mysql uuid gotchas

http://dev.mysql.com/doc/refman/5.1/en/miscellaneous-functions.html#function_uuid

mysql uuid gotchas

• Two calls to UUID() are expected to generate two different values, even if these calls are performed on two separate computers that are not connected to each other.
• The fifth number is an IEEE 802 node number that provides spatial uniqueness. A random number is substituted if the latter is not available (for example, because the host computer has no Ethernet card, or we do not know how to find the hardware address of an interface on your operating system). In this case, spatial uniqueness cannot be guaranteed. Nevertheless, a collision should have very low probability.
• Although UUID() values are intended to be unique, they are not necessarily unguessable or unpredictable. If unpredictability is required, UUID values should be generated some other way.