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Posted to issues@spark.apache.org by "Xiangrui Meng (Jira)" <ji...@apache.org> on 2019/11/09 03:22:00 UTC

[jira] [Resolved] (SPARK-28978) PySpark: Can't pass more than 256 arguments to a UDF

     [ https://issues.apache.org/jira/browse/SPARK-28978?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xiangrui Meng resolved SPARK-28978.
-----------------------------------
    Fix Version/s: 3.0.0
         Assignee: Bago Amirbekian
       Resolution: Fixed

> PySpark: Can't pass more than 256 arguments to a UDF
> ----------------------------------------------------
>
>                 Key: SPARK-28978
>                 URL: https://issues.apache.org/jira/browse/SPARK-28978
>             Project: Spark
>          Issue Type: Bug
>          Components: PySpark
>    Affects Versions: 2.3.2, 2.4.0, 2.4.4
>            Reporter: Jim Fulton
>            Assignee: Bago Amirbekian
>            Priority: Major
>              Labels: koalas, mlflow, pyspark
>             Fix For: 3.0.0
>
>
> This code:
> [https://github.com/apache/spark/blob/712874fa0937f0784f47740b127c3bab20da8569/python/pyspark/worker.py#L367-L379]
> Creates Python lambdas that call UDF functions passing arguments singly, rather than using varargs.  For example: `lambda a: f(a[0], a[1], ...)`.
> This fails when there are more than 256 arguments.
> mlflow, when generating model predictions, uses an argument for each feature column.  I have a model with > 500 features.
> I was able to easily hack around this by changing the generated lambdas to use varargs, as in `lambda a: f(*a)`. 
> IDK why these lambdas were created the way they were.  Using varargs is much simpler and works fine in my testing.
>  
>  



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