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https://issues.apache.org/jira/browse/SPARK-21985?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-21985:
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Assignee: Apache Spark
> PySpark PairDeserializer is broken for double-zipped RDDs
> ---------------------------------------------------------
>
> Key: SPARK-21985
> URL: https://issues.apache.org/jira/browse/SPARK-21985
> Project: Spark
> Issue Type: Bug
> Components: PySpark
> Affects Versions: 2.1.0, 2.1.1, 2.2.0
> Reporter: Stuart Berg
> Assignee: Apache Spark
> Labels: bug
>
> PySpark fails to deserialize double-zipped RDDs. For example, the following
> example used to work in Spark 2.0.2:
> {code:}
> >>> a = sc.parallelize('aaa')
> >>> b = sc.parallelize('bbb')
> >>> c = sc.parallelize('ccc')
> >>> a_bc = a.zip( b.zip(c) )
> >>> a_bc.collect()
> [('a', ('b', 'c')), ('a', ('b', 'c')), ('a', ('b', 'c'))]
> {code}
> But in Spark >=2.1.0, it fails (regardless of Python 2 vs 3):
> {code:}
> >>> a_bc.collect()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "/workspace/spark-2.2.0-bin-hadoop2.7/python/pyspark/rdd.py", line
> 810, in collect
> return list(_load_from_socket(port, self._jrdd_deserializer))
> File "/workspace/spark-2.2.0-bin-hadoop2.7/python/pyspark/serializers.py",
> line 329, in _load_stream_without_unbatching
> if len(key_batch) != len(val_batch):
> TypeError: object of type 'itertools.izip' has no len()
> {code}
> As you can see, the error seems to be caused by [a check in the
> PairDeserializer
> class|https://github.com/apache/spark/blob/d03aebbe6508ba441dc87f9546f27aeb27553d77/python/pyspark/serializers.py#L346-L348]:
> {code:}
> if len(key_batch) != len(val_batch):
> raise ValueError("Can not deserialize PairRDD with different number of
> items"
> " in batches: (%d, %d)" % (len(key_batch),
> len(val_batch)))
> {code}
> If that check is removed, then the example above works without error. Can
> the check simply be removed?
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