paging_model_enumerator.rb

class PagingModelEnumerator # sketchy version :D
  include Enumerable
  
  def initialize(model, opts)
    @model = model
    @find_opts, @count_opts = parse_opts(opts)
  end
  
  def each(&block)
    page_size = 50
    count = @model.count(@count_opts)
    full_pages, incomplete_pages = count.divmod(page_size)
    page_count = full_pages + (incomplete_pages.zero? ? 0 : 1)
    
    page_count.times do |page_num|
      find_opts = @find_opts.merge :offset => (page_num*page_size), :limit => page_size
      @model.find(:all, find_opts).each(&block)
    end
  end
  
  private
    def parse_opts(opts)
      if opts.key?(:find) || opts.key?(:count)
        [opts.fetch(:find, {}), opts.fetch(:count, {})]
      else
        [opts, opts]
      end
    end
end

class ActiveRecord::Base
  def self.enumerator(opts = {})
    PagingModelEnumerator.new(self, opts)
  end
end