[jira] [Created] (KAFKA-4726) ValueMapper should have (read) access to key

["Steven Schlansker (JIRA)" <ji...@apache.org>]

Steven Schlansker created KAFKA-4726:
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             Summary: ValueMapper should have (read) access to key
                 Key: KAFKA-4726
                 URL: https://issues.apache.org/jira/browse/KAFKA-4726
             Project: Kafka
          Issue Type: Improvement
          Components: streams
    Affects Versions: 0.10.1.1
            Reporter: Steven Schlansker


{{ValueMapper}} should have read-only access to the key for the value it is mapping.  Sometimes the value transformation will depend on the key.

It is possible to do this with a full blown {{KeyValueMapper}} but that loses the promise that you won't change the key -- so you might introduce a re-keying phase that is totally unnecessary.

[ If mapValues() is guaranteed to be no less efficient than map() the issue may be moot, but I presume there are some optimizations that are valid with the former but not latter. ]



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