Github user jerryshao commented on a diff in the pull request:
https://github.com/apache/spark/pull/8881#discussion_r41481438
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/dstream/TransformedDStream.scala
---
@@ -38,6 +39,11 @@ class TransformedDStream[U: ClassTag] (
override def compute(validTime: Time): Option[RDD[U]] = {
val parentRDDs = parents.map(_.getOrCompute(validTime).orNull).toSeq
- Some(transformFunc(parentRDDs, validTime))
+ val transformedRDD = transformFunc(parentRDDs, validTime)
+ if (transformedRDD == null) {
+ throw new SparkException("Transform function must not return null. "
+
+ "Return RDD.empty to return no elements as the result of the
transformation.")
--- End diff --
"Return RDD.empty instead to represent no element as the result of
transformation" ?
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