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[SPARK-8373][PySpark]Add emptyRDD to pyspark and fix the issue when calling sum on an empty RDD #6826

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zsxwing wants to merge 2 commits into from
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[SPARK-8373][PySpark]Add emptyRDD to pyspark and fix the issue when calling sum on an empty RDD #6826

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Add emptyRDD to pyspark and fix the issue when calling sum on an empt…
zsxwing Jun 15, 2015
b36993f
Update the return type to JavaRDD[T]
zsxwing Jun 15, 2015
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5 changes: 5 additions & 0 deletions core/src/main/scala/org/apache/spark/api/python/PythonRDD.scala
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Expand Up @@ -425,6 +425,11 @@ private[spark] object PythonRDD extends Logging {
iter.foreach(write)
}

/** Create an RDD that has no partitions or elements. */
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@srowen srowen Jun 15, 2015

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emptyRDD[T] should produce an RDD of T, not byte arrays right?

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@zsxwing zsxwing Jun 15, 2015

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T in the return type is not used. Actually, it can be an arbitrary type.

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@zsxwing zsxwing Jun 15, 2015

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I will update it to T

def emptyRDD[T](sc: JavaSparkContext): JavaRDD[Array[Byte]] = {
sc.emptyRDD[Array[Byte]]
}

/**
* Create an RDD from a path using [[org.apache.hadoop.mapred.SequenceFileInputFormat]],
* key and value class.
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6 changes: 6 additions & 0 deletions python/pyspark/context.py
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Expand Up @@ -324,6 +324,12 @@ def stop(self):
with SparkContext._lock:
SparkContext._active_spark_context = None

def emptyRDD(self):
"""
Create an RDD that has no partitions or elements.
"""
return RDD(self._jsc.emptyRDD(), self, NoOpSerializer())

def range(self, start, end=None, step=1, numSlices=None):
"""
Create a new RDD of int containing elements from `start` to `end`
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2 changes: 1 addition & 1 deletion python/pyspark/rdd.py
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Expand Up @@ -960,7 +960,7 @@ def sum(self):
>>> sc.parallelize([1.0, 2.0, 3.0]).sum()
6.0
"""
return self.mapPartitions(lambda x: [sum(x)]).reduce(operator.add)
return self.mapPartitions(lambda x: [sum(x)]).fold(0, operator.add)

def count(self):
"""
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8 changes: 8 additions & 0 deletions python/pyspark/tests.py
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Expand Up @@ -458,6 +458,14 @@ def test_id(self):
self.assertEqual(id + 1, id2)
self.assertEqual(id2, rdd2.id())

def test_empty_rdd(self):
rdd = self.sc.emptyRDD()
self.assertTrue(rdd.isEmpty())

def test_sum(self):
self.assertEqual(0, self.sc.emptyRDD().sum())
self.assertEqual(6, self.sc.parallelize([1, 2, 3]).sum())

def test_save_as_textfile_with_unicode(self):
# Regression test for SPARK-970
x = u"\u00A1Hola, mundo!"
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