[jira] [Commented] (KAFKA-7492) Explain `null` handling for reduce and aggregate

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-7492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16771310#comment-16771310 ] 

ASF GitHub Bot commented on KAFKA-7492:
---------------------------------------

asutosh936 commented on pull request #6285: KAFKA-7492 : Updated javadocs for aggregate and reduce methods returning null behavior.
URL: https://github.com/apache/kafka/pull/6285
 
 
   *More detailed description of your change,
   if necessary. The PR title and PR message become
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   comment to ping reviewers.*
   
   - This is update to the existing javadocs for KGroupedStream class. More details are available at 
   https://stackoverflow.com/questions/52692202/what-happens-if-the-aggregator-of-a-kgroupedstream-returns-null
   
   
   *Summary of testing strategy (including rationale)
   for the feature or bug fix. Unit and/or integration
   tests are expected for any behaviour change and
   system tests should be considered for larger changes.*
   
   ### Committer Checklist (excluded from commit message)
   - [ ] Verify design and implementation 
   - [ ] Verify test coverage and CI build status
   - [ ] Verify documentation (including upgrade notes)
   
 
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> Explain `null` handling for reduce and aggregate
> ------------------------------------------------
>
>                 Key: KAFKA-7492
>                 URL: https://issues.apache.org/jira/browse/KAFKA-7492
>             Project: Kafka
>          Issue Type: Improvement
>          Components: documentation, streams
>            Reporter: Matthias J. Sax
>            Priority: Minor
>              Labels: beginner, docs, newbie
>
> We currently don't explain how records with `null` value are handled in reduce and aggregate. In particular, what happens when the users' aggregation/reduce `apply()` implementation returns `null`.
> We should update the JavaDocs accordingly and maybe also update the docs on the web page.
> Cf. https://stackoverflow.com/questions/52692202/what-happens-if-the-aggregator-of-a-kgroupedstream-returns-null



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