apache/spark — pull request #1858 by erikerlandson (2014-08-08 19:51:38+00:00)
Title: [SPARK-2911] apply parent[T](j) to clarify UnionRDD code

References to dependencies(j) for actually obtaining RDD parents are less common than I originally estimated. It does clarify UnionRDD (also will clarify some of my other PRs)

Use of firstParent[T] is ubiquitous, but not as sure that benefits from being replaced with parent(0)[T].