5:22:12jcowanmoon-child: That's the whole idea: you add the UUID (or half-UUID or whatever) only to objects that have been moved, which is a minority of objects
5:22:40jcowanthen you just need a bit to tell you if there is a UUID at all
6:06:10moon-childjcowan: sure; 128 bits is still a lot, though. I think a segmented incrementing counter + 64-bit perfect hash would be better
13:24:05jcowanbeach: the case you described (statically known values from a totally ordered domain) is a natural application for perfect hashing.
13:34:14beachI know, and I am explicitly trying something else.