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https://issues.apache.org/jira/browse/KAFKA-7918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17241139#comment-17241139
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Matthias J. Sax commented on KAFKA-7918:
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The existing caching layer also collapses writes into the changelog for the
same key – but if you don't do the serialization, it's very hard to budget the
used memory. It could make the system unstable and your JVM might crash with
ouf-of-memory errors.
> Streams store cleanup: inline byte-store generic parameters
> -----------------------------------------------------------
>
> Key: KAFKA-7918
> URL: https://issues.apache.org/jira/browse/KAFKA-7918
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: John Roesler
> Assignee: A. Sophie Blee-Goldman
> Priority: Major
> Fix For: 2.3.0
>
>
> Currently, the fundamental layer of stores in Streams is the "bytes store".
> The easiest way to identify this is in
> `org.apache.kafka.streams.state.Stores`, all the `StoreBuilder`s require a
> `XXBytesStoreSupplier`.
> We provide several implementations of these bytes stores, typically an
> in-memory one and a persistent one (aka RocksDB).
> Inside these bytes stores, the key is always `Bytes` and the value is always
> `byte[]` (serialization happens at a higher level). However, the store
> implementations are generically typed, just `K` and `V`.
> This is good for flexibility, but it makes the code a little harder to
> understand. I think that we used to do serialization at a lower level, so the
> generics are a hold-over from that.
> It would simplify the code if we just inlined the actual k/v types and maybe
> even renamed the classes from (e.g.) `InMemoryKeyValueStore<K,V>` to
> `InMemoryKeyValueBytesStore`, and so forth.
>
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