spark-instrumented-optimizer/python/pyspark/broadcast.py

#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
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# distributed under the License is distributed on an "AS IS" BASIS,
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#

"""
>>> from pyspark.context import SparkContext
>>> sc = SparkContext('local', 'test')
>>> b = sc.broadcast([1, 2, 3, 4, 5])
>>> b.value
[1, 2, 3, 4, 5]

>>> from pyspark.broadcast import _broadcastRegistry
>>> _broadcastRegistry[b.bid] = b
>>> from cPickle import dumps, loads
>>> loads(dumps(b)).value
[1, 2, 3, 4, 5]

>>> sc.parallelize([0, 0]).flatMap(lambda x: b.value).collect()
[1, 2, 3, 4, 5, 1, 2, 3, 4, 5]

>>> large_broadcast = sc.broadcast(list(range(10000)))
"""
# Holds broadcasted data received from Java, keyed by its id.
_broadcastRegistry = {}


def _from_id(bid):
    from pyspark.broadcast import _broadcastRegistry
    if bid not in _broadcastRegistry:
        raise Exception("Broadcast variable '%s' not loaded!" % bid)
    return _broadcastRegistry[bid]


class Broadcast(object):
    """
    A broadcast variable created with
    L{SparkContext.broadcast()<pyspark.context.SparkContext.broadcast>}.
    Access its value through C{.value}.
    """

    def __init__(self, bid, value, java_broadcast=None, pickle_registry=None):
        """
        Should not be called directly by users -- use
        L{SparkContext.broadcast()<pyspark.context.SparkContext.broadcast>}
        instead.
        """
        self.value = value
        self.bid = bid
        self._jbroadcast = java_broadcast
        self._pickle_registry = pickle_registry

    def __reduce__(self):
        self._pickle_registry.add(self)
        return (_from_id, (self.bid, ))