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BUG: resolve left/right key names overlap in merge #665

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BUG: resolve left/right key names overlap in merge #665

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merge overlap non regression test
ogrisel Jan 22, 2012
62fbd81
FIX: handle overlap when explicit left or right keys are passed expli…
ogrisel Jan 22, 2012
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12 changes: 9 additions & 3 deletions pandas/tools/merge.py
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@ def get_result(self):
join_index, left_indexer, right_indexer = self._get_join_info()

# this is a bit kludgy
ldata, rdata = self._get_merge_data(self.join_names)
ldata, rdata = self._get_merge_data()

# TODO: more efficiently handle group keys to avoid extra consolidation!
join_op = _BlockJoinOperation([ldata, rdata], join_index,
Expand Down Expand Up @@ -154,13 +154,19 @@ def _get_join_info(self):

return join_index, left_indexer, right_indexer

def _get_merge_data(self, join_names):
def _get_merge_data(self):
"""
Handles overlapping column names etc.
"""
ldata, rdata = self.left._data, self.right._data
lsuf, rsuf = self.suffixes
exclude_names = [x for x in join_names if x is not None]
exclude_names = set(x for x in self.join_names if x is not None)
if self.left_on is not None:
exclude_names -= set(c.name if hasattr(c, 'name') else c
for c in self.left_on)
if self.right_on is not None:
exclude_names -= set(c.name if hasattr(c, 'name') else c
for c in self.right_on)
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@ogrisel I'm struggling to find a case where exclude_names would be non-empty after this block of code. Any ideas (since you worked on this most recently)? Gonna keep hacking at it a bit here

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I don't think it can, actually. Just going to remove this code as the test suite is pretty exhaustive and never passes non-empty exclude names to the maybe_rename_join method

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Basically I implemented this to make the new test_handle_overlap_arbitrary_key test pass.

ldata, rdata = ldata._maybe_rename_join(rdata, lsuf, rsuf,
exclude=exclude_names,
copydata=False)
Expand Down
8 changes: 8 additions & 0 deletions pandas/tools/tests/test_merge.py
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Expand Up @@ -177,6 +177,14 @@ def test_handle_overlap(self):
self.assert_('key1.foo' in joined)
self.assert_('key1.bar' in joined)

def test_handle_overlap_arbitrary_key(self):
joined = merge(self.df, self.df2,
left_on='key2', right_on='key1',
suffixes=['.foo', '.bar'])

self.assert_('key1.foo' in joined)
self.assert_('key2.bar' in joined)

def test_merge_common(self):
joined = merge(self.df, self.df2)
exp = merge(self.df, self.df2, on=['key1', 'key2'])
Expand Down