[SPARK-2088] fix NPE in toString

After deserialization, the transient field creationSiteInfo does not get backfilled with the default value, but the toString method, which is invoked by the serializer, expects the field to always be non-null. An NPE is thrown when toString is called by the serializer when creationSiteInfo is null.

Author: Doris Xin <doris.s.xin@gmail.com>

Closes #1028 from dorx/toStringNPE and squashes the following commits:

f20021e [Doris Xin] unit test for toString after desrialization
6f0a586 [Doris Xin] Merge branch 'master' into toStringNPE
f47fecf [Doris Xin] Merge branch 'master' into toStringNPE
76199c6 [Doris Xin] [SPARK-2088] fix NPE in toString

2 files changed, 9 insertions, 2 deletions

diff --git a/core/src/main/scala/org/apache/spark/rdd/RDD.scala b/core/src/main/scala/org/apache/spark/rdd/RDD.scala
index 54bdc3e7cb..b6fc4b13ad 100644
--- a/core/src/main/scala/org/apache/spark/rdd/RDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/RDD.scala
@@ -1180,7 +1180,7 @@ abstract class RDD[T: ClassTag](
 
   /** User code that created this RDD (e.g. `textFile`, `parallelize`). */
   @transient private[spark] val creationSiteInfo = Utils.getCallSiteInfo
-  private[spark] def getCreationSite: String = creationSiteInfo.toString
+  private[spark] def getCreationSite: String = Option(creationSiteInfo).getOrElse("").toString
 
   private[spark] def elementClassTag: ClassTag[T] = classTag[T]
 
diff --git a/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala b/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
index 55af1666df..2e2ccc5a18 100644
--- a/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
+++ b/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
@@ -24,7 +24,7 @@ import org.scalatest.FunSuite
 
 import org.apache.spark._
 import org.apache.spark.SparkContext._
-import org.apache.spark.rdd._
+import org.apache.spark.util.Utils
 
 class RDDSuite extends FunSuite with SharedSparkContext {
 
@@ -66,6 +66,13 @@ class RDDSuite extends FunSuite with SharedSparkContext {
     }
   }
 
+  test("serialization") {
+    val empty = new EmptyRDD[Int](sc)
+    val serial = Utils.serialize(empty)
+    val deserial: EmptyRDD[Int] = Utils.deserialize(serial)
+    assert(!deserial.toString().isEmpty())
+  }
+
   test("countApproxDistinct") {
 
     def error(est: Long, size: Long) = math.abs(est - size) / size.toDouble