "Change pg_backend_memory_contexts.level to
> be one-based", d9e03864b applied the same change to
> pg_log_backend_memory_contexts().

Oh, I looked at that commit:

	commit 706cbed3510
	Author: Fujii Masao <fujii@postgresql.org>
	Date:   Mon Apr 21 14:53:25 2025 +0900
	
	    doc: Fix memory context level in pg_log_backend_memory_contexts() example.
	
	    Commit d9e03864b6b changed the memory context level numbers shown by
	    pg_log_backend_memory_contexts() to be 1-based. However, the example in
	    the documentation was not updated and still used 0-based numbering.
	
	    This commit updates the example to match the current 1-based output.
	
	    Author: Fujii Masao <masao.fujii@gmail.com>
	    Reviewed-by: David Rowley <drowleyml@gmail.com>
	    Discussion: https://postgr.es/m/1ad6d388-1b43-400d-bec9-36d52f755f74@oss.nttdata.com

and didn't realize it was an SQL function, though the documentation
mention makes that clear.  Applied 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.

  61. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-08T00:47:22Z

    On Thu, 8 May 2025 at 12:36, Bruce Momjian <bruce@momjian.us> wrote:
> +Change pg_backend_memory_contexts.level and pg_log_backend_memory_contexts()() to be one-based (Melih Mutlu, Fujii Masao)

There's an extra set of parentheses on that function name. There's
also an inconsistency between the commit link you added and the author
you added. You've put the author of 706cbed3510 but the commit link
contains d9e03864b.

David

  62. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-08T01:11:53Z

    On Thu, May  8, 2025 at 12:47:22PM +1200, David Rowley wrote:
> On Thu, 8 May 2025 at 12:36, Bruce Momjian <bruce@momjian.us> wrote:
> > +Change pg_backend_memory_contexts.level and pg_log_backend_memory_contexts()() to be one-based (Melih Mutlu, Fujii Masao)
> 
> There's an extra set of parentheses on that function name. There's
> also an inconsistency between the commit link you added and the author
> you added. You've put the author of 706cbed3510 but the commit link
> contains d9e03864b.

Ah, I see those now.  It was two commits.  For some reason the edits are
hard for me;  applied 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.

  63. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-08T01:16:45Z

    On Thu, 8 May 2025 at 13:11, Bruce Momjian <bruce@momjian.us> wrote:
> Ah, I see those now.  It was two commits.  For some reason the edits are
> hard for me;  applied patch attached.

Thanks.  There's been lots of work done in the last year, so lots of
work to understand it all to a level where you can write meaningful
and brief commentary for. Not an easy task. The work you're doing is
appreciated, thank you.

David

  64. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-08T01:42:41Z

    On Thu, May  8, 2025 at 01:16:45PM +1200, David Rowley wrote:
> On Thu, 8 May 2025 at 13:11, Bruce Momjian <bruce@momjian.us> wrote:
> > Ah, I see those now.  It was two commits.  For some reason the edits are
> > hard for me;  applied patch attached.
> 
> Thanks.  There's been lots of work done in the last year, so lots of
> work to understand it all to a level where you can write meaningful
> and brief commentary for. Not an easy task. The work you're doing is
> appreciated, thank you.

I think during the edits, I don't stop everything I am thinking about to
focus, and then can't keep all the details in my head at the same time,
i.e., I am not in the "zone".

-- 
  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.

  65. Re: PG 18 release notes draft committed

    jian he <jian.universality@gmail.com> — 2025-05-08T07:45:00Z

    On Fri, May 2, 2025 at 10:44 AM Bruce Momjian <bruce@momjian.us> wrote:
>
>         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
>

hi.

Add OLD/NEW support to RETURNING in DML queries (Dean Rasheed) §

Previously RETURNING only returned new values for INSERT and UPDATE, old values
for DELETE; MERGE would return the appropriate value for the internal query
executed. This new syntax allows INSERT with an ON CONFLICT action to return old
values, UPDATE to return old values, and DELETE to return new values if the
query assigned to an ON DELETE row would return new values. New syntax allows
changeable relation aliases "old" and "new" to specify which values should be
returned.
--------------------------------------------------------
I am not sure I understand the last sentence, especially "changeable
relation aliases".
looking at the commit message, the following is what i come up with:

Previously RETURNING only returned new values for INSERT and UPDATE, old values
for DELETE; MERGE would return the appropriate value for the internal query
executed.  This allows the RETURNING list of INSERT/UPDATE/DELETE/MERGE queries
to explicitly return old and new values by using the special aliases "old" and
"new".  There are no restrictions on the use of "old" and "new" in any DML
queries.

  66. Re: PG 18 release notes draft committed

    Richard Guo <guofenglinux@gmail.com> — 2025-05-08T10:46:11Z

    On Thu, May 8, 2025 at 5:41 AM Bruce Momjian <bruce@momjian.us> wrote:
> On Wed, May  7, 2025 at 03:03:32PM +0900, Richard Guo wrote:
> > I'm wondering if we should consider mentioning that several
> > long-standing issues related to grouping sets have been fixed starting
> > from PostgreSQL v18.  I understand that we typically don't include bug
> > fixes in the release notes, but these particular issues have been
> > present since grouping sets were first introduced, and currently they
> > still exist in the back branches (yeah, for some reason we do not have
> > back-branch fixes; we only fix them in v18 and going forward).
> >
> > There have been complaints from users about grouping sets giving
> > incorrect results in certain cases, which has made them hesitant to
> > use PostgreSQL for analytical workloads.  Since these issues are fixed
> > in v18, it might be worthwhile to point this out — if only to reassure
> > users that these issues are no longer a concern going forward.
> >
> > (FWIW, the related commits are 247dea89f, f5050f795, and cc5d98525).
>
> Agreed, any fix that commonly used to return wrong results should be
> mentioned.  Applied patch attached.

I'm not sure whether it's appropriate to put the incorrect-result
fixes under the item "Allow some HAVING clauses on GROUPING SETS to
be pushed to WHERE clauses", since that item is an optimization and
does not fix these incorrect-result issues.

But I'm also unsure where else they should go.  Would it make sense to
list them as a new item instead?

Thanks
Richard

  67. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-08T15:14:19Z

    On Thu, May  8, 2025 at 03:45:00PM +0800, jian he wrote:
> On Fri, May 2, 2025 at 10:44 AM Bruce Momjian <bruce@momjian.us> wrote:
> >
> >         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
> >
> 
> hi.
> 
> Add OLD/NEW support to RETURNING in DML queries (Dean Rasheed) §
> 
> Previously RETURNING only returned new values for INSERT and UPDATE, old values
> for DELETE; MERGE would return the appropriate value for the internal query
> executed. This new syntax allows INSERT with an ON CONFLICT action to return old
> values, UPDATE to return old values, and DELETE to return new values if the
> query assigned to an ON DELETE row would return new values. New syntax allows
> changeable relation aliases "old" and "new" to specify which values should be
> returned.
> --------------------------------------------------------
> I am not sure I understand the last sentence, especially "changeable
> relation aliases".
> looking at the commit message, the following is what i come up with:
> 
> Previously RETURNING only returned new values for INSERT and UPDATE, old values
> for DELETE; MERGE would return the appropriate value for the internal query
> executed.  This allows the RETURNING list of INSERT/UPDATE/DELETE/MERGE queries
> to explicitly return old and new values by using the special aliases "old" and
> "new".  There are no restrictions on the use of "old" and "new" in any DML
> queries.

Yes, I like your new text better than mine.  I retained "This new
syntax" so "This" is clear, and adjusted the last sentence to connect
the alias with the ability to rename to avoid conflicts.  Applied 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.

  68. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-08T15:18:11Z

    On Thu, May  8, 2025 at 07:46:11PM +0900, Richard Guo wrote:
> On Thu, May 8, 2025 at 5:41 AM Bruce Momjian <bruce@momjian.us> wrote:
> > On Wed, May  7, 2025 at 03:03:32PM +0900, Richard Guo wrote:
> > > I'm wondering if we should consider mentioning that several
> > > long-standing issues related to grouping sets have been fixed starting
> > > from PostgreSQL v18.  I understand that we typically don't include bug
> > > fixes in the release notes, but these particular issues have been
> > > present since grouping sets were first introduced, and currently they
> > > still exist in the back branches (yeah, for some reason we do not have
> > > back-branch fixes; we only fix them in v18 and going forward).
> > >
> > > There have been complaints from users about grouping sets giving
> > > incorrect results in certain cases, which has made them hesitant to
> > > use PostgreSQL for analytical workloads.  Since these issues are fixed
> > > in v18, it might be worthwhile to point this out — if only to reassure
> > > users that these issues are no longer a concern going forward.
> > >
> > > (FWIW, the related commits are 247dea89f, f5050f795, and cc5d98525).
> >
> > Agreed, any fix that commonly used to return wrong results should be
> > mentioned.  Applied patch attached.
> 
> I'm not sure whether it's appropriate to put the incorrect-result
> fixes under the item "Allow some HAVING clauses on GROUPING SETS to
> be pushed to WHERE clauses", since that item is an optimization and
> does not fix these incorrect-result issues.
> 
> But I'm also unsure where else they should go.  Would it make sense to
> list them as a new item instead?

I put it there because that is the only mention of GROUPING SETS.  If we
create a separate item, would the text just be "This release fixes
some GROUPING SETS queries that used to return incorrect results."  Is
there any pattern to the fix?  Seems NULLs or subqueries were involved. 
Is this an incompatibility?  Could people be relying on the old
behavior?

-- 
  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.

  69. Re: PG 18 release notes draft committed

    Richard Guo <guofenglinux@gmail.com> — 2025-05-09T02:47:19Z

    On Fri, May 9, 2025 at 12:18 AM Bruce Momjian <bruce@momjian.us> wrote:
> On Thu, May  8, 2025 at 07:46:11PM +0900, Richard Guo wrote:
> > On Thu, May 8, 2025 at 5:41 AM Bruce Momjian <bruce@momjian.us> wrote:
> > > On Wed, May  7, 2025 at 03:03:32PM +0900, Richard Guo wrote:
> > > > I'm wondering if we should consider mentioning that several
> > > > long-standing issues related to grouping sets have been fixed starting
> > > > from PostgreSQL v18.  I understand that we typically don't include bug
> > > > fixes in the release notes, but these particular issues have been
> > > > present since grouping sets were first introduced, and currently they
> > > > still exist in the back branches (yeah, for some reason we do not have
> > > > back-branch fixes; we only fix them in v18 and going forward).
> > > >
> > > > There have been complaints from users about grouping sets giving
> > > > incorrect results in certain cases, which has made them hesitant to
> > > > use PostgreSQL for analytical workloads.  Since these issues are fixed
> > > > in v18, it might be worthwhile to point this out — if only to reassure
> > > > users that these issues are no longer a concern going forward.
> > > >
> > > > (FWIW, the related commits are 247dea89f, f5050f795, and cc5d98525).
> > >
> > > Agreed, any fix that commonly used to return wrong results should be
> > > mentioned.  Applied patch attached.
> >
> > I'm not sure whether it's appropriate to put the incorrect-result
> > fixes under the item "Allow some HAVING clauses on GROUPING SETS to
> > be pushed to WHERE clauses", since that item is an optimization and
> > does not fix these incorrect-result issues.
> >
> > But I'm also unsure where else they should go.  Would it make sense to
> > list them as a new item instead?
>
> I put it there because that is the only mention of GROUPING SETS.  If we
> create a separate item, would the text just be "This release fixes
> some GROUPING SETS queries that used to return incorrect results."  Is
> there any pattern to the fix?  Seems NULLs or subqueries were involved.
> Is this an incompatibility?  Could people be relying on the old
> behavior?

I think there are two patterns here:

* 247dea89f and cc5d98525 fix cases where grouping expressions fail to
match lower-level target items due to expression preprocessing or
subquery pull-up.  Subqueries are one example of such expressions.

* f5050f795 fixes cases where some seemingly redundant grouping or
ordering expressions were incorrectly ignored, without recognizing
that they could be nulled by grouping sets.

I don't think this constitutes an incompatibility, and it's unlikely
that anyone is relying on the old behavior, as it was clearly
incorrect.

(I realize these descriptions are too technical, but I'm not sure how
to express them in a more user-facing way.)

Thanks
Richard

  70. Re: PG 18 release notes draft committed

    Richard Guo <guofenglinux@gmail.com> — 2025-05-09T03:05:07Z

    On Fri, May 9, 2025 at 11:47 AM Richard Guo <guofenglinux@gmail.com> wrote:
> On Fri, May 9, 2025 at 12:18 AM Bruce Momjian <bruce@momjian.us> wrote:
> > On Thu, May  8, 2025 at 07:46:11PM +0900, Richard Guo wrote:
> > > On Thu, May 8, 2025 at 5:41 AM Bruce Momjian <bruce@momjian.us> wrote:
> > > > On Wed, May  7, 2025 at 03:03:32PM +0900, Richard Guo wrote:
> > > > > I'm wondering if we should consider mentioning that several
> > > > > long-standing issues related to grouping sets have been fixed starting
> > > > > from PostgreSQL v18.  I understand that we typically don't include bug
> > > > > fixes in the release notes, but these particular issues have been
> > > > > present since grouping sets were first introduced, and currently they
> > > > > still exist in the back branches (yeah, for some reason we do not have
> > > > > back-branch fixes; we only fix them in v18 and going forward).
> > > > >
> > > > > There have been complaints from users about grouping sets giving
> > > > > incorrect results in certain cases, which has made them hesitant to
> > > > > use PostgreSQL for analytical workloads.  Since these issues are fixed
> > > > > in v18, it might be worthwhile to point this out — if only to reassure
> > > > > users that these issues are no longer a concern going forward.
> > > > >
> > > > > (FWIW, the related commits are 247dea89f, f5050f795, and cc5d98525).
> > > >
> > > > Agreed, any fix that commonly used to return wrong results should be
> > > > mentioned.  Applied patch attached.
> > >
> > > I'm not sure whether it's appropriate to put the incorrect-result
> > > fixes under the item "Allow some HAVING clauses on GROUPING SETS to
> > > be pushed to WHERE clauses", since that item is an optimization and
> > > does not fix these incorrect-result issues.
> > >
> > > But I'm also unsure where else they should go.  Would it make sense to
> > > list them as a new item instead?
> >
> > I put it there because that is the only mention of GROUPING SETS.  If we
> > create a separate item, would the text just be "This release fixes
> > some GROUPING SETS queries that used to return incorrect results."  Is
> > there any pattern to the fix?  Seems NULLs or subqueries were involved.
> > Is this an incompatibility?  Could people be relying on the old
> > behavior?
>
> I think there are two patterns here:
>
> * 247dea89f and cc5d98525 fix cases where grouping expressions fail to
> match lower-level target items due to expression preprocessing or
> subquery pull-up.  Subqueries are one example of such expressions.
>
> * f5050f795 fixes cases where some seemingly redundant grouping or
> ordering expressions were incorrectly ignored, without recognizing
> that they could be nulled by grouping sets.
>
> I don't think this constitutes an incompatibility, and it's unlikely
> that anyone is relying on the old behavior, as it was clearly
> incorrect.
>
> (I realize these descriptions are too technical, but I'm not sure how
> to express them in a more user-facing way.)

How about putting them this way:

* 247dea89f and cc5d98525 fix queries in which GROUP BY columns
contain expressions that are complex or originate from subqueries.

* f5050f795 fixes queries in which ORDER BY columns contain
expressions that are used in grouping sets.

Thanks
Richard

  71. Re: PG 18 release notes draft committed

    Steven Niu <niushiji@gmail.com> — 2025-05-09T08:51:03Z

    Hi, Bruce,

I have one comment, in E.1.3.4. Functions, crc32c also needs bracket.
"Add functions crc32() and crc32c to compute CRC values" -->
"Add functions crc32() and crc32c() to compute CRC values"

Regards,
Steven


在 2025/5/2 10:44, Bruce Momjian 写道:
> I have committd the first draft of the PG 18 release notes.  The item
> count looks strong:
>
>       release-7.4:  263
>       release-8.0:  230
>       release-8.1:  174
>       release-8.2:  215
>       release-8.3:  214
>       release-8.4:  314
>       release-9.0:  237
>       release-9.1:  203
>       release-9.2:  238
>       release-9.3:  177
>       release-9.4:  211
>       release-9.5:  193
>       release-9.6:  214
>       release-10:   189
>       release-11:   170
>       release-12:   180
>       release-13:   178
>       release-14:   220
>       release-15:   184
>       release-16:   206
>       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
>

  72. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-09T18:03:10Z

    On Fri, May  9, 2025 at 12:05:07PM +0900, Richard Guo wrote:
> > I think there are two patterns here:
> >
> > * 247dea89f and cc5d98525 fix cases where grouping expressions fail to
> > match lower-level target items due to expression preprocessing or
> > subquery pull-up.  Subqueries are one example of such expressions.
> >
> > * f5050f795 fixes cases where some seemingly redundant grouping or
> > ordering expressions were incorrectly ignored, without recognizing
> > that they could be nulled by grouping sets.
> >
> > I don't think this constitutes an incompatibility, and it's unlikely
> > that anyone is relying on the old behavior, as it was clearly
> > incorrect.
> >
> > (I realize these descriptions are too technical, but I'm not sure how
> > to express them in a more user-facing way.)
> 
> How about putting them this way:
> 
> * 247dea89f and cc5d98525 fix queries in which GROUP BY columns
> contain expressions that are complex or originate from subqueries.
> 
> * f5050f795 fixes queries in which ORDER BY columns contain
> expressions that are used in grouping sets.

Okay, that is clear.  Let's stay with what we have in the release notes
and see if we get any feedback from users during the beta period;  that
might give us direction on whether we want to expand what we already
have.  Thanks.

-- 
  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.

  73. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-09T18:16:14Z

    On Fri, May  9, 2025 at 04:51:03PM +0800, Steven Niu wrote:
> Hi, Bruce,
> 
> I have one comment, in E.1.3.4. Functions, crc32c also needs bracket.
> "Add functions crc32() and crc32c to compute CRC values" -->
> "Add functions crc32() and crc32c() to compute CRC values"

Thanks, fixed.

-- 
  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.

  74. Re: PG 18 release notes draft committed

    David Rowley <dgrowleyml@gmail.com> — 2025-05-09T22:38:06Z

    On Fri, 2 May 2025 at 14:44, Bruce Momjian <bruce@momjian.us> wrote:
> 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.  ;-)

Minor detail, but "Improve the performance and reduce memory usage of
hash joins and GROUP BY" probably fits better in "E.1.3.1.3. General
Performance" as none of those changes touched anything in the planner.

David

  75. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-10T03:39:49Z

    On Sat, May 10, 2025 at 10:38:06AM +1200, David Rowley wrote:
> On Fri, 2 May 2025 at 14:44, Bruce Momjian <bruce@momjian.us> wrote:
> > 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.  ;-)
> 
> Minor detail, but "Improve the performance and reduce memory usage of
> hash joins and GROUP BY" probably fits better in "E.1.3.1.3. General
> Performance" as none of those changes touched anything in the planner.

Agreed, moved, thanks.

-- 
  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.

  76. Re: PG 18 release notes draft committed

    David G. Johnston <david.g.johnston@gmail.com> — 2025-05-13T03:27:40Z

    On Thursday, May 1, 2025, Bruce Momjian <bruce@momjian.us> wrote:
>
>
> 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.  ;-)
>

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).

David J.

  77. Re: PG 18 release notes draft committed

    Laurenz Albe <laurenz.albe@cybertec.at> — 2025-05-13T06:05:24Z

    On Mon, 2025-05-12 at 20:27 -0700, David G. Johnston wrote:
> On Thursday, May 1, 2025, Bruce Momjian <bruce@momjian.us> wrote:
> > 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.  ;-)
> > 
> 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.

Yours,
Laurenz Albe

  78. Re: PG 18 release notes draft committed

    Álvaro Herrera <alvherre@kurilemu.de> — 2025-05-15T18:02:02Z

    On 2025-May-13, Laurenz Albe wrote:

> 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.

I think it might be useful to distinguish changes to views, which are
intended to be user-facing, from changes to "internal" catalogs, which
aren't.  I would think that it's reasonable to list changes to system
views in the incompatibility section, but not changes to the system
catalog tables.

As related anecdote, the rename of columns in pg_stat_activity a few
years back caused some pg_upgrade pain, which IMO was understandable;
it's reasonable to call that kind of thing out as a possible
incompatibility, at least IMO.

> The "Migration" section also doesn't list changes to the exported
> PostgreSQL functins, which has bitten me as extension developer several
> times.

Hmm.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"No me acuerdo, pero no es cierto.  No es cierto, y si fuera cierto,
 no me acuerdo."                 (Augusto Pinochet a una corte de justicia)

  79. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-20T12:01:47Z

    On Thu, May 15, 2025 at 02:02:02PM -0400, Álvaro Herrera wrote:
> As related anecdote, the rename of columns in pg_stat_activity a few
> years back caused some pg_upgrade pain, which IMO was understandable;
> it's reasonable to call that kind of thing out as a possible
> incompatibility, at least IMO.
> 
> > The "Migration" section also doesn't list changes to the exported
> > PostgreSQL functins, which has bitten me as extension developer several
> > times.
> 
> Hmm.

I have thought about such issues, and I feel there are so many items
that would be interesting to extension developers that adding just a few
to the release notes would not be very helpful, and if we add all of
them it would be distracting for the majority of users.  It might be
helpful for someone to write a wiki page specifically for that audience.

-- 
  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.

  80. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-20T12:28:18Z

    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.

  81. Re: PG 18 release notes draft committed

    Nazir Bilal Yavuz <byavuz81@gmail.com> — 2025-05-20T12:46:44Z

    Hi,

Thanks for working on this!

On Fri, 2 May 2025 at 05:44, Bruce Momjian <bruce@momjian.us> wrote:
>
> 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.  ;-)

+<listitem>
+<para>
+Add server variable file_copy_method to control the file copying
method (Nazir Bilal Yavuz)
+<ulink url="&commit_baseurl;f78ca6f3e">&sect;</ulink>
+</para>

A minor fix; I co-authored this with Thomas Munro, he is the actual author.

--
Regards,
Nazir Bilal Yavuz
Microsoft

  82. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-20T13:52:17Z

    On Tue, May 20, 2025 at 03:46:44PM +0300, Nazir Bilal Yavuz wrote:
> Hi,
> 
> Thanks for working on this!
> 
> On Fri, 2 May 2025 at 05:44, Bruce Momjian <bruce@momjian.us> wrote:
> >
> > 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.  ;-)
> 
> +<listitem>
> +<para>
> +Add server variable file_copy_method to control the file copying
> method (Nazir Bilal Yavuz)
> +<ulink url="&commit_baseurl;f78ca6f3e">&sect;</ulink>
> +</para>

Uh, the commit is:

	commit f78ca6f3ebb
	Author: Thomas Munro <tmunro@postgresql.org>
	Date:   Tue Apr 8 20:52:47 2025 +1200
	
	    Introduce file_copy_method setting.
	
	    It can be set to either COPY (the default) or CLONE if the system
	    supports it.  CLONE causes callers of copydir(), currently CREATE
	    DATABASE ... STRATEGY=FILE_COPY and ALTER DATABASE ... SET TABLESPACE =
	    ..., to use copy_file_range (Linux, FreeBSD) or copyfile (macOS) to copy
	    files instead of a read-write loop over the contents.
	
	    CLONE gives the kernel the opportunity to share block ranges on
	    copy-on-write file systems and push copying down to storage on others,
	    depending on configuration.  On some systems CLONE can be used to clone
	    large databases quickly with CREATE DATABASE ... TEMPLATE=source
	    STRATEGY=FILE_COPY.
	
	    Other operating systems could be supported; patches welcome.
	
	    Co-authored-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
	    Reviewed-by: Robert Haas <robertmhaas@gmail.com>
	    Reviewed-by: Ranier Vilela <ranier.vf@gmail.com>
	    Discussion: https://postgr.es/m/CA%2BhUKGLM%2Bt%2BSwBU-cHeMUXJCOgBxSHLGZutV5zCwY4qrCcE02w%40mail.gmail.com

As of the date of the commit, "Co-authored-by:" is listed as:

	https://wiki.postgresql.org/wiki/Commit_Message_Guidance

	"Co-authored-by:" is used by committers when they want to give full credit
	to the named individuals, but also indicate that they made significant
	changes.

> A minor fix; I co-authored this with Thomas Munro, he is the actual author.

Uh, does this mean I should add Thomas Munro before or after your name,
or remove your name and list only Thomas Munro?

-- 
  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.

  83. Re: PG 18 release notes draft committed

    Nazir Bilal Yavuz <byavuz81@gmail.com> — 2025-05-20T14:15:54Z

    Hi,

On Tue, 20 May 2025 at 16:52, Bruce Momjian <bruce@momjian.us> wrote:
>
> On Tue, May 20, 2025 at 03:46:44PM +0300, Nazir Bilal Yavuz wrote:
> > Hi,
> >
> > Thanks for working on this!
> >
> > On Fri, 2 May 2025 at 05:44, Bruce Momjian <bruce@momjian.us> wrote:
> > >
> > > 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.  ;-)
> >
> > +<listitem>
> > +<para>
> > +Add server variable file_copy_method to control the file copying
> > method (Nazir Bilal Yavuz)
> > +<ulink url="&commit_baseurl;f78ca6f3e">&sect;</ulink>
> > +</para>
>
> Uh, the commit is:
>
>         commit f78ca6f3ebb
>         Author: Thomas Munro <tmunro@postgresql.org>
>         Date:   Tue Apr 8 20:52:47 2025 +1200
>
>             Introduce file_copy_method setting.
>
>             It can be set to either COPY (the default) or CLONE if the system
>             supports it.  CLONE causes callers of copydir(), currently CREATE
>             DATABASE ... STRATEGY=FILE_COPY and ALTER DATABASE ... SET TABLESPACE =
>             ..., to use copy_file_range (Linux, FreeBSD) or copyfile (macOS) to copy
>             files instead of a read-write loop over the contents.
>
>             CLONE gives the kernel the opportunity to share block ranges on
>             copy-on-write file systems and push copying down to storage on others,
>             depending on configuration.  On some systems CLONE can be used to clone
>             large databases quickly with CREATE DATABASE ... TEMPLATE=source
>             STRATEGY=FILE_COPY.
>
>             Other operating systems could be supported; patches welcome.
>
>             Co-authored-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
>             Reviewed-by: Robert Haas <robertmhaas@gmail.com>
>             Reviewed-by: Ranier Vilela <ranier.vf@gmail.com>
>             Discussion: https://postgr.es/m/CA%2BhUKGLM%2Bt%2BSwBU-cHeMUXJCOgBxSHLGZutV5zCwY4qrCcE02w%40mail.gmail.com
>
> As of the date of the commit, "Co-authored-by:" is listed as:
>
>         https://wiki.postgresql.org/wiki/Commit_Message_Guidance
>
>         "Co-authored-by:" is used by committers when they want to give full credit
>         to the named individuals, but also indicate that they made significant
>         changes.
>
> > A minor fix; I co-authored this with Thomas Munro, he is the actual author.
>
> Uh, does this mean I should add Thomas Munro before or after your name,
> or remove your name and list only Thomas Munro?

Sorry for taking your time, I did not know that. Then, I am okay with
how it is right now.

-- 
Regards,
Nazir Bilal Yavuz
Microsoft

  84. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-20T14:41:48Z

    On Tue, May 20, 2025 at 05:15:54PM +0300, Nazir Bilal Yavuz wrote:
> > As of the date of the commit, "Co-authored-by:" is listed as:
> >
> >         https://wiki.postgresql.org/wiki/Commit_Message_Guidance
> >
> >         "Co-authored-by:" is used by committers when they want to give full credit
> >         to the named individuals, but also indicate that they made significant
> >         changes.
> >
> > > A minor fix; I co-authored this with Thomas Munro, he is the actual author.
> >
> > Uh, does this mean I should add Thomas Munro before or after your name,
> > or remove your name and list only Thomas Munro?
> 
> Sorry for taking your time, I did not know that. Then, I am okay with
> how it is right now.

No problem.  The "Co-authored-by:" guidance was only written down in
January of this year.  I assume Thomas Munro was following that guidance
when he wrote the commit message.

-- 
  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.

  85. Re: PG 18 release notes draft committed

    Peter Geoghegan <pg@bowt.ie> — 2025-05-21T21:57:07Z

    On Thu, May 1, 2025 at 10:44 PM Bruce Momjian <bruce@momjian.us> wrote:
> I have committd the first draft of the PG 18 release notes.

I suggest that you use something like the following wording for the
skip scan feature:

Add the "skip scan" optimization, which enables more efficient scans
of multicolumn B-tree indexes for queries that omit an "=" condition
on one or more prefix index columns.

This is similar to the wording that appeared in the beta1 announcement.

The term "skip scan" has significant baggage -- we need to be careful
to not add to the confusion. There are naming conflicts, which seem
likely to confuse some users. Various community members have in the
past referred to a feature that MySQL calls loose index scan as skip
scan, which seems wrong to me -- it clashes with the naming
conventions used by other RDBMSs, for no good reason. Skip scan and
loose index scan are in fact rather different features.

For example, TimescaleDB offers Loose index scan as part of the
TimescaleDB Postgres extension, which (for whatever reason) they chose
to call skip scan:

https://www.timescale.com/blog/how-we-made-distinct-queries-up-to-8000x-faster-on-postgresql

Note that loose index scan can only be used with certain kinds of
queries involving DISTINCT or GROUP BY. Whereas skip scan (in Oracle
and now in Postgres) can work with any query that omits one or more
"=" conditions on a prefix index column from a multicolumn index (when
a later index column has some condition that can be used by the scan)
-- it doesn't have to involve aggregation. I believe that describing
the feature along these lines will make it less likely that users will
be confused by the apparent naming conflict.

FWIW, I don't think that it's important that the release notes point
out that skip scan is only helpful when the leading/skipped column is
low cardinality (though that detail is accurate).

-- 
Peter Geoghegan

  86. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-23T02:24:51Z

    On Wed, May 21, 2025 at 05:57:07PM -0400, Peter Geoghegan wrote:
> On Thu, May 1, 2025 at 10:44 PM Bruce Momjian <bruce@momjian.us> wrote:
> > I have committd the first draft of the PG 18 release notes.
> 
> I suggest that you use something like the following wording for the
> skip scan feature:
> 
> Add the "skip scan" optimization, which enables more efficient scans
> of multicolumn B-tree indexes for queries that omit an "=" condition
> on one or more prefix index columns.
> 
> This is similar to the wording that appeared in the beta1 announcement.
> 
> The term "skip scan" has significant baggage -- we need to be careful
> to not add to the confusion. There are naming conflicts, which seem
> likely to confuse some users. Various community members have in the
> past referred to a feature that MySQL calls loose index scan as skip
> scan, which seems wrong to me -- it clashes with the naming
> conventions used by other RDBMSs, for no good reason. Skip scan and
> loose index scan are in fact rather different features.
> 
> For example, TimescaleDB offers Loose index scan as part of the
> TimescaleDB Postgres extension, which (for whatever reason) they chose
> to call skip scan:
> 
> https://www.timescale.com/blog/how-we-made-distinct-queries-up-to-8000x-faster-on-postgresql
> 
> Note that loose index scan can only be used with certain kinds of
> queries involving DISTINCT or GROUP BY. Whereas skip scan (in Oracle
> and now in Postgres) can work with any query that omits one or more
> "=" conditions on a prefix index column from a multicolumn index (when
> a later index column has some condition that can be used by the scan)
> -- it doesn't have to involve aggregation. I believe that describing
> the feature along these lines will make it less likely that users will
> be confused by the apparent naming conflict.
> 
> FWIW, I don't think that it's important that the release notes point
> out that skip scan is only helpful when the leading/skipped column is
> low cardinality (though that detail is accurate).

I see your point that we are not defining what this does.  I went with
the attached text.

-- 
  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.

  87. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-23T02:31:29Z

    On Wed, May 21, 2025 at 05:57:07PM -0400, Peter Geoghegan wrote:
> For example, TimescaleDB offers Loose index scan as part of the
> TimescaleDB Postgres extension, which (for whatever reason) they chose
> to call skip scan:
> 
> https://www.timescale.com/blog/how-we-made-distinct-queries-up-to-8000x-faster-on-postgresql
> 
> Note that loose index scan can only be used with certain kinds of
> queries involving DISTINCT or GROUP BY. Whereas skip scan (in Oracle
> and now in Postgres) can work with any query that omits one or more
> "=" conditions on a prefix index column from a multicolumn index (when
> a later index column has some condition that can be used by the scan)
> -- it doesn't have to involve aggregation. I believe that describing
> the feature along these lines will make it less likely that users will
> be confused by the apparent naming conflict.

Yes, I understand this "loose index scan" feature as preventing DISTINCT
from traversing all matching indexed values, and then removing
duplicates.  Rather it stops after finding the first match for each
distinct value.

-- 
  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.

  88. Re: PG 18 release notes draft committed

    vignesh C <vignesh21@gmail.com> — 2025-05-23T02:49:15Z

    On Fri, 2 May 2025 at 08:14, Bruce Momjian <bruce@momjian.us> wrote:
>
> I have committd the first draft of the PG 18 release notes.  The item
> count looks strong:
>
> 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.  ;-)

Regarding the following:
Change the default CREATE SUBSCRIPTION streaming option from "off" to
"parallel" (Hayato Kuroda, Masahiko Sawada, Peter Smith, Amit Kapila)

The author name was incorrectly listed in the commit; it should be
"Vignesh C". This correction is noted in the follow-up to the commit
email at [1].
[1] - https://www.postgresql.org/message-id/CAA4eK1K_M6%3DTB7sMKhBS5e819ePknB1_bT3a8LAnzV2dv64wjA%40mail.gmail.com

Regards,
Vignesh

  89. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-23T03:03:02Z

    On Fri, May 23, 2025 at 08:19:15AM +0530, vignesh C wrote:
> On Fri, 2 May 2025 at 08:14, Bruce Momjian <bruce@momjian.us> wrote:
> >
> > I have committd the first draft of the PG 18 release notes.  The item
> > count looks strong:
> >
> > 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.  ;-)
> 
> Regarding the following:
> Change the default CREATE SUBSCRIPTION streaming option from "off" to
> "parallel" (Hayato Kuroda, Masahiko Sawada, Peter Smith, Amit Kapila)
> 
> The author name was incorrectly listed in the commit; it should be
> "Vignesh C". This correction is noted in the follow-up to the commit
> email at [1].
> [1] - https://www.postgresql.org/message-id/CAA4eK1K_M6%3DTB7sMKhBS5e819ePknB1_bT3a8LAnzV2dv64wjA%40mail.gmail.com

Ah, I see, fixed with the attached patch.  It might be nice if we had a
more organized way of recording such commit corrections.

-- 
  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.

  90. Re: PG 18 release notes draft committed

    Michael Paquier <michael@paquier.xyz> — 2025-05-23T06:16:51Z

    On Thu, May 01, 2025 at 10:44:50PM -0400, Bruce Momjian wrote:
> 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.  ;-)

May I suggest the attached addition for the release notes, following
commit 371f2db8b that has added support for runtime parameters in
injection points?
--
Michael

  91. Re: PG 18 release notes draft committed

    Álvaro Herrera <alvherre@kurilemu.de> — 2025-05-23T07:54:54Z

    On 2025-May-20, Bruce Momjian wrote:

> On Tue, May 20, 2025 at 05:15:54PM +0300, Nazir Bilal Yavuz wrote:
> > > As of the date of the commit, "Co-authored-by:" is listed as:
> > >
> > >         https://wiki.postgresql.org/wiki/Commit_Message_Guidance

> No problem.  The "Co-authored-by:" guidance was only written down in
> January of this year.  I assume Thomas Munro was following that guidance
> when he wrote the commit message.

FWIW I have not taken to following that page yet, particularly because
the chosen page title is pretty random, there are no links to it, and I
couldn't find it when I searched for it; I wouldn't assume anyone is
using it as if it were already gospel.

Anyway, in order to contribute I added a few links to it, and also fixed
the markup some.


TBH I don't agree with everything the page says.  For instance, I don't
think we should care about what gitweb does with the commit title.
gitweb is a dying interface and we'd do good to get rid of it, relying
instead on cgit only.  cgit shows more than 50 chars of the commit
title, so I don't think there's a reason to limit oneself to 50 chars
there.

I also think that showing an XML-ish format of a commit message is
unhelpful, not to mention hard to read.  Showing a few actual examples
would be better.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
¡Ay, ay, ay!  Con lo mucho que yo lo quería (bis)
se fue de mi vera ... se fue para siempre, pa toíta ... pa toíta la vida
¡Ay Camarón! ¡Ay Camarón!                                (Paco de Lucía)

  92. Re: PG 18 release notes draft committed

    Álvaro Herrera <alvherre@kurilemu.de> — 2025-05-23T08:46:09Z

    On 2025-May-22, Bruce Momjian wrote:

> Ah, I see, fixed with the attached patch.  It might be nice if we had a
> more organized way of recording such commit corrections.

`git notes` can do that.  They can also be used to indicate things such
as commits being reverted.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
 Are you not unsure you want to delete Firefox?
       [Not unsure]     [Not not unsure]    [Cancel]
                   http://smylers.hates-software.com/2008/01/03/566e45b2.html

  93. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-23T13:37:42Z

    On Fri, May 23, 2025 at 10:46:09AM +0200, Álvaro Herrera wrote:
> On 2025-May-22, Bruce Momjian wrote:
> 
> > Ah, I see, fixed with the attached patch.  It might be nice if we had a
> > more organized way of recording such commit corrections.
> 
> `git notes` can do that.  They can also be used to indicate things such
> as commits being reverted.

That seems useful.  This web page explains how it can be used:

	https://stackoverflow.com/questions/20324417/git-get-all-notes-of-a-branch

I suppose I would get all of the notes that apply to the commits I am
reviewing.

-- 
  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.

  94. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-23T13:47:42Z

    On Fri, May 23, 2025 at 09:54:54AM +0200, Álvaro Herrera wrote:
> On 2025-May-20, Bruce Momjian wrote:
> 
> > On Tue, May 20, 2025 at 05:15:54PM +0300, Nazir Bilal Yavuz wrote:
> > > > As of the date of the commit, "Co-authored-by:" is listed as:
> > > >
> > > >         https://wiki.postgresql.org/wiki/Commit_Message_Guidance
> 
> > No problem.  The "Co-authored-by:" guidance was only written down in
> > January of this year.  I assume Thomas Munro was following that guidance
> > when he wrote the commit message.
> 
> FWIW I have not taken to following that page yet, particularly because
> the chosen page title is pretty random, there are no links to it, and I
> couldn't find it when I searched for it; I wouldn't assume anyone is
> using it as if it were already gospel.
> 
> Anyway, in order to contribute I added a few links to it, and also fixed
> the markup some.

Great, thanks.

> TBH I don't agree with everything the page says.  For instance, I don't
> think we should care about what gitweb does with the commit title.
> gitweb is a dying interface and we'd do good to get rid of it, relying
> instead on cgit only.  cgit shows more than 50 chars of the commit
> title, so I don't think there's a reason to limit oneself to 50 chars
> there.

Agreed, gitweb limit removed.

> I also think that showing an XML-ish format of a commit message is
> unhelpful, not to mention hard to read.  Showing a few actual examples
> would be better.

Agreed, but the XML came from Joe Conway so I am hesitant to remove it
myself without feedback from him.

-- 
  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.

  95. Re: PG 18 release notes draft committed

    Peter Geoghegan <pg@bowt.ie> — 2025-05-23T14:01:13Z

    On Thu, May 22, 2025 at 10:24 PM Bruce Momjian <bruce@momjian.us> wrote:
> I see your point that we are not defining what this does.  I went with
> the attached text.

You propose the wording is "This allows muti-column btree indexes to
be used by queries that only reference the second or later indexed
columns".

I think that your wording is a big improvement. I personally would
have emphasized the absence of a "=" condition, rather than the
presence of another condition on a later column, since there are cases
where the first column is referenced but skip scan can still be used
(e.g., when there one or more inequalities on the first column, plus a
"=" condition on the second column). I can live with this wording,
though.

Thanks
-- 
Peter Geoghegan

  96. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-23T20:01:41Z

    On Fri, May 23, 2025 at 03:16:51PM +0900, Michael Paquier wrote:
> On Thu, May 01, 2025 at 10:44:50PM -0400, Bruce Momjian wrote:
> > 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.  ;-)
> 
> May I suggest the attached addition for the release notes, following
> commit 371f2db8b that has added support for runtime parameters in
> injection points?

I updated the release notes to current and included your patch,
attached, thanks.

-- 
  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.

  97. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-23T21:03:53Z

    On Fri, May 23, 2025 at 10:01:13AM -0400, Peter Geoghegan wrote:
> On Thu, May 22, 2025 at 10:24 PM Bruce Momjian <bruce@momjian.us> wrote:
> > I see your point that we are not defining what this does.  I went with
> > the attached text.
> 
> You propose the wording is "This allows muti-column btree indexes to
> be used by queries that only reference the second or later indexed
> columns".
> 
> I think that your wording is a big improvement. I personally would
> have emphasized the absence of a "=" condition, rather than the
> presence of another condition on a later column, since there are cases
> where the first column is referenced but skip scan can still be used
> (e.g., when there one or more inequalities on the first column, plus a
> "=" condition on the second column). I can live with this wording,
> though.

I was able to squeeze in this detail in the attached, applied patch.

-- 
  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.

  98. Re: PG 18 release notes draft committed

    Michael Paquier <michael@paquier.xyz> — 2025-05-24T00:10:50Z

    On Fri, May 23, 2025 at 04:01:41PM -0400, Bruce Momjian wrote:
> I updated the release notes to current and included your patch,
> attached, thanks.

Just noticed 1ca583f6c0f9.  Thanks for the commit.
--
Michael

  99. Re: PG 18 release notes draft committed

    Joe Conway <mail@joeconway.com> — 2025-05-26T14:20:08Z

    On 5/23/25 09:47, Bruce Momjian wrote:
> On Fri, May 23, 2025 at 09:54:54AM +0200, Álvaro Herrera wrote:
>> I also think that showing an XML-ish format of a commit message is
>> unhelpful, not to mention hard to read.  Showing a few actual examples
>> would be better.
> 
> Agreed, but the XML came from Joe Conway so I am hesitant to remove it
> myself without feedback from him.


I am not married to it, but I would say that I find pure examples 
confusing/ambiguous. To me at least the XML-ish specification is easier 
to understand.

Perhaps both the specification as-is and one or two examples added?

-- 
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

  100. Re: PG 18 release notes draft committed

    Peter Smith <smithpb2250@gmail.com> — 2025-05-26T22:13:24Z

    Hi,

There seems to be some unexpected ">" here:

"E.1.3.7.3. Logical Replication Applications>"

======
Kind Regards,
Peter Smith.
Fujitsu Australia

  101. Re: PG 18 release notes draft committed

    Nathan Bossart <nathandbossart@gmail.com> — 2025-05-27T14:26:41Z

    For the "Deprecate MD5 password authentication" item, IMHO we should
emphasize that support for MD5 passwords will be removed in a future major
release, as we did for the 18beta1 announcement.  Here's an attempt:

	Deprecate MD5 password authentication (Nathan Bossart)

	Support for MD5 passwords will be removed in a future major version
	release.  CREATE ROLE and ALTER ROLE now emit deprecation warnings when
	setting MD5 passwords.  These warnings can be disabled by setting the
	md5_password_warnings parameter to "off".

-- 
nathan

  102. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-27T21:27:56Z

    On Mon, May 26, 2025 at 10:20:08AM -0400, Joe Conway wrote:
> On 5/23/25 09:47, Bruce Momjian wrote:
> > On Fri, May 23, 2025 at 09:54:54AM +0200, Álvaro Herrera wrote:
> > > I also think that showing an XML-ish format of a commit message is
> > > unhelpful, not to mention hard to read.  Showing a few actual examples
> > > would be better.
> > 
> > Agreed, but the XML came from Joe Conway so I am hesitant to remove it
> > myself without feedback from him.
> 
> 
> I am not married to it, but I would say that I find pure examples
> confusing/ambiguous. To me at least the XML-ish specification is easier to
> understand.
> 
> Perhaps both the specification as-is and one or two examples added?

Yeah, I think some people like syntax, others like examples.

-- 
  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.

  103. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-27T21:35:11Z

    On Tue, May 27, 2025 at 08:13:24AM +1000, Peter Smith wrote:
> Hi,
> 
> There seems to be some unexpected ">" here:
> 
> "E.1.3.7.3. Logical Replication Applications>"

Yes, a mistake, fixed.

-- 
  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.

  104. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-27T21:51:13Z

    On Tue, May 27, 2025 at 09:26:41AM -0500, Nathan Bossart wrote:
> For the "Deprecate MD5 password authentication" item, IMHO we should
> emphasize that support for MD5 passwords will be removed in a future major
> release, as we did for the 18beta1 announcement.  Here's an attempt:
> 
> 	Deprecate MD5 password authentication (Nathan Bossart)
> 
> 	Support for MD5 passwords will be removed in a future major version
> 	release.  CREATE ROLE and ALTER ROLE now emit deprecation warnings when
> 	setting MD5 passwords.  These warnings can be disabled by setting the
> 	md5_password_warnings parameter to "off".

Agree, I have replaced the item text with your text.

-- 
  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.

  105. Re: PG 18 release notes draft committed

    Dean Rasheed <dean.a.rasheed@gmail.com> — 2025-05-28T09:55:50Z

    For "Improve the speed of multiplication", I think it should say
"numeric multiplication" rather than simply "multiplication", and I
think it's worth also linking to commits ca481d3c9ab and c4e44224cf6
which were part of the same work.

I think it's also worth mentioning 9428c001f67, which sped up numeric
division. That can be included in the same item, as in the attached
patch, unless you think it's worth listing it as a separate item.

Regards,
Dean

  106. Re: PG 18 release notes draft committed

    Yugo Nagata <nagata@sraoss.co.jp> — 2025-05-28T14:14:36Z

    On Thu, 1 May 2025 22:44:50 -0400
Bruce Momjian <bruce@momjian.us> wrote:

> I have committd the first draft of the PG 18 release notes.  The item
> count looks strong:

Some items in the "EXPLAIN" section are actually not about the EXPLAIN
but the ANALYZE command. The attached patch is move them to the
"Utility Commands" section with a little edit of wordings.

Regards,
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>

  107. Re: PG 18 release notes draft committed

    Yugo Nagata <nagata@sraoss.co.jp> — 2025-05-28T14:25:03Z

    On Wed, 28 May 2025 23:14:36 +0900
Yugo Nagata <nagata@sraoss.co.jp> wrote:

> On Thu, 1 May 2025 22:44:50 -0400
> Bruce Momjian <bruce@momjian.us> wrote:
> 
> > I have committd the first draft of the PG 18 release notes.  The item
> > count looks strong:
> 
> Some items in the "EXPLAIN" section are actually not about the EXPLAIN
> but the ANALYZE command. The attached patch is move them to the
> "Utility Commands" section with a little edit of wordings.

... or, perhaps they should be moved to the "Monitoring" section.
I've attached a patch in this version.

Regards
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>

  108. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-28T16:34:22Z

    On Wed, May 28, 2025 at 10:55:50AM +0100, Dean Rasheed wrote:
> For "Improve the speed of multiplication", I think it should say
> "numeric multiplication" rather than simply "multiplication", and I
> think it's worth also linking to commits ca481d3c9ab and c4e44224cf6
> which were part of the same work.
> 
> I think it's also worth mentioning 9428c001f67, which sped up numeric
> division. That can be included in the same item, as in the attached
> patch, unless you think it's worth listing it as a separate item.

Great, patch applied.

-- 
  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.

  109. Re: PG 18 release notes draft committed

    Joe Conway <mail@joeconway.com> — 2025-05-28T18:54:29Z

    On 5/27/25 17:27, Bruce Momjian wrote:
> On Mon, May 26, 2025 at 10:20:08AM -0400, Joe Conway wrote:
>> On 5/23/25 09:47, Bruce Momjian wrote:
>> > On Fri, May 23, 2025 at 09:54:54AM +0200, Álvaro Herrera wrote:
>> > > I also think that showing an XML-ish format of a commit message is
>> > > unhelpful, not to mention hard to read.  Showing a few actual examples
>> > > would be better.
>> > 
>> > Agreed, but the XML came from Joe Conway so I am hesitant to remove it
>> > myself without feedback from him.
>> 
>> 
>> I am not married to it, but I would say that I find pure examples
>> confusing/ambiguous. To me at least the XML-ish specification is easier to
>> understand.
>> 
>> Perhaps both the specification as-is and one or two examples added?
> 
> Yeah, I think some people like syntax, others like examples.

What do you think about providing links into the archives for good 
representative log messages rather than making up a contrived example 
and/or copy/pasting them into the wiki page itself?

Also, looking at the wiki page, my inclination would be to add an 
"Examples" section at the bottom of the wiki page -- does that work or 
do you think it ought to go just under the "General layout" syntax section?

-- 
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

  110. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-28T22:44:09Z

    On Wed, May 28, 2025 at 11:25:03PM +0900, Yugo Nagata wrote:
> On Wed, 28 May 2025 23:14:36 +0900
> Yugo Nagata <nagata@sraoss.co.jp> wrote:
> 
> > On Thu, 1 May 2025 22:44:50 -0400
> > Bruce Momjian <bruce@momjian.us> wrote:
> > 
> > > I have committd the first draft of the PG 18 release notes.  The item
> > > count looks strong:
> > 
> > Some items in the "EXPLAIN" section are actually not about the EXPLAIN
> > but the ANALYZE command. The attached patch is move them to the
> > "Utility Commands" section with a little edit of wordings.
> 
> ... or, perhaps they should be moved to the "Monitoring" section.
> I've attached a patch in this version.

I see you split the ANALYZE and EXPLAIN shared item, and moved the
ANALYZE item;  patch applied, thanks.

-- 
  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.

  111. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-28T22:46:18Z

    On Wed, May 28, 2025 at 02:54:29PM -0400, Joe Conway wrote:
> On 5/27/25 17:27, Bruce Momjian wrote:
> > On Mon, May 26, 2025 at 10:20:08AM -0400, Joe Conway wrote:
> > > On 5/23/25 09:47, Bruce Momjian wrote:
> > > > On Fri, May 23, 2025 at 09:54:54AM +0200, Álvaro Herrera wrote:
> > > > > I also think that showing an XML-ish format of a commit message is
> > > > > unhelpful, not to mention hard to read.  Showing a few actual examples
> > > > > would be better.
> > > > > Agreed, but the XML came from Joe Conway so I am hesitant to
> > > remove it
> > > > myself without feedback from him.
> > > 
> > > 
> > > I am not married to it, but I would say that I find pure examples
> > > confusing/ambiguous. To me at least the XML-ish specification is easier to
> > > understand.
> > > 
> > > Perhaps both the specification as-is and one or two examples added?
> > 
> > Yeah, I think some people like syntax, others like examples.
> 
> What do you think about providing links into the archives for good
> representative log messages rather than making up a contrived example and/or
> copy/pasting them into the wiki page itself?

Sure, we can just link to:

	https://www.postgresql.org/list/pgsql-committers/

and they can choose any recent commit.

> Also, looking at the wiki page, my inclination would be to add an "Examples"
> section at the bottom of the wiki page -- does that work or do you think it
> ought to go just under the "General layout" syntax section?

Sure, makes sense.

-- 
  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.

  112. Re: PG 18 release notes draft committed

    Melanie Plageman <melanieplageman@gmail.com> — 2025-05-29T00:07:20Z

    On Thu, May 1, 2025 at 10:44 PM Bruce Momjian <bruce@momjian.us> wrote:
>
> I will continue improving it until beta 1, and until the final release.

Hi Bruce,

Thanks so much for putting these together.

For the item:

"Increase the logging granularity of server variable log_connections"

I noticed that you cite the commit 9219093cab2 that actually does
modularize the GUC but you also cite a separate following commit
18cd15e706ac which adds a new option that logs the duration of various
parts of connection establishment and backend setup. That is, it is a
separate feature.

9219093cab2 made it so we could add options and have them be
individually enabled or disabled in logging. But 18cd15e706ac is only
related insomuch as we probably wouldn't have added it if
log_connections had been just a boolean and it was enabled by default.

Anyway, it might be worth separately calling out that now you can
configure log_connections to log the durations of various parts of
connection establishment and backend setup -- which is a distinct
feature from modularization.

For the item:

"Add an asynchronous I/O subsystem"

I notice we don't call out any of the operations where users could
expect to see asynchronous IO be used. Some were enabled in 17 (like
sequential scans, analyze, and pg_prewarm), but most of the read
stream users went in this release:

d9c7911e1a5, 043799fa08c, e215166c9c8, 69273b818b1, c5c239e26e3,
2b73a8cd33b, 9256822608f, c3e775e608f, 8720a15e9ab12, 65c310b310a

I have had users ask me already which operations they can expect to
use asynchronous I/O. The most commonly encountered AIO operations are
probably be vacuum, bitmap heap scan, and sequential scans, but it
might be worth having a list somewhere of what uses AIO. I expect
we'll get the question quite often.

And finally, for the item:

"Allow specification of the fixed number of dead tuples that will
trigger an autovacuum"

We also added a kind of corollary for insert-triggered vacuums in
06eae9e6218ab2a which attempts to deal with a similar problem of big
tables not being autovacuumed enough but for insert-mostly tables.
Perhaps because there is no exposed configuration it is not worth
mentioning, but I thought I would bring it up since their purposes are
related.

- Melanie

  113. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-29T02:49:47Z

    On Wed, May 28, 2025 at 08:07:20PM -0400, Melanie Plageman wrote:
> For the item:
> 
> "Increase the logging granularity of server variable log_connections"
> 
> I noticed that you cite the commit 9219093cab2 that actually does
> modularize the GUC but you also cite a separate following commit
> 18cd15e706ac which adds a new option that logs the duration of various
> parts of connection establishment and backend setup. That is, it is a
> separate feature.
> 
> 9219093cab2 made it so we could add options and have them be
> individually enabled or disabled in logging. But 18cd15e706ac is only
> related insomuch as we probably wouldn't have added it if
> log_connections had been just a boolean and it was enabled by default.
> 
> Anyway, it might be worth separately calling out that now you can
> configure log_connections to log the durations of various parts of
> connection establishment and backend setup -- which is a distinct
> feature from modularization.

Yes, I can now see it is two items so I have split it into two in the
attached, applied patch.  In a separate commit I adjusted the docs for
log_connections to more clearly explain the new "setup_durations"
output.

> For the item:
> 
> "Add an asynchronous I/O subsystem"
> 
> I notice we don't call out any of the operations where users could
> expect to see asynchronous IO be used. Some were enabled in 17 (like
> sequential scans, analyze, and pg_prewarm), but most of the read
> stream users went in this release:
> 
> d9c7911e1a5, 043799fa08c, e215166c9c8, 69273b818b1, c5c239e26e3,
> 2b73a8cd33b, 9256822608f, c3e775e608f, 8720a15e9ab12, 65c310b310a
> 
> I have had users ask me already which operations they can expect to
> use asynchronous I/O. The most commonly encountered AIO operations are
> probably be vacuum, bitmap heap scan, and sequential scans, but it
> might be worth having a list somewhere of what uses AIO. I expect
> we'll get the question quite often.

Yes, I knew I needed more detail on this.  I have added text in this
commit to try to improve that.

> And finally, for the item:
> 
> "Allow specification of the fixed number of dead tuples that will
> trigger an autovacuum"
> 
> We also added a kind of corollary for insert-triggered vacuums in
> 06eae9e6218ab2a which attempts to deal with a similar problem of big
> tables not being autovacuumed enough but for insert-mostly tables.
> Perhaps because there is no exposed configuration it is not worth
> mentioning, but I thought I would bring it up since their purposes are
> related.

I studied this and I can't figure out how to clearly explain it in a
useful way.  I am now thinking it is more of a bug or behavior fix or
that would not be usually mentioned.

-- 
  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.

  114. Re: PG 18 release notes draft committed

    Álvaro Herrera <alvherre@kurilemu.de> — 2025-05-29T11:53:50Z

    On 2025-May-28, Bruce Momjian wrote:

> Sure, we can just link to:
> 
> 	https://www.postgresql.org/list/pgsql-committers/
> 
> and they can choose any recent commit.

IMO this is useless, because there's no assurance that the "recent
commit" they choose is actually following good practices.

> > Also, looking at the wiki page, my inclination would be to add an
> > "Examples" section at the bottom of the wiki page -- does that work
> > or do you think it ought to go just under the "General layout"
> > syntax section?

I think we ought to show examples of each rules we're talking about in
each section.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Nunca confiaré en un traidor.  Ni siquiera si el traidor lo he creado yo"
(Barón Vladimir Harkonnen)

  115. Re: PG 18 release notes draft committed

    Joe Conway <mail@joeconway.com> — 2025-05-29T12:18:21Z

    On 5/29/25 07:53, Álvaro Herrera wrote:
> On 2025-May-28, Bruce Momjian wrote:
> 
>> Sure, we can just link to:
>> 
>> 	https://www.postgresql.org/list/pgsql-committers/
>> 
>> and they can choose any recent commit.
> 
> IMO this is useless, because there's no assurance that the "recent
> commit" they choose is actually following good practices.

My intent was to pick some specific examples that we agree are good 
ones, not this.

>> > Also, looking at the wiki page, my inclination would be to add an
>> > "Examples" section at the bottom of the wiki page -- does that work
>> > or do you think it ought to go just under the "General layout"
>> > syntax section?
> 
> I think we ought to show examples of each rules we're talking about in
> each section.

That could be useful too, but I think complete examples are still good 
to have.

-- 
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

  116. Re: PG 18 release notes draft committed

    Melanie Plageman <melanieplageman@gmail.com> — 2025-05-29T13:42:30Z

    On Wed, May 28, 2025 at 10:49 PM Bruce Momjian <bruce@momjian.us> wrote:
>
> On Wed, May 28, 2025 at 08:07:20PM -0400, Melanie Plageman wrote:
>
> Yes, I can now see it is two items so I have split it into two in the
> attached, applied patch.  In a separate commit I adjusted the docs for
> log_connections to more clearly explain the new "setup_durations"
> output.

Cool, thanks!

> > "Add an asynchronous I/O subsystem"
> >
> > I notice we don't call out any of the operations where users could
> > expect to see asynchronous IO be used. Some were enabled in 17 (like
> > sequential scans, analyze, and pg_prewarm), but most of the read
> > stream users went in this release:
> >
> > d9c7911e1a5, 043799fa08c, e215166c9c8, 69273b818b1, c5c239e26e3,
> > 2b73a8cd33b, 9256822608f, c3e775e608f, 8720a15e9ab12, 65c310b310a
> >
> > I have had users ask me already which operations they can expect to
> > use asynchronous I/O. The most commonly encountered AIO operations are
> > probably be vacuum, bitmap heap scan, and sequential scans, but it
> > might be worth having a list somewhere of what uses AIO. I expect
> > we'll get the question quite often.
>
> Yes, I knew I needed more detail on this.  I have added text in this
> commit to try to improve that.

Maybe it is worth saying something at the end like "amongst other
operations" to clarify it isn't just those.
I noticed in the PG 17 release notes [1] we did include the shas of
each of the commits for the read stream users. Should we do that here
as well? Those are what enable those operations to use AIO.

> > "Allow specification of the fixed number of dead tuples that will
> > trigger an autovacuum"
> >
> > We also added a kind of corollary for insert-triggered vacuums in
> > 06eae9e6218ab2a which attempts to deal with a similar problem of big
> > tables not being autovacuumed enough but for insert-mostly tables.
> > Perhaps because there is no exposed configuration it is not worth
> > mentioning, but I thought I would bring it up since their purposes are
> > related.
>
> I studied this and I can't figure out how to clearly explain it in a
> useful way.  I am now thinking it is more of a bug or behavior fix or
> that would not be usually mentioned.

 Makes sense

- Melanie

[1] https://www.postgresql.org/docs/current/release-17.html

  117. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-05-29T16:41:17Z

    On Thu, May 29, 2025 at 09:42:30AM -0400, Melanie Plageman wrote:
> > > "Add an asynchronous I/O subsystem"
> > >
> > > I notice we don't call out any of the operations where users could
> > > expect to see asynchronous IO be used. Some were enabled in 17 (like
> > > sequential scans, analyze, and pg_prewarm), but most of the read
> > > stream users went in this release:
> > >
> > > d9c7911e1a5, 043799fa08c, e215166c9c8, 69273b818b1, c5c239e26e3,
> > > 2b73a8cd33b, 9256822608f, c3e775e608f, 8720a15e9ab12, 65c310b310a
> > >
> > > I have had users ask me already which operations they can expect to
> > > use asynchronous I/O. The most commonly encountered AIO operations are
> > > probably be vacuum, bitmap heap scan, and sequential scans, but it
> > > might be worth having a list somewhere of what uses AIO. I expect
> > > we'll get the question quite often.
> >
> > Yes, I knew I needed more detail on this.  I have added text in this
> > commit to try to improve that.
> 
> Maybe it is worth saying something at the end like "amongst other
> operations" to clarify it isn't just those.

I am not a fan of "etc." but in this case it makes sense, so added it in
the attached, applied patch.

> I noticed in the PG 17 release notes [1] we did include the shas of
> each of the commits for the read stream users. Should we do that here
> as well? Those are what enable those operations to use AIO.

So, I added the read stream item to PG 17 since that was a new
infrastructure feature, but for PG 18, we are just improving that
internal infrastructure, so didn't mention it.  If you think we should
add those commits, I can do it.

-- 
  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.

  118. Re: PG 18 release notes draft committed

    Noah Misch <noah@leadboat.com> — 2025-06-03T17:21:23Z

    On Thu, May 01, 2025 at 10:44:50PM -0400, Bruce Momjian wrote:
> I have committd the first draft of the PG 18 release notes.

When a commit changes the user that runs a function in existing queries, I
think that almost always needs a release notes entry.  It would follow that
commit 01463e1 needs an entry.  I recommend text "Run each deferred trigger as
the role that caused the trigger to fire."

  119. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-06-04T20:45:18Z

    On Tue, Jun  3, 2025 at 10:21:23AM -0700, Noah Misch wrote:
> On Thu, May 01, 2025 at 10:44:50PM -0400, Bruce Momjian wrote:
> > I have committd the first draft of the PG 18 release notes.
> 
> When a commit changes the user that runs a function in existing queries, I
> think that almost always needs a release notes entry.  It would follow that
> commit 01463e1 needs an entry.  I recommend text "Run each deferred trigger as
> the role that caused the trigger to fire."

Okay, let's look at the commit:

	commit 01463e1cccd
	Author: Tom Lane <tgl@sss.pgh.pa.us>
	Date:   Thu Jan 23 12:25:45 2025 -0500
	
	    Ensure that AFTER triggers run as the instigating user.
	
	    With deferred triggers, it is possible that the current role changes
	    between the time when the trigger is queued and the time it is
	    executed (for example, the triggering data modification could have
	    been executed in a SECURITY DEFINER function).
	
	    Up to now, deferred trigger functions would run with the current role
	    set to whatever was active at commit time.  That does not matter for
	    foreign-key constraints, whose correctness doesn't depend on the
	    current role.  But for user-written triggers, the current role
	    certainly can matter.
	
	    Hence, fix things so that AFTER triggers are fired under the role
	    that was active when they were queued, matching the behavior of
	    BEFORE triggers which would have actually fired at that time.
	    (If the trigger function is marked SECURITY DEFINER, that of course
	    overrides this, as it always has.)
	
	    This does not create any new security exposure: if you do DML on a
	    table owned by a hostile user, that user has always had various ways
	    to exploit your permissions, such as the aforementioned BEFORE
	    triggers, default expressions, etc.  It might remove some security
	    exposure, because the old behavior could potentially expose some
	    other role besides the one directly modifying the table.
	
	    There was discussion of making a larger change, such as running as
	    the trigger's owner.  However, that would break the common idiom of
	    capturing the value of CURRENT_USER in a trigger for auditing/logging
	    purposes.  This change will make no difference in the typical scenario
	    where the current role doesn't change before commit.
	
	    Arguably this is a bug fix, but it seems too big a semantic change
	    to consider for back-patching.
	
	    Author: Laurenz Albe <laurenz.albe@cybertec.at>
	    Reviewed-by: Joseph Koshakow <koshy44@gmail.com>
	    Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>
	    Discussion: https://postgr.es/m/77ee784cf248e842f74588418f55c2931e47bd78.camel@cybertec.at

There are two questions --- should it be mentioned in the release notes,
and should it be listed in the incompatibility section.

It is called a bug fix, which I think means it is just implementing a
behavior that users already expected.  (Yes, there is a doc addition to
clarify this.)  I thought it was an edge case that didn't warrant
mention in the release notes, and the rare cases would be caught in
application testing.

Now, if we do want to mention it, it should be done in a way that makes
it clear to readers whether they are affected by this change.  We can
try text like:

	Execute non-SECURITY-DEFINER AFTER triggers as the role that was
	active at the time the trigger was fired
	
	Previously such triggers were run as the role that was active at
	commit time.

Seems like this would be in the incompatibility section, if we want to
add it.

-- 
  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.

  120. Re: PG 18 release notes draft committed

    David G. Johnston <david.g.johnston@gmail.com> — 2025-06-04T21:02:38Z

    On Wed, Jun 4, 2025 at 1:45 PM Bruce Momjian <bruce@momjian.us> wrote:

> Now, if we do want to mention it, it should be done in a way that makes
> it clear to readers whether they are affected by this change.  We can
> try text like:
>
>         Execute non-SECURITY-DEFINER AFTER triggers as the role that was
>         active at the time the trigger was fired
>
>         Previously such triggers were run as the role that was active at
>         commit time.
>

"Deferred constraint triggers now run as the role active when the trigger
was fired: previously they used the role active when execution began."

The timing is not only at commit, and it makes more sense to me to focus on
"deferred constraint" instead of the more general "after" trigger.

The trigger doesn't have a security definer clause - the function does and
would of course take effect during execution.  Not strongly opposed to
keeping the note.

David J.

  121. Re: PG 18 release notes draft committed

    Noah Misch <noah@leadboat.com> — 2025-06-04T21:29:46Z

    On Wed, Jun 04, 2025 at 04:45:18PM -0400, Bruce Momjian wrote:
> On Tue, Jun  3, 2025 at 10:21:23AM -0700, Noah Misch wrote:
> > When a commit changes the user that runs a function in existing queries, I
> > think that almost always needs a release notes entry.  It would follow that
> > commit 01463e1 needs an entry.  I recommend text "Run each deferred trigger as
> > the role that caused the trigger to fire."

> There are two questions --- should it be mentioned in the release notes,
> and should it be listed in the incompatibility section.
> 
> It is called a bug fix, which I think means it is just implementing a
> behavior that users already expected.  (Yes, there is a doc addition to
> clarify this.)  I thought it was an edge case that didn't warrant
> mention in the release notes, and the rare cases would be caught in
> application testing.
> 
> Now, if we do want to mention it, it should be done in a way that makes
> it clear to readers whether they are affected by this change.  We can
> try text like:
> 
> 	Execute non-SECURITY-DEFINER AFTER triggers as the role that was
> 	active at the time the trigger was fired
> 	
> 	Previously such triggers were run as the role that was active at
> 	commit time.

I agree with David G. Johnston's feedback on this.  My draft didn't mention
SECURITY DEFINER, because I consider it redundant from a user's perspective.
If a function is SECURITY DEFINER, that always overrides other sources of user
identity.  No need to mention it each time.

That said, I'm not too picky about the exact wording.  The way you have it
wouldn't bother me.

> Seems like this would be in the incompatibility section, if we want to
> add it.

Works for me.

  122. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-06-04T21:52:19Z

    On Wed, Jun  4, 2025 at 02:02:38PM -0700, David G. Johnston wrote:
> On Wed, Jun 4, 2025 at 1:45 PM Bruce Momjian <bruce@momjian.us> wrote:
> 
>     Now, if we do want to mention it, it should be done in a way that makes
>     it clear to readers whether they are affected by this change.  We can
>     try text like:
> 
>             Execute non-SECURITY-DEFINER AFTER triggers as the role that was
>             active at the time the trigger was fired
> 
>             Previously such triggers were run as the role that was active at
>             commit time.
> 
> 
> "Deferred constraint triggers now run as the role active when the trigger was
> fired: previously they used the role active when execution began."
> 
> The timing is not only at commit, and it makes more sense to me to focus on
> "deferred constraint" instead of the more general "after" trigger.

Ah, yes, I see your point --- it is really only deferred after triggers,
not before triggers, and deferrability is only available for constraint
triggers.

> The trigger doesn't have a security definer clause - the function does and
> would of course take effect during execution.  Not strongly opposed to keeping
> the note.

I think we have to keep the non-SECURITY-DEFINER designation to keep the
text accurate, but you are right it is part of the function, not the
trigger:

	Execute deferred constraint triggers attached to
	non-SECURITY-DEFINER functions as the role that was active at
	the time the trigger was fired

	Previously such triggers were run as the role that was active at
	commit/execution time.

As you can see, this is going to be hard to read, and I don't know if a
sufficient number of people will care.

-- 
  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.

  123. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-06-04T21:53:38Z

    On Wed, Jun  4, 2025 at 02:29:46PM -0700, Noah Misch wrote:
> I agree with David G. Johnston's feedback on this.  My draft didn't mention
> SECURITY DEFINER, because I consider it redundant from a user's perspective.
> If a function is SECURITY DEFINER, that always overrides other sources of user
> identity.  No need to mention it each time.

Well, if it is a SECURITY DEFINER function, it is not going to be run as
the user who is active at commit/execution time, so I think we have to
specify that.

-- 
  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.

  124. Re: PG 18 release notes draft committed

    Tom Lane <tgl@sss.pgh.pa.us> — 2025-06-04T22:10:38Z

    Bruce Momjian <bruce@momjian.us> writes:
> I think we have to keep the non-SECURITY-DEFINER designation to keep the
> text accurate, but you are right it is part of the function, not the
> trigger:

> 	Execute deferred constraint triggers attached to
> 	non-SECURITY-DEFINER functions as the role that was active at
> 	the time the trigger was fired

> 	Previously such triggers were run as the role that was active at
> 	commit/execution time.

> As you can see, this is going to be hard to read, and I don't know if a
> sufficient number of people will care.

It's still inaccurate -- to my mind, a "deferred" trigger is one that
runs later than the end of the triggering statement.  I think you
should use "after trigger".  Also, "fired" is a fairly confusing
choice of word here; I think most people would take that as meaning
the act of running the trigger.  How about

	Execute AFTER triggers as the role that was active at the
	moment the trigger event was queued

 	Previously such triggers were run as the role that is active
	when it is time to execute the trigger (e.g., at COMMIT).

I concur that this needs to be called out as an incompatibility.

			regards, tom lane

  125. Re: PG 18 release notes draft committed

    Noah Misch <noah@leadboat.com> — 2025-06-04T22:17:10Z

    On Wed, Jun 04, 2025 at 06:10:38PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > I think we have to keep the non-SECURITY-DEFINER designation to keep the
> > text accurate,

I don't see it that way, because there's currently no experiment the user can
perform to distinguish between the following alternatives:

1. We switch to the user that fired the trigger, then call the SECURITY
   DEFINER function.  As always, the first step of executing a SECURITY
   DEFINER function is to switch to its owner.

2. We know it's a SECURITY DEFINER function, so we don't switch.  We just call
   the SECURITY DEFINER function.  As always, the first step of executing a
   SECURITY DEFINER function is to switch to its owner.

The actual implementation is (1), for what it's worth.  The src/backend part
of the commit didn't special-case SECURITY DEFINER.

> but you are right it is part of the function, not the
> > trigger:
> 
> > 	Execute deferred constraint triggers attached to
> > 	non-SECURITY-DEFINER functions as the role that was active at
> > 	the time the trigger was fired
> 
> > 	Previously such triggers were run as the role that was active at
> > 	commit/execution time.

> It's still inaccurate -- to my mind, a "deferred" trigger is one that
> runs later than the end of the triggering statement.  I think you
> should use "after trigger".  Also, "fired" is a fairly confusing
> choice of word here; I think most people would take that as meaning
> the act of running the trigger.  How about
> 
> 	Execute AFTER triggers as the role that was active at the
> 	moment the trigger event was queued
> 
>  	Previously such triggers were run as the role that is active
> 	when it is time to execute the trigger (e.g., at COMMIT).

I like that.

  126. Re: PG 18 release notes draft committed

    David G. Johnston <david.g.johnston@gmail.com> — 2025-06-04T22:25:54Z

    On Wed, Jun 4, 2025 at 3:17 PM Noah Misch <noah@leadboat.com> wrote:

> On Wed, Jun 04, 2025 at 06:10:38PM -0400, Tom Lane wrote:
> > Bruce Momjian <bruce@momjian.us> writes:
>
> > but you are right it is part of the function, not the
> > > trigger:
> >
> > >     Execute deferred constraint triggers attached to
> > >     non-SECURITY-DEFINER functions as the role that was active at
> > >     the time the trigger was fired
> >
> > >     Previously such triggers were run as the role that was active at
> > >     commit/execution time.
>
> > It's still inaccurate -- to my mind, a "deferred" trigger is one that
> > runs later than the end of the triggering statement.  I think you
> > should use "after trigger".


Is this covering the case of executing at the end of an outer SQL command
(thus not deferred) that contains volatile DML functions that temporarily
change current_user within the function?

  Also, "fired" is a fairly confusing

> choice of word here; I think most people would take that as meaning
> > the act of running the trigger.


Agreed


>   How about
> >
> >       Execute AFTER triggers as the role that was active at the
> >       moment the trigger event was queued
> >
> >       Previously such triggers were run as the role that is active
> >       when it is time to execute the trigger (e.g., at COMMIT).
>
> I like that.
>

I do as well.

David J.

  127. Re: PG 18 release notes draft committed

    Tom Lane <tgl@sss.pgh.pa.us> — 2025-06-04T22:37:57Z

    "David G. Johnston" <david.g.johnston@gmail.com> writes:
> Is this covering the case of executing at the end of an outer SQL command
> (thus not deferred) that contains volatile DML functions that temporarily
> change current_user within the function?

Not quite.  I think that a non-deferred AFTER trigger would ordinarily
run as the same user that was active when we queued the event, earlier
in the same statement --- but it's possible that some function that
runs in between would change the active role in a non-temporary way.
Doing that will now have different effects than it did before.

			regards, tom lane

  128. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-06-04T22:40:11Z

    On Wed, Jun  4, 2025 at 06:37:57PM -0400, Tom Lane wrote:
> "David G. Johnston" <david.g.johnston@gmail.com> writes:
> > Is this covering the case of executing at the end of an outer SQL command
> > (thus not deferred) that contains volatile DML functions that temporarily
> > change current_user within the function?
> 
> Not quite.  I think that a non-deferred AFTER trigger would ordinarily
> run as the same user that was active when we queued the event, earlier
> in the same statement --- but it's possible that some function that
> runs in between would change the active role in a non-temporary way.
> Doing that will now have different effects than it did before.

Yes, I wonder if we need to work that angle into the description.

-- 
  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.

  129. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-06-06T00:32:44Z

    On Wed, Jun  4, 2025 at 05:53:38PM -0400, Bruce Momjian wrote:
> On Wed, Jun  4, 2025 at 02:29:46PM -0700, Noah Misch wrote:
> > I agree with David G. Johnston's feedback on this.  My draft didn't mention
> > SECURITY DEFINER, because I consider it redundant from a user's perspective.
> > If a function is SECURITY DEFINER, that always overrides other sources of user
> > identity.  No need to mention it each time.
> 
> Well, if it is a SECURITY DEFINER function, it is not going to be run as
> the user who is active at commit/execution time, so I think we have to
> specify that.

I came up with this text:

	Execute AFTER triggers as the role that was active when trigger
	events were queued

	Previously such triggers were run as the role that was active at
	trigger execution time (e.g., at COMMIT).  This is significant
	for cases where the role is changed between queue time and
	transaction commit.

-- 
  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.

  130. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-06-07T15:25:55Z

    On Thu, Jun  5, 2025 at 08:32:44PM -0400, Bruce Momjian wrote:
> On Wed, Jun  4, 2025 at 05:53:38PM -0400, Bruce Momjian wrote:
> > On Wed, Jun  4, 2025 at 02:29:46PM -0700, Noah Misch wrote:
> > > I agree with David G. Johnston's feedback on this.  My draft didn't mention
> > > SECURITY DEFINER, because I consider it redundant from a user's perspective.
> > > If a function is SECURITY DEFINER, that always overrides other sources of user
> > > identity.  No need to mention it each time.
> > 
> > Well, if it is a SECURITY DEFINER function, it is not going to be run as
> > the user who is active at commit/execution time, so I think we have to
> > specify that.
> 
> I came up with this text:
> 
> 	Execute AFTER triggers as the role that was active when trigger
> 	events were queued
> 
> 	Previously such triggers were run as the role that was active at
> 	trigger execution time (e.g., at COMMIT).  This is significant
> 	for cases where the role is changed between queue time and
> 	transaction commit.

Item added to the incompatibilities section of the release notes.

-- 
  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.

  131. Re: PG 18 release notes draft committed

    Melanie Plageman <melanieplageman@gmail.com> — 2025-06-11T18:45:58Z

    On Thu, May 29, 2025 at 12:41 PM Bruce Momjian <bruce@momjian.us> wrote:
>
> On Thu, May 29, 2025 at 09:42:30AM -0400, Melanie Plageman wrote:
> > > > "Add an asynchronous I/O subsystem"
> > I noticed in the PG 17 release notes [1] we did include the shas of
> > each of the commits for the read stream users. Should we do that here
> > as well? Those are what enable those operations to use AIO.
>
> So, I added the read stream item to PG 17 since that was a new
> infrastructure feature, but for PG 18, we are just improving that
> internal infrastructure, so didn't mention it.  If you think we should
> add those commits, I can do it.

I wouldn't consider it as improving internal infrastructure exactly.
My understanding is that usually when we add new features, even if
they use an existing API, we still include them, as relevant, in the
release notes. For example, next release we hope to have index
prefetching -- but it may be implemented using the read stream API.
Does that mean we wouldn't mention it in the release notes?

- Melanie

  132. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-06-11T19:51:00Z

    On Wed, Jun 11, 2025 at 02:45:58PM -0400, Melanie Plageman wrote:
> On Thu, May 29, 2025 at 12:41 PM Bruce Momjian <bruce@momjian.us> wrote:
> >
> > On Thu, May 29, 2025 at 09:42:30AM -0400, Melanie Plageman wrote:
> > > > > "Add an asynchronous I/O subsystem"
> > > I noticed in the PG 17 release notes [1] we did include the shas of
> > > each of the commits for the read stream users. Should we do that here
> > > as well? Those are what enable those operations to use AIO.
> >
> > So, I added the read stream item to PG 17 since that was a new
> > infrastructure feature, but for PG 18, we are just improving that
> > internal infrastructure, so didn't mention it.  If you think we should
> > add those commits, I can do it.
> 
> I wouldn't consider it as improving internal infrastructure exactly.
> My understanding is that usually when we add new features, even if
> they use an existing API, we still include them, as relevant, in the
> release notes. For example, next release we hope to have index
> prefetching -- but it may be implemented using the read stream API.
> Does that mean we wouldn't mention it in the release notes?

We certainly would mention index prefetching, but probably not the
changes to the read stream API unless those were separately relevant.

-- 
  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.

  133. Re: PG 18 release notes draft committed

    Amit Kapila <amit.kapila16@gmail.com> — 2025-08-13T06:08:33Z

    On Fri, May 2, 2025 at 8:14 AM Bruce Momjian <bruce@momjian.us> wrote:
>
> I have committd the first draft of the PG 18 release notes.
>

I think it is worth mentioning about commit
7c99dc587a010a0c40d72a0e435111ca7a371c02 as that changes the behavior
of how the system behaves for missing publications. Previously, we
used to stop replication with ERROR if the required publication is
missing, now we skip the missing publication and let replication
continue. Though it may sound the new behavior is intuitive but still
there could be some users relying on old behavior, so it is better to
list this item explicitly.

-- 
With Regards,
Amit Kapila.

  134. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-08-13T14:17:55Z

    On Wed, Aug 13, 2025 at 11:38:33AM +0530, Amit Kapila wrote:
> On Fri, May 2, 2025 at 8:14 AM Bruce Momjian <bruce@momjian.us> wrote:
> >
> > I have committed the first draft of the PG 18 release notes.
> >
> 
> I think it is worth mentioning about commit
> 7c99dc587a010a0c40d72a0e435111ca7a371c02 as that changes the behavior
> of how the system behaves for missing publications. Previously, we
> used to stop replication with ERROR if the required publication is
> missing, now we skip the missing publication and let replication
> continue. Though it may sound the new behavior is intuitive but still
> there could be some users relying on old behavior, so it is better to
> list this item explicitly.

Huh, looking at the commit message, I can see why I didn't add it:

*  no user reports, only buildfarm
*  used to throw an unexpected error, now works
*  an uncommon failure

We usually don't document those in the release notes.  Can someone else
give an opinion here?

-- 
  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.

  135. Re: PG 18 release notes draft committed

    Jelte Fennema-Nio <postgres@jeltef.nl> — 2025-08-31T20:53:23Z

    On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
>
> I have committd the first draft of the PG 18 release notes.  The item
> count looks strong:

Since we're getting close to the release. I wanted to call out that I
still think this commit[1] should be made part of the release notes,
because it significantly improves performance of the common functions
lower() and upper().

Note that this change is actually mentioned in the first release
post[2], so it seems strange not to have it in the release notes.

[1]: https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=27bdec06841d1bb004ca7627eac97808b08a7ac7
[2]: https://www.postgresql.org/about/news/postgresql-18-beta-1-released-3070/

  136. Re: PG 18 release notes draft committed

    Yugo Nagata <nagata@sraoss.co.jp> — 2025-09-01T11:01:48Z

    On Thu, 1 May 2025 22:44:50 -0400
Bruce Momjian <bruce@momjian.us> wrote:

> I have committd the first draft of the PG 18 release notes.  The item
> count looks strong:

I noticed that the following commit seems to be missing from the release notes:

 2024-09-17 [89f908a6d] Add temporal FOREIGN KEY contraints

I believe this is worth including, especially with a mention of the new
keyword PERIOD, since that would help users discover that a new keyword
has been introduced.

I've attached a draft patch to fix the existing release note entry for
temporal (non-overlapping) PRIMARY KEY and UNIQUE constraints.

Regards,
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>

  137. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-09-16T13:58:36Z

    On Sun, Aug 31, 2025 at 10:53:23PM +0200, Jelte Fennema-Nio wrote:
> On Fri, 2 May 2025 at 04:45, Bruce Momjian <bruce@momjian.us> wrote:
> >
> > I have committd the first draft of the PG 18 release notes.  The item
> > count looks strong:
> 
> Since we're getting close to the release. I wanted to call out that I
> still think this commit[1] should be made part of the release notes,
> because it significantly improves performance of the common functions
> lower() and upper().
> 
> Note that this change is actually mentioned in the first release
> post[2], so it seems strange not to have it in the release notes.
> 
> [1]: https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=27bdec06841d1bb004ca7627eac97808b08a7ac7
> [2]: https://www.postgresql.org/about/news/postgresql-18-beta-1-released-3070/

You received an answer in May 2025:

	https://www.postgresql.org/message-id/flat/aBbBFG8Z32ke31sF%40momjian.us#5e9d0f9bf3da039bc2d5afb8f2d847fb

with some additional replies.  I did not see any feedback indicating we
should make a change for this.

-- 
  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.

  138. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-09-16T15:49:11Z

    On Mon, Sep  1, 2025 at 08:01:48PM +0900, Yugo Nagata wrote:
> On Thu, 1 May 2025 22:44:50 -0400
> Bruce Momjian <bruce@momjian.us> wrote:
> 
> > I have committd the first draft of the PG 18 release notes.  The item
> > count looks strong:
> 
> I noticed that the following commit seems to be missing from the release notes:
> 
>  2024-09-17 [89f908a6d] Add temporal FOREIGN KEY contraints
> 
> I believe this is worth including, especially with a mention of the new
> keyword PERIOD, since that would help users discover that a new keyword
> has been introduced.
> 
> I've attached a draft patch to fix the existing release note entry for
> temporal (non-overlapping) PRIMARY KEY and UNIQUE constraints.

Wow, sorry I missed that detail, patch applied, thanks.

-- 
  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.

  139. Re: PG 18 release notes draft committed

    Peter Geoghegan <pg@bowt.ie> — 2025-09-16T17:59:07Z

    On Fri, May 23, 2025 at 5:03 PM Bruce Momjian <bruce@momjian.us> wrote:
> I was able to squeeze in this detail in the attached, applied patch.

I noticed that Crunchy Data had a blog post about the skip scan, where
the author got tripped up by the description of skip scan that current
appears in the release notes.

See: https://www.crunchydata.com/blog/get-excited-about-postgres-18

The blog post incorrectly says "Note that this optimization only works
for queries which use the = operator, so it will not work with
inequalities or ranges". This is incorrect; skip scan works perfectly
fine with inequality operators. I'm sure that this confusion arose
because of the wording from the release notes.

Adding to the confusion, Crunchy also had a Tweet about skip scan that
used an inequality operator (which will work correctly):

https://x.com/crunchydata/status/1965751871848468499

I'm sure that this was due to the release note description, since
there was some discussion of it on a LinkedIn post that promoted the
blog post.

In light of all this, I propose that we change the current feature
description, from:

"This allows multi-column btree indexes to be used by queries that
only equality-reference the second or later indexed columns."

to:

"This allows multi-column btree indexes to be used by queries that
only specify conditions on the second or later indexed columns."

-- 
Peter Geoghegan

  140. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-09-17T10:58:33Z

    On Tue, Sep 16, 2025 at 01:59:07PM -0400, Peter Geoghegan wrote:
> On Fri, May 23, 2025 at 5:03 PM Bruce Momjian <bruce@momjian.us> wrote:
> > I was able to squeeze in this detail in the attached, applied patch.
> 
> I noticed that Crunchy Data had a blog post about the skip scan, where
> the author got tripped up by the description of skip scan that current
> appears in the release notes.
> 
> See: https://www.crunchydata.com/blog/get-excited-about-postgres-18
> 
> The blog post incorrectly says "Note that this optimization only works
> for queries which use the = operator, so it will not work with
> inequalities or ranges". This is incorrect; skip scan works perfectly
> fine with inequality operators. I'm sure that this confusion arose
> because of the wording from the release notes.
> 
> Adding to the confusion, Crunchy also had a Tweet about skip scan that
> used an inequality operator (which will work correctly):
> 
> https://x.com/crunchydata/status/1965751871848468499
> 
> I'm sure that this was due to the release note description, since
> there was some discussion of it on a LinkedIn post that promoted the
> blog post.

Yes, clearly we need to fix the description we have now.  However, we
have already updated this item twice, so I think we need to be careful
to get it right this time:

	https://www.postgresql.org/message-id/aC_ccwyZj1ijlM5l%40momjian.us
	https://www.postgresql.org/message-id/aDDiuUv4Zk4IyFR2%40momjian.us

> In light of all this, I propose that we change the current feature
> description, from:
> 
> "This allows multi-column btree indexes to be used by queries that
> only equality-reference the second or later indexed columns."
> 
> to:
> 
> "This allows multi-column btree indexes to be used by queries that
> only specify conditions on the second or later indexed columns."

I think your new text is inaccurate because you state here that the
first column can be referenced and skip-scan still be used:

	https://www.postgresql.org/message-id/CAH2-Wzko57%2BsT%3DFcxHHo7jnPLhh35up_5aAvogLtj_D9bATsgQ%40mail.gmail.com
	
	I think that your wording is a big improvement. I personally
	would have emphasized the absence of a "=" condition, rather than
	the presence of another condition on a later column, since there
	are cases where the first column is referenced but skip scan can
	still be used (e.g., when there one or more inequalities on the
	first column, plus a "=" condition on the second column). I can
	live with this wording, though.

I think we need to highlight new cases where indexes can now be used by
skip scan:

*  missing early indexed column references
*  early indexed column references that use non-equality comparisons and
   the comparisons are not sufficiently restrictive on their own to use
   the index.

And, at the same time, not fall into the trip of saying the later column
references must be equality-only.

I am coming to the conclusion I am trying to be too clever here, and I
need to be more verbose.  Here is what I have so far:

	Previously, multi-column btree indexes could only be used by
	queries that either equality-referenced the first indexed column
	or referenced that column in a restrictive-enough way for index
	lookups to be efficient.  With skip scans, references to the first
	indexed btree column, or multiple early indexed columns, can be
	missing or insufficiently restrictive as long as these columns
	have low cardinality, and later indexed columns are restrictive
	enough for index lookups to be efficient.

I apologize for people who got the wrong impression of the feature and I
hope they see this email thread or the updated text.

-- 
  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.

  141. Re: PG 18 release notes draft committed

    Daniel Gustafsson <daniel@yesql.se> — 2025-09-17T11:07:56Z

    > On 17 Sep 2025, at 12:58, Bruce Momjian <bruce@momjian.us> wrote:

> Yes, clearly we need to fix the description we have now.  However, we
> have already updated this item twice, so I think we need to be careful
> to get it right this time:

Maybe we should move to a model where the release notes are worked on as a
normal docs patch on the list and only committed at around RC1 to keep us from
changing and removing from (in case of reverts) documentation published on
postgresql.org?

--
Daniel Gustafsson

  142. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-09-17T12:30:19Z

    On Wed, Sep 17, 2025 at 01:07:56PM +0200, Daniel Gustafsson wrote:
> > On 17 Sep 2025, at 12:58, Bruce Momjian <bruce@momjian.us> wrote:
> 
> > Yes, clearly we need to fix the description we have now.  However, we
> > have already updated this item twice, so I think we need to be careful
> > to get it right this time:
> 
> Maybe we should move to a model where the release notes are worked on as a
> normal docs patch on the list and only committed at around RC1 to keep us from
> changing and removing from (in case of reverts) documentation published on
> postgresql.org?

Well, then no one who downloads the software has any visibility on what
is changed/new, etc?  Seems worse than that you are trying to fix.

-- 
  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.

  143. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-09-17T12:37:51Z

    On Wed, Sep 17, 2025 at 08:30:19AM -0400, Bruce Momjian wrote:
> On Wed, Sep 17, 2025 at 01:07:56PM +0200, Daniel Gustafsson wrote:
> > > On 17 Sep 2025, at 12:58, Bruce Momjian <bruce@momjian.us> wrote:
> > 
> > > Yes, clearly we need to fix the description we have now.  However, we
> > > have already updated this item twice, so I think we need to be careful
> > > to get it right this time:
> > 
> > Maybe we should move to a model where the release notes are worked on as a
> > normal docs patch on the list and only committed at around RC1 to keep us from
> > changing and removing from (in case of reverts) documentation published on
> > postgresql.org?
> 
> Well, then no one who downloads the software has any visibility on what
> is changed/new, etc?  Seems worse than that you are trying to fix.

In addition, we only found out about this mistake because someone read
it and we saw it was wrong.  Withholding information only delays us
finding these mistakes.

I frankly don't understand how your suggestion makes anything better.

-- 
  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.

  144. Re: PG 18 release notes draft committed

    Peter Geoghegan <pg@bowt.ie> — 2025-09-17T15:46:58Z

    On Wed, Sep 17, 2025 at 6:58 AM Bruce Momjian <bruce@momjian.us> wrote:
> > In light of all this, I propose that we change the current feature
> > description, from:
> >
> > "This allows multi-column btree indexes to be used by queries that
> > only equality-reference the second or later indexed columns."
> >
> > to:
> >
> > "This allows multi-column btree indexes to be used by queries that
> > only specify conditions on the second or later indexed columns."
>
> I think your new text is inaccurate because you state here that the
> first column can be referenced and skip-scan still be used:

It's true that that's also possible. Skip scan will always "fill-in"
*any* index column that lacks a = condition that comes from the query
itself, by adding a skip array for that column during nbtree
preprocessing (note that a column that has a < or a > condition counts
as not having an = condition, and so will get its own skip array). A
skip array is an artificial "= ANY(<all possible column values>)"
condition/constraint that makes up for the fact that the user's query
did not provide us with a conventional = condition/constraint. nbtree
preprocessing always does this to the extent required to enable
repositioning the scan using *all* of the keys that actually come from
the query itself.

So we'll reliably read only those B-Tree leaf pages that might have
matching index tuples, no matter the details -- even with absurdly
complicated/unrealistic index scans. Note that adding a skip array
doesn't necessarily make us skip (skipping only happens when the scan
finds that it actually allows us to skip over something, otherwise we
just step to the next page on the leaf level as before). Skipping is
purely a runtime choice (adding skip arrays merely enables us to make
this choice, but it still has to make sense for us to do it).

To be clear, I don't think that the release notes need to go into
anything like this level of detail. My point is just that there are
just about no limitations. This isn't useful because we actually
expect users to have really complicated index scans, with varied
operators/conditions on only a subset of index columns (though some
may); it's useful because users don't have to think about it at all.

> I think we need to highlight new cases where indexes can now be used by
> skip scan:
>
> *  missing early indexed column references
> *  early indexed column references that use non-equality comparisons and
>    the comparisons are not sufficiently restrictive on their own to use
>    the index.

There isn't that much difference between these 2 things, from an
implementation point of view. They're both cases where a query/scan
initially lacks an = condition on a column where it'd be useful to
have one, so as to be able to use at least one later condition that
comes from the query to reposition the scan.

If there is an inequality condition on a column that gets a skip array
(because it didn't initially have a = condition), then the skip array
will only generate values that satisfy the inequalities. For example,
a skip array on "x" will only generate the values 1 and 2 given a qual
such as "WHERE x BETWEEN 1 AND 2 AND y = 66". The runtime behavior is
very similar to what we'd get in Postgres 17 for a qual "WHERE x =
ANY('{1, 2}') AND y = 66".

> And, at the same time, not fall into the trip of saying the later column
> references must be equality-only.

Right. This later condition could be a simple scalar equality or
inequality condition, it could be an IN() condition, or a row compare
inequality -- it could be anything.

> Here is what I have so far:
>
>         Previously, multi-column btree indexes could only be used by
>         queries that either equality-referenced the first indexed column
>         or referenced that column in a restrictive-enough way for index
>         lookups to be efficient.

It's hard to pin this down, since it has always been possible to make
*some* use of index columns, even in these tricky cases (we at least
didn't have to go to the heap to eliminate non-matching rows). Skip
scan just makes the B-Tree code find the most efficient way of
*navigating through the index*, by skipping over groups of
provably-irrelevant index leaf pages. This makes it much more likely
that the optimizer will actually choose such an index scan in the
first place.

I suggest the following alternative, which has the merit of being a
bit less verbose:

"Skip scan allows B-Tree index scans to find the most efficient way of
navigating through a multicolumn index when one or more of its columns
initially lacks a = condition and comes before a column that is
directly used by the query. Such an index scan can now be broken down
into multiple "index searches" by generating an implementation level =
condition on any underspecified columns. This allows the scan to skip
over irrelevant sections of the index, though only when the generated
= condition is on a column that has relatively few distinct values."

Note that "index searches" is a term that now appears in EXPLAIN ANALYZE output.

> I apologize for people who got the wrong impression of the feature and I
> hope they see this email thread or the updated text.

It's tough to get this right. There are many ways in which this could
be unnecessarily confusing, or misleading.

-- 
Peter Geoghegan

  145. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-09-17T20:45:14Z

    On Wed, Sep 17, 2025 at 11:46:58AM -0400, Peter Geoghegan wrote:
> I suggest the following alternative, which has the merit of being a
> bit less verbose:
> 
> "Skip scan allows B-Tree index scans to find the most efficient way of
> navigating through a multicolumn index when one or more of its columns
> initially lacks a = condition and comes before a column that is
> directly used by the query. Such an index scan can now be broken down
> into multiple "index searches" by generating an implementation level =
> condition on any underspecified columns. This allows the scan to skip
> over irrelevant sections of the index, though only when the generated
> = condition is on a column that has relatively few distinct values."
> 
> Note that "index searches" is a term that now appears in EXPLAIN ANALYZE output.

I went with this text, which is more "aspirational" rather than
"proscriptive", and the right level of detail:

	This allows multi-column btree indexes to be used in more cases
	such as when there are no restrictions on the first or early
	indexed columns (or they are non-equality ones), and there are
	useful restrictions on later indexed columns.

-- 
  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.

  146. Re: PG 18 release notes draft committed

    Bruce Momjian <bruce@momjian.us> — 2025-09-18T14:20:51Z

    On Wed, Sep 17, 2025 at 04:45:14PM -0400, Bruce Momjian wrote:
> On Wed, Sep 17, 2025 at 11:46:58AM -0400, Peter Geoghegan wrote:
> > I suggest the following alternative, which has the merit of being a
> > bit less verbose:
> > 
> > "Skip scan allows B-Tree index scans to find the most efficient way of
> > navigating through a multicolumn index when one or more of its columns
> > initially lacks a = condition and comes before a column that is
> > directly used by the query. Such an index scan can now be broken down
> > into multiple "index searches" by generating an implementation level =
> > condition on any underspecified columns. This allows the scan to skip
> > over irrelevant sections of the index, though only when the generated
> > = condition is on a column that has relatively few distinct values."
> > 
> > Note that "index searches" is a term that now appears in EXPLAIN ANALYZE output.
> 
> I went with this text, which is more "aspirational" rather than
> "proscriptive", and the right level of detail:
> 
> 	This allows multi-column btree indexes to be used in more cases
> 	such as when there are no restrictions on the first or early
> 	indexed columns (or they are non-equality ones), and there are
> 	useful restrictions on later indexed columns.

With our GA release dates close, I committed the attached patch.

-- 
  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.