Comment 0 for bug 1258464

use db1

CREATE TABLE `c_uid` (
  `id` bigint(24) NOT NULL AUTO_INCREMENT,
  `keycode` varchar(100) COLLATE utf8_bin DEFAULT NULL,
  `uid` varchar(100) COLLATE utf8_bin DEFAULT NULL,
  `poid` int(11) DEFAULT '1',
  `createtime` datetime DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `c_uid_index_1` (`keycode`),
  KEY `c_uid_index_2` (`uid`)
) ENGINE=InnoDB

 ........1000000 rows insert into c_uid .

use db2

CREATE TABLE `uid` (
  `id` bigint(24) NOT NULL AUTO_INCREMENT,
  `keycode` varchar(100) COLLATE utf8_bin DEFAULT NULL,
  `uid` varchar(100) COLLATE utf8_bin DEFAULT NULL,
  `poid` int(11) DEFAULT '1',
  `createtime` datetime DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `c_uid_index_1` (`keycode`),
  KEY `c_uid_index_2` (`uid`)
) ENGINE=InnoDB

use db1 | | use db2
alter table c_uid add col_test int ; | At the same time | insert into uid(keycode,uid,poid,createtime) ......
Query OK, 1000000 rows affected (29.41 sec) | | Query OK, 1 row affected (28.51 sec)
Records: 1000000 Duplicates: 0 Warnings: 0 | |

db1 DDL operations blocked the db2 DML oprations .