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esper

Esper detect events dissimilar to previous events in a sliding time window

I am trying to write an EPStatement that will match any event that does not have a specified field "similar" to another event in a sliding time window. For example only match events where "value" is at least distance 3 from any other event in the sliding window,

At t=t_0, E0={value=0}  // Match
At t=t_1, E1={value=9}  // Match
At t=t_2, E2={value=1}  // Don't match since value is within 3 of E0.value

I am looking for a statement where I could use any expression that compares two values as the "similarity" metric. I looked at using patterns or match recognize but they don't seem to support this type of dynamic comparison to an unknown number of previous events.

Solution 
  • select * from SomeEvent#keepall as e 
having not window(*).anyOf(p => Math.abs(p.value - e.value) <= 3 and p.id != e.id)

    The window(*) holds all events. The anyOf goes thru the window to find any that match. The p.id=e.id excludes the current event. field id being a unique id of the event that you may or may not have as an event property on the event.