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https://issues.apache.org/jira/browse/KAFKA-10847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17273417#comment-17273417
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Guozhang Wang commented on KAFKA-10847:
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Hello [~spena], thanks for the detailed implementation design. One thing I'd
like to bring up, but not requesting that we should fix as part of the scope of
this JIRA is that, today we use a kv-store to buffer the stream records which
is sub-optimal: for stream buffering, we do not need to override any old values
with new values with the same key, and hence we'd have to add a sequence id to
the key so that all inserts are effectively just "appends", and never
"overwrites". We can, of course, have a better byte format to buffer stream
records than a kv store.
> Avoid spurious left/outer join results in stream-stream join
> -------------------------------------------------------------
>
> Key: KAFKA-10847
> URL: https://issues.apache.org/jira/browse/KAFKA-10847
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Matthias J. Sax
> Assignee: Sergio Peña
> Priority: Major
>
> KafkaStreams follows an eager execution model, ie, it never buffers input
> records but processes them right away. For left/outer stream-stream join,
> this implies that left/outer join result might be emitted before the window
> end (or window close) time is reached. Thus, a record what will be an
> inner-join result, might produce a eager (and spurious) left/outer join
> result.
> We should change the implementation of the join, to not emit eager left/outer
> join result, but instead delay the emission of such result after the window
> grace period passed.
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