Merge remote-tracking branch 'origin/master' into issue_6899

modin/core/dataframe/pandas/dataframe/dataframe.py

@@ -3912,7 +3912,9 @@ def compute_aligned_columns(*dfs, initial_columns=None):
                 # aligned columns
                 parts = result._partitions.flatten()
                 aligned_columns = parts[0].apply(
-                    compute_aligned_columns,
+                    # TODO: unidist on MPI execution requires for this function to be preprocessed,
+                    # otherwise, the execution fails. Look into the issue later.
+                    self._partition_mgr_cls.preprocess_func(compute_aligned_columns),
                     *[part._data for part in parts[1:]],
                     initial_columns=self.columns,
                 )