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https://issues.apache.org/jira/browse/KAFKA-8295?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sagar Rao updated KAFKA-8295:
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Summary: Add merge() operator to State Stores. (was: Optimize count()
using RocksDB merge operator)
> Add merge() operator to State Stores.
> -------------------------------------
>
> Key: KAFKA-8295
> URL: https://issues.apache.org/jira/browse/KAFKA-8295
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: A. Sophie Blee-Goldman
> Assignee: Sagar Rao
> Priority: Major
>
> In addition to regular put/get/delete RocksDB provides a fourth operation,
> merge. This essentially provides an optimized read/update/write path in a
> single operation. One of the built-in (C++) merge operators exposed over the
> Java API is a counter. We should be able to leverage this for a more
> efficient implementation of count()
>
> (Note: Unfortunately it seems unlikely we can use this to optimize general
> aggregations, even if RocksJava allowed for a custom merge operator, unless
> we provide a way for the user to specify and connect a C++ implemented
> aggregator – otherwise we incur too much cost crossing the jni for a net
> performance benefit)
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