Github user snuyanzin commented on the issue:
https://github.com/apache/flink/pull/6233
@hequn8128 thank you for your idea about Row. I used it in tests. Also I
checked usages of `org.apache.flink.table.client.cli.CliStrings#NULL_COLUMN` it
was added only recently and used only in CliUtils before. For that reason I
think it could be set to "null" what I did in PR. @twalthr @hequn8128 please
let me know if you have any objections---
