ruby on rails - Limit queries in custom Rails4 model validation -

trying ruby on rails fiddling around making small application. far rails way. have model administration has manager , organisation.

i want make sure - using validations - manager assigned adminisration associated organisation administrator belongs to.

i have working validation, gut-feeling says it's expensive on queries.

class administration < activerecord::base      belongs_to :organisation     belongs_to :manager, :class_name => "user", :foreign_key => 'manager_id'      validates :code, numericality: true     validates :manager_id, :presence => true     validates :organisation_id, :presence => true     validates :code, uniqueness: { scope: :organisation_id, message: 'bb: code in use' }      validate :manager_belongs_to_organisation      def manager_belongs_to_organisation         errors.add(:base, 'bb: manager not exist') unless organisation.find(self.organisation_id).users.include?(user.find(self.manager_id))     end end 

any thoughts on matter?

one way work around issue assign manager administration. organization_id automatically inserted using before_save callback:

class administration    ...     before_save :update_organization_id     ...     def update_organization_id      self.organization_id = self.manager.organization_id    end end