Slashdot Mirror
Facebook Goes To 64 Bit User IDs
NewsCloud writes "Facebook has announced to developers that they are moving to a 64 bit user ID in November. At 32 bits, the current ID allows nearly 4.3 billion user accounts. Yet, despite having only 47 million users today, Facebook's move to 64 bits will allow it to have more than 18 quintillion (18,446,744,074,000,000,000) user accounts. Of course, there are currently only about 6.5 billion people in the world. Is Facebook setting their sights beyond Earth or just trying to avoid what happened when Slashdot ran out of space for comment IDs last year. Perhaps they are planning to implement personas."
Not all of the bits of an ID are necessarily there for uniqueness. Wider ID's allow for features such as check digits (being able to tell whether an ID is valid without doing an existence query in a remote database) and other information. Namely, various immutable properties of the object that is denoted by the ID can be stored in the ID itself. This is similar to using spare bits within a machine address for tagging an object with a type or other attribute. It may be very useful to be able to tell something about an object just from the ID alone.