[jira] [Resolved] (KAFKA-5648) make Merger extend Aggregator

["Clemens Valiente (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-5648?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Clemens Valiente resolved KAFKA-5648.
-------------------------------------
    Resolution: Won't Fix

> make Merger extend Aggregator
> -----------------------------
>
>                 Key: KAFKA-5648
>                 URL: https://issues.apache.org/jira/browse/KAFKA-5648
>             Project: Kafka
>          Issue Type: New Feature
>          Components: streams
>    Affects Versions: 0.11.0.0
>            Reporter: Clemens Valiente
>            Assignee: Clemens Valiente
>            Priority: Minor
>
> Hi,
> I suggest that Merger<K,V> should extend Aggregator<K,V,V>.
> reason:
> Both classes usually do very similar things. A merger takes two sessions and combines them, an aggregator takes an existing session and aggregates new values into it.
> in some use cases it is actually the same thing, e.g.:
> <null, log_event> -> .map() to <session_id,SingletonList<log_event>> -> .groupByKey().aggregate() to <session_id, List<log_event>>
> In this case both merger and aggregator do the same thing: take two lists and combine them into one.
> With the proposed change we could pass the Merger as both the merger and aggregator to the .aggregate() method and keep our business logic within one merger class.
> Or in other words: The Merger is simply an Aggregator that happens to aggregate two objects of the same class



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