[jira] [Created] (KAFKA-4729) Stores for kstream-kstream join cannot be in-memory

["Eno Thereska (JIRA)" <ji...@apache.org>]

Eno Thereska created KAFKA-4729:
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             Summary: Stores for kstream-kstream join cannot be in-memory
                 Key: KAFKA-4729
                 URL: https://issues.apache.org/jira/browse/KAFKA-4729
             Project: Kafka
          Issue Type: Improvement
          Components: streams
    Affects Versions: 0.10.2.0
            Reporter: Eno Thereska
             Fix For: 0.10.3.0


Whereas we can specify in the DSL that stores used for aggregates can be RocksDb-based on in-memory, we cannot do that for stores used for KStream-KStream joins. E.g., the join() methon in KStreamImpl.java creates two state stores and the user does not have the option of having them be in-memory:

StateStoreSupplier thisWindow =
                createWindowedStateStore(windows, keySerde, lhsValueSerde, joinThisName + "-store");

            StateStoreSupplier otherWindow =
                createWindowedStateStore(windows, keySerde, otherValueSerde, joinOtherName + "-store");


Part of the problem is that for joins, stores are not exposed to the user. We might want to rethink that.



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