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wso2siddhiwso2-cep

Siddhi query for to calculate a new value using current event's value and last event's value

Whenever an event arrives there needs be a query to calculate a new value using current event's value and last event's value and insert it in to a new stream. For an example:

event [1]              : speed =  0 timestamp = 1410513924817    Calculated value(Acceleration) : 0
event [2]              : speed =  5 timestamp = 1410513924818    Calculated value(Acceleration) : ( 5 - 0)/1 = 5
event [3]              : speed = 10 timestamp = 1410513924819    Calculated value(Acceleration) : (10- 5)/1  = 5
event [4]              : speed = 13 timestamp = 1410513924820    Calculated value(Acceleration) : (13-10)/1  = 3
event [5]              : speed = 14 timestamp = 1410513924821    Calculated value(Acceleration) : (14-13)/1  = 1
event [6](current)     : speed = 15 timestamp = 1410513924822    Calculated value(Acceleration) : (15-14)/1  = 1

When using #window.lengthBatch(2) it allows to calculate the acceleration once for each two events. Does not fulfil the requirement. Any thoughts?

Solution

  • you can use a sequence,

    E.g 

    from a=SpeedStream,b=SpeedStream
select b.speed-a.speed as acceleration, b.speed as currentSpeed
insert into AccelerationStream