Why hibernated does not create tables automatically?

[zhmt via Digitalmars-d-learn]

how to update table schema automatically:

this()
	{
		mdb = new MysqlDB(connStr);

		auto conn = mdb.lockConnection();
		scope(exit) conn.close();
		MysqlOrmUtil.updateTableSchema!(Customer)(conn);
		MysqlOrmUtil.updateTableSchema!(Card)(conn);
		MysqlOrmUtil.updateTableSchema!(Agent)(conn);
	}