mongodb复合索引的ESR原则
2013 年 3 月 28 日
For compound indexes, this rule of thumb is helpful in deciding the order of fields in the index:
- First, add those fields against which Equality queries are run.
- The next fields to be indexed should reflect the Sort order of the query.
- The last fields represent the Range of data to be accessed.
出处： https://www.mongodb.com/blog/post/performance-best-practices-indexing
简单来说就是索引的字段顺序应该是等值查询字段最前面，然后是排序字段，最后是范围查询字段。
这是一个超级有用的小原则。关于mongodb查询性能优化，这系列文章讲得还挺不错的。这篇也有提到一个小技巧：
To determine whether a query is a covered query, use the explain() method. If the explain() output displays totalDocsExamined as 0, this shows the query is covered by an index.
实用。
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