[SPARK-15261][SQL] Remove experimental tag from DataFrameReader/Writer

## What changes were proposed in this pull request?
This patch removes experimental tag from DataFrameReader and DataFrameWriter, and explicitly tags a few methods added for structured streaming as experimental.

## How was this patch tested?
N/A

Author: Reynold Xin <rxin@databricks.com>

Closes #13038 from rxin/SPARK-15261.

1 files changed, 9 insertions, 5 deletions

diff --git a/python/pyspark/sql/readwriter.py b/python/pyspark/sql/readwriter.py
index e2ee9db049..20250b431b 100644
--- a/python/pyspark/sql/readwriter.py
+++ b/python/pyspark/sql/readwriter.py
@@ -50,8 +50,6 @@ class DataFrameReader(object):
     (e.g. file systems, key-value stores, etc). Use :func:`SQLContext.read`
     to access this.
 
-    ::Note: Experimental
-
     .. versionadded:: 1.4
     """
 
@@ -143,6 +141,8 @@ class DataFrameReader(object):
     def stream(self, path=None, format=None, schema=None, **options):
         """Loads a data stream from a data source and returns it as a :class`DataFrame`.
 
+        .. note:: Experimental.
+
         :param path: optional string for file-system backed data sources.
         :param format: optional string for format of the data source. Default to 'parquet'.
         :param schema: optional :class:`StructType` for the input schema.
@@ -462,8 +462,6 @@ class DataFrameWriter(object):
     (e.g. file systems, key-value stores, etc). Use :func:`DataFrame.write`
     to access this.
 
-    ::Note: Experimental
-
     .. versionadded:: 1.4
     """
     def __init__(self, df):
@@ -540,7 +538,9 @@ class DataFrameWriter(object):
     def queryName(self, queryName):
         """Specifies the name of the :class:`ContinuousQuery` that can be started with
         :func:`startStream`. This name must be unique among all the currently active queries
-        in the associated SQLContext.
+        in the associated SQLContext
+
+        .. note:: Experimental.
 
         :param queryName: unique name for the query
 
@@ -557,6 +557,8 @@ class DataFrameWriter(object):
         """Set the trigger for the stream query. If this is not set it will run the query as fast
         as possible, which is equivalent to setting the trigger to ``processingTime='0 seconds'``.
 
+        .. note:: Experimental.
+
         :param processingTime: a processing time interval as a string, e.g. '5 seconds', '1 minute'.
 
         >>> # trigger the query for execution every 5 seconds
@@ -614,6 +616,8 @@ class DataFrameWriter(object):
         If ``format`` is not specified, the default data source configured by
         ``spark.sql.sources.default`` will be used.
 
+        .. note:: Experimental.
+
         :param path: the path in a Hadoop supported file system
         :param format: the format used to save