I want to find an account by name (in a MongoDB collection of 50K accounts)
我想按名称查找一个帐户(在MongoDB的50K帐户集合中)
In the usual way: we find with string
用通常的方法:我们用字符串查找
db.accounts.find({ name: 'Jon Skeet' }) // indexes help improve performance!
How about with regular expression? Is it an expensive operation?
正则表达式呢?这是一个昂贵的手术吗?
db.accounts.find( { name: /Jon Skeet/ }) // worry! how indexes work with regex?
Edit:
编辑:
According to WiredPrairie:
MongoDB use prefix of RegEx to lookup indexes (ex: /^prefix.*/):
根据WiredPrairie:MongoDB使用前缀的正则表达式查找索引(例:/ ^前缀。* /):
db.accounts.find( { name: /^Jon Skeet/ }) // indexes will help!'
MongoDB美元正则表达式
1 个解决方案
#1
22
Actually according to the documentation,
实际上根据文件，
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.
如果该字段存在索引，则MongoDB将正则表达式与索引中的值匹配，这比收集扫描要快。如果正则表达式是“前缀表达式”，则可以进行进一步的优化，这意味着所有潜在匹配都以相同的字符串开始。这允许MongoDB从这个前缀构造一个“范围”，并且只与该范围内的索引中的值匹配。
http://docs.mongodb.org/manual/reference/operator/query/regex/#index-use
http://docs.mongodb.org/manual/reference/operator/query/regex/ index-use
In other words:
换句话说:
For /Jon Skeet/ regex ,mongo will full scan the keys in the index then will fetch the matched documents, which can be faster than collection scan.
对于/Jon Skeet/ regex,mongo将完全扫描索引中的键，然后获取匹配的文档，这比收集扫描要快。
For /^Jon Skeet/ regex ,mongo will scan only the range that start with the regex in the index, which will be faster.
/ ^ Jon水瓢/正则表达式,蒙戈只扫描的范围从该指数的正则表达式,将更快。
#1
22
Actually according to the documentation,
实际上根据文件，
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.
如果该字段存在索引，则MongoDB将正则表达式与索引中的值匹配，这比收集扫描要快。如果正则表达式是“前缀表达式”，则可以进行进一步的优化，这意味着所有潜在匹配都以相同的字符串开始。这允许MongoDB从这个前缀构造一个“范围”，并且只与该范围内的索引中的值匹配。
http://docs.mongodb.org/manual/reference/operator/query/regex/#index-use
http://docs.mongodb.org/manual/reference/operator/query/regex/ index-use
In other words:
换句话说:
For /Jon Skeet/ regex ,mongo will full scan the keys in the index then will fetch the matched documents, which can be faster than collection scan.
对于/Jon Skeet/ regex,mongo将完全扫描索引中的键，然后获取匹配的文档，这比收集扫描要快。
For /^Jon Skeet/ regex ,mongo will scan only the range that start with the regex in the index, which will be faster.
/ ^ Jon水瓢/正则表达式,蒙戈只扫描的范围从该指数的正则表达式,将更快。