title: Forcing output in Esper
body: <p>I have a non real time Esper configuration where I feed a stream that I read from a file. I'm trying to create an expression that computes a statistic over the entire stream and outputs one value at the very end. Esper has semantics for forcing a view to output every X seconds, for instance, but is there a semantic for asking the view or the engine to "flush" the output  when you know there are no more events to feed.</p>