[SPARK-3971] [MLLib] [PySpark] hotfix: Customized pickler should work in cluster mode

Customized pickler should be registered before unpickling, but in executor, there is no way to register the picklers before run the tasks.

So, we need to register the picklers in the tasks itself, duplicate the javaToPython() and pythonToJava() in MLlib, call SerDe.initialize() before pickling or unpickling.

Author: Davies Liu <davies.liu@gmail.com>

Closes #2830 from davies/fix_pickle and squashes the following commits:

0c85fb9 [Davies Liu] revert the privacy change
6b94e15 [Davies Liu] use JavaConverters instead of JavaConversions
0f02050 [Davies Liu] hotfix: Customized pickler does not work in cluster

1 files changed, 4 insertions, 3 deletions

diff --git a/python/pyspark/mllib/stat.py b/python/pyspark/mllib/stat.py
index b9de0909a6..a6019dadf7 100644
--- a/python/pyspark/mllib/stat.py
+++ b/python/pyspark/mllib/stat.py
@@ -22,6 +22,7 @@ Python package for statistical functions in MLlib.
 from functools import wraps
 
 from pyspark import PickleSerializer
+from pyspark.mllib.linalg import _to_java_object_rdd
 
 
 __all__ = ['MultivariateStatisticalSummary', 'Statistics']
@@ -106,7 +107,7 @@ class Statistics(object):
         array([ 2.,  0.,  0., -2.])
         """
         sc = rdd.ctx
-        jrdd = rdd._to_java_object_rdd()
+        jrdd = _to_java_object_rdd(rdd)
         cStats = sc._jvm.PythonMLLibAPI().colStats(jrdd)
         return MultivariateStatisticalSummary(sc, cStats)
 
@@ -162,14 +163,14 @@ class Statistics(object):
         if type(y) == str:
             raise TypeError("Use 'method=' to specify method name.")
 
-        jx = x._to_java_object_rdd()
+        jx = _to_java_object_rdd(x)
         if not y:
             resultMat = sc._jvm.PythonMLLibAPI().corr(jx, method)
             bytes = sc._jvm.SerDe.dumps(resultMat)
             ser = PickleSerializer()
             return ser.loads(str(bytes)).toArray()
         else:
-            jy = y._to_java_object_rdd()
+            jy = _to_java_object_rdd(y)
             return sc._jvm.PythonMLLibAPI().corr(jx, jy, method)