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sc.textFile("README.md").flatMap(line => line.split(" ")).map(word => (word,1)).reduceByKey(_ + _).collect
sc.textFile("README.md").flatMap(line => line.split(" ")).map(word => (word,1)).reduceByKey((a,b) => a + b).collect




























总结:

第一个stage :
HadoopRDD -> MapPartitionRDD -> MapPartitionsRDD -> MapPartitionsRDD -> MapPartitionsRDD

第二个stage :
Stage shuffledRDD -> MapPartitionsRDD










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原文地址:http://www.cnblogs.com/zlslch/p/5906198.html