set_readonly_option!

# File activerecord/lib/active_record/base.rb, line 2447
        def set_readonly_option!(options) #:nodoc:
          # Inherit :readonly from finder scope if set.  Otherwise,
          # if :joins is not blank then :readonly defaults to true.
          unless options.has_key?(:readonly)
            if scoped_readonly = scope(:find, :readonly)
              options[:readonly] = scoped_readonly
            elsif !options[:joins].blank? && !options[:select]
              options[:readonly] = true
            end
          end
        end