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[SPARK-24868][PYTHON]add sequence function in Python #21820

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[SPARK-24868][PYTHON]add sequence function in Python #21820

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[SPARK-24868][PYTHON]add sequence function in Python
huaxingao Jul 19, 2018
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huaxingao Jul 20, 2018
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22 changes: 22 additions & 0 deletions python/pyspark/sql/functions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2551,6 +2551,28 @@ def map_concat(*cols):
return Column(jc)


@since(2.4)
def sequence(start, stop, step=None):
"""
Generate a sequence of integers from `start` to `stop`, incrementing by `step`.
If `step` is not set, incrementing by 1 if `start` is less than or equal to `stop`,
otherwise -1.

>>> df1 = spark.createDataFrame([(-2, 2)], ('C1', 'C2'))
>>> df1.select(sequence('C1', 'C2').alias('r')).collect()
[Row(r=[-2, -1, 0, 1, 2])]
>>> df2 = spark.createDataFrame([(4, -4, -2)], ('C1', 'C2', 'C3'))
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@HyukjinKwon HyukjinKwon Jul 20, 2018

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What happens if the step is positive in this case?

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@huaxingao huaxingao Jul 20, 2018

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It will throw java.lang.IllegalArgumentException.
There is a check in collectionOperations.scala

    require(
      (step > num.zero && start <= stop)
        || (step < num.zero && start >= stop)
        || (step == num.zero && start == stop),
      s"Illegal sequence boundaries: $start to $stop by $step")

>>> df2.select(sequence('C1', 'C2', 'C3').alias('r')).collect()
[Row(r=[4, 2, 0, -2, -4])]
"""
sc = SparkContext._active_spark_context
if step is None:
return Column(sc._jvm.functions.sequence(_to_java_column(start), _to_java_column(stop)))
else:
return Column(sc._jvm.functions.sequence(
_to_java_column(start), _to_java_column(stop), _to_java_column(step)))


# ---------------------------- User Defined Function ----------------------------------

class PandasUDFType(object):
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