SPARK-1822: Some minor cleanup work on SchemaRDD.count()

Minor cleanup following #841.

Author: Reynold Xin <rxin@apache.org>

Closes #868 from rxin/schema-count and squashes the following commits:

5442651 [Reynold Xin] SPARK-1822: Some minor cleanup work on SchemaRDD.count()

1 files changed, 4 insertions, 1 deletions

diff --git a/python/pyspark/sql.py b/python/pyspark/sql.py
index f2001afae4..fa4b9c7b68 100644
--- a/python/pyspark/sql.py
+++ b/python/pyspark/sql.py
@@ -323,7 +323,10 @@ class SchemaRDD(RDD):
 
     def count(self):
         """
-        Return the number of elements in this RDD.
+        Return the number of elements in this RDD. Unlike the base RDD
+        implementation of count, this implementation leverages the query
+        optimizer to compute the count on the SchemaRDD, which supports
+        features such as filter pushdown.
 
         >>> srdd = sqlCtx.inferSchema(rdd)
         >>> srdd.count()