[jira] [Commented] (FLINK-20158) KafkaSource does not implement ResultTypeQueryable

["Robert Metzger (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-20158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17231758#comment-17231758 ] 

Robert Metzger commented on FLINK-20158:
----------------------------------------

[~becket_qin] I guess this would be a nice usability extension. I haven't checked if this works with the new "env.fromSource()", but I see no reason why it shouldn't.

> KafkaSource does not implement ResultTypeQueryable
> --------------------------------------------------
>
>                 Key: FLINK-20158
>                 URL: https://issues.apache.org/jira/browse/FLINK-20158
>             Project: Flink
>          Issue Type: Bug
>          Components: Connectors / Kafka
>    Affects Versions: 1.12.0
>            Reporter: Robert Metzger
>            Priority: Critical
>             Fix For: 1.12.0
>
>
> As a user of the new Kafka Source introduced in (FLINK-18323), I always have to specify the return type:
> {code}
> DataStream<Event> events = env.fromSource(source, WatermarkStrategy.noWatermarks(),
> 			"Kafka Source").returns(TypeInformation.of(Event.class));
> {code}
> The old Kafka source implementation implements {{ResultTypeQueryable}}, which allows the DataStream API to get the return type from the deserializer.
> The new Kafka Source also should have access to the produced type from the deserializer to forward it.



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