Comment 4 for bug 1062324

This was not fixed in 2.1.6 as well, see below.

[root@ovaistariq-net bin]# ./pt-online-schema-change --version
pt-online-schema-change 2.1.6

[root@ovaistariq-net bin]# ./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 ./pt-online-schema-change line 9414.