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https://issues.apache.org/jira/browse/KAFKA-20020?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Federico Valeri reassigned KAFKA-20020:
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Assignee: Federico Valeri
> Improve UUID nullability description in API readme
> --------------------------------------------------
>
> Key: KAFKA-20020
> URL: https://issues.apache.org/jira/browse/KAFKA-20020
> Project: Kafka
> Issue Type: Bug
> Components: documentation
> Affects Versions: 4.1.1
> Reporter: Federico Valeri
> Assignee: Federico Valeri
> Priority: Major
>
> The Nullable Fields section in the Kafka message protocol readme can make
> people think that they can declare nullable a field of type Uuid:
> {code}
> Booleans, ints, and floats can never be null. However, fields that are
> strings,
> bytes, uuid, records, or arrays may optionally be "nullable". When a field is
> "nullable", that simply means that we are prepared to serialize and
> deserialize
> null entries for that field.
> ...
> If a field is declared as non-nullable, and it is present in the message
> version you are using, you should set it to a non-null value before
> serializing
> the message. Otherwise, you will get a runtime error.
> {code}
> This is not possible by design as the UUIDFieldType class does NOT override
> canBeNullable(), so it inherits the default implementation which returns
> false. Uuid fields use a special zero uuid value (all bits set to 0) as a
> sentinel to represent "no UUID" instead of null.
>
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