Re: InnoDB to MyIsam Migration - What will happen to Foreign keys ?

[Rick James]

A FOREIGN KEY gives you two things:
* Protection from certain coding mistakes -- presumably you have fixed all of them by now, so you don't need PKs for that.
* CASCADING DELETEs, etc. Triggers might work -- if your provider allows triggers. Probably better to code them yourself. You knew what had to be done when you added the CASCADE clause; now you simply have to do it in code.

You will lose BEGIN...COMMIT functionality. Generally that can be replaced with LOCK...UNLOCK statements, although they are more aggressive -- they lock the table(s), not just the row(s). OTOH, MyISAM is quite fast, so the locks may rarely be a problem.

You may find some SELECTs run faster, some run slower. This is likely to be because INDEXes are implement quite differently between the engines.