instance method extract_default

# File activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb, line 29
      def extract_default(default)
        if sql_type =~ /blob/i || type == :text
          if default.blank?
            return null ? 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