[jira] [Created] (KAFKA-9611) KGroupedTable.aggregate(...) emits incorrect values

[Neil Green (Jira)]

Neil Green created KAFKA-9611:
---------------------------------

             Summary: KGroupedTable.aggregate(...) emits incorrect values
                 Key: KAFKA-9611
                 URL: https://issues.apache.org/jira/browse/KAFKA-9611
             Project: Kafka
          Issue Type: Bug
          Components: streams
    Affects Versions: 2.4.0
            Reporter: Neil Green


I've run into what appears to be strange behaviour in a streams app.

I have a KTable produced from a topic. The table contains entries like 
"abc1234/signal1" : 1, "abc1234/signal2" : 3
The key is "id/signal name" and the value is an int. I want to produce a 
aggregate ktable containing the sum all of the
signals for a given id.

{{So if source ktable contains:}}

{{+-----------------+---+}}
{{| abc1234/signal1 | 2 |}}
{{| abc1234/signal2 | 4 |}}
{{| abc4566/signal1 | 3 |}}
{{+-----------------+---+}}

{{Then the output should contain}}

{{+---------+---+}}
{{| abc1234 | 6 |}}
{{| abc4566 | 3 |}}
{{+---------+---+}}




{{On a change}}

{{+-----------------+---+}}
{{| abc1234/signal1 | 3 |}}
{{+-----------------+---+}}
{{```}}
{{I would expect the change}}
{{```}}
{{+---------+---+}}
{{| abc1234 | 7 |}}
{{+---------+---+}}

{{to be published.}}

In fact there are two changelog entries published

{{+---------+---+}}
{{| abc1234 | 4 | // This is incorrect. The sum of the signals is never 4.}}
{{+---------+---+}}

Then

{{+---------+---+}}
{{| abc1234 | 7 |}}
{{+---------+---+}}



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