gistfile1.txt

1.9.3-p429 :001 > d = Dictionary.first
  Dictionary Load (0.1ms)  SELECT "dictionaries".* FROM "dictionaries" LIMIT 1
 => #<Dictionary id: 1, language: "English", enabled: true, created_at: "2013-06-24 00:11:31", updated_at: "2013-06-24 00:11:31", dictionary_words_count: 178691> 
1.9.3-p429 :002 > d.dictionary_words.count
   (453.5ms)  SELECT COUNT(*) FROM "dictionary_words" WHERE "dictionary_words"."dictionary_id" = 1
 => 178691 

class DictionaryWord < ActiveRecord::Base
  belongs_to :dictionary, :counter_cache => true
end