Spark Actions

Actions Spark任何一个计算任务,有且仅有一个动作算子,用于触发job的执行。将RDD中的数据写出到外围系统或者传递给Driver主程序。 reduce(func) Aggregate the elements of the dataset using a function func (which takes two arguments and returns one). The function should be commutative and associative so that it can be computed correctly in parallel. 该算子能够对