[EMAIL PROTECTED] writes: > If I understand correctly, and I've sort of just worked on this > assumption, a sequence does not nessisarily produce a sequence of numbers. > It produces a succession of numbers that are guarenteed to increase, but > not nessisarily with a specific interval (usually one).
It produces a series of numbers that are guaranteed to be *different*. The always-increasing property is valid as far as the numbers delivered in a single session go, but it doesn't hold across backends, so I think the extent to which you can rely on it is pretty limited. > The "addval" is similar, you can add a value to a sequence. It should be > OK, but is not guarented to be MVCC. The admin or developer will have to > correct any rollbacks. This strikes me as a complete nonstarter. How would a failed transaction fix anything, or even tell anyone else that there was now something needing to be fixed? You'd have to rely on the client to start a fresh transaction and do the fixup. In practice the total would get out of sync in no time. Also, I don't see how you would actually use this without needing addval to accept negative increments (for decrementing totals on delete, etc). That seems to create a whole new set of semantic issues, because now you no longer have the "it's the same as N consecutive nextval's" rule to define the behavior for you. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]