[jira] [Commented] (SPARK-15258) Nested/Chained case statements generate codegen over 64k exception

["Qifan Pu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-15258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15392521#comment-15392521 ] 

Qifan Pu commented on SPARK-15258:
----------------------------------

Just want to leave a note that we might want to limit method size to be < 8K. Beyond 8K JIT won't compile and can cause performance degradation. This can happen for queries with wide schema.

> Nested/Chained case statements generate codegen over 64k exception
> ------------------------------------------------------------------
>
>                 Key: SPARK-15258
>                 URL: https://issues.apache.org/jira/browse/SPARK-15258
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 1.6.1
>            Reporter: Jonathan Gray
>         Attachments: NestedCases.scala
>
>
> Nested/Chained case-when expressions generate a codegen goes beyound 64k exception.
> A test attached demonstrates this behaviour.
> I'd like to try and fix this but don't really know the best place to start.  Ideally, I'd like to avoid the codegen fallback as with large volumes this hurts performance.
> This is similar(ish) to SPARK-13242 but I'd like to see if there are any alternatives to the codegen fallback approach.



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