Bad idea to deep copy indexes.

Author: dcherian

xarray/core/dataarray.py

@@ -494,7 +494,7 @@ def _to_dataset_whole(
         if shallow_copy:
             for k in variables:
                 variables[k] = variables[k].copy(deep=False)
-        indexes = copy_indexes(self._indexes, deep=(not shallow_copy))
+        indexes = copy_indexes(self._indexes)
 
         coord_names = set(self._coords)
         dataset = Dataset._from_vars_and_coord_names(
@@ -943,7 +943,7 @@ def copy(self, deep: bool = True, data: Any = None) -> "DataArray":
         """
         variable = self.variable.copy(deep=deep, data=data)
         coords = {k: v.copy(deep=deep) for k, v in self._coords.items()}
-        indexes = copy_indexes(self._indexes, deep=deep)
+        indexes = copy_indexes(self._indexes)
         return self._replace(variable, coords, indexes=indexes)
 
     def __copy__(self) -> "DataArray":

xarray/core/indexes.py

@@ -101,20 +101,18 @@ def roll_index(index: pd.Index, count: int, axis: int = 0) -> pd.Index:
 
 
 def copy_indexes(
-    indexes: Optional[Dict[Hashable, pd.Index]],
-    deep: bool = True,
-    exclude: Optional[Any] = None,
+    indexes: Optional[Dict[Hashable, pd.Index]], exclude: Optional[Any] = None
 ) -> Optional[Dict[Hashable, pd.Index]]:
+    """ Creates new indexes dict from existing dict optionally excluding some dimensions.
+    """
     if exclude is None:
         exclude = ()
 
     if is_scalar(exclude):
         exclude = (exclude,)
 
     if indexes is not None:
-        new_indexes = {
-            k: v.copy(deep=deep) for k, v in indexes.items() if k not in exclude
-        }
+        new_indexes = {k: v for k, v in indexes.items() if k not in exclude}
     else:
         new_indexes = None  # type: ignore