Simpler countByValue using collections' Counter

Author: kamalbanga

python/pyspark/rdd.py

@@ -28,7 +28,7 @@
 from subprocess import Popen, PIPE
 from tempfile import NamedTemporaryFile
 from threading import Thread
-from collections import defaultdict
+from collections import defaultdict, Counter
 from itertools import chain
 from functools import reduce
 from math import sqrt, log, isinf, isnan, pow, ceil
@@ -1321,16 +1321,9 @@ def countByValue(self):
         [(1, 2), (2, 3)]
         """
         def countPartition(iterator):
-            counts = defaultdict(int)
-            for obj in iterator:
-                counts[obj] += 1
-            yield counts
+            yield Counter(iterator)
 
-        def mergeMaps(m1, m2):
-            for k, v in m2.items():
-                m1[k] += v
-            return m1
-        return self.mapPartitions(countPartition).reduce(mergeMaps)
+        return self.mapPartitions(countPartition).reduce(operator.add)
 
     def top(self, num, key=None):
         """