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From: Lukas Fittl <lukas@fittl.com>
Date: Fri, 27 Mar 2026 01:31:11 -0700
Message-ID: 
 <CAP53Pkxak127z_Xp7xW5G0+X4FELCBzNyoWCqTQ-xGfLog3KyQ@mail.gmail.com>
Subject: Re: pg_plan_advice
To: Jakub Wartak <jakub.wartak@enterprisedb.com>,
 Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Precedence: bulk

On Fri, Mar 27, 2026 at 1:00=E2=80=AFAM Jakub Wartak
<jakub.wartak@enterprisedb.com> wrote:
>
> On Thu, Mar 26, 2026 at 6:20=E2=80=AFPM Robert Haas <robertmhaas@gmail.co=
m> wrote:
> >[..v23]
>
> 0003: please be the judge here, as I'm not sure. Isn't there some too hig=
h
> concurrency hit in pg_get_collected_shared_advice? If I do

I've been thinking more about 0003 (pg_collect_advice) today, and I'm
getting increasingly skeptical that we should try to get that into 19.
It just feels like there is more design work to be done here, and I
don't see the pressing need to have this in place.

Instead, I wonder if we should just add a "debug_log_plan_advice"
setting to pg_plan_advice, that always logs the plan advice when
enabled. Basically like "always_store_advice_details", but emit a log
line in addition to doing the work. That could either be enabled on a
single session with a sufficiently high client_min_messages to consume
it directly, or written to the log for a few minutes when trying to
capture production activity (on small production systems where the
logging overhead is acceptable).

I don't see a log-based approach be less useful than the shared memory
approach, because I think our aggregation design here is not right yet
(and doesn't scale to production traffic), and so we might as well
have the community try out some things with the log output instead.

For the other one 0004 (pg_stash_advice) I feel its worth trying to
get it in, if we can figure out the remaining issues. I'll try to do
another pass on that tomorrow after some sleep.

Thanks,
Lukas

--=20
Lukas Fittl