Funny scopes

gistfile1.rb

class Feed < ActiveRecord::Base
  scope :searchable, where(some_conditions)

  scope :matchable, lambda {
    where("url in
         (SELECT du.url from
                        (SELECT url, count(*) cc
                         FROM feeds
                         WHERE (#{Feed.searchable_conditions})
                         GROUP by url
                         HAVING cc=1) du) and #{Feed.searchable_conditions}")
    # First Feed.searchable_conditions only for optimization
  }

  def self.searchable_conditions
    searchable_sql_array = searchable.where_values
    ActiveRecord::Base.send(:sanitize_sql_array, searchable_sql_array)
  end
end

# After refactoring

class Feed < ActiveRecord::Base
  scope :searchable, where(some_conditions)

  scope :matchable, searchable.group("url").having("count(*)=1")
end