Message-ID: <386d8c06-0f96-40bb-b1b1-107db209c676@gmail.com>
Date: Sat, 4 Apr 2026 11:34:35 +0200
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Subject: Re: pg_plan_advice
To: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>
Cc: Alexander Lakhin <exclusion@gmail.com>, Lukas Fittl <lukas@fittl.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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From: Andrei Lepikhov <lepihov@gmail.com>
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On 4/4/26 05:14, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> The terms that I'm thinking in are "how much redesign will we accept
> post-feature-freeze, in either pg_plan_advice or test_plan_advice,
> before choosing to revert those modules entirely for v19?".  I think
> that running those tests serially is a sufficiently low-risk option
> that it'd be okay to put it in post-freeze, even very long after.
> I'm not sure that any of the other group-1 or group-2 options you
> suggested would be okay post-freeze.  (Of course, ultimately that'd
> be the RMT's decision not mine.)
> 
> I believe that we probably will need to do something in this
> area before v19 release.  If we're willing to commit to it being
> "run the tests serially", then sure we can wait awhile before
> actually doing that.  Maybe we'll even think of a better idea
> ... but what we can do about this post-freeze seems pretty
> constrained to me.

As you work on the code, please keep the pg_plan_advice issue [1] in 
mind. I came across it while designing the optimisation in [2]. Even if 
[2] is not added to the Postgres core, this still looks like a valid 
query plan and may be proposed by an extension. So, the hinting module 
should avoid conflicts with other extensions, just as pg_hint_plan does.

[1] pg_plan_advice fails when NestLoop outer side is Sort over FunctionScan
https://www.postgresql.org/message-id/78dd9572-7569-4025-984d-e07d7f381b6e@gmail.com
[2] Try a presorted outer path when referenced by an ORDER BY prefix
https://www.postgresql.org/message-id/19a9265c-c441-4a43-bc0d-dac533438da0%40gmail.com

-- 
regards, Andrei Lepikhov,
pgEdge