From: Tom Lane <tgl@sss.pgh.pa.us>
To: Paul A Jungwirth <pj@illuminatedcomputing.com>
cc: Kirill Reshke <reshkekirill@gmail.com>,
        jian he <jian.universality@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: domain for WITHOUT OVERLAPS
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Comments: In-reply-to Paul A Jungwirth <pj@illuminatedcomputing.com>
	message dated "Tue, 10 Mar 2026 09:33:18 -0700"
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Date: Tue, 07 Apr 2026 14:57:40 -0400
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Paul A Jungwirth <pj@illuminatedcomputing.com> writes:
> Thanks for taking a look! I changed places we say `-- not unique` to
> now say `-- overlaps`. v5 is attached to my reply to jian he.

I pushed this patch, but not without significant revisions:

* I didn't think the case had been made for adding this field to
typcache.  There's only one user, it's in a very minority-interest
code path, and it'd add both space in TypeCacheEntry and a
noticeable number of cycles to TYPECACHE_DOMAIN_BASE_INFO requests.
(Admittedly the extra-cycles complaint is weak, since we expect
TypeCacheEntries to live a long time once populated.)  The other
problem was that the patch was buggy anyway: there is more than
one place in typcache.c that'd have to change.  I just moved the
get_typtype(typcache->domainBaseType) call to runtime instead.
We can revisit that if more potential uses appear.

* I thought the number of new regression test cases was quite
excessive compared to the value.  On my machine, the runtime for
without_overlaps.sql went from ~420ms to ~500ms, and it's already
the slowest in its parallel group by a good margin.  I cut it back to
just testing the base domain-over-range and range-over-domain cases,
which added only ~5ms.  (To be clear, I think it was worth making
those tests just to verify there are no other holes.  But carrying
them forward forevermore is another matter.)

* I happened to notice that the loop just above the changes in
transformIndexConstraint was buggy: it had "break" where it
should have had "continue".  That bug can be demonstrated with

CREATE TABLE temporal_rng4 (
  id int4range,
  bogus int,
  valid_at int4
);

ALTER TABLE temporal_rng4 DROP COLUMN bogus;

ALTER TABLE temporal_rng4 ADD
  CONSTRAINT temporal_rng4_pk UNIQUE (id, valid_at WITHOUT OVERLAPS);

which gave different errors with and without the DROP COLUMN
step.

			regards, tom lane