Analyze performance of a query - mongoDB

问题

I have to analyze the performance of a MongoDB query. I read I must use:

cursor.explain("executionStats")

So in my case, I used to analyze my query:

> db.team.find({common_name:"Milan"},{_id:0, "stadium.name":1}).explain("executionStats")

And this is the result:

{
        "queryPlanner" : {
                "plannerVersion" : 1,
                "namespace" : "Progettino.team",
                "indexFilterSet" : false,
                "parsedQuery" : {
                        "common_name" : {
                                "$eq" : "Milan"
                        }
                },
                "winningPlan" : {
                        "stage" : "PROJECTION",
                        "transformBy" : {
                                "_id" : 0,
                                "stadium.name" : 1
                        },
                        "inputStage" : {
                                "stage" : "COLLSCAN",
                                "filter" : {
                                        "common_name" : {
                                                "$eq" : "Milan"
                                        }
                                },
                                "direction" : "forward"
                        }
                },
                "rejectedPlans" : [ ]
        },
        "executionStats" : {
                "executionSuccess" : true,
                "nReturned" : 1,
                "executionTimeMillis" : 0,
                "totalKeysExamined" : 0,
                "totalDocsExamined" : 87,
                "executionStages" : {
                        "stage" : "PROJECTION",
                        "nReturned" : 1,
                        "executionTimeMillisEstimate" : 0,
                        "works" : 89,
                        "advanced" : 1,
                        "needTime" : 87,
                        "needFetch" : 0,
                        "saveState" : 0,
                        "restoreState" : 0,
                        "isEOF" : 1,
                        "invalidates" : 0,
                        "transformBy" : {
                                "_id" : 0,
                                "stadium.name" : 1
                        },
                        "inputStage" : {
                                "stage" : "COLLSCAN",
                                "filter" : {
                                        "common_name" : {
                                                "$eq" : "Milan"
                                        }
                                },
                                "nReturned" : 1,
                                "executionTimeMillisEstimate" : 0,
                                "works" : 89,
                                "advanced" : 1,
                                "needTime" : 87,
                                "needFetch" : 0,
                                "saveState" : 0,
                                "restoreState" : 0,
                                "isEOF" : 1,
                                "invalidates" : 0,
                                "direction" : "forward",
                                "docsExamined" : 87
                        }
                }
        }

I want to know how long the query takes to be executed. I don't understand which is the the field containing this information.

回答1:

The time your looking for is the executionTimeInMillis however your query is only going over it looks like 87 documents so the execution time is extremely small.

来源：https://stackoverflow.com/questions/31775959/analyze-performance-of-a-query-mongodb