FIX-modin-project#5232: Stop changing original series names during bi…

…nary ops. (modin-project#5249)

Signed-off-by: mvashishtha <mahesh@ponder.io>
Co-authored-by: Anatoly Myachev <anatoliimyachev@mail.com>

modin/pandas/series.py

@@ -2409,12 +2409,15 @@ def _prepare_inter_op(self, other):
             Prepared `other`.
         """
         if isinstance(other, Series):
-            # NB: deep=False is important for performance bc it retains obj.index._id
-            new_self = self.copy(deep=False)
-            new_other = other.copy(deep=False)
-            if self.name == other.name:
-                new_self.name = new_other.name = self.name
-            else:
+            names_different = self.name != other.name
+            # NB: if we don't need a rename, do the interaction with shallow
+            # copies so that we preserve obj.index._id. It's fine to work
+            # with shallow copies because we'll discard the copies but keep
+            # the result after the interaction opreation. We can't do a rename
+            # on shallow copies because we'll mutate the original objects.
+            new_self = self.copy(deep=names_different)
+            new_other = other.copy(deep=names_different)
+            if names_different:
                 new_self.name = new_other.name = MODIN_UNNAMED_SERIES_LABEL
         else:
             new_self = self

modin/pandas/test/test_series.py

@@ -620,6 +620,17 @@ def test_add(data):
     inter_df_math_helper(modin_series, pandas_series, "add")
 
 
+def test_add_does_not_change_original_series_name():
+    # See https://github.com/modin-project/modin/issues/5232
+    s1 = pd.Series(1, name=1)
+    s2 = pd.Series(2, name=2)
+    original_s1 = s1.copy(deep=True)
+    original_s2 = s2.copy(deep=True)
+    _ = s1 + s2
+    df_equals(s1, original_s1)
+    df_equals(s2, original_s2)
+
+
 @pytest.mark.parametrize("data", test_data_values, ids=test_data_keys)
 def test_add_prefix(data):
     modin_series, pandas_series = create_test_series(data)