I've a entity, which have a child table based on two of the fields of that entity, but they are not the primary key. I want to set up a relation and use prefetch path to fetch the entity and this child table.

In the LLBLGen designer, relation is only allowed to set up on a primary key, is it possible to set up the relation for non-primary key?

In the LLBLGen designer, relation is only allowed to set up on a primary key, is it possible to set up the relation for non-primary key?

No, you can only customly create a relation based on any field in the code. But PrefetchPaths is only available for relations created at design time.