[SQL] Tighten up visibility for JavaDoc.

I went through all the JavaDocs and tightened up visibility.

Author: Reynold Xin <rxin@databricks.com>

Closes #6526 from rxin/sql-1.4-visibility-for-docs and squashes the following commits:

bc37d1e [Reynold Xin] Tighten up visibility for JavaDoc.

3 files changed, 23 insertions, 5 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala b/sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala
index 516ba2ac23..c4ceb0c173 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala
@@ -40,22 +40,22 @@ private[sql] object GroupedData {
   /**
    * The Grouping Type
    */
-  trait GroupType
+  private[sql] trait GroupType
 
   /**
    * To indicate it's the GroupBy
    */
-  object GroupByType extends GroupType
+  private[sql] object GroupByType extends GroupType
 
   /**
    * To indicate it's the CUBE
    */
-  object CubeType extends GroupType
+  private[sql] object CubeType extends GroupType
 
   /**
    * To indicate it's the ROLLUP
    */
-  object RollupType extends GroupType
+  private[sql] object RollupType extends GroupType
 }
 
 /**
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/expressions/Window.scala b/sql/core/src/main/scala/org/apache/spark/sql/expressions/Window.scala
index d4003b2d9c..e9b60841fc 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/expressions/Window.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/expressions/Window.scala
@@ -79,3 +79,20 @@ object Window {
   }
 
 }
+
+/**
+ * :: Experimental ::
+ * Utility functions for defining window in DataFrames.
+ *
+ * {{{
+ *   // PARTITION BY country ORDER BY date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
+ *   Window.partitionBy("country").orderBy("date").rowsBetween(Long.MinValue, 0)
+ *
+ *   // PARTITION BY country ORDER BY date ROWS BETWEEN 3 PRECEDING AND 3 FOLLOWING
+ *   Window.partitionBy("country").orderBy("date").rowsBetween(-3, 3)
+ * }}}
+ *
+ * @since 1.4.0
+ */
+@Experimental
+class Window private()  // So we can see Window in JavaDoc.
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala b/sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala
index c06026e042..b1b997c030 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala
@@ -93,7 +93,7 @@ trait SchemaRelationProvider {
 }
 
 /**
- * ::DeveloperApi::
+ * ::Experimental::
  * Implemented by objects that produce relations for a specific kind of data source
  * with a given schema and partitioned columns.  When Spark SQL is given a DDL operation with a
  * USING clause specified (to specify the implemented [[HadoopFsRelationProvider]]), a user defined
@@ -115,6 +115,7 @@ trait SchemaRelationProvider {
  *
  * @since 1.4.0
  */
+@Experimental
 trait HadoopFsRelationProvider {
   /**
    * Returns a new base relation with the given parameters, a user defined schema, and a list of