GitHub user superbobry opened a pull request:
https://github.com/apache/spark/pull/23008
[SPARK-22674][PYTHON] Removed the namedtuple pickling patch
## What changes were proposed in this pull request?
Prior to this PR PySpark patched ``collections.namedtuple`` to make
namedtuple instances serializable even if the namedtuple class has been
defined outside of ``globals()``, e.g.
def do_something():
Foo = namedtuple("Foo", ["foo"])
sc.parallelize(range(1)).map(lambda _: Foo(42))
The patch changed the pickled representation of the namedtuple instance
to include the structure of namedtuple class, and recreate the class on
each unpickling. This behaviour causes hard to diagnose failures both
in the user code with namedtuples, as well as third-party libraries
relying on them. See [1] and [2] for details.
[1]:
https://superbobry.github.io/pyspark-silently-breaks-your-namedtuples.html
[2]:
https://superbobry.github.io/tensorflowonspark-or-the-namedtuple-patch-strikes-again.html
The PR changes the default serializer to `CloudPickleSerializer` which
natively supports pickling namedtuples and does not require the aforementioned
patch. To the best of my knowledge, this is **not** a breaking change.
## How was this patch tested?
PySpark test suite.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/superbobry/spark no-hijack-namedtuple
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/23008.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #23008
----
commit 36ff69717c411e72f60c3006eb6a491c3d88862d
Author: Sergei Lebedev <superbobry@...>
Date: 2018-11-11T21:05:07Z
Removed namedtuple hack and made cloudpickle the default serializer
This is a followup of the discussion in #21157. See the PR and the
linked JIRA ticket for context and motivation.
commit 9a818797603f5804b32202d28474493c80966f58
Author: Sergei Lebedev <superbobry@...>
Date: 2018-11-11T22:11:02Z
Changed SerializationTestCase to use cloudpickle
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