Scaladoc.

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

@@ -21,10 +21,16 @@ import scala.language.dynamics
 
 import org.apache.spark.sql.catalyst.types.DataType
 
+/**
+ * The data type representing [[DynamicRow]] values.
+ */
 case object DynamicType extends DataType {
   def simpleString: String = "dynamic"
 }
 
+/**
+ * Wrap a [[Row]] as a [[DynamicRow]].
+ */
 case class WrapDynamic(children: Seq[Attribute]) extends Expression {
   type EvaluatedType = DynamicRow
 
@@ -39,6 +45,11 @@ case class WrapDynamic(children: Seq[Attribute]) extends Expression {
   }
 }
 
+/**
+ * DynamicRows use scala's Dynamic trait to emulate an ORM of in a dynamically typed language.
+ * Since the type of the column is not known at compile time, all attributes are converted to
+ * strings before being passed to the function.
+ */
 class DynamicRow(val schema: Seq[Attribute], values: Array[Any])
   extends GenericRow(values) with Dynamic {
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/dataTypes.scala

@@ -266,6 +266,13 @@ object ArrayType {
   def apply(elementType: DataType): ArrayType = ArrayType(elementType, false)
 }
 
+/**
+ * The data type for collections of multiple values.
+ * Internally these are represented as columns that contain a ``scala.collection.Seq``.
+ *
+ * @param elementType The data type of values.
+ * @param containsNull Indicates if values have `null` values
+ */
 case class ArrayType(elementType: DataType, containsNull: Boolean) extends DataType {
   private[sql] def buildFormattedString(prefix: String, builder: StringBuilder): Unit = {
     builder.append(
@@ -276,6 +283,12 @@ case class ArrayType(elementType: DataType, containsNull: Boolean) extends DataT
   def simpleString: String = "array"
 }
 
+/**
+ * A field inside a StructType.
+ * @param name The name of this field.
+ * @param dataType The data type of this field.
+ * @param nullable Indicates if values of this field can be `null` values.
+ */
 case class StructField(name: String, dataType: DataType, nullable: Boolean) {
 
   private[sql] def buildFormattedString(prefix: String, builder: StringBuilder): Unit = {
@@ -353,6 +366,12 @@ object MapType {
     MapType(keyType: DataType, valueType: DataType, true)
 }
 
+/**
+ * The data type for Maps. Keys in a map are not allowed to have `null` values.
+ * @param keyType The data type of map keys.
+ * @param valueType The data type of map values.
+ * @param valueContainsNull Indicates if map values have `null` values.
+ */
 case class MapType(
     keyType: DataType,
     valueType: DataType,