class type view_t = object .. end
A view is a high-level transaction, involving both the local db and
the slaves
method pre_commit : journal
Prepares the commit, and returns the journal to commit
method post_commit : bool -> unit
Needs to be called after a commit. post_commit true if the
commit was successful, and commit_commit false if not.
This is important for updating the state of caches: In the
first case cache modifications are made permanent, in the
second case they are undone.
method rollback : unit -> unit
Rolls this view back
