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https://issues.apache.org/jira/browse/KAFKA-3511?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15234370#comment-15234370
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Guozhang Wang commented on KAFKA-3511:
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I like [~jkreps] suggestion about giving the aggregators instead of adding more
and more built-in operators. The problem we need to solve is that, there is
more than one functions in aggregate: initializer and adder for KStream,
initializer, adder and subtractor for KTable. So to achieve this simple
interface we need to have an overloading
aggregate(aggregator, <serdes>)... where aggregator will have multiple APIs and
hence cannot be re-written in lambda expression; but as long as we make it
clear that it is only for customizing common aggregations that would be fine.
> Provide built-in aggregators sum() and avg() in Kafka Streams DSL
> -----------------------------------------------------------------
>
> Key: KAFKA-3511
> URL: https://issues.apache.org/jira/browse/KAFKA-3511
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Reporter: Guozhang Wang
> Labels: api, newbie
> Fix For: 0.10.0.0
>
>
> Currently we only have one built-in aggregate function count() in the Kafka
> Streams DSL, but we want to add more aggregation functions like sum() and
> avg().
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