There are many tables using MyISAM. I have to change their engine to InnoDB; But there are follow difficulties:

1、These tables doesn't have primary key or unique key, so pt-ost tools couldm't add trigger to change it.

2、As they use MyISAM, if I use 

“Alter table table\_name ENGINE=InnoDB” 

or "ADD COLUMN id bigint(10) NOT NULL AUTO\_INCREMENT, ADD PRIMARY KEY (id)", 

the table would be locked for a long time, whick make some features online doesn't work

PS：MySQL version is 5.6.17