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https://issues.apache.org/jira/browse/KAFKA-5684?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16109412#comment-16109412
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Guozhang Wang commented on KAFKA-5684:
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Thanks for filing the JIRA.
I think we made a mistake when discussing KIP-160, that the key/valueSerde and
mapper are actually overlapped. In the end we will only call key/valueSerde
only when the K/V types are byte[], but due to that we are making a runtime
instanceof check each time which is unnecessary since as users have provided
the mapper whose output is a {{String}}, so it should take care of the
deserialization if K/V are really byte[].
So I suggest we can change its internal impl as well along with this JIRA such
that (cc [~james.c] WDYT):
a) if mapper is provided, ignore serdes and always print as {{label:
mapper(k, v)}} without checking the k/v types at runtime at all, label can be
the default value if it is not provided.
b) if mapper is not provided, print as {{label: toString(serialized(k),
serialized(v))}} where label and serde could be default if they are not
provided.
> KStreamPrintProcessor as customized KStreamPeekProcessor
> --------------------------------------------------------
>
> Key: KAFKA-5684
> URL: https://issues.apache.org/jira/browse/KAFKA-5684
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Paolo Patierno
> Assignee: Paolo Patierno
> Priority: Minor
>
> Hi,
> the {{KStreamPrintProcessor}} is implemented from scratch (from the
> {{AbstractProcessor}}) and the same for the related supplier.
> It looks to me that it's just a special {{KStreamPeekProcessor}} with
> forwardDownStream to false and that allows the possibility to specify Serdes
> instances used if key/values are bytes.
> At same time used by a {{print()}} method it provides a fast way to print
> data flowing through the pipeline (while using just {{peek()}} you need to
> write the code).
> I think that it could be useful to refactoring the {{KStreamPrintProcessor}}
> as derived from the {{KStreamPeekProcessor}} customizing its behavior.
> Thanks,
> Paolo.
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