diff --git a/doc/source/whatsnew/v0.24.1.rst b/doc/source/whatsnew/v0.24.1.rst index 3ac2ed73ea53f..ee4b7ab62b31a 100644 --- a/doc/source/whatsnew/v0.24.1.rst +++ b/doc/source/whatsnew/v0.24.1.rst @@ -63,9 +63,6 @@ Bug Fixes - - -**Reshaping** - -- Bug in :func:`merge` when merging by index name would sometimes result in an incorrectly numbered index (:issue:`24212`) **Other** diff --git a/pandas/core/reshape/merge.py b/pandas/core/reshape/merge.py index 1dd19a7c1514e..e11847d2b8ce2 100644 --- a/pandas/core/reshape/merge.py +++ b/pandas/core/reshape/merge.py @@ -757,21 +757,13 @@ def _get_join_info(self): if self.right_index: if len(self.left) > 0: - join_index = self._create_join_index(self.left.index, - self.right.index, - left_indexer, - right_indexer, - how='right') + join_index = self.left.index.take(left_indexer) else: join_index = self.right.index.take(right_indexer) left_indexer = np.array([-1] * len(join_index)) elif self.left_index: if len(self.right) > 0: - join_index = self._create_join_index(self.right.index, - self.left.index, - right_indexer, - left_indexer, - how='left') + join_index = self.right.index.take(right_indexer) else: join_index = self.left.index.take(left_indexer) right_indexer = np.array([-1] * len(join_index)) @@ -782,39 +774,6 @@ def _get_join_info(self): join_index = join_index.astype(object) return join_index, left_indexer, right_indexer - def _create_join_index(self, index, other_index, indexer, - other_indexer, how='left'): - """ - Create a join index by rearranging one index to match another - - Parameters - ---------- - index: Index being rearranged - other_index: Index used to supply values not found in index - indexer: how to rearrange index - how: replacement is only necessary if indexer based on other_index - - Returns - ------- - join_index - """ - join_index = index.take(indexer) - if (self.how in (how, 'outer') and - not isinstance(other_index, MultiIndex)): - # if final index requires values in other_index but not target - # index, indexer may hold missing (-1) values, causing Index.take - # to take the final value in target index - mask = indexer == -1 - if np.any(mask): - # if values missing (-1) from target index, - # take from other_index instead - join_list = join_index.to_numpy() - other_list = other_index.take(other_indexer).to_numpy() - join_list[mask] = other_list[mask] - join_index = Index(join_list, dtype=join_index.dtype, - name=join_index.name) - return join_index - def _get_merge_keys(self): """ Note: has side effects (copy/delete key columns) diff --git a/pandas/tests/reshape/merge/test_merge.py b/pandas/tests/reshape/merge/test_merge.py index c17c301968269..f0a3ddc8ce8a4 100644 --- a/pandas/tests/reshape/merge/test_merge.py +++ b/pandas/tests/reshape/merge/test_merge.py @@ -939,22 +939,25 @@ def test_merge_two_empty_df_no_division_error(self): with np.errstate(divide='raise'): merge(a, a, on=('a', 'b')) - @pytest.mark.parametrize('how', ['right', 'outer']) + @pytest.mark.parametrize('how', ['left', 'outer']) + @pytest.mark.xfail(reason="GH-24897") def test_merge_on_index_with_more_values(self, how): # GH 24212 - # pd.merge gets [0, 1, 2, -1, -1, -1] as left_indexer, ensure that - # -1 is interpreted as a missing value instead of the last element - df1 = pd.DataFrame({'a': [1, 2, 3], 'key': [0, 2, 2]}) - df2 = pd.DataFrame({'b': [1, 2, 3, 4, 5]}) - result = df1.merge(df2, left_on='key', right_index=True, how=how) - expected = pd.DataFrame([[1.0, 0, 1], - [2.0, 2, 3], - [3.0, 2, 3], - [np.nan, 1, 2], - [np.nan, 3, 4], - [np.nan, 4, 5]], - columns=['a', 'key', 'b']) - expected.set_index(Int64Index([0, 1, 2, 1, 3, 4]), inplace=True) + # pd.merge gets [-1, -1, 0, 1] as right_indexer, ensure that -1 is + # interpreted as a missing value instead of the last element + df1 = pd.DataFrame([[1, 2], [2, 4], [3, 6], [4, 8]], + columns=['a', 'b']) + df2 = pd.DataFrame([[3, 30], [4, 40]], + columns=['a', 'c']) + df1.set_index('a', drop=False, inplace=True) + df2.set_index('a', inplace=True) + result = pd.merge(df1, df2, left_index=True, right_on='a', how=how) + expected = pd.DataFrame([[1, 2, np.nan], + [2, 4, np.nan], + [3, 6, 30.0], + [4, 8, 40.0]], + columns=['a', 'b', 'c']) + expected.set_index('a', drop=False, inplace=True) assert_frame_equal(result, expected) def test_merge_right_index_right(self):