无法打印RDD的内容 [英] Cannot print the contents of RDD

问题描述

我尝试打印RDD RDD[(String,List[(String,String)])]的内容:

I try to print the contents of my RDD RDD[(String,List[(String,String)])]:

val sc = new SparkContext(conf)
val splitted = rdd.map(line => line.split(","))
val processed = splitted.map(x=>(x(1),List((x(0),x(2),x(3),x(4)))))
val grouped = processed.reduceByKey((x,y) => (x ++ y))
System.out.println(grouped)

但是我没有看到内容:

ShuffledRDD[4] at reduceByKey at Consumer.scala:88

更新:

TXT文件的内容:

100001082016,230,111,1,1 
100001082016,121,111,1,1
100001082016,110,111,1,1

UPDATE 2(整个代码):

UPDATE 2 (the whole code):

class Consumer()
{

def run() = {
    val conf = new SparkConf()
                              .setAppName("TEST")
                              .setMaster("local[*]") 
    val sc = new SparkContext(conf)
    val rdd = sc.textFile("file:///usr/test/myfile.txt")
    val splitted = rdd.map(line => line.split(","))
    val processed = splitted.map(x=>(x(1),List((x(0),x(2),x(3),x(4)))))
    val grouped = processed.reduceByKey((x,y) => (x ++ y))
    System.out.println(grouped)
}

}

推荐答案

这里没有问题:

scala> val rdd = sc.parallelize(Seq("100001082016,230,111,1,1","100001082016,121,111,1,1","100001082016,110,111,1,1"))
// rdd: org.apache.spark.rdd.RDD[String] = ParallelCollectionRDD[0] at parallelize at <console>:27

scala> val splitted = rdd.map(line => line.split(","))
// splitted: org.apache.spark.rdd.RDD[Array[String]] = MapPartitionsRDD[1] at map at <console>:29

scala> val processed = splitted.map(x=>(x(1),List((x(0),x(2),x(3),x(4)))))
// processed: org.apache.spark.rdd.RDD[(String, List[(String, String, String, String)])] = MapPartitionsRDD[2] at map at <console>:31

scala> val grouped = processed.reduceByKey((x,y) => (x ++ y))
// grouped: org.apache.spark.rdd.RDD[(String, List[(String, String, String, String)])] = ShuffledRDD[3] at reduceByKey at <console>:33

scala> grouped.collect().foreach(println)
// (121,List((100001082016,111,1,1)))
// (110,List((100001082016,111,1,1)))
// (230,List((100001082016,111,1,1)))

以下错误.它可以按预期工作，但是您必须正确理解该语言才能知道所期望的情况:

The following is wrong. It works as expect but you have to understand the language correctly to know what is expect :

scala> System.out.println(grouped)
// ShuffledRDD[3] at reduceByKey at <console>:33

编辑:要清楚一点，如果您希望打印一个集合，则需要使用该集合可用的mkString方法，您需要将其转换为格式才能进行打印你想要的.

Just to be clear, if you wish to print a collection, you'll need to use the mkString method available for the collection that you'd need to print converting it into the format you'd want.

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