Display MongoDB explain query plan?

For information on query plan, use explain() in MongoDB. Let us create a collection with documents −

> 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") }

Display all documents from a collection with the help of find() method −

> db.demo202.find();

This will produce the following output −

{ "_id" : ObjectId("5e3c3bd103d395bdc21346e8"), "StudentFirstName" : "Chris", "StudentAge" : 21 } { "_id" : ObjectId("5e3c3bd803d395bdc21346e9"), "StudentFirstName" : "David", "StudentAge" : 23 } { "_id" : ObjectId("5e3c3bde03d395bdc21346ea"), "StudentFirstName" : "Bob", "StudentAge" : 22 }

Following is the query to display explain query plan −

> db.demo202.find({"StudentFirstName":"David"}).explain();

This will produce the following output −

{    "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 }