fixups

Author: WillAyd

pandas/_libs/arrays.pyx

@@ -469,7 +469,7 @@ cdef class BitmaskArray:
     def __getitem__(self, key):
         cdef Py_ssize_t ckey
         # to_numpy can be expensive, so try to avoid for simple cases
-        if isinstance(key, int):
+        if isinstance(key, int) and self.ndim == 1:
             ckey = key
             if ckey >= 0 and ckey < self.bitmap.size_bits:
                 return bool(ArrowBitGet(self.bitmap.buffer.data, ckey))

pandas/core/arrays/masked.py

@@ -191,21 +191,13 @@ def __getitem__(self, item: SequenceIndexer) -> Self:
     def __getitem__(self, item: PositionalIndexer) -> Self | Any:
         item = check_array_indexer(self, item)
 
-        # TODO: some of the numpy semantics for handling 2D indexing
-        # are not implemented in the bitmaskarray, hence the to_numpy()
-        # requirement, though that slows things down
-        np_mask = self._mask.to_numpy()
-        newmask = np_mask[item]
+        newmask = self._mask[item]
         if is_bool(newmask):
             # This is a scalar indexing
             if newmask:
                 return self.dtype.na_value
             return self._data[item]
 
-        # sending self._mask avoids copy of buffer
-        if np.array_equal(newmask, np_mask):
-            return self._simple_new(self._data[item], self._mask)
-
         return self._simple_new(self._data[item], newmask)
 
     def pad_or_backfill(

pandas/tests/arrays/masked/test_bitmask.py

@@ -19,7 +19,7 @@
         pytest.param(np.array([True, False] * 8), bytes([0x55, 0x55]), id="multibyte"),
         pytest.param(
             np.array([[False, False], [True, True], [False, False]])[:, 0],
-            [False, True, False],
+            bytes([0x2]),
             id="non-contiguous",
         ),
     ],