[jira] [Assigned] (SPARK-3847) Enum.hashCode is only consistent within the same JVM

["Apache Spark (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-3847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Spark reassigned SPARK-3847:
-----------------------------------

    Assignee:     (was: Apache Spark)

> Enum.hashCode is only consistent within the same JVM
> ----------------------------------------------------
>
>                 Key: SPARK-3847
>                 URL: https://issues.apache.org/jira/browse/SPARK-3847
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>    Affects Versions: 1.1.0
>         Environment: Oracle JDK 7u51 64bit on Ubuntu 12.04
>            Reporter: Nathan Bijnens
>              Labels: enum
>
> When using java Enum's as key in some operations the results will be very unexpected. The issue is that the Java Enum.hashCode returns the memoryposition, which is different on each JVM. 
> {code}
> messages.filter(_.getHeader.getKind == Kind.EVENT).count
> >> 503650
> val tmp = messages.filter(_.getHeader.getKind == Kind.EVENT)
> tmp.map(_.getHeader.getKind).countByValue
> >> Map(EVENT -> 1389)
> {code}
> Because it's actually a JVM issue we either should reject with an error enums as key or implement a workaround.
> A good writeup of the issue can be found here (and a workaround):
> http://dev.bizo.com/2014/02/beware-enums-in-spark.html
> Somewhat more on the hash codes and Enum's:
> https://stackoverflow.com/questions/4885095/what-is-the-reason-behind-enum-hashcode
> And some issues (most of them rejected) at the Oracle Bug Java database:
> - http://bugs.java.com/bugdatabase/view_bug.do?bug_id=8050217
> - http://bugs.java.com/bugdatabase/view_bug.do?bug_id=7190798



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