[jira] [Commented] (KAFKA-4468) Correctly calculate the window end timestamp after read from state stores

["Evgeny Veretennikov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-4468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16076281#comment-16076281 ] 

Evgeny Veretennikov commented on KAFKA-4468:
--------------------------------------------

I have researched windowed stores a bit more and noticed, that {{WindowedDeserializer}} isn't used in Kafka source codes, including internals:

{noformat}
$ grep -Rl WindowedDeserializer | grep java | grep -v test
streams/src/main/java/org/apache/kafka/streams/kstream/internals/WindowedDeserializer.java
{noformat}

It's not a part of API too (as it's in {{internals}} package). {{RocksDBWindowStore}} doesn't use {{WindowedDeserializer}} to deserialize windowed keys, but uses {{WindowStoreUtils}} static methods instead, including {{timeWindowForSize()}} method, which already uses {{windowSize}} to calculate proper {{TimeWindow}}.

So, shouldn't we just remove {{WindowedDeserializer}}?

> Correctly calculate the window end timestamp after read from state stores
> -------------------------------------------------------------------------
>
>                 Key: KAFKA-4468
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4468
>             Project: Kafka
>          Issue Type: Bug
>          Components: streams
>            Reporter: Guozhang Wang
>              Labels: architecture
>
> When storing the WindowedStore on the persistent KV store, we only use the start timestamp of the window as part of the combo-key as (start-timestamp, key). The reason that we do not add the end-timestamp as well is that we can always calculate it from the start timestamp + window_length, and hence we can save 8 bytes per key on the persistent KV store.
> However, after read it (via {{WindowedDeserializer}}) we do not set its end timestamp correctly but just read it as an {{UnlimitedWindow}}. We should fix this by calculating its end timestamp as mentioned above.



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