[jira] [Assigned] (KAFKA-3561) Auto create through topic for KStream aggregation and join

["Damian Guy (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-3561?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Damian Guy reassigned KAFKA-3561:
---------------------------------

    Assignee: Damian Guy

> Auto create through topic for KStream aggregation and join
> ----------------------------------------------------------
>
>                 Key: KAFKA-3561
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3561
>             Project: Kafka
>          Issue Type: Bug
>          Components: streams
>            Reporter: Guozhang Wang
>            Assignee: Damian Guy
>              Labels: api
>             Fix For: 0.10.1.0
>
>
> For KStream.join / aggregateByKey operations that requires the streams to be partitioned on the record key, today users should repartition themselves through the "through" call:
> {code}
> stream1 = builder.stream("topic1");
> stream2 = builder.stream("topic2");
> stream3 = stream1.map(/* set the right key for join*/).through("topic3");
> stream4 = stream2.map(/* set the right key for join*/).through("topic4");
> stream3.join(stream4, ..)
> {code}
> This pattern can actually be done by the Streams DSL itself instead of requiring users to specify themselves, i.e. users can just set the right key like (see KAFKA-3430) and then call join, which will be translated by adding the "internal topic for repartition".
> Another thing is that today if user do not call "through" after setting a new key, the aggregation result would not be correct as the aggregation is based on key B while the source partitions is partitioned by key A and hence each task will only get a partial aggregation for all keys. But this is not validated in the DSL today. We should do both the auto-translation and validation.



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