Whether the `apply` function is implemented using the pandas_udf function?

[rain]

Whether the apply function is implemented using the pandas_udf function?

[Haejoon Lee]

Yeah, for some case we use mapInPandas which leveraging the pandas_udf internally.

koalas/databricks/koalas/frame.py

Lines 2557 to 2563 in 07d8462

 if should_use_map_in_pandas: 
     output_func = GroupBy._make_pandas_df_builder_func( 
         self_applied, apply_func, return_schema, retain_index=True 
     ) 
     sdf = self_applied._internal.to_internal_spark_frame.mapInPandas( 
         lambda iterator: map(output_func, iterator), schema=return_schema 
     )