lamber-ken edited a comment on issue #8583: [FLINK-11820][serialization] SimpleStringSchema handle message record which value is null URL: https://github.com/apache/flink/pull/8583#issuecomment-503081914 Hi, @aljoscha, your point is right. I have two cents: 1, If I understand correctly that user can use `TypeInformationKeyValueSerializationSchema` to handle the `DELETE` semantic message, it'll return `new Tuple2<>(key,null)` when value is null. 2, but, the `SimpleStringSchema` is just a simple serializer, which doesn't have `DELETE` semantic. <br /> [DISCUSS Connectors and NULL handling](https://lists.apache.org/thread.html/2991b6b3c520380a9172588bc1f6d7e6d632c3d421458a1b44c71c01@%3Cdev.flink.apache.org%3E) > In light of the last one I’d like to look again at the first two. What they introduced is that when the deserialisation schema returns NULL, the Kafka consumer (and maybe also the Kinesis consumer) silently drops the record. In Kafka NULL values have semantic meaning, i.e. they usually encode a DELETE for the key of the message. If SimpleStringSchema returned that null, our consumer would silently drop it and we would lose that DELETE message. That doesn’t seem right.
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