1、取正序前k个数

scala> var rdd1=sc.makeRDD(Seq(8,3,6,2,5))
rdd1: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[0] at makeRDD at <console>:24

scala> var myOrder1=implicitly[Ordering[Int]]
myOrder1: Ordering[Int] = scala.math.Ordering$Int$@45127d5b

scala> rdd1.takeOrdered(3)(myOrder1)
res0: Array[Int] = Array(2, 3, 5)    

scala> var rdd1=sc.makeRDD(Seq(8,3,6,2,5))
rdd1: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[0] at makeRDD at <console>:24

scala> val myOrder2=implicitly[Ordering[Int]].reverse
myOrder2: scala.math.Ordering[Int] = scala.math.Ordering$$anon$4@2f43af5

scala> rdd1.takeOrdered(3)(myOrder2)
res1: Array[Int] = Array(8, 6, 5)

一个创业中的苦逼程序员