class ActiveRecord::ConnectionAdapters::MysqlAdapter

def change_column(table_name, column_name, type, options = {}) #:nodoc:
  column = column_for(table_name, column_name)
  unless options_include_default?(options)
    options[:default] = column.default
  end
  unless options.has_key?(:null)
    options[:null] = column.null
  end
  change_column_sql = "ALTER TABLE #{quote_table_name(table_name)} CHANGE #{quote_column_name(column_name)} #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
  add_column_options!(change_column_sql, options)
  add_column_position!(change_column_sql, options)
  execute(change_column_sql)
end