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https://issues.apache.org/jira/browse/KAFKA-8713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17044972#comment-17044972
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Randall Hauch commented on KAFKA-8713:
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[~pan3793], I agree that the current behavior is incorrect. But correcting this
would change behavior, and we'll have to worry about how this affects existing
users that upgrade to a version where this might get fixed. And AK's policy is
that such changes require a KIP to identify all potential compatibility
concerns. For example, we should consider whether we need to introduce a
configuration property on the JSON converter that enables/disables this
behavior so that existing users don't see any changes unless they want to
enable it.
> [Connect] JsonConverter NULL Values are replaced by default values even in
> NULLABLE fields
> ------------------------------------------------------------------------------------------
>
> Key: KAFKA-8713
> URL: https://issues.apache.org/jira/browse/KAFKA-8713
> Project: Kafka
> Issue Type: Bug
> Components: KafkaConnect
> Affects Versions: 2.0.0, 2.0.1, 2.1.0, 2.2.0, 2.3.0, 2.2.1
> Reporter: Cheng Pan
> Priority: Major
>
> Class JsonConverter line: 582
> {code:java}
> private static JsonNode convertToJson(Schema schema, Object logicalValue)
> {
> if (logicalValue == null) {
> if (schema == null) // Any schema is valid and we don't have a
> default, so treat this as an optional schema
> return null;
> if (schema.defaultValue() != null)
> return convertToJson(schema, schema.defaultValue());
> if (schema.isOptional())
> return JsonNodeFactory.instance.nullNode();
> throw new DataException("Conversion error: null value for field
> that is required and has no default value");
> }
> ....
> }
> {code}
> h1.Expect:
> Value `null` is valid for an optional filed, even though the filed has a
> default value.
> Only when field is required, the converter return default value fallback
> when value is `null`.
> h1.Actual:
> Always return default value if `null` was given.
> h1. Example:
> I'm not sure if the current behavior is the exactly expected, but at least on
> MySQL, a table define as
> {code:sql}
> create table t1 {
> name varchar(40) not null,
> create_time datetime default '1999-01-01 11:11:11' null,
> update_time datetime default '1999-01-01 11:11:11' null
> }
> {code}
> Just insert a record:
> {code:sql}
> INSERT INTO `t1` (`name`, `update_time`) VALUES ('kafka', null);
> {code}
> The result is:
> {code:json}
> {
> "name": "kafka",
> "create_time": "1999-01-01 11:11:11",
> "update_time": null
> }
> {code}
> But when I use debezium pull binlog and send the record to Kafka with
> JsonConverter, the result changed to:
> {code:json}
> {
> "name": "kafka",
> "create_time": "1999-01-01 11:11:11",
> "update_time": "1999-01-01 11:11:11"
> }
> {code}
> For more details, see: https://issues.jboss.org/browse/DBZ-1064
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