node.js - Avoid duplicates in mongoose insertMany() -

this question has answer here:

• how ignore duplicate key errors safely using insert_many 1 answer
• how update if exists otherwise insert new document? 3 answers

the question marked duplicate wrongly. different situation together.

i have database containing 27000 users. want insert more users csv file. each user can uniquely identified email id. want enter 43000 more such emails database. planning use

users.insertmany(emailarray,options,callback) 

i want if email id exists, should not enter record database. checking each email id in database , updating individually seems inefficient. insertmany seems faster. can work way around using insertmany?

current approach::

csv()     .fromfile(path)     .on('json', (jsonobj) => {     var email = jsonobj.email;     delete jsonobj.email;     var profile = jsonobj;     user.addemails(email, profile, function (err, res) {         if (err == "user exists") {             console.log("user exists");             } else {             console.log(res);             }         })     })     .on('done', (error) => {         console.log('end');         fs.unlink(path);         callback(null, "done");     }) 

add emails function

module.addemails = function(email, profile, callback){     user.findone({email: email}, function(err, res){         if(err)             throw err;         else if(res){             callback("user exists");         }         else{             user.create({email: email, profile: profile},callback);                      }     }) }