lidavidm commented on a change in pull request #31738: URL: https://github.com/apache/spark/pull/31738#discussion_r589571748
########## File path: python/docs/source/user_guide/arrow_pandas.rst ########## @@ -410,3 +410,11 @@ described in `SPARK-29367 <https://issues.apache.org/jira/browse/SPARK-29367>`_ ``pandas_udf``\s or :meth:`DataFrame.toPandas` with Arrow enabled. More information about the Arrow IPC change can be read on the Arrow 0.15.0 release `blog <https://arrow.apache.org/blog/2019/10/06/0.15.0-release/#columnar-streaming-protocol-change-since-0140>`_. +Setting Arrow ``self_destruct`` for memory savings +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Since Spark 3.2, the Spark configuration ``spark.sql.execution.arrow.pyspark.selfDestruct.enabled`` can be used to enable PyArrow's ``self_destruct`` feature, which can save memory when creating a Pandas dataframe via ``toPandas`` by freeing Arrow-allocated memory while building the Pandas dataframe. +This option is experimental, and some operations may fail on the resulting Pandas dataframe due to immutable backing arrays. +Typically, you would see the error ``ValueError: buffer source array is read-only``. +Newer versions of Pandas may fix these errors by improving support for such cases. +Additionally, this conversion may be slower because it is single-threaded. Review comment: I think I haven't fully explained the nature of this - it's not any single issue in Pandas, nor is it specific to any particular version. Instead, it's just that depending on how each Pandas operation was implemented underneath, it may or may not have been _declared_ to accept an immutable backing array, independently of whether that operation _could be implemented_ on an immutable array. So whether you see this will depend on what exactly you do with the dataframe, and there's no one version range we can list or one issue we can link to. And indeed, you could see this error see this _without_ this Arrow option enabled; it's just much less likely, since there will be few cases that Arrow can perform a zero-copy conversion in that case. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
