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https://issues.apache.org/jira/browse/KAFKA-4887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15922789#comment-15922789
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Guozhang Wang commented on KAFKA-4887:
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Thanks Elias, this does sound a bug to me.
Just curious what is your scenario that you'd like to insert duplicated records
with caching turned on? Or do you actually prefer to not have caching since it
seems you do not want any dedupping anyways but cannot do that?
> Enabling caching on a persistent window store breaks support for duplicate
> insertion
> ------------------------------------------------------------------------------------
>
> Key: KAFKA-4887
> URL: https://issues.apache.org/jira/browse/KAFKA-4887
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 0.10.2.0
> Reporter: Elias Levy
>
> {{CachingWindowStore}} and {{RocksDBWindowStore}} interact badly when
> duplicate insertion support is enabled by passing {{true}} as the fourth
> argument to {{windowed}} in the state store supplier.
> When the feature is enabled, {{RocksDBWindowStore}} correct handles
> duplicates by assigning a unique sequence number to each element on insertion
> and using the number within the key.
> When caching is enabled by calling {{enableCaching}} on the supplier,
> {{CachingWindowStore}} fails to the the same. Thus, of multiple values
> inserted with the same key, only the last one survives.
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