added lineage tracking code

graph/src/main/scala/org/apache/spark/graph/impl/GraphImpl.scala

@@ -109,7 +109,7 @@ class GraphImpl[VD: ClassManifest, ED: ClassManifest] protected (
 
   /** Return a RDD of edges. */
   @transient override val edges: RDD[Edge[ED]] = {
-    eTable.mapPartitions { iter => iter.next()._2.iterator }
+    eTable.mapPartitions( iter => iter.next()._2.iterator , true )
   }
 
 
@@ -142,6 +142,64 @@ class GraphImpl[VD: ClassManifest, ED: ClassManifest] protected (
   }
 
 
+  /**
+   * Display the lineage information for this graph.
+   */
+  def printLineage() = {
+
+    def traverseLineage(rdd: RDD[_], indent: String = "", visited: Map[Int, String] = Map.empty[Int, String]) {
+      if(visited.contains(rdd.id)) {
+        println(indent + visited(rdd.id))
+        println(indent)
+      } else {
+        val locs = rdd.partitions.map( p => rdd.preferredLocations(p) )
+        val cacheLevel = rdd.getStorageLevel
+        val name = rdd.id
+        val deps = rdd.dependencies
+        val partitioner = rdd.partitioner
+        val numparts = partitioner match { case Some(p) => p.numPartitions; case None => 0}
+        println(indent + name + ": " + cacheLevel.description + " (partitioner: " + partitioner + ", " + numparts +")")
+        println(indent + " |--->  Deps:    " + deps.map(d => (d, d.rdd.id) ).toString)
+        println(indent + " |--->  PrefLoc: " + locs.map(x=> x.toString).mkString(", "))
+        deps.foreach(d => traverseLineage(d.rdd, indent + " | ", visited))        
+      }
+    }
+ 
+    println("eTable ------------------------------------------")
+    traverseLineage(eTable, "  ")
+    var visited = Map(eTable.id -> "eTable")
+
+    println("\n\nvTable.index ------------------------------------")
+    traverseLineage(vTable.index.rdd, "  ", visited)
+    visited += (vTable.index.rdd.id -> "vTable.index")
+
+    println("\n\nvTable.values ------------------------------------")
+    traverseLineage(vTable.valuesRDD, "  ", visited)
+    visited += (vTable.valuesRDD.id -> "vTable.values")
+
+    println("\n\nvTable ------------------------------------------")
+    traverseLineage(vTable, "  ", visited)
+    visited += (vTable.id -> "vTable")
+
+    println("\n\nvid2pid -----------------------------------------")
+    traverseLineage(vid2pid, "  ", visited)
+    visited += (vid2pid.id -> "vid2pid")
+    visited += (vid2pid.valuesRDD.id -> "vid2pid.values")
+    
+    println("\n\nlocalVidMap -------------------------------------")
+    traverseLineage(localVidMap, "  ", visited)
+    visited += (localVidMap.id -> "localVidMap")
+    
+    println("\n\nvTableReplicatedValues --------------------------")
+    traverseLineage(vTableReplicatedValues, "  ", visited)
+    visited += (vTableReplicatedValues.id -> "vTableReplicatedValues")
+
+    println("\n\ntriplets ----------------------------------------")
+    traverseLineage(triplets, "  ", visited)
+    println(visited)
+  } // end of print lineage
+
+
   override def reverse: Graph[VD, ED] = {
     val newEtable = eTable.mapPartitions( _.map{ case (pid, epart) => (pid, epart.reverse) }, 
       preservesPartitioning = true)
@@ -342,16 +400,6 @@ class GraphImpl[VD: ClassManifest, ED: ClassManifest] protected (
 
 
 
-
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-
 object GraphImpl {
 
   def apply[VD: ClassManifest, ED: ClassManifest](