Mark Wong <mark@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. I think we
implement DESC by negating the comparator's result, which explains
why only the DESC case fails.
regards, tom lane