[GitHub] [superset] zhaoyongjie commented on a diff in pull request #19776: feat: add renameOperator

[GitBox <gi...@apache.org>]

zhaoyongjie commented on code in PR #19776:
URL: https://github.com/apache/superset/pull/19776#discussion_r853840894


##########
superset/utils/pandas_postprocessing/flatten.py:
##########
@@ -81,14 +81,16 @@ def flatten(
     """
     if _is_multi_index_on_columns(df):
         df.columns = df.columns.droplevel(drop_levels)
-        # every cell should be converted to string
-        df.columns = [
-            FLAT_COLUMN_SEPARATOR.join(
-                # pylint: disable=superfluous-parens
-                [str(cell) for cell in (series if is_sequence(series) else [series])]
-            )
-            for series in df.columns.to_flat_index()
-        ]
+        _columns = []
+        for series in df.columns.to_flat_index():
+            _cells = []
+            for cell in series if is_sequence(series) else [series]:
+                if pd.notnull(cell):

Review Comment:
   The top-level columns are might set to `None` in the rename operator. Flatten skip the `None` level.



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