Re: Custom ordering operator for type xid - Mailing list pgsql-admin

From Tom Lane
Subject Re: Custom ordering operator for type xid
Date
Msg-id 3179495.1718636638@sss.pgh.pa.us
Whole thread Raw
In response to Custom ordering operator for type xid  (Alexander Lipatov <lipatov@mindbox.cloud>)
Responses Re: Custom ordering operator for type xid
List pgsql-admin
Alexander Lipatov <lipatov@mindbox.cloud> writes:
> **Question**: Is it safe to create custom ordering operators for the `xid` type and a default operator class with
theseoperators? 

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



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