I'm looking for a way to implement aggregation/fold function on a window that also have a state. I understand how to aggregate on a window, and how to use key/global state - but not both.
Just to be clear, when I say a window with state - I mean that the state should be initialized (nullified) every time the window is changed/moved.
For example: I want to count the number of events keyed by event type every 5 minutes. But in addition to event type (which is the window key) the event has some id field - and I would like to count each id only once - so I need to save a state of all the ids I've already counted in that window.
Is there a simple way to do this in Flink?
