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[SPARK-25666][PYTHON] Internally document type conversion between Python data and SQL types in normal UDFs #22655

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[SPARK-25666][PYTHON] Internally document type conversion between Python data and SQL types in normal UDFs #22655

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Internally document type conversion between Python data and SQL types…
HyukjinKwon Oct 6, 2018
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HyukjinKwon Oct 8, 2018
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was -> is
HyukjinKwon Oct 8, 2018
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27 changes: 27 additions & 0 deletions python/pyspark/sql/functions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2733,6 +2733,33 @@ def udf(f=None, returnType=StringType()):
| 8| JOHN DOE| 22|
+----------+--------------+------------+
"""

# The following table shows most of Python data and SQL type conversions in normal UDFs that
# are not yet visible to the user. Some of behaviors are buggy and might be changed in the near
# future. The table might have to be eventually documented externally.
# Please see SPARK-25666's PR to see the codes in order to generate the table below.
#
# +-----------------------------+--------------+----------+------+-------+------+----------+--------------------+-----------------------------+----------+----------------------+---------+--------------------+--------------+----------+--------------+-------------+-------------+ # noqa
# |SQL Type \ Python Value(Type)|None(NoneType)|True(bool)|1(int)|1(long)|a(str)|a(unicode)| 1970-01-01(date)|1970-01-01 00:00:00(datetime)|1.0(float)|array('i', [1])(array)|[1](list)| (1,)(tuple)|ABC(bytearray)|1(Decimal)|{'a': 1}(dict)|Row(a=1)(Row)|Row(a=1)(Row)| # noqa
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@viirya viirya Oct 7, 2018

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Any difference between last two Row(a=1)(Row)?

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@HyukjinKwon HyukjinKwon Oct 7, 2018

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Right, one was Row(a=1) and the other one was namedtuple approach Row("a")(1). Let me try to update.

# +-----------------------------+--------------+----------+------+-------+------+----------+--------------------+-----------------------------+----------+----------------------+---------+--------------------+--------------+----------+--------------+-------------+-------------+ # noqa
# | null| None| None| None| None| None| None| None| None| None| None| None| None| None| None| None| X| X| # noqa
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@viirya viirya Oct 7, 2018

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We seems have to document what X means in this table?

# | boolean| None| True| None| None| None| None| None| None| None| None| None| None| None| None| None| X| X| # noqa
# | tinyint| None| None| 1| 1| None| None| None| None| None| None| None| None| None| None| None| X| X| # noqa
# | smallint| None| None| 1| 1| None| None| None| None| None| None| None| None| None| None| None| X| X| # noqa
# | int| None| None| 1| 1| None| None| None| None| None| None| None| None| None| None| None| X| X| # noqa
# | bigint| None| None| 1| 1| None| None| None| None| None| None| None| None| None| None| None| X| X| # noqa
# | string| None| true| 1| 1| a| a|java.util.Gregori...| java.util.Gregori...| 1.0| [I@7f1970e1| [1]|[Ljava.lang.Objec...| [B@284838a9| 1| {a=1}| X| X| # noqa
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@viirya viirya Oct 7, 2018

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true means a string 'true'? Shall we add quotes for strings?

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@viirya viirya Oct 7, 2018

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Is it meaningful for [B@284838a9 in this table?

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@HyukjinKwon HyukjinKwon Oct 7, 2018

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Hmmmmm .. I see the type is not clear here. Let me think about this a bit more.

[B@284838a9 is a quite buggy behaviour - we should fix. So I was thinking of documenting internally since we already spent much time to figure out how it works for each case individually (at #20163).

# | date| None| X| X| X| X| X| 1970-01-01| 1970-01-01| X| X| X| X| X| X| X| X| X| # noqa
# | timestamp| None| X| X| X| X| X| X| 1970-01-01 00:00:00| X| X| X| X| X| X| X| X| X| # noqa
# | float| None| None| None| None| None| None| None| None| 1.0| None| None| None| None| None| None| X| X| # noqa
# | double| None| None| None| None| None| None| None| None| 1.0| None| None| None| None| None| None| X| X| # noqa
# | array<int>| None| None| None| None| None| None| None| None| None| [1]| [1]| [1]| [65, 66, 67]| None| None| X| X| # noqa
# | binary| None| None| None| None| a| a| None| None| None| None| None| None| ABC| None| None| X| X| # noqa
# | decimal(10,0)| None| None| None| None| None| None| None| None| None| None| None| None| None| 1| None| X| X| # noqa
# | map<string,int>| None| None| None| None| None| None| None| None| None| None| None| None| None| None| {u'a': 1}| X| X| # noqa
# | struct<_1:int>| None| X| X| X| X| X| X| X| X| X|Row(_1=1)| Row(_1=1)| X| X| Row(_1=None)| Row(_1=1)| Row(_1=1)| # noqa
# +-----------------------------+--------------+----------+------+-------+------+----------+--------------------+-----------------------------+----------+----------------------+---------+--------------------+--------------+----------+--------------+-------------+-------------+ # noqa

# decorator @udf, @udf(), @udf(dataType())
if f is None or isinstance(f, (str, DataType)):
# If DataType has been passed as a positional argument
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