regex - MongoDB，通过正则表达式对索引字段的查询性能

Question

我想按名称查找帐户(在 50K 帐户的 MongoDB 集合中)

以通常的方式:我们用字符串查找

db.accounts.find({ name: 'Jon Skeet' })  // indexes help improve performance!

用正则表达式怎么样？这是一项昂贵的手术吗？

db.accounts.find( { name: /Jon Skeet/ }) // worry! how indexes work with regex?

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编辑:

根据 WiredPrairie:
MongoDB 使用 RegEx 的 prefix 来查找索引(例如:/^prefix.*/):

db.accounts.find( { name: /^Jon Skeet/ })  // indexes will help!'

MongoDB $regex

Answer 1

其实根据文档，

If an index exists for the field, then MongoDB matches the regular expression against the values in the index, which can be faster than a collection scan. Further optimization can occur if the regular expression is a “prefix expression”, which means that all potential matches start with the same string. This allows MongoDB to construct a “range” from that prefix and only match against those values from the index that fall within that range.

http://docs.mongodb.org/manual/reference/operator/query/regex/#index-use

换句话说:

对于 /Jon Skeet/ 正则表达式，mongo 会完整扫描索引中的键，然后会获取匹配的文档，这可能比集合扫描更快。

对于 /^Jon Skeet/ 正则表达式，mongo 将只扫描索引中以正则表达式开头的范围，这样会更快。