[Bug] SELECT @@variables does not return column names due to regression introduced in 2.0.2 when enable_nereids_planner = true

[geoffreytran]

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• I had searched in the issues and found no similar issues.

Version

2.0.2

What's Wrong?

With enable_nereids_planner = true when selecting SELECT @@variables, query does not return column names in 2.0.2 compared to previous versions. This causes Mysql clients that check connection information to fail on connect.

When disabling the nereids planner in 2.0.2, the correct column names are returned.

What You Expected?

SELECT @@max_allowed_packet, @@character_set_client, @@character_set_connection, @@license, @@sql_mode, @@lower_case_table_names;

Query Results for Doris <2.0.1.1

@@max_allowed_packet | @@character_set_client | @@character_set_connection | @@license | @@sql_mode | @@lower_case_table_names
1048576 | utf8 | utf8 | Apache License, Version 2.0 |   | 0

We expect to see "@@max_allowed_packet | @@character_set_client | @@character_set_connection | @@license | @@sql_mode | @@lower_case_table_names" returned.

Query Results for Doris 2.0.2 BUG

1048576 | 'utf8' | 'utf8' | 'Apache License, Version 2.0' | '' | 0
1048576 | utf8 | utf8 | Apache License, Version 2.0 |   | 0

How to Reproduce?

Run the following query on Doris 2.0.2:

SELECT @@max_allowed_packet, @@character_set_client, @@character_set_connection, @@license, @@sql_mode, @@lower_case_table_names;

Anything Else?

Temporary workaround is to disable Nereids planner:

SET GLOBAL enable_nereids_planner = false;

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

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