extract_default

# File activerecord/lib/active_record/connection_adapters/mysql_adapter.rb, line 96
      def extract_default(default)
        if type == :binary || type == :text
          if default.blank?
            nil
          else
            raise ArgumentError, "#{type} columns cannot have a default value: #{default.inspect}"
          end
        elsif missing_default_forged_as_empty_string?(default)
          nil
        else
          super
        end
      end