From c031381c1ee7c8d56ab80640cc83ac6285f9a78e Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Mon, 17 Jun 2024 16:31:14 -0700
Subject: [PATCH 1/2] Use more shallow copies in indexing operations

---
 python/cudf/cudf/core/_base_index.py |  6 +++---
 python/cudf/cudf/core/index.py       |  2 +-
 python/cudf/cudf/tests/test_index.py | 21 +++++++++++++++++++++
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/python/cudf/cudf/core/_base_index.py b/python/cudf/cudf/core/_base_index.py
index e71e45e410e..8d055ea68a1 100644
--- a/python/cudf/cudf/core/_base_index.py
+++ b/python/cudf/cudf/core/_base_index.py
@@ -1122,7 +1122,7 @@ def difference(self, other, sort=None):
         res_name = _get_result_name(self.name, other.name)
 
         if is_mixed_with_object_dtype(self, other) or len(other) == 0:
-            difference = self.copy().unique()
+            difference = self.unique()
             difference.name = res_name
             if sort is True:
                 return difference.sort_values()
@@ -1746,7 +1746,7 @@ def rename(self, name, inplace=False):
             self.name = name
             return None
         else:
-            out = self.copy(deep=True)
+            out = self.copy(deep=False)
             out.name = name
             return out
 
@@ -2070,7 +2070,7 @@ def dropna(self, how="any"):
             raise ValueError(f"{how=} must be 'any' or 'all'")
         try:
             if not self.hasnans:
-                return self.copy()
+                return self.copy(deep=False)
         except NotImplementedError:
             pass
         # This is to be consistent with IndexedFrame.dropna to handle nans
diff --git a/python/cudf/cudf/core/index.py b/python/cudf/cudf/core/index.py
index df21d392311..dca5c4557e0 100644
--- a/python/cudf/cudf/core/index.py
+++ b/python/cudf/cudf/core/index.py
@@ -526,7 +526,7 @@ def memory_usage(self, deep: bool = False) -> int:
 
     def unique(self) -> Self:
         # RangeIndex always has unique values
-        return self
+        return self.copy()
 
     @_cudf_nvtx_annotate
     def __mul__(self, other):
diff --git a/python/cudf/cudf/tests/test_index.py b/python/cudf/cudf/tests/test_index.py
index 3d6c71ebc1b..5b3c434b9a4 100644
--- a/python/cudf/cudf/tests/test_index.py
+++ b/python/cudf/cudf/tests/test_index.py
@@ -3214,6 +3214,27 @@ def test_rangeindex_dropna():
     assert_eq(result, expected)
 
 
+def test_rangeindex_unique_shallow_copy():
+    ri_pandas = pd.RangeIndex(1)
+    result = ri_pandas.unique()
+    assert result is not ri_pandas
+
+    ri_cudf = cudf.RangeIndex(1)
+    result = ri_cudf.unique()
+    assert result is not ri_cudf
+    assert_eq(result, ri_cudf)
+
+
+def test_rename_shallow_copy():
+    idx = pd.Index([1])
+    result = idx.rename("a")
+    assert idx.to_numpy(copy=False) is result.to_numpy(copy=False)
+
+    idx = cudf.Index([1])
+    result = idx.rename("a")
+    assert idx._column is result._column
+
+
 @pytest.mark.parametrize("data", [range(2), [10, 11, 12]])
 def test_index_contains_hashable(data):
     gidx = cudf.Index(data)

From 1f72292444e030e9835a94d17cd72eba263f2631 Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Mon, 17 Jun 2024 17:00:53 -0700
Subject: [PATCH 2/2] Fix other test avoid a copy in get_indexer

---
 python/cudf/cudf/core/index.py       | 3 ++-
 python/cudf/cudf/tests/test_index.py | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/python/cudf/cudf/core/index.py b/python/cudf/cudf/core/index.py
index dca5c4557e0..9554b39b2f5 100644
--- a/python/cudf/cudf/core/index.py
+++ b/python/cudf/cudf/core/index.py
@@ -3206,7 +3206,8 @@ def _get_nearest_indexer(
     )
     right_indexer = _get_indexer_basic(
         index=index,
-        positions=positions.copy(deep=True),
+        # positions no longer used so don't copy
+        positions=positions,
         method="backfill",
         target_col=target_col,
         tolerance=tolerance,
diff --git a/python/cudf/cudf/tests/test_index.py b/python/cudf/cudf/tests/test_index.py
index 5b3c434b9a4..a59836df5ba 100644
--- a/python/cudf/cudf/tests/test_index.py
+++ b/python/cudf/cudf/tests/test_index.py
@@ -252,10 +252,10 @@ def test_index_rename_inplace():
     pds = pd.Index([1, 2, 3], name="asdf")
     gds = Index(pds)
 
-    # inplace=False should yield a deep copy
+    # inplace=False should yield a shallow copy
     gds_renamed_deep = gds.rename("new_name", inplace=False)
 
-    assert gds_renamed_deep._values.data_ptr != gds._values.data_ptr
+    assert gds_renamed_deep._values.data_ptr == gds._values.data_ptr
 
     # inplace=True returns none
     expected_ptr = gds._values.data_ptr