Question

Here is my problem:

Domain: I have following Entities: [Sensor] that can be positioned at [Location]. It is a many-to-many relationship. I break it into two one-to-many to aggregate a [Position] of a [Sensor] at [Location]. Intermediate Entity is [SensorPosition].

Mapping for [SensorPosition] is as follows:

 CompositeId().KeyReference(sp => sp.Sensor).KeyReference(sp => sp.Location);
        References(sp => sp.Sensor).ForeignKey().Not.Nullable();
        References(sp => sp.Location).ForeignKey().Not.Nullable();
        Component(sp => sp.Position, p =>
                                         {
                                             p.Map(pos => pos.X);
                                             p.Map(pos => pos.Y);
                                             p.Map(pos => pos.Z);
                                         });

I’m using a CompositeId() to enforce constraint of only one [Sensor] at one [Location]. (Same [Sensor] can be at different [Location]s, it is a business logic twist)

My question is: Can I add a generated primary key (Id) to this? I’ve tried it, but with CompositeId() in the mapping it is not being generated. Or is there any other way to enforce this constraint fluently?

Answer 1

I would avoid using composite primary keys. Uniquenes can be enforced by this mapping:

References(sp => sp.Sensor).UniqueKey("KeyName");
References(sp => sp.Location).UniqueKey("KeyName");

For more details see this question.