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[SPARK-10073] [SQL] Python withColumn should replace the old column #8300

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[SPARK-10073] [SQL] Python withColumn should replace the old column #8300

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withColumn should replace the old column
Aug 19, 2015
68ff0a9
Update dataframe.py
Aug 19, 2015
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13 changes: 7 additions & 6 deletions python/pyspark/sql/dataframe.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1202,15 +1202,18 @@ def freqItems(self, cols, support=None):
@ignore_unicode_prefix
@since(1.3)
def withColumn(self, colName, col):
"""Returns a new :class:`DataFrame` by adding a column.
"""
Returns a new :class:`DataFrame` by adding a column or replacing the
existing column that has the same name.

:param colName: string, name of the new column.
:param col: a :class:`Column` expression for the new column.

>>> df.withColumn('age2', df.age + 2).collect()
[Row(age=2, name=u'Alice', age2=4), Row(age=5, name=u'Bob', age2=7)]
"""
return self.select('*', col.alias(colName))
assert isinstance(col, Column), "col should be Column"
return DataFrame(self._jdf.withColumn(colName, col._jc), self.sql_ctx)

@ignore_unicode_prefix
@since(1.3)
Expand All @@ -1223,10 +1226,8 @@ def withColumnRenamed(self, existing, new):
>>> df.withColumnRenamed('age', 'age2').collect()
[Row(age2=2, name=u'Alice'), Row(age2=5, name=u'Bob')]
"""
cols = [Column(_to_java_column(c)).alias(new)
if c == existing else c
for c in self.columns]
return self.select(*cols)
assert existing in self.columns, "%s is not an existing column" % existing
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@cloud-fan cloud-fan Aug 19, 2015

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This is not consistent with scala version, see the doc, we should not report error here.

Actually I'm wondering why we need to do checking at python side(not only this one)? Can we just call the scala API and catch the java exception?

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@davies davies Aug 19, 2015

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Good catch, will remove it. I'm really surprised by the behavior in Scala.

The reason we want to have some check on Python side is that the Java exception is not easy to understand for Python programmer (nested inside a Py4j exception). The Python exception or messages does improve the experience for Python programmer, especially beginners.

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@marmbrus marmbrus Aug 19, 2015

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Forgive my lack of python skills... could have have a generic wrapper that we use whenever we call back into scala that catches and unwraps certain expressions nicely?

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@davies davies Aug 19, 2015

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We already did this for some of them, for example, AnalysisException and IllegalArgumentException, these could help.

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@marmbrus marmbrus Aug 19, 2015

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Oh cool, ideally we will pretty much only throw those two unless there is a bug. If there are cases where that is not true we should consider fixing on the scala side.

return DataFrame(self._jdf.withColumnRenamed(existing, new), self.sql_ctx)

@since(1.4)
@ignore_unicode_prefix
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4 changes: 4 additions & 0 deletions python/pyspark/sql/tests.py
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Expand Up @@ -1035,6 +1035,10 @@ def test_capture_illegalargument_exception(self):
self.assertRaisesRegexp(IllegalArgumentException, "1024 is not in the permitted values",
lambda: df.select(sha2(df.a, 1024)).collect())

def test_with_column_with_existing_name(self):
keys = self.df.withColumn("key", self.df.key).select("key").collect()
self.assertEqual([r.key for r in keys], list(range(100)))


class HiveContextSQLTests(ReusedPySparkTestCase):

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3 changes: 2 additions & 1 deletion sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala
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Expand Up @@ -1133,7 +1133,8 @@ class DataFrame private[sql](
/////////////////////////////////////////////////////////////////////////////

/**
* Returns a new [[DataFrame]] by adding a column.
* Returns a new [[DataFrame]] by adding a column or replacing the existing column that has
* the same name.
* @group dfops
* @since 1.3.0
*/
Expand Down