SPARK-1757 Failing test for saving null primitives with .saveAsParquetFile()

https://issues.apache.org/jira/browse/SPARK-1757

The first test succeeds, but the second test fails with exception:

```
[info] - save and load case class RDD with Nones as parquet *** FAILED *** (14 milliseconds)
[info]   java.lang.RuntimeException: Unsupported datatype StructType(List())
[info]   at scala.sys.package$.error(package.scala:27)
[info]   at org.apache.spark.sql.parquet.ParquetTypesConverter$.fromDataType(ParquetRelation.scala:201)
[info]   at org.apache.spark.sql.parquet.ParquetTypesConverter$$anonfun$1.apply(ParquetRelation.scala:235)
[info]   at org.apache.spark.sql.parquet.ParquetTypesConverter$$anonfun$1.apply(ParquetRelation.scala:235)
[info]   at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
[info]   at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
[info]   at scala.collection.immutable.List.foreach(List.scala:318)
[info]   at scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
[info]   at scala.collection.AbstractTraversable.map(Traversable.scala:105)
[info]   at org.apache.spark.sql.parquet.ParquetTypesConverter$.convertFromAttributes(ParquetRelation.scala:234)
[info]   at org.apache.spark.sql.parquet.ParquetTypesConverter$.writeMetaData(ParquetRelation.scala:267)
[info]   at org.apache.spark.sql.parquet.ParquetRelation$.createEmpty(ParquetRelation.scala:143)
[info]   at org.apache.spark.sql.parquet.ParquetRelation$.create(ParquetRelation.scala:122)
[info]   at org.apache.spark.sql.execution.SparkStrategies$ParquetOperations$.apply(SparkStrategies.scala:139)
[info]   at org.apache.spark.sql.catalyst.planning.QueryPlanner$$anonfun$1.apply(QueryPlanner.scala:58)
[info]   at org.apache.spark.sql.catalyst.planning.QueryPlanner$$anonfun$1.apply(QueryPlanner.scala:58)
[info]   at scala.collection.Iterator$$anon$13.hasNext(Iterator.scala:371)
[info]   at org.apache.spark.sql.catalyst.planning.QueryPlanner.apply(QueryPlanner.scala:59)
[info]   at org.apache.spark.sql.SQLContext$QueryExecution.sparkPlan$lzycompute(SQLContext.scala:264)
[info]   at org.apache.spark.sql.SQLContext$QueryExecution.sparkPlan(SQLContext.scala:264)
[info]   at org.apache.spark.sql.SQLContext$QueryExecution.executedPlan$lzycompute(SQLContext.scala:265)
[info]   at org.apache.spark.sql.SQLContext$QueryExecution.executedPlan(SQLContext.scala:265)
[info]   at org.apache.spark.sql.SQLContext$QueryExecution.toRdd$lzycompute(SQLContext.scala:268)
[info]   at org.apache.spark.sql.SQLContext$QueryExecution.toRdd(SQLContext.scala:268)
[info]   at org.apache.spark.sql.SchemaRDDLike$class.saveAsParquetFile(SchemaRDDLike.scala:66)
[info]   at org.apache.spark.sql.SchemaRDD.saveAsParquetFile(SchemaRDD.scala:98)
```

Author: Andrew Ash <andrew@andrewash.com>
Author: Michael Armbrust <michael@databricks.com>

Closes #690 from ash211/rdd-parquet-save and squashes the following commits:

747a0b9 [Andrew Ash] Merge pull request #1 from marmbrus/pr/690
54bd00e [Michael Armbrust] Need to put Option first since Option <: Seq.
8f3f281 [Andrew Ash] SPARK-1757 Add failing test for saving SparkSQL Schemas with Option[?] fields as parquet

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala

@@ -41,6 +41,9 @@ object ScalaReflection {
 
   /** Returns a catalyst DataType for the given Scala Type using reflection. */
   def schemaFor(tpe: `Type`): DataType = tpe match {
+    case t if t <:< typeOf[Option[_]] =>
+      val TypeRef(_, _, Seq(optType)) = t
+      schemaFor(optType)
     case t if t <:< typeOf[Product] =>
       val params = t.member("<init>": TermName).asMethod.paramss
       StructType(
@@ -59,9 +62,6 @@ object ScalaReflection {
     case t if t <:< typeOf[String] => StringType
     case t if t <:< typeOf[Timestamp] => TimestampType
     case t if t <:< typeOf[BigDecimal] => DecimalType
-    case t if t <:< typeOf[Option[_]] =>
-      val TypeRef(_, _, Seq(optType)) = t
-      schemaFor(optType)
     case t if t <:< typeOf[java.lang.Integer] => IntegerType
     case t if t <:< typeOf[java.lang.Long] => LongType
     case t if t <:< typeOf[java.lang.Double] => DoubleType

sql/core/src/test/scala/org/apache/spark/sql/parquet/ParquetQuerySuite.scala

@@ -42,6 +42,20 @@ import org.apache.spark.sql.test.TestSQLContext._
 
 case class TestRDDEntry(key: Int, value: String)
 
+case class NullReflectData(
+    intField: java.lang.Integer,
+    longField: java.lang.Long,
+    floatField: java.lang.Float,
+    doubleField: java.lang.Double,
+    booleanField: java.lang.Boolean)
+
+case class OptionalReflectData(
+    intField: Option[Int],
+    longField: Option[Long],
+    floatField: Option[Float],
+    doubleField: Option[Double],
+    booleanField: Option[Boolean])
+
 class ParquetQuerySuite extends QueryTest with FunSuite with BeforeAndAfterAll {
   import TestData._
   TestData // Load test data tables.
@@ -195,5 +209,35 @@ class ParquetQuerySuite extends QueryTest with FunSuite with BeforeAndAfterAll {
     Utils.deleteRecursively(ParquetTestData.testDir)
     ParquetTestData.writeFile()
   }
+
+  test("save and load case class RDD with nulls as parquet") {
+    val data = NullReflectData(null, null, null, null, null)
+    val rdd = sparkContext.parallelize(data :: Nil)
+
+    val file = getTempFilePath("parquet")
+    val path = file.toString
+    rdd.saveAsParquetFile(path)
+    val readFile = parquetFile(path)
+
+    val rdd_saved = readFile.collect()
+    assert(rdd_saved(0) === Seq.fill(5)(null))
+    Utils.deleteRecursively(file)
+    assert(true)
+  }
+
+  test("save and load case class RDD with Nones as parquet") {
+    val data = OptionalReflectData(null, null, null, null, null)
+    val rdd = sparkContext.parallelize(data :: Nil)
+
+    val file = getTempFilePath("parquet")
+    val path = file.toString
+    rdd.saveAsParquetFile(path)
+    val readFile = parquetFile(path)
+
+    val rdd_saved = readFile.collect()
+    assert(rdd_saved(0) === Seq.fill(5)(null))
+    Utils.deleteRecursively(file)
+    assert(true)
+  }
 }