Skip to content

Backport PR #38638 on branch 1.2.x (BUG: Fix regression in pandas merge) #38639

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Dec 22, 2020
Merged

Backport PR #38638 on branch 1.2.x (BUG: Fix regression in pandas merge) #38639

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion pandas/core/reshape/merge.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -859,7 +859,7 @@ def _maybe_add_join_keys(self, result, left_indexer, right_indexer):
mask_right = right_indexer == -1
if mask_left.all():
key_col = rvals
elif mask_right.all():
elif right_indexer is not None and mask_right.all():
key_col = lvals
else:
key_col = Index(lvals).where(~mask_left, rvals)
Expand Down
17 changes: 17 additions & 0 deletions pandas/tests/reshape/merge/test_merge.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2349,3 +2349,20 @@ def test_merge_join_cols_error_reporting_on_and_index(func, kwargs):
)
with pytest.raises(MergeError, match=msg):
getattr(pd, func)(left, right, on="a", **kwargs)


def test_merge_right_left_index():
# GH#38616
left = DataFrame({"x": [1, 1], "z": ["foo", "foo"]})
right = DataFrame({"x": [1, 1], "z": ["foo", "foo"]})
result = pd.merge(left, right, how="right", left_index=True, right_on="x")
expected = DataFrame(
{
"x": [1, 1],
"x_x": [1, 1],
"z_x": ["foo", "foo"],
"x_y": [1, 1],
"z_y": ["foo", "foo"],
}
)
tm.assert_frame_equal(result, expected)