If you're open to alternatives, I highly recommend using Sequel. It integrates fairly well with Rails, optimizes extremely well on JRuby, has a consistent update schedule, and has a real API for developing plugins against. I realize it's not part of the standard Rails stack, but it actually makes upgrading Rails easier because you're not constantly chasing a non-standard API that changes release to release (even on MRI, ActiveRecord "plugins" break with almost every release).

Disclaimer: I now work on JRuby full time. But prior to this I ran Mogotest and switched to Sequel successfully on that project.