public function alterColumn($table, $column, $type)
	{
		echo "    > alter column $column in table $table to $type ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->alterColumn($table, $column, $type);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}