-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > Well, unique is usually defined as "not equal to any other". And "not > equal" also fails transitive law [...]
> But it should be trivial to test at insertion time if the interval > overlaps with any existing intervals [...] Putting your point another way: you might construe an equivalence relation by grouping together all intervals which (directly or indirectly) touch each other. Let's say they are "connected". But then the problem becomes clear: let's assume A and C are not connected (i.e. they are in different equivalence classes). Now you add B, which happens to overlap A and C. Now A and C are connected. How do you care for that in your index? That can't happen with a "classical" equivalence relation, which wouldn't change among existing elements when you add a new one. Regards - -- tomás -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) iD8DBQFF2TmLBcgs9XrR2kYRAmIHAJ4+x1mOum1rvBkS8/Pypcu8w2QIIQCffFm5 No5aOh901rxfc2mpRYpJMAU= =7Isi -----END PGP SIGNATURE----- ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq