【spark】常用转换操作：keys 、values和mapValues
1.keys功能： 返回所有键值对的key示例 1 2 3 4 val list = List("hadoop","spark","hive","spark") val rdd = sc.parallelize(list) val pairRdd = rdd.map(x => (x,1)) pairRdd.keys.collect.foreach(print
