rename index forgot to rename the virtual generated column

[lance6716]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

mysql> create table t(j json);
Query OK, 0 rows affected (0.78 sec)

mysql> alter table t add index idx1((cast(j as char(10) array)));
Query OK, 0 rows affected (3.24 sec)

mysql> alter table t rename index idx1 to idx2;
Query OK, 0 rows affected (0.73 sec)

mysql> alter table t add index idx1((cast(j as char(10) array)));
ERROR 1060 (42S21): Duplicate column name '_V$_idx1_0'

mysql> show create table t;
+-------+------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                         |
+-------+------------------------------------------------------------------------------------------------------------------------------------------------------+
| t     | CREATE TABLE `t` (
  `j` json DEFAULT NULL,
  KEY `idx2` ((cast(`j` as char(10) array)))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.20 sec)

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

3. What did you see instead (Required)

4. What is your TiDB version? (Required)