MongoDB execute query from a file and measure time - mongodb

Question

I have a txt file with mongoDB queries, like this:
db.telephone.find({'brand' : 'Apple'});
db.telephone.find({'brand' : 'Samsung'});
...to a total of about 1500 rows. I am executing this query like this.
mongo myDatabase C:\path\mongoDB.txt
Now I need to measure the time how long it takes to execute all of these queries. I dont really care about the output, I really only care about the time it takes (as a part of an experiment).
I thought that if I create a collection times and insert current time to it like this db.times.insert({time: Date()}); at the beginning and end of the query file, it would do what I need, but it seemingly does not work, as both of these result times are the same in the end (and I believe that executing all these queries did take more than 1 second for sure).
Is this because I dont print the output, so the queries dont really get executed? Or why does this not work? And is there a better way how to measure the time it takes to execute these queries from a file? Thanks you.

Answer 1

You can assign start and end time in the file itself. The following is an example:
var start_time = new Date().valueOf();
db.telephone.find({'brand' : 'Apple'});
db.telephone.find({'brand' : 'Samsung'});
var end_time = new Date().valueOf();
print(end_time-start_time);
How we can precisely measure the execution time?
To analyze the query, we can use explain(). It returns the complete statistics of the query. The following is an example:
db.telephone.find({'brand' : 'Apple'}).explain("executionStats")
Output:
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "check.telephone",
"indexFilterSet" : false,
"parsedQuery" : {
"brand" : {
"$eq" : "Apple"
}
},
"winningPlan" : {
"stage" : "COLLSCAN",
"filter" : {
"brand" : {
"$eq" : "Apple"
}
},
"direction" : "forward"
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 35,
"totalKeysExamined" : 0,
"totalDocsExamined" : 1,
"executionStages" : {
"stage" : "COLLSCAN",
"filter" : {
"brand" : {
"$eq" : "Apple"
}
},
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 3,
"advanced" : 1,
"needTime" : 1,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 1
}
},
"serverInfo" : {
"host" : "theMechanic",
"port" : 27017,
"version" : "4.0.11",
"gitVersion" : "417d1a712e9f040d54beca8e4943edce218e9a8c"
},
"ok" : 1
}
Note: The executionStats.executionTimeMillis holds actual query execution time.