[GitHub] [spark] itholic commented on a diff in pull request #42994: [SPARK-43433][PS] Match `GroupBy.nth` behavior to the latest Pandas

["itholic (via GitHub)" <gi...@apache.org>]

itholic commented on code in PR #42994:
URL: https://github.com/apache/spark/pull/42994#discussion_r1331072003


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python/pyspark/pandas/groupby.py:
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@@ -1155,14 +1152,32 @@ def nth(self, n: int) -> FrameLike:
         else:
             sdf = sdf.select(*groupkey_names).distinct()
 
-        internal = internal.copy(
+        agg_columns = []
+        if not self._agg_columns_selected:

Review Comment:
   `groupkeys` is going to be a data column instead of index when it's not included by `agg_columns_selected`. And index should be kept without updating from Pandas 2.0.0 for `nth`. Therefore, we should include the `groupkeys` into agg_columns to make it as a data column and create a new `InternalFrame` manually.



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