因为索引会带来额外的数据更新开销，所以应该争取创建少量索引来覆盖尽可能多的查询。
Because each index incurs extra data updating overhead, the goal should be to create a small number of indexes to cover as many queries as possible.
为最常用和最重要的查询创建覆盖索引。
Create a covering index for often-used, high-impact queries.
为提高用户查询信息的覆盖面和检索结果的准确性，一种建立在搜索引擎之上的元搜索引擎成为目前研究与开发的热点。
To improve the coverage of user search information and the accuracy of the search results, people start to pay special attention to Meta Search Engine based on search engine.
应用推荐