如何缩短MongoDB中查询的执行时间
为了缩短查询的执行时间，请结合使用index和unique：true。让我们创建一个包含文档的集合-
> db.demo193.createIndex({"LastName":1},{unique:true});
{
"createdCollectionAutomatically" : true,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}
> db.demo193.insertOne({"FirstName":"John","LastName":"Doe"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ade1803d395bdc21346d1")
}
> db.demo193.insertOne({"FirstName":"John","LastName":"Smith"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ade1f03d395bdc21346d2")
}
> db.demo193.insertOne({"FirstName":"David","LastName":"Miller"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ade2803d395bdc21346d3")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo193.find();
这将产生以下输出-
{ "_id" : ObjectId("5e3ade1803d395bdc21346d1"), "FirstName" : "John", "LastName" : "Doe" }
{ "_id" : ObjectId("5e3ade1f03d395bdc21346d2"), "FirstName" : "John", "LastName" : "Smith" }
{ "_id" : ObjectId("5e3ade2803d395bdc21346d3"), "FirstName" : "David", "LastName" : "Miller" }以下是查找具有更快执行时间的值的查询-
> db.demo193.find({"LastName":"Smith"});这将产生以下输出-
{ "_id" : ObjectId("5e3ade1f03d395bdc21346d2"), "FirstName" : "John", "LastName" : "Smith" }