在MongoDB中limit()会提高查询速度吗？

不可以，使用LIMIT()可以减少带宽消耗，但不会提高查询速度。让我们看一个示例并创建包含文档的集合-

> db.demo197.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afde803d395bdc21346d8") } > db.demo197.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdef03d395bdc21346d9") } > db.demo197.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdf203d395bdc21346da") } > db.demo197.insertOne({"Name":"Sam"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdf603d395bdc21346db") } > db.demo197.insertOne({"Name":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afdf903d395bdc21346dc") } > db.demo197.insertOne({"Name":"Carol"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afe1603d395bdc21346dd") } > db.demo197.insertOne({"Name":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3afe2003d395bdc21346de") }

在find()方法的帮助下显示集合中的所有文档-

> db.demo197.find();

这将产生以下输出-

{ "_id" : ObjectId("5e3afde803d395bdc21346d8"), "Name" : "Chris" } { "_id" : ObjectId("5e3afdef03d395bdc21346d9"), "Name" : "Bob" } { "_id" : ObjectId("5e3afdf203d395bdc21346da"), "Name" : "David" } { "_id" : ObjectId("5e3afdf603d395bdc21346db"), "Name" : "Sam" } { "_id" : ObjectId("5e3afdf903d395bdc21346dc"), "Name" : "Mike" } { "_id" : ObjectId("5e3afe1603d395bdc21346dd"), "Name" : "Carol" } { "_id" : ObjectId("5e3afe2003d395bdc21346de"), "Name" : "John" }

以下是使用LIMIT()的查询-

> db.demo197.find().limit(4);

这将产生以下输出-

{ "_id" : ObjectId("5e3afde803d395bdc21346d8"), "Name" : "Chris" } { "_id" : ObjectId("5e3afdef03d395bdc21346d9"), "Name" : "Bob" } { "_id" : ObjectId("5e3afdf203d395bdc21346da"), "Name" : "David" } { "_id" : ObjectId("5e3afdf603d395bdc21346db"), "Name" : "Sam" }