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https://issues.apache.org/jira/browse/KAFKA-7497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16647138#comment-16647138
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Matthias J. Sax commented on KAFKA-7497:
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[~guozhang] I cannot follow? A self-join would still have a
sliding-join-window, and thus, all records with the same key within the window
would be joined. How can a stateless map achieve this? I want to add, that a
sliding-window aggregation might allow to compute the same thing – note,
though, that Kafka Streams only supports hopping/tumbling windows for
aggregations atm, but no sliding windows.
For the use case: this is also unclear to me to be honest though.
> Kafka Streams should support self-join on streams
> -------------------------------------------------
>
> Key: KAFKA-7497
> URL: https://issues.apache.org/jira/browse/KAFKA-7497
> Project: Kafka
> Issue Type: New Feature
> Components: streams
> Reporter: Robin Moffatt
> Priority: Major
> Labels: needs-kip
>
> There are valid reasons to want to join a stream to itself, but Kafka Streams
> does not currently support this ({{Invalid topology: Topic foo has already
> been registered by another source.}}). To perform the join requires creating
> a second stream as a clone of the first, and then doing a join between the
> two. This is a clunky workaround and results in unnecessary duplication of
> data.
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