Flink--DateSet的Transformation简单操作

flatMap函数

//初始化执行环境
val env: ExecutionEnvironment = ExecutionEnvironment.getExecutionEnvironment
//加载数据
val data = env.fromElements(("A" , 1) , ("B" , 1) , ("C" , 1))
//使用trasformation加载这些数据
//TODO map
val map_result = data.map(line => line._1+line._2)
map_result.print()
//TODO flatmap
val flatmap_result = data.flatMap(line => line._1+line._2)
flatmap_result.print()

练习：如下数据

A;B;C;D;B;D;C
B;D;A;E;D;C
A;B

要求：统计相邻字符串出现的次数

import org.apache.flink.api.scala.{DataSet, ExecutionEnvironment}
import org.apache.flink.streaming.api.scala._
/**
  * Created by angel；
  */
object demo {
/**
A;B;C;D;B;D;C
B;D;A;E;D;C
A;B
统计相邻字符串出现的次数(A+B , 2) (B+C , 1)....
  * */
  def main(args: Array[String]): Unit = {
    val env = ExecutionEnvironment.getExecutionEnvironment
    val data = env.fromElements("A;B;C;D;B;D;C;B;D;A;E;D;C;A;B")
    val map_data: DataSet[Array[String]] = data.map(line => line.split(";"))
    //[A,B,C,D] ---"A,B,C,D"
    //[A,B,C,D] ---> (x,1) , (y,1) -->groupBy--->sum--total
    val tupe_data = map_data.flatMap{
      line =>
        for(index <- 0 until line.length-1) yield (line(index)+"+"+line(index+1) , 1)
    }
    val gropudata = tupe_data.groupBy(0)
    val result = gropudata.sum(1)
    result.print()
  }
}

mapPartition函数

//TODO mapPartition
val ele_partition = elements.setParallelism(2)//将分区设置为2
val partition = ele_partition.mapPartition(line => line.map(x=> x+"======"))//line是每个分区下面的数据
partition.print()

mapPartition：是一个分区一个分区拿出来的 好处就是以后我们操作完数据了需要存储到mysql中，这样做的好处就是几个分区拿几个连接，如果用map的话，就是多少条数据拿多少个mysql的连接

filter函数

Filter函数在实际生产中特别实用，数据处理阶段可以过滤掉大部分不符合业务的内容，可以极大减轻整体flink的运算压力

//TODO fileter
val filter:DataSet[String] = elements.filter(line => line.contains("java"))//过滤出带java的数据
filter.print()

reduce函数

//TODO reduce
 val elements:DataSet[List[Tuple2[String , Int]]] = env.fromElements(List(("java" , 1) , ("scala" , 1) , ("java" , 1)))
  val tuple_map = elements.flatMap(x=> x)//拆开里面的list，编程tuple
  val group_map = tuple_map.groupBy(x => x._1)//按照单词聚合
val reduce = group_map.reduce((x,y) => (x._1 ,x._2+y._2))
reduce.print()

reduceGroup

reduceGroup是reduce的一种优化方案；

它会先分组reduce，然后在做整体的reduce；这样做的好处就是可以减少网络IO；

  //TODO reduceGroup

  val elements:DataSet[List[Tuple2[String , Int]]] = env.fromElements(List(("java" , 1) ,("java" , 1), ("scala" , 1)))
  val tuple_words = elements.flatMap(x=>x)
  val group_words = tuple_words.groupBy(x => x._1)
  val a = group_words.reduceGroup{
    (in:Iterator[(String,Int)],out:Collector[(String , Int)]) =>
      val result = in.reduce((x, y) => (x._1, x._2+y._2))
      out.collect(result)
  }
  a.print()
}

GroupReduceFunction和GroupCombineFunction（自定义函数）

import collection.JavaConverters._
class Tuple3GroupReduceWithCombine extends GroupReduceFunction[( String , Int), (String, Int)] with GroupCombineFunction[(String, Int), (String, Int)] {
  override def reduce(values: Iterable[(String, Int)], out: Collector[(String, Int)]): Unit = {

    for(in <- values.asScala){
      out.collect((in._1 , in._2))
    }
  }

  override def combine(values: Iterable[(String, Int)], out: Collector[(String, Int)]): Unit = {
    val map = new mutable.HashMap[String , Int]()
    var num = 0
    var s = ""
    for(in <- values.asScala){
        num += in._2
        s = in._1
    }
    out.collect((s , num))
  }
}

//  TODO GroupReduceFunction  GroupCombineFunction
val env = ExecutionEnvironment.getExecutionEnvironment
val elements:DataSet[List[Tuple2[String , Int]]] = env.fromElements(List(("java" , 3) ,("java" , 1), ("scala" , 1)))
val collection = elements.flatMap(line => line)
val groupDatas:GroupedDataSet[(String, Int)] = collection.groupBy(line => line._1)
//在reduceGroup下使用自定义的reduce和combiner函数
val result = groupDatas.reduceGroup(new Tuple3GroupReduceWithCombine())
val result_sort = result.collect().sortBy(x=>x._1)
println(result_sort)

combineGroup

使用之前的group操作，比如：reduceGroup或者GroupReduceFuncation；这种操作很容易造成内存溢出；因为要一次性把所有的数据一步转化到位，所以需要足够的内存支撑，如果内存不够的情况下，那么需要使用combineGroup； combineGroup在分组数据集上应用GroupCombineFunction。 GroupCombineFunction类似于GroupReduceFunction，但不执行完整的数据交换。 【注意】：使用combineGroup可能得不到完整的结果而是部分的结果

import collection.JavaConverters._
class MycombineGroup extends GroupCombineFunction[Tuple1[String] , (String , Int)]{
  override def combine(iterable: Iterable[Tuple1[String]], out: Collector[(String, Int)]): Unit = {
    var key: String = null
    var count = 0
    for(line <- iterable.asScala){
      key = line._1
      count += 1
    }
    out.collect((key, count))

  }
}

//TODO  combineGroup
val input = env.fromElements("a", "b", "c", "a").map(Tuple1(_))
val combinedWords = input.groupBy(0).combineGroup(new MycombineGroup())
combinedWords.print()

Aggregate

在数据集上进行聚合求最值（最大值、最小值） 注意：Aggregate只能作用于元组上

//TODO Aggregate
val data = new mutable.MutableList[(Int, String, Double)]
data.+=((1, "yuwen", 89.0))
data.+=((2, "shuxue", 92.2))
data.+=((3, "yingyu", 89.99))
data.+=((4, "wuli", 98.9))
data.+=((1, "yuwen", 88.88))
data.+=((1, "wuli", 93.00))
data.+=((1, "yuwen", 94.3))
//    //fromCollection将数据转化成DataSet
val input: DataSet[(Int, String, Double)] = env.fromCollection(Random.shuffle(data))
val output = input.groupBy(1).aggregate(Aggregations.MAX, 2)
output.print()

minBy和maxBy

//TODO MinBy / MaxBy
val data = new mutable.MutableList[(Int, String, Double)]
data.+=((1, "yuwen", 90.0))
data.+=((2, "shuxue", 20.0))
data.+=((3, "yingyu", 30.0))
data.+=((4, "wuli", 40.0))
data.+=((5, "yuwen", 50.0))
data.+=((6, "wuli", 60.0))
data.+=((7, "yuwen", 70.0))
//    //fromCollection将数据转化成DataSet
val input: DataSet[(Int, String, Double)] = env.fromCollection(Random.shuffle(data))
val output: DataSet[(Int, String, Double)] = input
  .groupBy(1)
  //求每个学科下的最小分数
  //minBy的参数代表要求哪个字段的最小值
  .minBy(2)
output.print()

distinct去重

//TODO distinct 去重
  val data = new mutable.MutableList[(Int, String, Double)]
  data.+=((1, "yuwen", 90.0))
  data.+=((2, "shuxue", 20.0))
  data.+=((3, "yingyu", 30.0))
  data.+=((4, "wuli", 40.0))
  data.+=((5, "yuwen", 50.0))
  data.+=((6, "wuli", 60.0))
  data.+=((7, "yuwen", 70.0))
  //    //fromCollection将数据转化成DataSet
  val input: DataSet[(Int, String, Double)] = env.fromCollection(Random.shuffle(data))
  val distinct = input.distinct(1)
  distinct.print()

join

Flink在操作过程中，有时候也会遇到关联组合操作，这样可以方便的返回想要的关联结果，比如：

求每个班级的每个学科的最高分数

//TODO join
    val data1 = new mutable.MutableList[(Int, String, Double)]
    //学生学号---学科---分数
    data1.+=((1, "yuwen", 90.0))
    data1.+=((2, "shuxue", 20.0))
    data1.+=((3, "yingyu", 30.0))
    data1.+=((4, "yuwen", 40.0))
    data1.+=((5, "shuxue", 50.0))
    data1.+=((6, "yingyu", 60.0))
    data1.+=((7, "yuwen", 70.0))
    data1.+=((8, "yuwen", 20.0))
    val data2 = new mutable.MutableList[(Int, String)]
    //学号 ---班级
    data2.+=((1,"class_1"))
    data2.+=((2,"class_1"))
    data2.+=((3,"class_2"))
    data2.+=((4,"class_2"))
    data2.+=((5,"class_3"))
    data2.+=((6,"class_3"))
    data2.+=((7,"class_4"))
    data2.+=((8,"class_1"))
    val input1: DataSet[(Int, String, Double)] = env.fromCollection(Random.shuffle(data1))
    val input2: DataSet[(Int, String)] = env.fromCollection(Random.shuffle(data2))
    //求每个班级下每个学科最高分数
    val joindata = input2.join(input1).where(0).equalTo(0){
      (input2 , input1) => (input2._1 , input2._2 , input1._2 , input1._3)
    }
//    joindata.print()
//    println("===================")
    val aggregateDataSet = joindata.groupBy(1,2).aggregate(Aggregations.MAX , 3)
    aggregateDataSet.print()

cross交叉操作

和join类似，但是这种交叉操作会产生笛卡尔积，在数据比较大的时候，是非常消耗内存的操作；

//TODO Cross 交叉操作，会产生笛卡尔积
val data1 = new mutable.MutableList[(Int, String, Double)]
//学生学号---学科---分数
data1.+=((1, "yuwen", 90.0))
data1.+=((2, "shuxue", 20.0))
data1.+=((3, "yingyu", 30.0))
data1.+=((4, "yuwen", 40.0))
data1.+=((5, "shuxue", 50.0))
data1.+=((6, "yingyu", 60.0))
data1.+=((7, "yuwen", 70.0))
data1.+=((8, "yuwen", 20.0))
val data2 = new mutable.MutableList[(Int, String)]
//学号 ---班级
data2.+=((1,"class_1"))
data2.+=((2,"class_1"))
data2.+=((3,"class_2"))
data2.+=((4,"class_2"))
data2.+=((5,"class_3"))
data2.+=((6,"class_3"))
data2.+=((7,"class_4"))
data2.+=((8,"class_1"))
val input1: DataSet[(Int, String, Double)] = env.fromCollection(Random.shuffle(data1))
val input2: DataSet[(Int, String)] = env.fromCollection(Random.shuffle(data2))
val cross = input1.cross(input2){
  (input1 , input2) => (input1._1,input1._2,input1._3,input2._2)
}
cross.print()

union

将多个DataSet合并成一个DataSet

【注意】：union合并的DataSet的类型必须是一致的

//TODO union联合操作
val elements1 = env.fromElements(("123"))
val elements2 = env.fromElements(("456"))
val elements3 = env.fromElements(("123"))
val union = elements1.union(elements2).union(elements3).distinct(line => line)
union.print()

rebalance

Flink也有数据倾斜的时候，比如当前有数据量大概10亿条数据需要处理，在处理过程中可能会发生如图所示的状况：

这个时候本来总体数据量只需要10分钟解决的问题，出现了数据倾斜，机器1上的任务需要4个小时才能完成，那么其他3台机器执行完毕也要等待机器1执行完毕后才算整体将任务完成；

所以在实际的工作中，出现这种情况比较好的解决方案就是本节课要讲解的—rebalance（内部使用round robin方法将数据均匀打散。这对于数据倾斜时是很好的选择。）

举例：

1：在不使用rebalance的情况下，观察每一个线程执行的任务特点

   val ds = env.generateSequence(1, 3000)
    val rebalanced = ds.filter(_ > 780)
//    val rebalanced = skewed.rebalance()
    val countsInPartition = rebalanced.map( new RichMapFunction[Long, (Int, Long)] {
      def map(in: Long) = {
        //获取并行时子任务的编号getRuntimeContext.getIndexOfThisSubtask
        (getRuntimeContext.getIndexOfThisSubtask, in)
      }
    })
    countsInPartition.print()
【数据随机的分发给各个子任务（分区）】

2：使用rebalance

//TODO rebalance
val ds = env.generateSequence(1, 3000)
val skewed = ds.filter(_ > 780)
val rebalanced = skewed.rebalance()
val countsInPartition = rebalanced.map( new RichMapFunction[Long, (Int, Long)] {
  def map(in: Long) = {
    //获取并行时子任务的编号getRuntimeContext.getIndexOfThisSubtask
    (getRuntimeContext.getIndexOfThisSubtask, in)
  }
})
countsInPartition.print()

每隔8一次循环（数据使用轮询的方式在各个子任务中执行）

first

//TODO first-取前N个
    val data = new mutable.MutableList[(Int, Long, String)]
    data.+=((1, 1L, "Hi"))
    data.+=((2, 2L, "Hello"))
    data.+=((3, 2L, "Hello world"))
    data.+=((4, 3L, "Hello world, how are you?"))
    data.+=((5, 3L, "I am fine."))
    data.+=((6, 3L, "Luke Skywalker"))
    data.+=((7, 4L, "Comment#1"))
    data.+=((8, 4L, "Comment#2"))
    data.+=((9, 4L, "Comment#3"))
    data.+=((10, 4L, "Comment#4"))
    data.+=((11, 5L, "Comment#5"))
    data.+=((12, 5L, "Comment#6"))
    data.+=((13, 5L, "Comment#7"))
    data.+=((14, 5L, "Comment#8"))
    data.+=((15, 5L, "Comment#9"))
    data.+=((16, 6L, "Comment#10"))
    data.+=((17, 6L, "Comment#11"))
    data.+=((18, 6L, "Comment#12"))
    data.+=((19, 6L, "Comment#13"))
    data.+=((20, 6L, "Comment#14"))
    data.+=((21, 6L, "Comment#15"))
    val ds = env.fromCollection(Random.shuffle(data))
//    ds.first(10).print()
    //还可以先goup分组，然后在使用first取值
    ds.groupBy(line => line._2).first(2).print()