From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <dgrowleyml@gmail.com>
cc: Andres Freund <andres@anarazel.de>, tel@jklm.no,
        pgsql-bugs@lists.postgresql.org, Peter Geoghegan <pg@bowt.ie>
Subject: Re: BUG #17975: Nested Loop Index Scan returning wrong result
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Comments: In-reply-to David Rowley <dgrowleyml@gmail.com>
	message dated "Thu, 15 Jun 2023 12:38:23 +1200"
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Date: Wed, 14 Jun 2023 20:50:53 -0400
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David Rowley <dgrowleyml@gmail.com> writes:
> On Thu, 15 Jun 2023 at 12:28, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I concur that we'd better just not use partial indexes in
>> relation_has_unique_index_for.

> I wonder if that's ok for a backpatch.  This affects both left join
> removals and unique joins.  Seems like suddenly making a left join
> removal not work might cause someone some pain.

I kind of doubt that this will affect any large number of users.
If it did, we'd have had reports sooner.

> Is it worth trying to jam in a new boolean field into IndexOptInfo
> into some spare padding to that we run predicate_implied_by() just
> using baserestrictinfo and use those in
> relation_has_unique_index_for()?

How will that work with the caching in innerrel_is_unique?
I also seriously doubt that we can make such a thing work
without adding parameters to any externally-visible functions.

			regards, tom lane