From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alexander Lipatov <lipatov@mindbox.cloud>
cc: pgsql-admin@postgresql.org
Subject: Re: Custom ordering operator for type xid
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Comments: In-reply-to Alexander Lipatov <lipatov@mindbox.cloud>
	message dated "Mon, 17 Jun 2024 13:49:53 +0300"
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Date: Mon, 17 Jun 2024 11:03:58 -0400
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Alexander Lipatov <lipatov@mindbox.cloud> writes:
> **Question**: Is it safe to create custom ordering operators for the `xi=
d` type and a default operator class with these operators?

I wouldn't do it, mainly because the semantics of what you've written
have nothing to do with the actual behavior of xids.  (The real
comparison behavior is "circular", which can't be modeled as a total
order, which is why there's not a built-in opclass already.)

What is that ORM doing with XIDs anyway, and is there a good reason
not to run away screaming from such an ill-thought-out product?
I don't believe for a minute that this is going to be the only
semantic issue you'll run into with an ORM that thinks it knows
how XIDs behave despite a clear lack of even the most minimal
investigation into the question.

			regards, tom lane