ShippableVertexPartition.initFrom: Don't run mergeFunc on default values

Author: ankurdave

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

@@ -406,8 +406,6 @@ object VertexRDD {
    * @param edges the [[EdgeRDD]] that these vertices may be joined with
    * @param defaultVal the vertex attribute to use when creating missing vertices
    * @param mergeFunc the commutative, associative duplicate vertex attribute merge function
-   * note that all vertices with default value created upon construction in VertexPartition
-   * so it will appear as b in (a, b) pair for mergeFunc.
    */
   def apply[VD: ClassTag](
       vertices: RDD[(VertexId, VD)], edges: EdgeRDD[_, _], defaultVal: VD, mergeFunc: (VD, VD) => VD

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

@@ -44,7 +44,7 @@ object ShippableVertexPartition {
    */
   def apply[VD: ClassTag](
       iter: Iterator[(VertexId, VD)], routingTable: RoutingTablePartition, defaultVal: VD)
-    : ShippableVertexPartition[VD] = 
+    : ShippableVertexPartition[VD] =
     apply(iter, routingTable, defaultVal, (a, b) => a)
 
   /**
@@ -54,12 +54,18 @@ object ShippableVertexPartition {
    */
   def apply[VD: ClassTag](
       iter: Iterator[(VertexId, VD)], routingTable: RoutingTablePartition, defaultVal: VD,
-      mergeFunc: (VD, VD) => VD
-  )
-    : ShippableVertexPartition[VD] = {
-    val fullIter = iter ++ routingTable.iterator.map(vid => (vid, defaultVal))
-    val (index, values, mask) = VertexPartitionBase.initFrom(fullIter, mergeFunc)
-    new ShippableVertexPartition(index, values, mask, routingTable)
+      mergeFunc: (VD, VD) => VD): ShippableVertexPartition[VD] = {
+    val map = new GraphXPrimitiveKeyOpenHashMap[VertexId, VD]
+    // Merge the given vertices using mergeFunc
+    iter.foreach { pair =>
+      map.setMerge(pair._1, pair._2, mergeFunc)
+    }
+    // Fill in missing vertices mentioned in the routing table
+    routingTable.iterator.foreach { vid =>
+      map.changeValue(vid, defaultVal, identity)
+    }
+
+    new ShippableVertexPartition(map.keySet, map._values, map.keySet.getBitSet, routingTable)
   }
 
   import scala.language.implicitConversions