set tidb_enable_ddl=false, but still can create table

[seiya-annie]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

mysql> show config where name like '%ddl%';
+------+-------------------+-----------------------------+-------+
| Type | Instance          | Name                        | Value |
+------+-------------------+-----------------------------+-------+
| tidb | 172.16.5.101:4000 | instance.ddl_slow_threshold | 300   |
| tidb | 172.16.5.101:4000 | instance.tidb_enable_ddl    | true  |
+------+-------------------+-----------------------------+-------+
2 rows in set (0.02 sec)

mysql> set tidb_enable_ddl=false;
ERROR 8246 (HY000): Error happened when enable/disable DDL: can not disable ddl when there is only one instance
mysql> set tidb_enable_ddl=false;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+-------------------------------------------------------------------------------+
| Level   | Code | Message                                                                       |
+---------+------+-------------------------------------------------------------------------------+
| Warning | 8142 | modifying tidb_enable_ddl will require SET GLOBAL in a future version of TiDB |
+---------+------+-------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> show config where name like '%ddl%';
+------+-------------------+-----------------------------+-------+
| Type | Instance          | Name                        | Value |
+------+-------------------+-----------------------------+-------+
| tidb | 172.16.5.101:4000 | instance.ddl_slow_threshold | 300   |
| tidb | 172.16.5.101:4000 | instance.tidb_enable_ddl    | false |
+------+-------------------+-----------------------------+-------+
2 rows in set (0.02 sec)

mysql> use test;
Database changed
mysql> create table t1(a int);
Query OK, 0 rows affected (1.09 sec)

2. What did you expect to see? (Required)

create table fail

3. What did you see instead (Required)

create table success

4. What is your TiDB version? (Required)

[tidb@101 ~]$ /home/tidb/deploy/tidb-4000/bin/tidb-server -V
Release Version: v6.5.0
Edition: Community
Git Commit Hash: 706c3fa
Git Branch: heads/refs/tags/v6.5.0
UTC Build Time: 2022-12-27 03:50:44
GoVersion: go1.19.3
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: unistore
[tidb@101 ~]$