[GitHub] [incubator-doris] morningman commented on pull request #3851: [Enhancement] Replace N/A use NULL

[GitBox <gi...@apache.org>]

morningman commented on pull request #3851:
URL: https://github.com/apache/incubator-doris/pull/3851#issuecomment-643276175


   Actually, in MySQL protocal, the `null` is represented as `(byte) (251 & 0xff)`.
   
   https://github.com/apache/incubator-doris/blob/88a5429165c65690eb443c017ed0b3bd7d786330/fe/src/main/java/org/apache/doris/mysql/MysqlSerializer.java#L64-L66
   
   https://github.com/apache/incubator-doris/blob/88a5429165c65690eb443c017ed0b3bd7d786330/be/src/util/mysql_row_buffer.cpp#L270-L281
   
   So If we want to make it compatible with real `null`, better to follow the protocol.
   
   I have a suggestion. Currently you are modifying the result set related to `Show`. The current ShowResultSet uses `String`. We can encapsulate a `NullableString`. In this way, when sending ShowResultSet, we can judge and return true `null`.
   
   It is not recommended to use `null` directly, because that will cause some results forwarded from the follower FE to not be able to be serialized to thrift.
   
   


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