Some questions I can't figure from reading the docs: indexes? Are they inferred by my selects or do I have to create them explicitly? Or do they just not exist? Ditto keys, although if you want FK constraints in a loose ad-hoc system like this it's probably the wrong tool for the job.

I imagine the nested transactions are implementation defined, since some dbs do "rollback rolls back current trans" and some do "rollback rolls back entire stack.