Github user rxin commented on a diff in the pull request: https://github.com/apache/spark/pull/3884#discussion_r22447822 --- Diff: core/src/main/scala/org/apache/spark/rdd/RDD.scala --- @@ -76,10 +76,22 @@ import org.apache.spark.util.random.{BernoulliSampler, PoissonSampler, Bernoulli * on RDD internals. */ abstract class RDD[T: ClassTag]( - @transient private var sc: SparkContext, + @transient private var _sc: SparkContext, @transient private var deps: Seq[Dependency[_]] ) extends Serializable with Logging { + if (classOf[RDD[_]].isAssignableFrom(elementClassTag.runtimeClass)) { + throw new SparkException("Spark does not support nested RDDs (see SPARK-5063)") + } + + private def sc: SparkContext = { + if (_sc == null) { + throw new SparkException( + "Can only define RDDs and perform actions on the driver, not in tasks (see SPARK-5063)") --- End diff -- Pointing to a JIRA ticket might not be the most friendly way for users. Maybe make it more verbose and explain it in one or two lines?
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