ddl: the 'max-index-length' check does not respect non-restricted sql_mode #34931
Description
Bug Report
Please answer these questions before submitting your issue. Thanks!
1. Minimal reproduce step (Required)
drop table if exists t;
set @@sql_mode='';
create table t (id int, name varchar(2048), index(name)) charset=utf8;
2. What did you expect to see? (Required)
In MySQL 5.7 & MySQL 8:
mysql> set @@sql_mode='';
Query OK, 0 rows affected (0.00 sec)
mysql> create table t (id int, name varchar(2048), index(name)) charset=utf8;
Query OK, 0 rows affected, 2 warnings (0.02 sec)
mysql> show warnings;
+---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message |
+---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 3719 | 'utf8' is currently an alias for the character set UTF8MB3, but will be an alias for UTF8MB4 in a future release. Please consider using UTF8MB4 in order to be unambiguous. |
| Warning | 1071 | Specified key was too long; max key length is 3072 bytes |
+---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)
mysql> show create table t;
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+
| t | CREATE TABLE `t` (
`id` int(11) DEFAULT NULL,
`name` varchar(2048) DEFAULT NULL,
KEY `name` (`name`(1024))
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
Notice that in non-strict SQL mode, MySQL converted the error to warning and truncated the index name as a prefix one("name(1024)"), which met the maximum length of index(3072 bytes / 3 bytes per utf8 encoding = 1024).
3. What did you see instead (Required)
In TiDB(all versions with default configuration):
mysql> set @@sql_mode='';
Query OK, 0 rows affected (0.00 sec)
tidb> create table t (id int, name varchar(2048), index(name)) charset=utf8;
ERROR 1071 (42000): Specified key was too long; max key length is 3072 bytes
4. What is your TiDB version? (Required)
tidb> select version();
+--------------------+
| version() |
+--------------------+
| 5.7.25-TiDB-v6.0.0 |
+--------------------+
1 row in set (0.00 sec)
I am using v6.0 but it applies to all existing versions.