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https://issues.apache.org/jira/browse/KAFKA-10578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17209253#comment-17209253
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Matthias J. Sax commented on KAFKA-10578:
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[~javier.freire] – I added you to the list of contributors and assigned the
ticket to you. You can know also self-assign tickets.
> Convert KTable to a KStream using the previous value
> ----------------------------------------------------
>
> Key: KAFKA-10578
> URL: https://issues.apache.org/jira/browse/KAFKA-10578
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Javier Freire Riobó
> Priority: Minor
> Labels: kip
>
> Imagine that we have an entity for which we want to emit the difference
> between the current and the previous state. The simplest case would be that
> the entity was an integer number and you want to emit the subtraction between
> the current and previous values.
> For example, for the input stream 4, 6, 3 the output 4 (4 - 0), 2 (6 - 4), -3
> (3 - 6) is expected.
> The way to achieve this with kafka streams would be through an aggregate.
> The main problem, apart from needing more code, is that if the same event is
> received twice at the same time and the commit time is not 0, the difference
> is deleted and nothing is emitted.
> KIP-675:
> [https://cwiki.apache.org/confluence/display/KAFKA/KIP-675%3A+Convert+KTable+to+a+KStream+using+the+previous+value]
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