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

["Mridul Muralidharan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-3847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14163407#comment-14163407 ] 

Mridul Muralidharan commented on SPARK-3847:
--------------------------------------------

Wow, nice bug ! This is unexpected - thanks for reporting this.

> 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



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@spark.apache.org
For additional commands, e-mail: issues-help@spark.apache.org