Delete all Items not referred to by at least one Toon

item.rb

class Item
  include DataMapper::Resource
  
  property :id, Integer, :key => true

  property :name, String
  property :icon_base, String
  property :item_type, String

  for prop in [:max_dura,:slot,:quality]
    property prop, Integer
  end
  
  has n, :toons, :through => Resource

  # ...

end

items.rb

# Original credit goes to dkubb in #datamapper on freenode

def clean_orphaned
# delete all Items not referred to by at least one Toon

    item_ids = Item.all(:fields => [ :id ]).map { |i| i.id }
    item_ids -= ItemToon.all(:fields => [ :item_id ], :unique => true).map { |j| j.item_id }
    Item.all(:id => item_ids).destroy!

# NOTE: a LEFT JOIN would probably be better, but this is
# the more efficient DataMapper approach I can think of
end

toon.rb

class Toon
  include DataMapper::Resource

  # ...
  
  property :id, Serial

  property :name, String
  property :realm, String
  property :guild, String, :lazy => [:show]
  property :level, Integer
  property :race, String, :lazy => [:show]
  property :klass, String, :lazy => [:show]
  
  property :armor, Integer, :lazy => [:show]

  # ...

  has n, :items, :through => Resource
  # ...
end