[SPARK-4841] fix zip with textFile()

UTF8Deserializer can not be used in BatchedSerializer, so always use PickleSerializer() when change batchSize in zip().

Also, if two RDD have the same batch size already, they did not need re-serialize any more.

Author: Davies Liu <davies@databricks.com>

Closes #3706 from davies/fix_4841 and squashes the following commits:

20ce3a3 [Davies Liu] fix bug in _reserialize()
e3ebf7c [Davies Liu] add comment
379d2c8 [Davies Liu] fix zip with textFile()

1 files changed, 9 insertions, 0 deletions

diff --git a/python/pyspark/tests.py b/python/pyspark/tests.py
index 32645778c2..bca52a7ce6 100644
--- a/python/pyspark/tests.py
+++ b/python/pyspark/tests.py
@@ -533,6 +533,15 @@ class RDDTests(ReusedPySparkTestCase):
         a = a._reserialize(BatchedSerializer(PickleSerializer(), 2))
         b = b._reserialize(MarshalSerializer())
         self.assertEqual(a.zip(b).collect(), [(0, 100), (1, 101), (2, 102), (3, 103), (4, 104)])
+        # regression test for SPARK-4841
+        path = os.path.join(SPARK_HOME, "python/test_support/hello.txt")
+        t = self.sc.textFile(path)
+        cnt = t.count()
+        self.assertEqual(cnt, t.zip(t).count())
+        rdd = t.map(str)
+        self.assertEqual(cnt, t.zip(rdd).count())
+        # regression test for bug in _reserializer()
+        self.assertEqual(cnt, t.zip(rdd).count())
 
     def test_zip_with_different_number_of_items(self):
         a = self.sc.parallelize(range(5), 2)