[jira] [Resolved] (SPARK-48302) Preserve nulls in map columns in PyArrow Tables

["Hyukjin Kwon (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-48302?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyukjin Kwon resolved SPARK-48302.
----------------------------------
    Fix Version/s: 4.0.0
       Resolution: Fixed

Issue resolved by pull request 46837
[https://github.com/apache/spark/pull/46837]

> Preserve nulls in map columns in PyArrow Tables
> -----------------------------------------------
>
>                 Key: SPARK-48302
>                 URL: https://issues.apache.org/jira/browse/SPARK-48302
>             Project: Spark
>          Issue Type: Sub-task
>          Components: PySpark
>    Affects Versions: 4.0.0, 3.5.1
>            Reporter: Ian Cook
>            Assignee: Ian Cook
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 4.0.0
>
>
> Because of a limitation in PyArrow, when PyArrow Tables containing MapArray columns with nested fields or timestamps are passed to {{{}spark.createDataFrame(){}}}, null values in the MapArray columns are replaced with empty lists.
> The PySpark function where this happens is {{{}pyspark.sql.pandas.types._check_arrow_array_timestamps_localize{}}}.
> Also see [https://github.com/apache/arrow/issues/41684].
> See the skipped tests and the TODO mentioning SPARK-48302.
> [Update] A fix for this has been implemented in PyArrow in [https://github.com/apache/arrow/pull/41757] by adding a {{mask}} argument to {{{}pa.MapArray.from_arrays{}}}. This will be released in PyArrow 17.0.0. Since older versions of PyArrow (which PySpark will still support for a while) won't have this argument, we will need to do a check like:
> {{LooseVersion(pa.\_\_version\_\_) >= LooseVersion("17.0.0")}}
> or
> {{from inspect import signature}}
> {{"mask" in signature(pa.MapArray.from_arrays).parameters}}
> and only pass {{mask}} if that's true.



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