How is a uuid column ordered in ORDER BY?

Question

How is a uuid column ordered when used with ORDER BY? Is it based on its string representation? I can't seem to find any documentation regarding this.

Answer 1

This function compares UUIDs in PostgreSQL:

/* internal uuid compare function */
static int
uuid_internal_cmp(const pg_uuid_t *arg1, const pg_uuid_t *arg2)
{
    return memcmp(arg1->data, arg2->data, UUID_LEN);
}

So UUIDs are compared lexically byte for byte using the binary values.