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From "Guozhang Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-4750) KeyValueIterator returns null values
Date Sun, 25 Jun 2017 17:29:00 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-4750?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16062384#comment-16062384
] 

Guozhang Wang commented on KAFKA-4750:
--------------------------------------

I think the Streams library should not assume that either 1) the serde will always return
{{null}} if the input is {{null}}, or 2) the serde will never return {{null}} if the input
is not {{null}}. On the other hand, since we are treating {{null}} to indicate deletion specifically,
checking null values before calling the serde makes sense to me.



> KeyValueIterator returns null values
> ------------------------------------
>
>                 Key: KAFKA-4750
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4750
>             Project: Kafka
>          Issue Type: Bug
>          Components: streams
>    Affects Versions: 0.10.1.1, 0.11.0.0, 0.10.2.1
>            Reporter: Michal Borowiecki
>            Assignee: Evgeny Veretennikov
>              Labels: newbie
>         Attachments: DeleteTest.java
>
>
> The API for ReadOnlyKeyValueStore.range method promises the returned iterator will not
return null values. However, after upgrading from 0.10.0.0 to 0.10.1.1 we found null values
are returned causing NPEs on our side.
> I found this happens after removing entries from the store and I found resemblance to
SAMZA-94 defect. The problem seems to be as it was there, when deleting entries and having
a serializer that does not return null when null is passed in, the state store doesn't actually
delete that key/value pair but the iterator will return null value for that key.
> When I modified our serilizer to return null when null is passed in, the problem went
away. However, I believe this should be fixed in kafka streams, perhaps with a similar approach
as SAMZA-94.



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