[SPARK-12439][SQL] Fix toCatalystArray and MapObjects

JIRA: https://issues.apache.org/jira/browse/SPARK-12439

In toCatalystArray, we should look at the data type returned by dataTypeFor instead of silentSchemaFor, to determine if the element is native type. An obvious problem is when the element is Option[Int] class, catalsilentSchemaFor will return Int, then we will wrongly recognize the element is native type.

There is another problem when using Option as array element. When we encode data like Seq(Some(1), Some(2), None) with encoder, we will use MapObjects to construct an array for it later. But in MapObjects, we don't check if the return value of lambdaFunction is null or not. That causes a bug that the decoded data for Seq(Some(1), Some(2), None) would be Seq(1, 2, -1), instead of Seq(1, 2, null).

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #10391 from viirya/fix-catalystarray.

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

@@ -405,7 +405,7 @@ object ScalaReflection extends ScalaReflection {
     def toCatalystArray(input: Expression, elementType: `Type`): Expression = {
       val externalDataType = dataTypeFor(elementType)
       val Schema(catalystType, nullable) = silentSchemaFor(elementType)
-      if (isNativeType(catalystType)) {
+      if (isNativeType(externalDataType)) {
         NewInstance(
           classOf[GenericArrayData],
           input :: Nil,

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/RowEncoder.scala

@@ -35,7 +35,8 @@ object RowEncoder {
   def apply(schema: StructType): ExpressionEncoder[Row] = {
     val cls = classOf[Row]
     val inputObject = BoundReference(0, ObjectType(cls), nullable = true)
-    val extractExpressions = extractorsFor(inputObject, schema)
+    // We use an If expression to wrap extractorsFor result of StructType
+    val extractExpressions = extractorsFor(inputObject, schema).asInstanceOf[If].falseValue
     val constructExpression = constructorFor(schema)
     new ExpressionEncoder[Row](
       schema,
@@ -129,7 +130,9 @@ object RowEncoder {
             Invoke(inputObject, method, externalDataTypeFor(f.dataType), Literal(i) :: Nil),
             f.dataType))
       }
-      CreateStruct(convertedFields)
+      If(IsNull(inputObject),
+        Literal.create(null, inputType),
+        CreateStruct(convertedFields))
   }
 
   private def externalDataTypeFor(dt: DataType): DataType = dt match {
@@ -220,6 +223,8 @@ object RowEncoder {
           Literal.create(null, externalDataTypeFor(f.dataType)),
           constructorFor(GetStructField(input, i)))
       }
-      CreateExternalRow(convertedFields)
+      If(IsNull(input),
+        Literal.create(null, externalDataTypeFor(input.dataType)),
+        CreateExternalRow(convertedFields))
   }
 }

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects.scala

@@ -456,10 +456,10 @@ case class MapObjects(
             ($elementJavaType)${genInputData.value}${itemAccessor(loopIndex)};
           $loopNullCheck
 
-          if (${loopVar.isNull}) {
+          ${genFunction.code}
+          if (${genFunction.isNull}) {
             $convertedArray[$loopIndex] = null;
           } else {
-            ${genFunction.code}
             $convertedArray[$loopIndex] = ${genFunction.value};
           }
 

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala

@@ -160,6 +160,9 @@ class ExpressionEncoderSuite extends SparkFunSuite {
 
   productTest(OptionalData(None, None, None, None, None, None, None, None))
 
+  encodeDecodeTest(Seq(Some(1), None), "Option in array")
+  encodeDecodeTest(Map(1 -> Some(10L), 2 -> Some(20L), 3 -> None), "Option in map")
+
   productTest(BoxedData(1, 1L, 1.0, 1.0f, 1.toShort, 1.toByte, true))
 
   productTest(BoxedData(null, null, null, null, null, null, null))