example of how to handle relation maps.

core.clj

(defn rel-map
  [ent sub-ent type opts]
  (assoc-in ent [:rel (:name sub-ent)]
            (delay
             (create-relation ent sub-ent type opts))))

(defmacro has-one
  "Add a has-one relationship for the given entity. It is assumed that the foreign key
  is on the sub-entity with the format table_id: user.id = address.user_id
  Opts can include a key for :fk to explicitly set the foreign key.

  (has-one users address {:fk :addressID})"
  [ent sub-ent & [opts]]
  (if (symbol? sub-ent)
    `(rel ~ent (var ~sub-ent) :has-one ~opts)
    `(rel-map ~ent ~sub-ent :has-one ~opts)))