From: Tom Lane <tgl@sss.pgh.pa.us>
To: Christoph Berg <myon@debian.org>
cc: Tommy Pavlicek <tommypav122@gmail.com>,
        Dagfinn Ilmari =?iso-8859-1?Q?Manns=E5ker?= <ilmari@ilmari.org>,
        pgsql-hackers@lists.postgresql.org,
        Tomas Vondra <tomas.vondra@enterprisedb.com>,
        jian.universality@gmail.com
Subject: Re: [PATCH] Extend ALTER OPERATOR to support adding commutator,
 negator, hashes, and merges
In-reply-to: <ZTfL1G1fBPQHVPWV@msg.df7cb.de>
References: <4077062.1687452468@sss.pgh.pa.us>
 <87r0q3qvxd.fsf@wibble.ilmari.org> <4082750.1687455374@sss.pgh.pa.us>
 <CAEhP-W_xGQVmiEJE_x0x5bbDSwsmaN1TQEawNadiMvQj2XK2Sg@mail.gmail.com>
 <15382.1687519306@sss.pgh.pa.us>
 <CAEhP-W-bY5CTXgrsH_J=NyKJpqMOgUPqMQ9-oTtx2N+zND1ZuA@mail.gmail.com>
 <1092363.1695932314@sss.pgh.pa.us>
 <CAEhP-W8MjoA0yDCipp=FgZvoQA-OVjQws3-XO6bpCWXunO8t8A@mail.gmail.com>
 <447166.1696969927@sss.pgh.pa.us>
 <CAEhP-W_1bMTLan2LtzS+xr=b-Wep56gw+OoirABQ8b2aOw+5yg@mail.gmail.com>
 <ZTfL1G1fBPQHVPWV@msg.df7cb.de>
Comments: In-reply-to Christoph Berg <myon@debian.org>
	message dated "Tue, 24 Oct 2023 15:51:16 +0200"
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Date: Tue, 24 Oct 2023 11:16:54 -0400
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Christoph Berg <myon@debian.org> writes:
> This change is breaking pgsphere which has <@ @> operator pairs, but
> for historical reasons also includes alternative spellings of these
> operators (both called @ with swapped operand types) which now
> explodes because we can't add them with the "proper" commutator and
> negators declared (which point to the canonical <@ @> !<@ !@>
> operators).

Should have guessed that somebody might be depending on the previous
squishy behavior.  Still, I can't see how the above situation is a
good idea.  Commutators/negators should come in pairs, not have
completely random links.  I think it's only accidental that this
setup isn't triggering other strange behavior.

> We might be able to simply delete the @ operators, but doesn't this
> new check break the general possibility to have more than one spelling
> for the same operator?

You can have more than one operator atop the same function.
But why didn't you make the @ operators commutators of each other,
rather than this mess?

			regards, tom lane