Keys larger than 2 Billion

We have an application where we want to plan for some of our tables to have more than 2 billion rows. Currently we have a primary key that is a SERIAL type column, but this will only handle unique IDs up to 2 billion rows. We have thought about having a composite primary key with the first value being a julian day or some kind of month and a second column that is serial. Another idea is to handle incrementing ourselves by storing a current value in some control table, but this will add more overhead to an insert. Does anyone have any input on this? Has anyone seen anything like this done? I am sure that there are probably a hundred ways to do this, I am looking for a good discussion of the pros and cons of different approaches. Any help would be appreciated. Thanks, Frank Dickinson (frdi@gate.net) ====================================================== Metal forged of the hottest flame is strongest! ======================================================