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https://issues.apache.org/jira/browse/KAFKA-8295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17317613#comment-17317613
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Sagar Rao commented on KAFKA-8295:
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Thanks Sophie for the background. I do plan to run some benchmarks by extending
the rocksjava benchmarks for my use case. I can probably share the performance
numbers here which might help us to decide if it should be considered or not.
Yeah, this merge operator mayn't be applicable for most other state stores so
if it comes to a KIP for this, I would look at 617- which I have seen before
while implementing KIP-614. Thanks for sharing that!
> Optimize count() using RocksDB merge operator
> ---------------------------------------------
>
> Key: KAFKA-8295
> URL: https://issues.apache.org/jira/browse/KAFKA-8295
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: A. Sophie Blee-Goldman
> 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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