MySQL time zone settings is broken in 0.4

[sunng87]

What type of bug is this?

Incorrect result

What subsystems are affected?

Frontend

What happened?

Cannot set timezone in mysql any more

MySQL [public]> SET time_zone = 'UTC';
Query OK, 0 rows affected (0.001 sec)

MySQL [public]> SELECT @@time_zone;
+-------------+
| @@time_zone |
+-------------+
|             |
+-------------+
1 row in set (0.000 sec)

MySQL [public]> SET time_zone = '+08:00';
Query OK, 0 rows affected (0.000 sec)

MySQL [public]> SELECT @@time_zone;
+-------------+
| @@time_zone |
+-------------+
|             |
+-------------+
1 row in set (0.000 sec)

MySQL [public]> SET time_zone = 'Europe/Berlin';
Query OK, 0 rows affected (0.000 sec)

MySQL [public]> SELECT @@time_zone;
+-------------+
| @@time_zone |
+-------------+
|             |
+-------------+
1 row in set (0.000 sec)

What operating system did you use?

any

Relevant log output and stack trace

No response

How can we reproduce the bug?

Open a mysql client console and follow docs: https://docs.greptime.com/user-guide/protocols/mysql#time-zone

Execute SELECT @@time_zone returns empty result

[killme2008]

Broken by e0aecc9

Always new a QueryContext for every request. Must use session.context() instead.