How to prevent pushing in the document with same attribute in Mongodb - node.js

Question

I have the following structure. I would like to prevent pushing in the document with the same attribute.
E.g. Basically, i find the user object first. If i have another vid (with is already inside), it will not get pushed in. Try using $addToSet, but failed.
I am using Mongoose.
This is my Model Structure:
var User = mongoose.model('User', {
oauthID: Number,
name: String,
username: String,
email: String,
location: String,
birthday: String,
joindate: Date,
pvideos: Array
});
This is my code for pushing into Mongo
exports.pinkvideo = function(req, res) {
var vid = req.body.vid;
var oauthid = req.body.oauthid;
var User = require('../models/user.js');
var user = User.findOne({
oauthID: oauthid
}, function(err, obj) {
if (!err && obj != null) {
obj.pvideos.push({
vid: vid
});
obj.save(function(err) {
res.json({
status: 'success'
});
});
}
});
};

Answer 1

You want the .update() method rather than retrieving the document and using .save() after making your changes.
This not only gives you access to the $addToSet operator that was mentioned, and it's intent is to avoid duplicates in arrays it is a lot more efficient as you are only sending your changes to the database rather than the whole document back and forth:
User.update(
{ oauthID: oauthid },
{ "$addToSet": { "pVideos": vid } },
function( err, numAffected ) {
// check error
res.json({ status: "success" })
}
)
The only possible problem there is it does depend on what you are actually pushing onto the array and expecting it to be unique. So if your array already looked like this:
[ { "name": "A", "value": 1 } ]
And you sent and update with an array element like this:
{ "name": "A", "value": 2 }
Then that document would not be considered to exist purely on the value of "A" in "name" and would add an additional document rather than just replace the existing document.
So you need to be careful about what your intent is, and if this is the sort of logic you are looking for then you would need to find the document and test the existing array entries for the conditions that you want.
But for basic scenarios where you simply don't want to add a clear duplicate then $addToSet as shown is what you want.