extract_default

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 15
        def extract_default(default)
          if sql_type =~ /blob/ || 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