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Posted to dev@kafka.apache.org by "Matthias J. Sax (JIRA)" <ji...@apache.org> on 2018/10/09 01:46:00 UTC

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

Matthias J. Sax created KAFKA-7492:
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             Summary: 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


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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