From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <dgrowleyml@gmail.com>
cc: Sergei Glukhov <s.glukhov@postgrespro.ru>,
        pgsql-hackers@lists.postgresql.org
Subject: Re: Partial hash index is not used for implied qual.
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Comments: In-reply-to David Rowley <dgrowleyml@gmail.com>
	message dated "Tue, 25 Nov 2025 13:49:16 +1300"
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Date: Mon, 24 Nov 2025 20:23:18 -0500
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David Rowley <dgrowleyml@gmail.com> writes:
> so, that leads me to believe the location you're adjusting is probably
> the best place to fix this issue.

Wouldn't it be better to handle it more like the is_target_rel logic
a few lines further up?  I also object to putting the test between
the contain_mutable_functions and predicate_implied_by calls; that's
both confusing and probably wrong.  We're only calling
contain_mutable_functions to guard an assumption that
predicate_implied_by makes.

A larger point is that I think leaving such quals in indrestrictinfo
probably distorts our estimates of indexscan costs: we are likely to
think they contribute selectivity when they don't.  Maybe that's a
problem to address separately, but it should be looked at.  We skated
past the same problem for is_target_rel cases on the grounds that that
consideration affects all indexes on the rel equally; but as proposed,
this will probably result in an improper bias towards a partial hash
index.

			regards, tom lane