Unique array values in Mongoose

Question

Currently trailing out Mongoose and MongoDB for a project of mine but come across a segment where the API is not clear.

I have a Model which contains several keys and documents, and one of those keys os called watchList. This is an array of ID's that the user is watching, But I need to be sure that these values stay unique.

Here is some sample code:

var MyObject = new Mongoose.Schema({
    //....
    watching : {type: Array, required: false},
    //....
});

So my question is how can I make sure that the values pushed into the array only ever store one, so making the values unique, can i just use unique: true ?

Thanks

Community · Accepted Answer · 2017-05-23 12:24:43Z

15

To my knowledge, the only way to do this in mongoose is to call the underlying Mongo operator (mentioned by danmactough). In mongoose, that'd look like:

var idToUpdate, theIdToAdd; /* set elsewhere */
Model.update({ _id: idToUpdate }, 
             { $addToSet: { theModelsArray: theIdToAdd } }, 
             function(err) { /*...*/ }
);

Note: this functionality requires mongoose version >= 2.2.2

edited May 23, 2017 at 12:24

CommunityBot

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answered Mar 11, 2012 at 23:04

frank hadder

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4 Comments

RobertPitt Over a year ago

can theIdToAdd be an array, such as ["ID1", "ID2"] ?

Ustaman Sangat Over a year ago

I guess u could use $each for that.

superiggy Over a year ago

@RoberPitt excellent point... theIdToAdd cannot be an array. If you do that, the item to be inserted will be that array. I'm trying to find a way to solve this :-(

Maksim Nesterenko Over a year ago

If theIdToAdd is array use $each docs.mongodb.com/manual/reference/operator/update/addToSet/…

danmactough · Accepted Answer · 2012-03-10 00:23:56Z

7

Take a look at the Mongo documentation on the $addToSet operator.

answered Mar 10, 2012 at 0:23

danmactough

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1 Comment

Ustaman Sangat Over a year ago

So, $addToSet will add a new element into the array if it already doesn't contain a duplicate. Is there a way (e.g. creating a unique index), which will ensure there never are duplicated in an array? Basically, I want a Set instead of a Sequence.

TaylorMac · Accepted Answer · 2014-03-10 06:11:39Z

1

Mongoose is an object model for mongodb, so one option is to treat the document as a normal javascript object.

MyModel.exec(function (err, model) {
   if(model.watching.indexOf(watchId) !== -1) model.watching.push(watchId);

   model.save(...callback);
});

Although, I do agree that mongoose should have some support for this built in the form of a validator for the collection document reference feature-- especially because most of the time you want to add only unique references.

answered Mar 10, 2014 at 6:11

TaylorMac

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1 Comment

ninja123 Over a year ago

This won't work if the set was added to the model by a concurrent operation, and in your example, you will be checking if the set exists in a stale copy of the model. Hence needing an enforced database level unique index.

Hammad Tariq · Accepted Answer · 2020-01-25 12:03:34Z

0

That's how you can do it using Mongoose,

IF your upcoming value is an Array

Model
    .findOneAndUpdate({ _id: yourID }, 
    { $addToSet: { watching: { $each: yourWatchingArr } } },
    function(err) { /*...*/ }
    );

IF your upcoming value is a string

Model
    .findOneAndUpdate({ _id: yourID }, 
    { $addToSet: { watching: yourStringValue } },
    function(err) { /*...*/ }
    );

answered Jan 25, 2020 at 12:03

Hammad Tariq

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