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https://issues.apache.org/jira/browse/KAFKA-8037?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16787319#comment-16787319
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Patrik Kleindl commented on KAFKA-8037:
---------------------------------------

Sorry for the mess, I thought I had to re-create the PR when I fixed something.

[https://github.com/apache/kafka/pull/6398] has the current changes.

Performance test with 1 mio. good records shows no difference, with 1 mio. bad 
records I see a 50% increase in time, but this might have been due to the 
excessive logging.

> KTable restore may load bad data
> --------------------------------
>
>                 Key: KAFKA-8037
>                 URL: https://issues.apache.org/jira/browse/KAFKA-8037
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>            Reporter: Matthias J. Sax
>            Assignee: Patrik Kleindl
>            Priority: Minor
>              Labels: pull-request-available
>
> If an input topic contains bad data, users can specify a 
> `deserialization.exception.handler` to drop corrupted records on read. 
> However, this mechanism may be by-passed on restore. Assume a 
> `builder.table()` call reads and drops a corrupted record. If the table state 
> is lost and restored from the changelog topic, the corrupted record may be 
> copied into the store, because on restore plain bytes are copied.
> If the KTable is used in a join, an internal `store.get()` call to lookup the 
> record would fail with a deserialization exception if the value part cannot 
> be deserialized.
> GlobalKTables are affected, too (cf. KAFKA-7663 that may allow a fix for 
> GlobalKTable case). It's unclear to me atm, how this issue could be addressed 
> for KTables though.
> Note, that user state stores are not affected, because they always have a 
> dedicated changelog topic (and don't reuse an input topic) and thus the 
> corrupted record would not be written into the changelog.



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