Comment 1 for bug 1103672

From the first bug:

This bug is still reproducible in percona-toolkit version 2.1.8:

[root@ovaistariq-net msb_5_5_29]# pt-online-schema-change --version
pt-online-schema-change 2.1.8

mysql [localhost] {msandbox} (test) > show create table test\G
*************************** 1. row ***************************
       Table: test
Create Table: CREATE TABLE `test` (
  `id` int(10) unsigned NOT NULL,
  `x` char(3) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

When trying to alter the above table to add a new primary key column, pt-osc fails as below:

[root@ovaistariq-net msb_5_5_29]# pt-online-schema-change --alter "drop primary key, add column _id int unsigned not null primary key auto_increment FIRST" D=test,t=test,S=/tmp/mysql_sandbox5529.sock,u=msandbox,p=msandbox --execute
Altering `test`.`test`...
Creating new table...
Created new table test._test_new OK.
Altering new table...
Altered `test`.`_test_new` OK.
Creating triggers...
Dropping triggers...
Dropped triggers OK.
Dropping new table...
Dropped new table OK.
`test`.`test` was not altered.
Error creating triggers: DBD::mysql::db do failed: Unknown column '_id' in 'OLD' [for Statement "CREATE TRIGGER `pt_osc_test_test_del` AFTER DELETE ON `test`.`test` FOR EACH ROW DELETE IGNORE FROM `test`.`_test_new` WHERE `test`.`_test_new`.`_id` <=> OLD.`_id`"] at /usr/bin/pt-online-schema-change line 9613.

Note, how DELETE trigger is referencing the wrong column from the original table.