[jira] [Created] (FLINK-5111) Change the assignToKeyGroup() method to not use Object.hashCode()

["Kostas Kloudas (JIRA)" <ji...@apache.org>]

Kostas Kloudas created FLINK-5111:
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             Summary: Change the assignToKeyGroup() method to not use Object.hashCode()
                 Key: FLINK-5111
                 URL: https://issues.apache.org/jira/browse/FLINK-5111
             Project: Flink
          Issue Type: Bug
    Affects Versions: 1.2.0
            Reporter: Kostas Kloudas
            Priority: Blocker
             Fix For: 1.2.0


Currently we use the Object.hashCode method as an intermediate step to assign an item to a key group. According to the java documentation:

"This integer (returned by the method) need not remain consistent from one execution of an application to another execution of the same application."

This means that a key may be assigned to another keygroup after restoring. This can easily break the semantics of a pipeline.



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