pub fn advance_time(&mut self, time: &Time) {
        use differential_dataflow::trace::TraceReader;
        use timely::progress::frontier::Antichain;
        let frontier = Antichain::from_elem(time.clone());
        for trace in self.inputs.values_mut() {
            trace.set_logical_compaction(frontier.borrow());
            trace.set_physical_compaction(frontier.borrow());
        }
        for map in self.arrangements.values_mut() {
            for trace in map.values_mut() {
                trace.set_logical_compaction(frontier.borrow());
                trace.set_physical_compaction(frontier.borrow());
            }
        }
    }
Advances the frontier of each maintained trace.
interactive/src/manager.rs