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Commit a160ae6

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jorisvandenbosschejbrockmendel
andauthored
[backport 2.3.x] BUG[string]: incorrect index downcast in DataFrame.join (#61771) (#61800)
* BUG[string]: incorrect index downcast in DataFrame.join (#61771) Co-authored-by: Joris Van den Bossche <jorisvandenbossche@gmail.com> * avoid warning --------- Co-authored-by: jbrockmendel <jbrockmendel@gmail.com>
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3 files changed

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-16
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3 files changed

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-16
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‎doc/source/whatsnew/v2.3.1.rst‎

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Original file line numberDiff line numberDiff line change
@@ -57,6 +57,7 @@ correctly, rather than defaulting to ``object`` dtype. For example:
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Bug fixes
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^^^^^^^^^
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- Bug in :meth:`.DataFrameGroupBy.min`, :meth:`.DataFrameGroupBy.max`, :meth:`.Resampler.min`, :meth:`.Resampler.max` where all NA values of string dtype would return float instead of string dtype (:issue:`60810`)
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- Bug in :meth:`DataFrame.join` incorrectly downcasting object-dtype indexes (:issue:`61771`)
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- Bug in :meth:`DataFrame.sum` with ``axis=1``, :meth:`.DataFrameGroupBy.sum` or :meth:`.SeriesGroupBy.sum` with ``skipna=True``, and :meth:`.Resampler.sum` with all NA values of :class:`StringDtype` resulted in ``0`` instead of the empty string ``""`` (:issue:`60229`)
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- Fixed bug in :meth:`DataFrame.explode` and :meth:`Series.explode` where methods would fail with ``dtype="str"`` (:issue:`61623`)
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- Fixed bug in unpickling objects pickled in pandas versions pre-2.3.0 that used :class:`StringDtype` (:issue:`61763`).

‎pandas/core/reshape/merge.py‎

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1076,13 +1076,13 @@ def _maybe_add_join_keys(
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# if we have an all missing left_indexer
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# make sure to just use the right values or vice-versa
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if left_indexer is not None and (left_indexer == -1).all():
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key_col = Index(rvals)
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key_col = Index(rvals, dtype=rvals.dtype, copy=False)
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result_dtype = rvals.dtype
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elif right_indexer is not None and (right_indexer == -1).all():
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key_col = Index(lvals)
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key_col = Index(lvals, dtype=lvals.dtype, copy=False)
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result_dtype = lvals.dtype
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else:
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key_col = Index(lvals)
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key_col = Index(lvals, dtype=lvals.dtype, copy=False)
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if left_indexer is not None:
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mask_left = left_indexer == -1
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key_col = key_col.where(~mask_left, rvals)
@@ -1112,7 +1112,8 @@ def _maybe_add_join_keys(
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result.set_index(idx_list, inplace=True)
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else:
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result.index = Index(key_col, name=name)
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key_col.name = name
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result.index = key_col
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else:
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result.insert(i, name or f"key_{i}", key_col)
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‎pandas/tests/copy_view/test_functions.py‎

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Original file line numberDiff line numberDiff line change
@@ -1,10 +1,6 @@
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import numpy as np
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import pytest
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4-
from pandas._config import using_string_dtype
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from pandas.compat import HAS_PYARROW
7-
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from pandas import (
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DataFrame,
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Index,
@@ -317,13 +313,9 @@ def test_merge_copy_keyword(using_copy_on_write, copy):
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assert not np.shares_memory(get_array(df2, "b"), get_array(result, "b"))
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320-
@pytest.mark.xfail(
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using_string_dtype() and HAS_PYARROW,
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reason="TODO(infer_string); result.index infers str dtype while both "
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"df1 and df2 index are object.",
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)
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def test_join_on_key(using_copy_on_write):
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df_index = Index(["a", "b", "c"], name="key", dtype=object)
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@pytest.mark.parametrize("dtype", [object, "str"])
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def test_join_on_key(dtype, using_copy_on_write):
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df_index = Index(["a", "b", "c"], name="key", dtype=dtype)
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df1 = DataFrame({"a": [1, 2, 3]}, index=df_index.copy(deep=True))
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df2 = DataFrame({"b": [4, 5, 6]}, index=df_index.copy(deep=True))
@@ -336,7 +328,7 @@ def test_join_on_key(using_copy_on_write):
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if using_copy_on_write:
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assert np.shares_memory(get_array(result, "a"), get_array(df1, "a"))
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assert np.shares_memory(get_array(result, "b"), get_array(df2, "b"))
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assert np.shares_memory(get_array(result.index), get_array(df1.index))
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assert tm.shares_memory(get_array(result.index), get_array(df1.index))
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assert not np.shares_memory(get_array(result.index), get_array(df2.index))
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else:
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assert not np.shares_memory(get_array(result, "a"), get_array(df1, "a"))

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