[GitHub] [spark] ueshin commented on a diff in pull request #42161: [SPARK-44479][PYTHON] Fix ArrowStreamPandasUDFSerializer to accept no-column pandas DataFrame

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

ueshin commented on code in PR #42161:
URL: https://github.com/apache/spark/pull/42161#discussion_r1274361664


##########
python/pyspark/sql/pandas/serializers.py:
##########
@@ -385,37 +385,28 @@ def _create_struct_array(self, df, arrow_struct_type):
         """
         import pyarrow as pa
 
-        # Input partition and result pandas.DataFrame empty, make empty Arrays with struct
-        if len(df) == 0 and len(df.columns) == 0:
-            arrs_names = [
-                (pa.array([], type=field.type), field.name) for field in arrow_struct_type
-            ]
+        if len(df.columns) == 0:
+            return pa.array([{}] * len(df), arrow_struct_type)

Review Comment:
   For example:
   
   ```py
   >>> pdf = pd.DataFrame(index=[1,2,3])
   >>> pdf
   Empty DataFrame
   Columns: []
   Index: [1, 2, 3]
   >>> len(pdf)
   3
   >>> len(pdf.columns)
   0
   ```



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