当数据需要做累加的时候需要设置累加变量(比如求UV VV的时候)
设置累加变量的步骤:
scala> val accum = sc.accumulator(0, "My Accumulator")
accum: spark.Accumulator[Int] = 0
scala> sc.parallelize(Array(1, 2, 3, 4)).foreach(x => accum += x)...10/09/29 18:41:08 INFO SparkContext: Tasks finished in 0.317106 s
scala> accum.valueres2: Int = 10