Github user pwendell commented on a diff in the pull request:
https://github.com/apache/spark/pull/1039#discussion_r14642773
--- Diff: core/src/main/scala/org/apache/spark/rdd/RDD.scala ---
@@ -1235,11 +1235,43 @@ abstract class RDD[T: ClassTag](
/** A description of this RDD and its recursive dependencies for
debugging. */
def toDebugString: String = {
- def debugString(rdd: RDD[_], prefix: String = ""): Seq[String] = {
- Seq(prefix + rdd + " (" + rdd.partitions.size + " partitions)") ++
- rdd.dependencies.flatMap(d => debugString(d.rdd, prefix + " "))
+ // Apply a different rule to the last child
+ def debugChildren(rdd: RDD[_], prefix: String): Seq[String] = {
+ val len = rdd.dependencies.length
+ len match {
+ case 0 => Seq.empty
+ case 1 =>
+ val d = rdd.dependencies.head
+ debugString(d.rdd, prefix,
d.isInstanceOf[ShuffleDependency[_,_]], true)
+ case _ =>
+ val frontDeps = rdd.dependencies.take(len - 1)
+ val endDep = rdd.dependencies.takeRight(1).head
+ (frontDeps.flatMap(d => debugString(d.rdd, prefix,
d.isInstanceOf[ShuffleDependency[_,_]]))
--- End diff --
For this it would be better to avoid this complex expression:
```
val frontDeps = rdd.dependencies.take(len - 1)
val frontDepStrings = frontDeps.flatMap(d => debugString(d.rdd, prefix,
d.isInstanceOf[ShuffleDependency[_,_]])
val lastDep = rdd.dependencies.last
val lastDepString = debugString(lastDep.rdd, prefix,
endDep.isInstanceOf[ShuffleDependency[_,_]], true)
(frontDepStrings ++ lastDepString)
```
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