added back the original diff method to sustain binary compatibility

Author: Brennon York

graphx/src/main/scala/org/apache/spark/graphx/VertexRDD.scala

@@ -129,6 +129,16 @@ abstract class VertexRDD[VD](
    */
   def diff(other: RDD[(VertexId, VD)]): VertexRDD[VD]
 
+  /**
+   * Hides vertices that are the same between `this` and `other`; for vertices that are different,
+   * keeps the values from `other`.
+   *
+   * SPARK-5922: Deprecates this method call in place of diff(other: RDD[(VertexID, VD)])
+   *
+   * @param other the other VertexRDD with which to diff.
+   */
+  def diff(other: VertexRDD[VD]): VertexRDD[VD]
+
   /**
    * Left joins this RDD with another VertexRDD with the same index. This function will fail if
    * both VertexRDDs do not share the same index. The resulting vertex set contains an entry for

graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala

@@ -114,6 +114,17 @@ class VertexRDDImpl[VD] private[graphx] (
     this.withPartitionsRDD(newPartitionsRDD)
   }
 
+  override def diff(other: VertexRDD[VD]): VertexRDD[VD] = {
+    val newPartitionsRDD = partitionsRDD.zipPartitions(
+      VertexRDD(other).partitionsRDD, preservesPartitioning = true
+    ) { (thisIter, otherIter) =>
+      val thisPart = thisIter.next()
+      val otherPart = otherIter.next()
+      Iterator(thisPart.diff(otherPart))
+    }
+    this.withPartitionsRDD(newPartitionsRDD)
+  }
+
   override def leftZipJoin[VD2: ClassTag, VD3: ClassTag]
       (other: VertexRDD[VD2])(f: (VertexId, VD, Option[VD2]) => VD3): VertexRDD[VD3] = {
     val newPartitionsRDD = partitionsRDD.zipPartitions(