On 01/05/2011 03:39 PM, Alban Hertroys wrote: >>> From wikipedia, "only after generating 1 billion UUIDs every second for >> the next 100 years, the probability of creating just one duplicate would >> be about 50%. The probability of one duplicate would be about 50% if >> every person on earth owns 600 million UUIDs." > > > Even if the chances of one person encountering a UUID collision are about > once in say 100 billion years, that could be tomorrow. It could also not > happen at all in that time span. That's how chance works. You can never > assume it won't happen. If the costs incurred by a collision are lower than > the costs of preventing it, you can choose to just take the hit, but that > doesn't go for _every_ problem domain. The medical systems mentioned > up-thread are an example of that. > > Next to that, UUID's are generated by computers. I have no doubts that the > numeric space that makes up a UUID allows for collision chances as low as > described, but are computers capable of generating those numbers sufficiently > random that they actually achieve that low a chance? I think that's pushing > it. > > Alban Hertroys > > -- > If you can't see the forest for the trees, > cut the trees and you'll see there is no forest. > > > !DSPAM:1214,4d24f31711541026711723! > > I'm not talking about chance. I'm talking about robust software. You have to expect some sort of rollback for any of a number of reasons and deal with them. The potential UUID collision is just one example of a contingency one might plan for after having taken care of all the more probable failure points.
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