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 <br...@momjian.us> https://momjian.us
EDB https://enterprisedb.com
Do not let urgent matters crowd out time for investment in the future.
commit a1de1b0833b
Author: Bruce Momjian <br...@momjian.us>
Date: Wed May 28 22:43:13 2025 -0400
doc PG 18 relnotes: split apart log_connections item
Also add details to asynchronous I/O item.
Reported-by: Melanie Plageman
Discussion: https://postgr.es/m/CAAKRu_YsVvyantS0X0Y_-vp_97=ygaoyjmxxycekr7pumah...@mail.gmail.com
diff --git a/doc/src/sgml/release-18.sgml b/doc/src/sgml/release-18.sgml
index 83ff2225396..718f7b20bf1 100644
--- a/doc/src/sgml/release-18.sgml
+++ b/doc/src/sgml/release-18.sgml
@@ -569,6 +569,7 @@ Add an asynchronous I/O subsystem (Andres Freund, Thomas Munro, Nazir Bilal Yavu
</para>
<para>
+This feature allows backends to queue multiple read requests, which allows for more efficient sequential scans, bitmap heap scans, and vacuums.
This is enabled by server variable io_method, with server variables io_combine_limit and io_max_combine_limit added to control it. This also enables
effective_io_concurrency and maintenance_io_concurrency values greater than zero for systems without fadvise() support. The new system view pg_aios shows the file handles being used
for asynchronous I/O.
@@ -682,15 +683,12 @@ This more accurately reflects modern hardware.
<!--
Author: Melanie Plageman <melanieplage...@gmail.com>
2025-03-12 [9219093ca] Modularize log_connections output
-Author: Melanie Plageman <melanieplage...@gmail.com>
-2025-03-12 [18cd15e70] Add connection establishment duration logging
-->
<listitem>
<para>
Increase the logging granularity of server variable log_connections (Melanie Plageman)
<ulink url="&commit_baseurl;9219093ca">§</ulink>
-<ulink url="&commit_baseurl;18cd15e70">§</ulink>
</para>
<para>
@@ -698,6 +696,18 @@ This server variable was previously only boolean; these options are still suppo
</para>
</listitem>
+<!--
+Author: Melanie Plageman <melanieplage...@gmail.com>
+2025-03-12 [18cd15e70] Add connection establishment duration logging
+-->
+
+<listitem>
+<para>
+Add log_connections option to report the duration of connection stages (Melanie Plageman)
+<ulink url="&commit_baseurl;18cd15e70">§</ulink>
+</para>
+</listitem>
+
<!--
Author: Tom Lane <t...@sss.pgh.pa.us>
2025-04-07 [3516ea768] Add local-address escape "%L" to log_line_prefix.
