We have an entity type "mandate" which references to an entity "fraction membership". When a politician changes his fraction during an active mandate a new fraction membership entity is created and referenced in a field of the corresponding mandate entity. What we need is an exposed filter for views "deputies who has changed the fraction membership" which is technically "get all mandates with more than one fraction memberships referenced".
Is there already a built-in solution for views for that or would I need to create a custom filter plugin for that?