This thread mentions "parallel queries" as a use case, but that means passing data between processes, and that requires being able to serialize and deserialize the aggregate state somehow. For actual data types that's not overly difficult I guess (we can use in/out functions), but what about aggretates using 'internal' state? I.e. aggregates passing pointers that we can't serialize?
This is a good question. I really don't know the answer to it as I've not looked at the Robert's API for passing data between backends yet.
