[jira] [Commented] (SPARK-2148) Document custom class as key needing equals() AND hashcode()

["Andrew Ash (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-2148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14032024#comment-14032024 ] 

Andrew Ash commented on SPARK-2148:
-----------------------------------

https://github.com/apache/spark/pull/1092

> Document custom class as key needing equals() AND hashcode()
> ------------------------------------------------------------
>
>                 Key: SPARK-2148
>                 URL: https://issues.apache.org/jira/browse/SPARK-2148
>             Project: Spark
>          Issue Type: Bug
>          Components: Documentation
>    Affects Versions: 1.0.0
>            Reporter: Andrew Ash
>
> Several support requests on user@ have been tracked down to using a custom class as the key in a {{groupByKey()}} or {{reduceByKey()}} that has a custom {{equals()}} method but not the corresponding custom {{hashCode()}} method.
> Let's add a note in the documentation that custom keys need both {{equals()}} and {{hashCode()}} overridden, never just {{equals()}}
> The right place for this addition might be as a sub-section or note in http://spark.apache.org/docs/latest/programming-guide.html#working-with-key-value-pairs
> It should probably include a link to http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#hashCode()



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