require 'dm-core'
require 'dm-migrations'
require 'dm-sqlite-adapter'

DataMapper.setup :default, "sqlite::memory:"

class User
  include DataMapper::Resource
  property :id, Serial
  belongs_to :site
end

class Site
  include DataMapper::Resource
  property :id, Serial
  has n, :users
end

DataMapper.auto_migrate!

site = Site.create
site.users.create
site.users.create

DataObjects::Sqlite3.logger = DataObjects::Logger.new($stdout, :debug)

Site.all(:links => [:users]).first
# SELECT "sites"."id"
# FROM "sites"
# INNER JOIN "sites" "sites_1" ON
#   "sites"."site_id" = "sites_1"."id" -- <= er...
# GROUP BY "sites"."id"
# ORDER BY "sites"."id"
# LIMIT 1