Several minor updates.

Author: yhuai

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala

@@ -128,7 +128,7 @@ abstract class QueryPlan[PlanType <: TreeNode[PlanType]] extends TreeNode[PlanTy
   def schema: StructType = StructType.fromAttributes(output)
 
   /** Returns the output schema in the tree format. */
-  def schemaString: String = schema.structString
+  def schemaString: String = schema.treeString
 
   /** Prints out the schema in the tree format */
   def printSchema(): Unit = println(schemaString)

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

@@ -314,7 +314,7 @@ case class StructType(fields: Seq[StructField]) extends DataType {
   protected[sql] def toAttributes =
     fields.map(f => AttributeReference(f.name, f.dataType, f.nullable)())
 
-  def structString: String = {
+  def treeString: String = {
     val builder = new StringBuilder
     builder.append("root\n")
     val prefix = " |"
@@ -323,7 +323,7 @@ case class StructType(fields: Seq[StructField]) extends DataType {
     builder.toString()
   }
 
-  def printStruct(): Unit = println(structString)
+  def printTreeString(): Unit = println(treeString)
 
   private[sql] def buildFormattedString(prefix: String, builder: StringBuilder): Unit = {
     fields.foreach(field => field.buildFormattedString(prefix, builder))
@@ -335,6 +335,7 @@ case class StructType(fields: Seq[StructField]) extends DataType {
 case class MapType(keyType: DataType, valueType: DataType) extends DataType {
   private[sql] def buildFormattedString(prefix: String, builder: StringBuilder): Unit = {
     builder.append(s"${prefix}-- key: ${keyType.simpleString}\n")
+    builder.append(s"${prefix}-- value: ${valueType.simpleString}\n")
     DataType.buildFormattedString(keyType, s"$prefix    |", builder)
     DataType.buildFormattedString(valueType, s"$prefix    |", builder)
   }

sql/core/src/main/scala/org/apache/spark/sql/SchemaRDD.scala

@@ -382,7 +382,7 @@ class SchemaRDD(
         case (obj, (attrName, dataType)) =>
           dataType match {
             case struct: StructType => map.put(attrName, rowToMap(obj.asInstanceOf[Row], struct))
-            case array @ ArrayType(struct: StructType) =>
+            case array @ ArrayType(struct: StructType, _) =>
               val arrayValues = obj match {
                 case seq: Seq[Any] =>
                   seq.map(element => rowToMap(element.asInstanceOf[Row], struct)).asJava

sql/core/src/main/scala/org/apache/spark/sql/SchemaRDDLike.scala

@@ -133,7 +133,7 @@ private[sql] trait SchemaRDDLike {
    *
    * @group schema
    */
-  def schemaString: String = schema.structString
+  def schemaString: String = schema.treeString
 
   /** Prints out the schema.
    *

sql/core/src/main/scala/org/apache/spark/sql/package.scala

@@ -24,7 +24,9 @@ import org.apache.spark.annotation.DeveloperApi
  *
  *  @groupname dataType Data types
  *  @groupdesc Spark SQL data types.
- *  @groupprio dataType -2
+ *  @groupprio dataType -3
+ *  @groupname field Field
+ *  @groupprio field -2
  *  @groupname row Row
  *  @groupprio row -1
  */
@@ -377,7 +379,7 @@ package object sql {
    * `dataType` specifies the data type of a `StructField`.
    * The field of `nullable` specifies if values of a `StructField` can contain `null` values.
    *
-   * @group dataType
+   * @group field
    */
   @DeveloperApi
   type StructField = catalyst.types.StructField