[GitHub] [spark] itholic commented on a change in pull request #33634: [SPARK-36369][PYTHON] Fix Index.union to follow pandas 1.3

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

itholic commented on a change in pull request #33634:
URL: https://github.com/apache/spark/pull/33634#discussion_r683955183



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File path: python/pyspark/pandas/indexes/base.py
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@@ -2292,9 +2292,7 @@ def union(
 
         sdf_self = self._internal.spark_frame.select(self._internal.index_spark_columns)
         sdf_other = other_idx._internal.spark_frame.select(other_idx._internal.index_spark_columns)
-        sdf = sdf_self.union(sdf_other.subtract(sdf_self))
-        if isinstance(self, MultiIndex):
-            sdf = sdf.drop_duplicates()
+        sdf = sdf_self.unionAll(sdf_other).exceptAll(sdf_self.intersectAll(sdf_other))
         if sort:

Review comment:
       Thanks, @HyukjinKwon !
   
   Seems like they said "dropping duplicate Index values" was a bug, and fixed in this release.
   
   Related discussion was made at https://github.com/pandas-dev/pandas/issues/36289.
   
   Also checked the `sort` and drop duplicates, works the same as pandas.




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