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Raise a more helpful error for duplicated columns in Join #820

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merged 2 commits into from
Sep 23, 2019
Merged

Raise a more helpful error for duplicated columns in Join #820

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636c44b
raise error on join-duplicate
thoo Sep 23, 2019
08f25bd
fix flake8
thoo Sep 23, 2019
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8 changes: 8 additions & 0 deletions databricks/koalas/frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5433,6 +5433,14 @@ def join(self, right: 'DataFrame', on: Optional[Union[str, List[str]]] = None,
2 K1 A1 B1
3 K2 A2 B2
"""
if isinstance(right, ks.Series):
common = list(self.columns.intersection([right.name]))
else:
common = list(self.columns.intersection(right.columns))
if len(common) > 0 and not lsuffix and not rsuffix:
raise ValueError(
"columns overlap but no suffix specified: "
"{rename}".format(rename=common))
if on:
self = self.set_index(on)
join_kdf = self.merge(right, left_index=True, right_index=True, how=how,
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6 changes: 6 additions & 0 deletions databricks/koalas/tests/test_dataframe.py
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Expand Up @@ -1001,6 +1001,7 @@ def test_join(self):
'A': ['A0', 'A1', 'A2', 'A3']}, columns=['key', 'A'])
kdf2 = ks.DataFrame({'key': ['K0', 'K1', 'K2'],
'B': ['B0', 'B1', 'B2']}, columns=['key', 'B'])
ks1 = ks.Series(['A1', 'A5'], index=[1, 2], name='A')
join_pdf = pdf1.join(pdf2, lsuffix='_left', rsuffix='_right')
join_pdf.sort_values(by=list(join_pdf.columns), inplace=True)

Expand All @@ -1009,6 +1010,11 @@ def test_join(self):

self.assert_eq(join_pdf, join_kdf)

# join with duplicated columns in Series and DataFrame
with self.assertRaisesRegex(ValueError,
"columns overlap but no suffix specified"):
kdf1.join(ks1, how='outer')
kdf1.join(kdf2, how='outer')
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Actually this only tests the first line.

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Sorry. I will fix it.

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Ah yes. Sorry for missing this one will take a closer look next time @ueshin

# check `on` parameter
join_pdf = pdf1.join(pdf2.set_index('key'), on='key', lsuffix='_left', rsuffix='_right')
join_pdf.sort_values(by=list(join_pdf.columns), inplace=True)
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