Mongodb query performance over ranges

原文链接

针对$in操作：

• index early

• index often

• index fully

  queries make use of indexes from left to right.

• index sorts

  If your queries will contain a sort or orderby clause, add the sorted field to your index.

• commands

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The order of fields in an index should be:

1. First, fields on which you will query for exact values.
2. Second, fields on which you will sort.
3. Finally, fields on which you will query for a range of values.

先对sort field部分，进行index，这样能及时保证sort之后的顺序能够得到保证