psql (12devel)
Type "help" for help.

postgres=# SELECT uuid_cmp('11111111-1111-1111-1111-111111111111'::uuid, '22222222-2222-2222-2222-222222222222'::uuid);
  uuid_cmp
-------------
 -2147483648
(1 row)

postgres=# SELECT uuid_cmp('11111111-1111-1111-1111-111111111111'::uuid, '11111111-1111-1111-1111-111111111111'::uuid);
 uuid_cmp
----------
        0
(1 row)

postgres=# SELECT uuid_cmp('11111111-1111-1111-1111-111111111111'::uuid, '11111113-1111-1111-1111-111111111111'::uuid);
  uuid_cmp
-------------
 -2147483648
(1 row)

postgres=# SELECT uuid_cmp('11111111-1111-1111-1111-111111111111'::uuid, '11111110-1111-1111-1111-111111111111'::uuid);
 uuid_cmp
----------
        1
(1 row)