[jira] [Commented] (KAFKA-3511) Provide built-in aggregators sum() and avg() in Kafka Streams DSL

["Jay Kreps (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-3511?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15227096#comment-15227096 ] 

Jay Kreps commented on KAFKA-3511:
----------------------------------

The issue is that there are dozens of common aggregation functions, which ones will be built in and which not? 

I would argue the other direction, why not remove countByKey and implement all of these as Aggregator implementations, so you would do something like:

myStream.aggregateByKey(new Count(), <serdes>)

> 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: kafka streams
>            Reporter: Guozhang Wang
>              Labels: 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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