[jira] [Commented] (KAFKA-2984) KTable should send old values along with new values to downstreams

["Dmitry Minkovsky (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-2984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16318939#comment-16318939 ] 

Dmitry Minkovsky commented on KAFKA-2984:
-----------------------------------------

I was thinking something like https://groups.google.com/d/msg/confluent-platform/jOr7pW4qH_A/rnYRph3oCAAJ, but I guess that's not related to these internals.

> 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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