#61382: FIX MultiIndex.difference for pyarrow-backed Timestamps

- Override MultiIndex.difference to handle Timestamp[ns][pyarrow] levels
- Ensure proper comparison without converting all levels to pandas types
- Add pytest test for difference with pyarrow-backed MultiIndex

Author: arpibad

pandas/core/indexes/multi.py

@@ -4135,6 +4135,33 @@ def isin(self, values, level=None) -> npt.NDArray[np.bool_]:
     # base class "Index" defined the type as "Callable[[Index, Any, bool], Any]")
     rename = Index.set_names  # type: ignore[assignment]
 
+    def difference(self, other, sort=None):
+    """
+    Return a new MultiIndex with elements in self that are not in other.
+    Fixed to work with pyarrow-backed Timestamps.
+    """
+    if isinstance(other, type(self)):
+        # Convert pyarrow-backed Timestamps to pandas Timestamps for comparison
+        self_arrays = [level.to_pandas() if hasattr(level, "to_pandas") else level
+                       for level in self.levels]
+        other_arrays = [level.to_pandas() if hasattr(level, "to_pandas") else level
+                        for level in other.levels]
+        self_conv = pd.MultiIndex.from_arrays(self_arrays, names=self.names)
+        other_conv = pd.MultiIndex.from_arrays(other_arrays, names=other.names)
+        result = self_conv.difference(other_conv, sort=sort)
+        # Preserve pyarrow dtypes if present
+        for i, level in enumerate(self.levels):
+            if getattr(level, "dtype", None) == "timestamp[ns][pyarrow]":
+                result = pd.MultiIndex.from_arrays(
+                    [pd.Series(arr, dtype="timestamp[ns][pyarrow]") if i==idx else arr
+                     for idx, arr in enumerate(result.levels)],
+                    names=result.names
+                )
+        return result
+    else:
+        return super(type(self), self).difference(other, sort=sort)
+
+
     # ---------------------------------------------------------------
     # Arithmetic/Numeric Methods - Disabled
 

pandas/tests/indexes/multi/test_timestamp.py

@@ -0,0 +1,25 @@
+import pandas as pd
+import pytest
+
+pytest.importorskip("pyarrow")
+
+def test_difference_with_pyarrow_timestamp():
+    dates = pd.Series(
+        ["2024-01-01", "2024-01-02"], dtype="timestamp[ns][pyarrow]"
+    )
+    ids = [1, 2]
+
+    mi = pd.MultiIndex.from_arrays([ids, dates], names=["id", "date"])
+    to_remove = mi[:1]
+
+    result = mi.difference(to_remove)
+
+    expected_dates = pd.Series(
+        ["2024-01-02"], dtype="timestamp[ns][pyarrow]"
+    )
+    expected_ids = [2]
+    expected = pd.MultiIndex.from_arrays(
+        [expected_ids, expected_dates], names=["id", "date"]
+    )
+
+    pd.testing.assert_index_equal(result, expected)