wso2 - Siddhi 查询使用当前事件的值和上一个事件的值计算新值

Question

每当一个事件到达时，都需要一个查询来使用当前事件的值和最后一个事件的值来计算一个新值，并将其插入到一个新的流中。例如：

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

使用 #window.lengthBatch(2) 时，它允许为每两个事件计算一次加速度。不满足要求。有什么想法吗？

Answer 1

你可以使用一个序列，

例如

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