Data that can be traced back to a person is covered by GDPR. If the user_ids have attached user datasets somewhere they are covered. If they don't have that, bu

Data that can be traced back to a person is covered by GDPR. If the user_ids have attached user datasets somewhere they are covered. If they don't have that, but the graph formed by user_ids and relationship_ids is isomorphic to publically known facts or facts that people with access to the graph have, that make people identifiable in the graph, it is covered by GDPR. One example would be a is-neighbour-of relation for peoples' addresses together with a public phone/address-book.