Using count() or findOne() for better performance?

Question

Using count() or findOne() for better performance?

I'm using NodeJs and native MongoDB driver for creating an application. I want to ensure that one record with a specific condition is exists or not and I want to know that which method is better?

collection.find({...}).count(function(err, count){
    if(count > 0) {
       //blah blah
    }
})

or

collection.findOne({...}, function(err, object){
    //blah blah
})

node.js
mongodb

Answer 1

See this question. I believe find with limit(1) is way to go in your case. (If you want to get actual document data with query, then use findOne).

In terms of mongodb-native, code will look something like this

function recordExists(selector, callback) {
  collection.find(selector, {limit: 1}, function(err, cursor) {
    if (err) return callback(err);
    cursor.count(function(err, cnt) {
      return callback(err, !!cnt);
    });
  });
}

I am little confused about this: collection.find({...}).count. Is native driver allows to do that? Is it cursor.count? Anyway, limit is your friend here.