相关疑难解决方法(0)

当我执行以下命令时:

scala> val rdd = sc.parallelize(List((1,2),(3,4),(3,6)),4).partitionBy(new HashPartitioner(10)).persist()
rdd: org.apache.spark.rdd.RDD[(Int, Int)] = ShuffledRDD[10] at partitionBy at <console>:22

scala> rdd.partitions.size
res9: Int = 10

scala> rdd.partitioner.isDefined
res10: Boolean = true


scala> rdd.partitioner.get
res11: org.apache.spark.Partitioner = org.apache.spark.HashPartitioner@a

它说有10个分区,分区完成使用HashPartitioner.但是当我执行以下命令时:

scala> val rdd = sc.parallelize(List((1,2),(3,4),(3,6)),4)
...
scala> rdd.partitions.size
res6: Int = 4
scala> rdd.partitioner.isDefined
res8: Boolean = false

它说有4个分区,并且没有定义分区器.那么,什么是Spark中的默认分区方案？/如何在第二种情况下对数据进行分区？

我正在使用Spark 1.3.1,我很好奇为什么Spark不允许在地图侧组合上使用数组键.一块combineByKey function:

if (keyClass.isArray) {
  if (mapSideCombine) {
    throw new SparkException("Cannot use map-side combining with array keys.")
  }
}