flatmapfunction spark 异步回调 guava异步回调 在如下笔记中提到,无论是join还是FutureTask都会阻塞主线程,无法实现真正的异步处理Guava可提供了一种异步回调方案,不会阻塞主线程,Guava中添加了几个相关接口FutureCallback: 主要对异步任务结束后的一些处理,在异步任务执行结束后被调用,包括onSuccess和onFailure两个方法,...
import org.apache.spark.{SparkConf, SparkContext} object MapAndFlatMap { def main(args: Array[String]): Unit = { val sc = new SparkContext(new SparkConf().setAppName("map_flatMap_demo").setMaster("local")) val arrayRDD =sc.parallelize(Array("a_b","c_d","e_f")) arrayRDD.for...
mapResult: org.apache.spark.rdd.RDD[Array[String]]= MapPartitionsRDD[2] at map at <console>:29scala>mapResult.collect res0: Array[Array[String]]= Array(Array(word,in, text), Array(hello, spark), Array(the, third, line)) flatMap的结果 scala> var flatMapResult = textFile.flatMap(lin...
val rdd = sc.parallelize(Seq("map vs flatMap", "apache spark")) rdd.map(_.split(" ")).collect res1: Array[String] = Array(Array("map", "vs", "flatMap"), Array("apache", "spark")) As we can see, themap()method takes the functionsplit(”“)as a parameter and applies it...
flatMap是函数式编程中的一个操作符,用于将一个嵌套的数据结构展平为一个扁平的数据结构。在JavaScript中,flatMap通常用于数组的操作。 具体来说,flatMap函数会对数组中的每个...
进一步观察FlatMapFunction发现,这个这个函数有两个泛型T和O,T是输入,O是输出,在使用时,要设置好对应的输入和输出数据类型。自定义函数最终归结为重写函数flatMap,函数的两个参数也与输入输出的泛型类型对应,即参数value的是flatMap的输入,数据类型是T,参数out是flatMap的输出,我们需要将类型为O的数据写入out。
4、mapValues(function) 原RDD中的Key保持不变,与新的Value一起组成新的RDD中的元素。因此,该函数只适用于元素为KV对的RDD。 mapValues(self, f) method of pyspark.rdd.RDD instance Pass each value in the key-value pair RDD through a map function ...
map .map(object:io.reactivex.rxjava3.functions.Function<ArrayList<Bean>,Boolean>{overridefunapply(...
sparkContext.clean(mapPartFunc), preservePartitioning) } 与其对比的map逻辑如下: /** Return a new DStream by applying a function to all elements of this DStream. */ def map[U: ClassTag](mapFunc: T => U): DStream[U] = ssc.withScope { new MappedDStream(this, context.sparkContext....
RDD.flatMap(<function>) where<function>is the transformation function that could return multiple elements to new RDD for each of the element of source RDD. Java Example – Spark RDD flatMap In this example, we will use flatMap() to convert a list of strings into a list of words. In ...