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SPARK-7836 and SPARK-7822: Python API of window functions
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Davies Liu
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# | ||
# 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 | ||
# | ||
# Unless required by applicable law or agreed to in writing, software | ||
# distributed under the License is distributed on an "AS IS" BASIS, | ||
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
# See the License for the specific language governing permissions and | ||
# limitations under the License. | ||
# | ||
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import sys | ||
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from pyspark import SparkContext | ||
from pyspark.sql import since | ||
from pyspark.sql.column import _to_seq, _to_java_column | ||
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__all__ = ["Window", "WindowSpec"] | ||
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def _to_java_cols(cols): | ||
sc = SparkContext._active_spark_context | ||
return _to_seq(sc, cols, _to_java_column) | ||
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class Window(object): | ||
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""" | ||
Utility functions for defining window in DataFrames. | ||
For example: | ||
PARTITION BY country ORDER BY date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW | ||
>>> window = Window.partitionBy("country").orderBy("date").rowsBetween(-sys.maxint, 0) | ||
PARTITION BY country ORDER BY date RANGE BETWEEN 3 PRECEDING AND 3 FOLLOWING | ||
>>> window = Window.orderBy("date").partitionBy("country").rangeBetween(-3, 3) | ||
.. versionadded:: 1.4 | ||
""" | ||
@staticmethod | ||
@since(1.4) | ||
def partitionBy(*cols): | ||
""" | ||
Creates a [[WindowSpec]] with the partitioning defined. | ||
""" | ||
sc = SparkContext._active_spark_context | ||
jspec = sc._jvm.org.apache.spark.sql.expressions.Window.partitionBy(_to_java_cols(cols)) | ||
return WindowSpec(jspec) | ||
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@staticmethod | ||
@since(1.4) | ||
def orderBy(*cols): | ||
""" | ||
Creates a [[WindowSpec]] with the partitioning defined. | ||
""" | ||
sc = SparkContext._active_spark_context | ||
jspec = sc._jvm.org.apache.spark.sql.expressions.Window.partitionBy(_to_java_cols(cols)) | ||
return WindowSpec(jspec) | ||
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class WindowSpec(object): | ||
""" | ||
A window specification that defines the partitioning, ordering, | ||
and frame boundaries. | ||
Use the static methods in :class:`Window` to create a :class:`WindowSpec`. | ||
.. versionadded:: 1.4 | ||
""" | ||
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JAVA_MAX_LONG = (1 << 63) - 1 | ||
JAVA_MIN_LONG = - (1 << 63) | ||
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def __init__(self, jspec): | ||
self._jspec = jspec | ||
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@since(1.4) | ||
def partitionBy(self, *cols): | ||
""" | ||
Defines the partitioning columns in a [[WindowSpec]]. | ||
:param cols: names of columns or expressions | ||
""" | ||
return WindowSpec(self._jspec.partitionBy(_to_java_cols(cols))) | ||
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@since(1.4) | ||
def orderBy(self, *cols): | ||
""" | ||
Defines the ordering columns in a [[WindowSpec]]. | ||
:param cols: names of columns or expressions | ||
""" | ||
return WindowSpec(self._jspec.orderBy(_to_java_cols(cols))) | ||
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@since(1.4) | ||
def rowsBetween(self, start=-sys.maxint, end=0): | ||
""" | ||
Defines the frame boundaries, from `start` (inclusive) to `end` (inclusive). | ||
Both `start` and `end` are relative positions from the current row. | ||
For example, "0" means "current row", while "-1" means the row before | ||
the current row, and "5" means the fifth row after the current row. | ||
:param start: boundary start, inclusive. | ||
The frame is unbounded if this is -sys.maxint(or lower). | ||
:param end: boundary end, inclusive. | ||
The frame is unbounded if this is sys.maxint(or higher). | ||
""" | ||
if start <= -sys.maxint: | ||
start = self.JAVA_MIN_LONG | ||
if end >= sys.maxint: | ||
end = self.JAVA_MAX_LONG | ||
return WindowSpec(self._jspec.rowsBetween(start, end)) | ||
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@since(1.4) | ||
def rangeBetween(self, start=-sys.maxint, end=0): | ||
""" | ||
Defines the frame boundaries, from `start` (inclusive) to `end` (inclusive). | ||
Both `start` and `end` are relative from the current row. For example, | ||
"0" means "current row", while "-1" means one off before the current row, | ||
and "5" means the five off after the current row. | ||
:param start: boundary start, inclusive. | ||
The frame is unbounded if this is -sys.maxint(or lower). | ||
:param end: boundary end, inclusive. | ||
The frame is unbounded if this is sys.maxint(or higher). | ||
""" | ||
if start <= -sys.maxint: | ||
start = self.JAVA_MIN_LONG | ||
if end >= sys.maxint: | ||
end = self.JAVA_MAX_LONG | ||
return WindowSpec(self._jspec.rangeBetween(start, end)) | ||
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def _test(): | ||
import doctest | ||
SparkContext('local[4]', 'PythonTest') | ||
(failure_count, test_count) = doctest.testmod() | ||
if failure_count: | ||
exit(-1) | ||
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if __name__ == "__main__": | ||
_test() |
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