# File lib/aws/simple_db/item_collection.rb, line 611
      def replace_positional_placeders(str, count, substitutions)
        str = str.gsub("?") do |placeholder|
          count += 1
          raise ArgumentError.new("missing value for placeholder #{count}") if
            substitutions.empty?
          coerce_substitution(substitutions.shift)
        end
        [str, count]
      end