如何显示MongoDB解释查询计划？
有关查询计划的信息，请在MongoDB中使用explain()。让我们创建一个包含文档的集合-
> db.demo202.insertOne({"StudentFirstName":"Chris","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3c3bd103d395bdc21346e8")
}
> db.demo202.insertOne({"StudentFirstName":"David","StudentAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3c3bd803d395bdc21346e9")
}
> db.demo202.insertOne({"StudentFirstName":"Bob","StudentAge":22});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3c3bde03d395bdc21346ea")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo202.find();
这将产生以下输出-
{ "_id" : ObjectId("5e3c3bd103d395bdc21346e8"), "StudentFirstName" : "Chris", "StudentAge" : 21 }
{ "_id" : ObjectId("5e3c3bd803d395bdc21346e9"), "StudentFirstName" : "David", "StudentAge" : 23 }
{ "_id" : ObjectId("5e3c3bde03d395bdc21346ea"), "StudentFirstName" : "Bob", "StudentAge" : 22 }以下是查询以显示解释查询计划-
> db.demo202.find({"StudentFirstName":"David"}).explain();这将产生以下输出-
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "test.demo202",
"indexFilterSet" : false,
"parsedQuery" : {
"StudentFirstName" : {
"$eq" : "David"
}
},
"winningPlan" : {
"stage" : "COLLSCAN",
"filter" : {
"StudentFirstName" : {
"$eq" : "David"
}
},
"direction" : "forward"
},
"rejectedPlans" : [ ]
},
"serverInfo" : {
"host" : "DESKTOP-QN2RB3H",
"port" : 27017,
"version" : "4.0.5",
"gitVersion" : "3739429dd92b92d1b0ab120911a23d50bf03c412"
},
"ok" : 1
}