On 2018-10-01 11:58:51 -0400, Tom Lane wrote: > Mark Wong <m...@2ndquadrant.com> writes: > > a | a > > | uuid_cmp > > --------------------------------------+--------------------------------------+------------- > > 11111111-1111-1111-1111-111111111111 | > > 11111111-1111-1111-1111-111111111111 | 0 > > 11111111-1111-1111-1111-111111111111 | > > 22222222-2222-2222-2222-222222222222 | -2147483648 > > 11111111-1111-1111-1111-111111111111 | > > 3f3e3c3b-3a30-3938-3736-353433a2313e | -2147483648 > > 22222222-2222-2222-2222-222222222222 | > > 11111111-1111-1111-1111-111111111111 | 1 > > 22222222-2222-2222-2222-222222222222 | > > 22222222-2222-2222-2222-222222222222 | 0 > > 22222222-2222-2222-2222-222222222222 | > > 3f3e3c3b-3a30-3938-3736-353433a2313e | -2147483648 > > 3f3e3c3b-3a30-3938-3736-353433a2313e | > > 11111111-1111-1111-1111-111111111111 | 1 > > 3f3e3c3b-3a30-3938-3736-353433a2313e | > > 22222222-2222-2222-2222-222222222222 | 1 > > 3f3e3c3b-3a30-3938-3736-353433a2313e | > > 3f3e3c3b-3a30-3938-3736-353433a2313e | 0 > > (9 rows) > > > Oooh ... apparently, on that platform, memcmp() is willing to produce > INT_MIN in some cases. That's not a safe value for a sort comparator > to produce --- we explicitly say that somewhere, IIRC.
Hm, that'd be pretty painful - memcmp() isn't guaranteed to return anything smaller. And we use memcmp in a fair number of comparators. > I think we implement DESC by negating the comparator's result, which > explains why only the DESC case fails. That makes sense. Greetings, Andres Freund
