optimizer_switch is read only #29040
Description
Bug Report
Please answer these questions before submitting your issue. Thanks!
1. Minimal reproduce step (Required)
SET @@optimizer_switch="derived_merge=off";2. What did you expect to see? (Required)
mysql> SET @@optimizer_switch="derived_merge=off";
Query OK, 0 rows affected (0.01 sec)3. What did you see instead (Required)
mysql> SET @@optimizer_switch="derived_merge=off";
ERROR 1238 (HY000): Variable 'optimizer_switch' is a read only variable4. What is your TiDB version? (Required)
| Release Version: v5.2.1
Edition: Community
Git Commit Hash: cd8fb24c5f7ebd9d479ed228bb41848bd5e97445
Git Branch: heads/refs/tags/v5.2.1
UTC Build Time: 2021-09-08 02:29:53
GoVersion: go1.16.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |