From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <dgrowleyml@gmail.com>
cc: william.duclot@gmail.com,
        PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17540: Prepared statement: PG switches to a generic query
 plan which is consistently much slower
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Comments: In-reply-to David Rowley <dgrowleyml@gmail.com>
	message dated "Thu, 07 Jul 2022 15:31:30 +1200"
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Date: Wed, 06 Jul 2022 23:50:48 -0400
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David Rowley <dgrowleyml@gmail.com> writes:
> Anyway, I've no current plans to take the attached any further. I
> think it'll be better to pursue your NULLable-Var stuff and see if we
> can do something more generic like remove provably redundant NullTests
> from baserestrictinfo.

Yeah, I suspect that the way forward is to allow
preprocess_minmax_aggregates to do what it does now, and then
remove the IS NOT NULL clause again later when we have the
info available to let us do that in a generic way.

In any case, as you said, it's just a band-aid that happens to
help in this exact scenario.  It's not doing much for the bad
cost estimation that's the root of the problem.

			regards, tom lane