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From "Matthias J. Sax (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-2984) KTable should send old values along with new values to downstreams
Date Tue, 05 Sep 2017 20:41:00 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-2984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16154267#comment-16154267
] 

Matthias J. Sax commented on KAFKA-2984:
----------------------------------------

What do you exactly mean by this? If you think about DSL level, there are no plans to expose
it. The DSL should be used to express your computation in an declarative way and you should
not need to worry about implementation details like this. Why would you need to access this
information?

> KTable should send old values along with new values to downstreams
> ------------------------------------------------------------------
>
>                 Key: KAFKA-2984
>                 URL: https://issues.apache.org/jira/browse/KAFKA-2984
>             Project: Kafka
>          Issue Type: Sub-task
>          Components: streams
>    Affects Versions: 0.10.0.0
>            Reporter: Yasuhiro Matsuda
>            Assignee: Yasuhiro Matsuda
>             Fix For: 0.10.0.0
>
>
> Old values are necessary for implementing aggregate functions. KTable should augment
an event with its old value. Basically KTable stream is a stream of (key, (new value, old
value)) internally. The old value may be omitted when it is not used in the topology.



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