PERF: Return RangeIndex from RangeIndex.reindex when possible

Author: mroeschke

doc/source/whatsnew/v3.0.0.rst

@@ -252,6 +252,7 @@ Performance improvements
 - Performance improvement in :meth:`Index.take` when ``indices`` is a full range indexer from zero to length of index (:issue:`56806`)
 - Performance improvement in :meth:`MultiIndex.equals` for equal length indexes (:issue:`56990`)
 - Performance improvement in :meth:`RangeIndex.append` when appending the same index (:issue:`57252`)
+- Performance improvement in :meth:`RangeIndex.reindex` returning a :class:`RangeIndex` instead of a :class:`Index` when possible. (:issue:`?`)
 - Performance improvement in :meth:`RangeIndex.take` returning a :class:`RangeIndex` instead of a :class:`Index` when possible. (:issue:`57445`)
 - Performance improvement in indexing operations for string dtypes (:issue:`56997`)
 - :meth:`Series.str.extract` returns a :class:`RangeIndex` columns instead of an :class:`Index` column when possible (:issue:`?``)

pandas/core/indexes/range.py

@@ -487,6 +487,10 @@ def _view(self) -> Self:
         result._cache = self._cache
         return result
 
+    def _wrap_reindex_result(self, target, indexer, preserve_names: bool):
+        target = self._shallow_copy(target._values)
+        return super()._wrap_reindex_result(target, indexer, preserve_names)
+
     @doc(Index.copy)
     def copy(self, name: Hashable | None = None, deep: bool = False) -> Self:
         name = self._validate_names(name=name, deep=deep)[0]

pandas/tests/indexes/ranges/test_range.py

@@ -608,6 +608,16 @@ def test_range_index_rsub_by_const(self):
         tm.assert_index_equal(result, expected)
 
 
+def test_reindex_returns_rangeindex():
+    ri = RangeIndex(2, name="foo")
+    result, result_indexer = ri.reindex([1, 2, 3])
+    expected = RangeIndex(1, 4, name="foo")
+    tm.assert_index_equal(result, expected, exact=True)
+
+    expected_indexer = np.array([1, -1, -1])
+    tm.assert_numpy_array_equal(result_indexer, expected_indexer)
+
+
 def test_take_return_rangeindex():
     ri = RangeIndex(5, name="foo")
     result = ri.take([])