viirya commented on a change in pull request #24997: [SPARK-28198][PYTHON] Add
mapPartitionsInPandas to allow an iterator of DataFrames
URL: https://github.com/apache/spark/pull/24997#discussion_r298950721
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File path: python/pyspark/sql/dataframe.py
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@@ -2192,6 +2193,51 @@ def toPandas(self):
_check_series_convert_timestamps_local_tz(pdf[field.name], timezone)
return pdf
+ def mapPartitionsInPandas(self, udf):
+ """
+ Maps each partition of the current :class:`DataFrame` using a pandas
udf and returns
+ the result as a `DataFrame`.
+
+ The user-defined function should take an iterator of
`pandas.DataFrame`s and return another
+ iterator of `pandas.DataFrame`s. For each partition, all columns are
passed together as an
+ iterator of `pandas.DataFrame`s to the user-function and the returned
iterator of
+ `pandas.DataFrame`s are combined as a :class:`DataFrame`.
+ Each `pandas.DataFrame` size can be controlled by
+ `spark.sql.execution.arrow.maxRecordsPerBatch`.
+ Its schema must match the returnType of the pandas udf.
+
+ :param udf: A function object returned by
:meth:`pyspark.sql.functions.pandas_udf`
+
+ >>> from pyspark.sql.functions import pandas_udf, PandasUDFType
+ >>> df = spark.createDataFrame([(1, 21), (2, 30)],
+ ... ("id", "age")) # doctest: +SKIP
+ >>> @pandas_udf(df.schema, PandasUDFType.SCALAR_ITER) # doctest: +SKIP
+ ... def filter_func(iterator):
+ ... for pdf in iterator:
+ ... yield pdf[pdf.id == 1]
+ >>> df.mapPartitionsInPandas(filter_func).show() # doctest: +SKIP
+ +---+---+
+ | id|age|
+ +---+---+
+ | 1| 21|
+ +---+---+
+
+ .. seealso:: :meth:`pyspark.sql.functions.pandas_udf`
+
+ """
+ # Columns are special because hasattr always return True
+ if isinstance(udf, Column) or not hasattr(udf, 'func') \
+ or udf.evalType != PythonEvalType.SQL_SCALAR_PANDAS_ITER_UDF:
+ raise ValueError("Invalid udf: the udf argument must be a
pandas_udf of type "
+ "SQL_SCALAR_PANDAS_ITER_UDF.")
Review comment:
Shall we say `PandasUDFType.SCALAR_ITER` instead of
`SQL_SCALAR_PANDAS_ITER_UDF`? Users should use `PandasUDFType`.
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