I've attached a maven test project basically using the code created in https://github.com/hibernate/hibernate-orm/pull/683.

I can see the following sql query is created:

delete collection row org.hibernate.test.collection.set.PersonInfoEntity.Infos */ delete
from
PersonInfo_Infos
where
entity_id=?
and height=?
and hair_color=?

I believe this is wrong when any value is null here.

I've tried to execute a query such as:
delete from PersonInfo_Infos
where
entity_id=2
and height=168
and hair_color=null;

It doesn't remove any row from the database.

But if I execute the query:
delete from PersonInfo_Infos
where
entity_id=2
and height=168
and hair_color is null;

It works as expected.