Spark常用Transformations算子(二)

介绍以下Transformations算子：
join
cogroup
cartesian
pipe
repartitionAndSortWithinPartitions
glom
randomSplit
zip
zipWithIndex
zipWithUniqueId

---

(2) join

object JoinTest {

  def main(args: Array[String]): Unit = {
    val conf = new SparkConf().setAppName("MapTest").setMaster("local")
    val sc = new SparkContext(conf)

    val nameList = List(
      (1,"Jed"),
      (2,"Tom"),
      (3,"Bob"),
      (4,"Tony")
    )

    val salaryArr = Array(
      (1,8000),
      (2,6000),
      (3,5000)
    )

    val nameRDD = sc.parallelize(nameList,2)
    val salaryRDD = sc.parallelize(salaryArr,3)

    // inner join
    val joinRDD = nameRDD.join(salaryRDD)
    joinRDD.foreach( x => {
      val id = x._1
      val name = x._2._1
      val salary = x._2._2
      println(id + "\t" + name + "\t" + salary)
    })
    /*
    1    Jed  8000
    2    Tom  6000
    3    Bob  5000
    */

    // left join
    val leftOuterJoinRDD = nameRDD.leftOuterJoin(salaryRDD)
    leftOuterJoinRDD.foreach( x => {
      val id = x._1
      val name = x._2._1
      val salary = x._2._2
      println(id + "\t" + name + "\t" + salary)
    })
    /*
    1    Jed  Some(8000)
    2    Tom  Some(6000)
    3    Bob  Some(5000)
    4    Tony None
    */

    // right join
    val rightOuterJoinRDD = nameRDD.rightOuterJoin(salaryRDD)
    rightOuterJoinRDD.foreach( x => {
      val id = x._1
      val name = x._2._1
      val salary = x._2._2
      println(id + "\t" + name + "\t" + salary)
    })
    /*
    1    Some(Jed)    8000
    2    Some(Tom)    6000
    3    Some(Bob)    5000
    */

    // full join
    val fullOuterJoinRDD = nameRDD.fullOuterJoin(salaryRDD)
    fullOuterJoinRDD.foreach( x => {
      val id = x._1
      val name = x._2._1
      val salary = x._2._2
      println(id + "\t" + name + "\t" + salary)
    })
    /*
      1    Some(Jed)     Some(8000)
      2    Some(Tom)     Some(6000)
      3    Some(Bob)     Some(5000)
      4    Some(Tony)    None
    */
  }
}

(3) cogroup：将多个RDD中同一个Key对应的Value组合到一起

val data1 = sc.parallelize(List((1, "Good"), (2, "Morning")))
val data2 = sc.parallelize(List((1, "How"), (2, "Are"), (3, "You")))
val data3 = sc.parallelize(List((1, "I"), (2, "Love"), (3, "U")))

val result = data1.cogroup(data2, data3)

result.foreach(println)

val data1 = sc.parallelize(List((1, "Good"), (2, "Morning")))
val data2 = sc.parallelize(List((1, "How"), (2, "Are"), (3, "You")))
val data3 = sc.parallelize(List((1, "I"), (2, "Love"), (3, "U")))

val result = data1.cogroup(data2, data3)

result.foreach(println)

/*
(1,(CompactBuffer(Good),CompactBuffer(How),CompactBuffer(I)))
(2,(CompactBuffer(Morning),CompactBuffer(Are),CompactBuffer(Love)))
(3,(CompactBuffer(),CompactBuffer(You),CompactBuffer(U)))
 */

(4) cartesian：求笛卡尔积

val rdd1 = sc.makeRDD(Array(1,2,3))
val rdd2 = sc.makeRDD(Array(4,5,6))
rdd1.cartesian(rdd2).foreach(println)

/*
(1,4)
(1,5)
(1,6)
(2,4)
(2,5)
(2,6)
(3,4)
(3,5)
(3,6)
 */

(6) repartitionAndSortWithinPartitions：重新分区并按照新分区排序

val arr = Array((1,"Tom"),(18,"Tony"),(23,"Ted"),
        (3,"Harry"),(56,"Bob"),(45,"Jack"),
        (22,"Jed"),(2,"Kobe"),(4,"Kate"),
        (23,"Mary"),(32,"Tracy"),(6,"Allen"),
        (7,"Caleb"),(19,"Alexande"),(9,"Nathan"))

val rdd = sc.makeRDD(arr,2)

rdd.foreachPartition(x => {
  println("=============")
  while(x.hasNext) {
    println(x.next())
  }
})
/*
=============
(1,Tom)
(18,Tony)
(23,Ted)
(3,Harry)
(56,Bob)
(45,Jack)
(22,Jed)
=============
(2,Kobe)
(4,Kate)
(23,Mary)
(32,Tracy)
(6,Allen)
(7,Caleb)
(19,Alexande)
(9,Nathan)
*/

// 改变为4个分区
rdd.repartitionAndSortWithinPartitions(new HashPartitioner(4))
  .foreachPartition(x => {
    println("=============")
    while(x.hasNext) {
      println(x.next())
    }
  })
/*
=============
(4,Kate)
(32,Tracy)
(56,Bob)
=============
(1,Tom)
(9,Nathan)
(45,Jack)
=============
(2,Kobe)
(6,Allen)
(18,Tony)
(22,Jed)
=============
(3,Harry)
(7,Caleb)
(19,Alexande)
(23,Ted)
(23,Mary)
*/

(7) glom：把分区中的元素封装到数组中

val rdd = sc.parallelize(1 to 10,2)

val glomRDD = rdd.glom()

glomRDD.foreach(x => {
  println("============")
  x.foreach(println)
})
println("glomRDD中的元素个数为：" + glomRDD.count())

/*
============
1
2
3
4
5
============
6
7
8
9
10
glomRDD中的元素个数为：2
*/

(8) randomSplit：拆分RDD

val rdd = sc.parallelize(1 to 10)
// 把原来的RDD按照1:2:3:4的比例拆分为4个RDD
rdd.randomSplit(Array(0.1,0.2,0.3,0.4)).foreach(x => {println(x.count)})

理论结果：
1
2
3
4
在数据量不大的情况下，实际结果不一定准确

(9) zip、zipWithIndex、zipWithUniqueId

package com.aura.transformations

import org.apache.spark.{SparkConf, SparkContext}

/**
  * Author: Jed
  * Description:
  * Date: Create in 2018/1/11
  */
object ZipTest {

  def main(args: Array[String]): Unit = {
    val conf = new SparkConf().setAppName("MapTest").setMaster("local")
    val sc = new SparkContext(conf)

    val arr = Array(1,2,3,4,5)
    val arr2 = Array("Tom","Jed","Tony","Terry","Kate")

    val rdd1 = sc.makeRDD(arr)
    val rdd2 = sc.makeRDD(arr2)

    rdd1.zip(rdd2).foreach(println)
    /*
    (1,Tom)
    (2,Jed)
    (3,Tony)
    (4,Terry)
    (5,Kate)
    */

    rdd2.zipWithIndex().foreach(println)
    /*
    (Tom,0)
    (Jed,1)
    (Tony,2)
    (Terry,3)
    (Kate,4)
    */

    rdd1.zipWithUniqueId().foreach(println)
    /*
    (1,0)
    (2,1)
    (3,2)
    (4,3)
    (5,4)
    */

  }

}

原理：

image.png