Imagine two domain object classes, A and B. A has a bidirectional one-to-many relationship to B. A is related to thousands of B. The relations must be unique, it's not possible to have a duplicate.

To check if an instance of B is already connected to a given instance of A, we could perform an easy INNER JOIN but this will only ensure the already persisted relations.

What about the current transient relations?

class A {
   @OneToMany
   private List<B> listOfB;
}

If we access the listOfB and perform a check of contains() this will fetch all the connected instances of B lazy from the datasource. I only want to validate them by their primary-key.

Is there an easy solution where I can do things like "Does this instance of A is connected with this instance of B?" Without loading all these data into memory and perform a based on collections?