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https://issues.apache.org/jira/browse/KAFKA-10847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17290685#comment-17290685
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Guozhang Wang commented on KAFKA-10847:
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I agree that we should delete upon emitting expired records' joined results.
Currently since we do range-query + deletion per input record, I guess in
practice each time we would only expire very few records.
If range query + deletion turns out to be an overhead in practice, we can
consider 1) do range-query + deletion less frequently so that each time we
would get a reasonable number of records to expire, and 2) use range deletion
(https://rocksdb.org/blog/2018/11/21/delete-range.html), which would be
efficient especially if we have more records to expire in one call.
bq. I do a single-lookup in the store to check if the key is there, if not,
then it continues; otherwise it calls the put(key, null) to delete it.
Just a syntax sugar, you can just call `putIfAbsent(key, null)` instead.
> 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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