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From "Richard Yu (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (KAFKA-4217) KStream.transform equivalent of flatMap
Date Fri, 01 Sep 2017 02:30:00 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-4217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16149928#comment-16149928
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Richard Yu edited comment on KAFKA-4217 at 9/1/17 2:29 AM:
-----------------------------------------------------------

[~guozhang] The flatTransform method that you mentioned earlier suggests that there is no
mapper in the the method input parameters. 
If the method does not have a mapper, it will be the same as the regular transform method.

Should there be a default mapper, or is one given to the method?


was (Author: yohan123):
[~guozhang] The flatTransform method that you mentioned earlier suggests that there is no
mapper in the the method input parameters. 
If the method does not have a mapper, it will be the same as the regular transfer method.

Should there be a default mapper, or is one given to the method?

> KStream.transform equivalent of flatMap
> ---------------------------------------
>
>                 Key: KAFKA-4217
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4217
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>    Affects Versions: 0.10.0.1
>            Reporter: Elias Levy
>              Labels: api, needs-kip, newbie
>
> {{KStream.transform}} gives you access to state stores while allowing you to return zero
or one transformed {{KeyValue}}.  Alas, it is unclear what method you should use if you want
to access state stores and return zero or multiple {{KeyValue}}.  Presumably you can use {{transform}},
always return {{null}}, and use {{ProcessorContext.forward}} to emit {{KeyValues}}.
> It may be good to introduce a {{transform}}-like {{flatMap}} equivalent, or allow store
access from other {{KStream}} methods, such as {{flatMap}} itself.



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