[SPARK-6591] [SQL] Python data source load options should auto convert common types into strings

JIRA: https://issues.apache.org/jira/browse/SPARK-6591

Author: Yijie Shen <henry.yijieshen@gmail.com>

Closes #7926 from yjshen/py_dsload_opt and squashes the following commits:

b207832 [Yijie Shen] fix style
efdf834 [Yijie Shen] resolve comment
7a8f6a2 [Yijie Shen] lowercase
822e769 [Yijie Shen] convert load opts to string

python/pyspark/sql/readwriter.py

@@ -24,6 +24,16 @@ from pyspark.sql.types import *
 __all__ = ["DataFrameReader", "DataFrameWriter"]
 
 
+def to_str(value):
+    """
+    A wrapper over str(), but convert bool values to lower case string
+    """
+    if isinstance(value, bool):
+        return str(value).lower()
+    else:
+        return str(value)
+
+
 class DataFrameReader(object):
     """
     Interface used to load a :class:`DataFrame` from external storage systems
@@ -77,7 +87,7 @@ class DataFrameReader(object):
     def option(self, key, value):
         """Adds an input option for the underlying data source.
         """
-        self._jreader = self._jreader.option(key, value)
+        self._jreader = self._jreader.option(key, to_str(value))
         return self
 
     @since(1.4)
@@ -85,7 +95,7 @@ class DataFrameReader(object):
         """Adds input options for the underlying data source.
         """
         for k in options:
-            self._jreader = self._jreader.option(k, options[k])
+            self._jreader = self._jreader.option(k, to_str(options[k]))
         return self
 
     @since(1.4)
@@ -97,7 +107,8 @@ class DataFrameReader(object):
         :param schema: optional :class:`StructType` for the input schema.
         :param options: all other string options
 
-        >>> df = sqlContext.read.load('python/test_support/sql/parquet_partitioned')
+        >>> df = sqlContext.read.load('python/test_support/sql/parquet_partitioned', opt1=True,
+        ...     opt2=1, opt3='str')
         >>> df.dtypes
         [('name', 'string'), ('year', 'int'), ('month', 'int'), ('day', 'int')]
         """