How to measure the query run time in MongoDB - mongodb

Question

I am trying to measure the query run time in MongoDB.
Steps:
I set the profiling in mongoDB and ran my query
When I did show Profile I got the below output.
db.blogpost.find({post:/.* NATO .*/i})
blogpost is the collection name, I searched for "NATO" keyword in query.
Output: It pulled out 20 records and after running the query to get execution results, I got the below output:
In the output I can see 3 time values, which one is similar to duration time in MySQL ?
query blogtrackernosql.blogpost **472ms** Wed Apr 11 2018 20:37:54
command:{
"find" : "blogpost",
"filter" : {
"post" : /.* NATO .*/i
},
"$db" : "blogtrackernosql"
} cursorid:99983342073 keysExamined:0 docsExamined:1122 numYield:19 locks:{
"Global" : {
"acquireCount" : {
"r" : NumberLong(40)
}
},
"Database" : {
"acquireCount" : {
"r" : NumberLong(20)
}
},
"Collection" : {
"acquireCount" : {
"r" : NumberLong(20)
}
}
} nreturned:101 responseLength:723471 protocol:op_msg planSummary:COLLSCAN
execStats:{
**"stage"** : "COLLSCAN",
"filter" : {
"post" : {
"$regex" : ".* NATO .*",
"$options" : "i"
}
},
"nReturned" : 101,
**"executionTimeMillisEstimate" : 422**,
"works" : 1123,
"advanced" : 101,
"needTime" : 1022,
"needYield" : 0,
"saveState" : 20,
"restoreState" : 19,
"isEOF" : 0,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 1122
} client:127.0.0.1 appName:MongoDB Shell allUsers:[ ] user:

Answer 1

This ...
"executionTimeMillisEstimate" : 422
... is MongoDB's estimation of how long that query will take to execute on the MongoDB server.
This ...
query blogtrackernosql.blogpost 472ms
... must be the end-to-end time including some client side piece (e.g. forming the query and sending it to the MongoDB server) plus the data transfer time from the MongoDB server back to your client.
So:
472ms is the total start-to-finish time
422ms is the time spent inside the MongoDb server
Note: the ouput also tells you that MongoDB has to scan the entire collection ("stage": "COLLSCAN") to perform this query. FWIW, the reason it has to scan the collection is that you are using a case insensitive $regex. According to the docs:
Case insensitive regular expression queries generally cannot use indexes effectively.