spark2.1：rdd.combineByKeyWithClassTag的用法示例

测试spark版本：

Spark context Web UI available at http://192.168.1.1:32735
Spark context available as 'sc' (master = local[*], app id = local-1380172893828).
Spark session available as 'spark'.
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /___/ .__/\_,_/_/ /_/\_\   version 2.1.0
      /_/
         
Using Scala version 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_72)
Type in expressions to have them evaluated.
Type :help for more information.

备注：spark1.5中没有提供rdd.combineByKeyWithClassTag算子，但提供的有rdd.combineByKey算子（spark2.1中依然保留）。

使用示例：

scala> case class FModel(cgridid: Int, angle: Double, drsrp: Double, distance: Double)
defined class FModel

scala>  val sample_rdd=sc.makeRDD(
     |       Array(
     |         (1,FModel(1,2.0,2.1,2.2)),
     |         (1,FModel(2,2.2,2.11,23.2)),
     |         (2,FModel(1,2.0,2.1,2.2)),
     |         (1,FModel(3,2.0,42.1,22.2)),
     |         (2,FModel(2,2.2,2.11,23.2)),
     |         (3,FModel(3,2.0,42.1,22.2))
     |       )
     |     )
sample_rdd: org.apache.spark.rdd.RDD[(Int, FModel)] = ParallelCollectionRDD[0] at makeRDD at <console>:26

scala> val combinByKeyRDD = sample_rdd.combineByKeyWithClassTag(
     |       (x: FModel) => (List(x), 1),
     |       (peo: (List[FModel], Int), x: FModel) => (x :: peo._1, peo._2 + 1),
     |       (sex1: (List[FModel], Int), sex2: (List[FModel], Int)) => (sex1._1 ::: sex2._1, sex1._2 + sex2._2))
combinByKeyRDD: org.apache.spark.rdd.RDD[(Int, (List[FModel], Int))] = ShuffledRDD[1] at combineByKeyWithClassTag at <console>:28

scala> combinByKeyRDD.foreach(println)
[Stage 0:>                                                         (0 + 0) / 12](3,(List(FModel(3,2.0,42.1,22.2)),1))
(2,(List(FModel(1,2.0,2.1,2.2), FModel(2,2.2,2.11,23.2)),2))
(1,(List(FModel(1,2.0,2.1,2.2), FModel(2,2.2,2.11,23.2), FModel(3,2.0,42.1,22.2)),3))
                                                                                
scala>