Some techniques for keeping individual queries fast involve splitting data across many tables. When the number of tables runs into the thousands or even millions, the overhead of dealing with all these tables becomes a new performance consideration.一些保持单个查询速度的技术涉及跨多个表拆分数据。当表的数量达到数千甚至数百万时，处理所有这些表的开销成为新的性能考虑因素。