There's a reason Oracle can charge an arse-load of money, and it's not because they're "evil": it's because their DB does some frigging incredible things when you know how to use it. I've worked with a 4 billion row star schema, partitioned by day then sub-partitioned for query optimization. It was OK to be "stale", so we inserted each day's data into an indexless table then swapped it in as a new partition over night.

Billions of rows in performance critical apps is pretty edge case. I think a lot of people paying for Oracle could pretty easily migrate away.