Javier Freire Riobó created KAFKA-10578:
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             Summary: KIP-675: 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: Wish
          Components: streams
            Reporter: Javier Freire Riobó


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.

 



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