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From "Stuart (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SPARK-21985) PySpark PairDeserializer is broken for double-zipped RDDs
Date Tue, 12 Sep 2017 16:07:00 GMT

     [ https://issues.apache.org/jira/browse/SPARK-21985?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Stuart updated SPARK-21985:
---------------------------
    Description: 
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:

{{
>>> a_bc.collect()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/magnetic/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 "/magnetic/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()
}}

As you can see, the error seems to be caused by [a check in the PairDeserializer class|https://github.com/apache/spark/blob/master/python/pyspark/serializers.py#L346-L348]:

{{
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)))
}}

If that check is removed, then the example above works without error.  Can the check simply
be removed?

  was:
PySpark fails to deserialize double-zipped RDDs.  For example, the following example used
to work in Spark 2.0.2:


{code:python}
>>> 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:

{{
>>> a_bc.collect()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/magnetic/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 "/magnetic/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()
}}

As you can see, the error seems to be caused by [a check in the PairDeserializer class|https://github.com/apache/spark/blob/master/python/pyspark/serializers.py#L346-L348]:

{{
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)))
}}

If that check is removed, then the example above works without error.  Can the check simply
be removed?


> 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
>              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:
> {{
> >>> a_bc.collect()
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/magnetic/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 "/magnetic/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()
> }}
> As you can see, the error seems to be caused by [a check in the PairDeserializer class|https://github.com/apache/spark/blob/master/python/pyspark/serializers.py#L346-L348]:
> {{
> 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)))
> }}
> If that check is removed, then the example above works without error.  Can the check
simply be removed?



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