LP #1246754: pt-online-schema-change loosing data when making non unique column a new PK

**Reported in Launchpad by Przemek last update 31-10-2013 19:14:21

CREATE TABLE `mytable` (
`userid` int(10) unsigned NOT NULL DEFAULT '0',
`time` int(10) unsigned NOT NULL DEFAULT '0',
`what` enum('paidaccount') DEFAULT NULL,
`action` enum('new','renew','expire','return','ext') DEFAULT NULL,
KEY `userid` (`userid`),
KEY `time` (`time`)
) ENGINE=InnoDB

mysql> select * from mytable;
--------------------------------+

--------------------------------+

--------------------------------+
3 rows in set (0.00 sec)

mysql> alter table mytable add primary key(userid);
ERROR 1062 (23000): Duplicate entry '32' for key 'PRIMARY'

mysql> select * from mytable;
--------------------------------+

--------------------------------+

--------------------------------+
3 rows in set (0.00 sec)

[root@lap-prz ~]# pt-online-schema-change --execute p=xxx,D=test,t=mytable --alter "ADD PRIMARY KEY(userid)"
Operation, tries, wait:
copy_rows, 10, 0.25
create_triggers, 10, 1
drop_triggers, 10, 1
swap_tables, 10, 1
update_foreign_keys, 10, 1
Altering `test`.`mytable`...
Creating new table...
Created new table test._mytable_new OK.
Altering new table...
Altered `test`.`_mytable_new` OK.
2013-10-31T15:39:43 Creating triggers...
2013-10-31T15:39:43 Created triggers OK.
2013-10-31T15:39:43 Copying approximately 3 rows...
2013-10-31T15:39:43 Copied rows OK.
2013-10-31T15:39:43 Swapping tables...
2013-10-31T15:39:43 Swapped original and new tables OK.
2013-10-31T15:39:43 Dropping old table...
2013-10-31T15:39:43 Dropped old table `test`.`_mytable_old` OK.
2013-10-31T15:39:43 Dropping triggers...
2013-10-31T15:39:43 Dropped triggers OK.
Successfully altered `test`.`mytable`.

mysql> select * from mytable;
--------------------------------+

--------------------------------+

--------------------------------+
1 row in set (0.00 sec)

mysql> show create table mytable\G

• • • • • • • • • • • • • • • • • • • • • • • • • • • 1. row ***************************
                                                      Table: mytable
                                                      Create Table: CREATE TABLE `mytable` (
                                                      `userid` int(10) unsigned NOT NULL DEFAULT '0',
                                                      `time` int(10) unsigned NOT NULL DEFAULT '0',
                                                      `what` enum('paidaccount') DEFAULT NULL,
                                                      `action` enum('new','renew','expire','return','ext') DEFAULT NULL,
                                                      PRIMARY KEY (`userid`),
                                                      KEY `userid` (`userid`),
                                                      KEY `time` (`time`)
                                                      ) ENGINE=InnoDB DEFAULT CHARSET=latin1
                                                      1 row in set (0.00 sec)