[FLINK-20825] Upsert-kafka should throw a better exception when the key of the record is NULL

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.12.0
• Component/s: Connectors / Kafka, Table SQL / API
• Assignee: Unassigned
• Reporter: Shengkai Fang
• Created: 31/Dec/20 09:39
• Updated: 31/Dec/20 09:39

Description

Currently, it will get NPE when reading from the upsert-kafka with record whose key is NULL.
The records in the compacted topic always have keys. Therefore, it's mainly wrong usage of the upsert-kafka that causing NPE. We can throw a better exception to notify the users.