On 24 Jan 2011, at 4:21pm, Duquette, William H (318K) wrote: > A question on using randomblob(16) to generate UUIDs, as the SQLite docs > suggest: what assurance do you have that the UUID really is universally > unique? It's a pseudo-random number, and you can replicate a stream of > pseudo-random numbers by setting the seed appropriately. Is randomblob() > doing some kind of magic in its seeding of the random number stream?
Your assurance is only statistical. Version 4 UUIDs have 30 4-bit higits and one 2-bit higit. That gives you (30 * 4) + 2 == 122 bits of randomness, which is about 5e36 different numbers. You can work out yourself how fast people would have to choose random numbers to stand a chance of one duplication in ten years. Simon. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
