Spark Transformations之mapValues
2015-06-24 00:00
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mapValues
mapValues顾名思义就是输入函数应用于RDD中Kev-Value的Value,原RDD中的Key保持不变,与新的Value一起组成新的RDD中的元素。因此,该函数只适用于元素为KV对的RDD。举例:
scala> val a = sc.parallelize(List("dog", "tiger", "lion", "cat", "panther", " eagle"), 2) scala> val b = a.map(x => (x.length, x)) scala> b.mapValues("x" + _ + "x").collect res5: Array[(Int, String)] = Array((3,xdogx), (5,xtigerx), (4,xlionx),(3,xcatx), (7,xpantherx), (5,xeaglex))
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