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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alexander Korotkov <a.korotkov@postgrespro.ru>
cc: Nikita Glukhov <n.gluhov@postgrespro.ru>,
        Fabien COELHO <coelho@cri.ensmp.fr>,
        PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Add missing operator <->(box, point)
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Comments: In-reply-to Alexander Korotkov <a.korotkov@postgrespro.ru>
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Alexander Korotkov <a.korotkov@postgrespro.ru> writes:
> On Tue, Jul 2, 2019 at 9:19 PM Nikita Glukhov <n.gluhov@postgrespro.ru> =
wrote:
>> We could use commuted "const <-> var" operators for kNN searches, but t=
he
>> current implementation requires the existence of "var <-> const" operat=
ors, and
>> order-by-op clauses are rebuilt using them (see match_clause_to_orderin=
g_op()
>> at /src/backend/optimizer/path/indxpath.c).

> But probably it's still worth to just add commutator for every <->
> operator and close this question.

Yeah, I was just thinking that it was weird not to have the commutator
operators, independently of indexing considerations.  Seems like a
usability thing.

			regards, tom lane