Hibernate version: 2.1
For a certain db application where we keep a queue of tasks to process in a table, we have traditionally used sql server's timestamp value as a guaranteed increasing, automatically generated binary key. (note: sql server's timestamp value is not the same as a standard SQL timestamp value) This allows us to treat the table as a queue, where we can store a timestamp value as our "current position" in the queue, and have a process wake up, and be able to step through the additions to this queue in the order they occurred, an dprocess them.

Now I am trying to get something like this to work with Hibernate, in a database-independent way. I've been looking over the different types of id generation, and some of them are sequential, but the descriptions of the algorithms are too brief (and my understanding too shallow) for me to know if any of these would be appropriate for such a situation.

The problem with using an actual "datetime" value is that the clocks of various clients could be out of sync. And I am not sure which of the hibernate generated ids are strictly increasing. The solution ideally would work with multiple clients, and as I said, be database independent.

Thanks for any advice,

Ken Larson

why don't you use the native generator (either sequence or identity depending the database)?

is that always strictly increasing over time?

For identity, that would be the case I believe.

For sequences, it would depend how you defined the sequence. Sequences can actually be configured to decrement, rather than increment.

thanks everyone for your help.

what exactly is the hi/lo algorithm? I've looked at the code, I've searched on the web, and I can't quite figure it out. does the hi/lo algorithm also always generate increasing values?

hi/lo can generate non incremental values (always unique however)