https://xkcd.com/221/ "The generation of random numbers is too important to be left to chance." -I forget who
A UUID is basically a 16 byte integer that people agree to type out in a standard way. All the properties of UUID's that you've mentioned below depend on the random number generator being actually random. "Guaranteed" means vastly different things to a mathematician, a programmer, and the extended warranty folks at Best Buy. From Wikipedia: "In other words, only after generating 1 billion UUIDs every second for the next 100 years, the probability of creating just one duplicate would be about 50%." A 1 in 2^128 (1 in 340,282,366,920,938,463,463,374,607,431,768,211,456. 340 undecillion?) chance of collision for any 2 honestly random UUID's means... Mathematician: They're not unique at all. If anything then it's absolutely guaranteed that there <will> be collisions... eventually. Programmer: "For all intents and purposes" unique. Good enough for government work. Best Buy: Would you like to buy extra collision insurance on your new UUID? You never know what could happen after all. Or maybe upgrade to the gold plated UUID's we have over there? -----Original Message----- From: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] On Behalf Of Jeffrey Mattox Sent: Wednesday, November 16, 2016 3:52 PM To: SQLite mailing list Subject: Re: [sqlite] Changing ID's to UUID I think this discussion is about apples and oranges. UUID stands for universally UNIQUE identifier, so there won't be any collisions. It looks random, but it never repeats. Here's one: "cb058c3a-ac3d-11e6-80f5-76304dec7eb7". I use a UUID [a non-random string guaranteed to be unique -- obtained via an iOS getUUID() function call] to match records in two databases on different machines. They are records for individuals that occasionally have to be merged. The UUID is acts as a guaranteed unique name for each individual. Jeff _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
