Mongoose: Feature Request: Allow Unique in Array Schema Definition

Created on 6 Sep 2015 · 35Comments · Source: Automattic/mongoose

The following page states currently supported Schema types: http://mongoosejs.com/docs/schematypes.html

One feature that would be nice is for Mongoose to enforce uniqueness in Arrays, which could guarantee unique values in an array in Mongoose, like the $addToSet functionality in the Mongo database query language.

Current Issue

I can only define an array to hold a list of values, which allows multiple instances of the same value. The following code example demonstrates the issue.

var schema = mongoose.Schema({
friends : [{type : mongoose.Schema.Types.ObjectId, ref : 'User' }]
})

model = new mongoose.model('User')

model['friends'].push(ObjectId('12345'))
model['friends'].push(ObjectId('12345'))

model.save()

Mongo document now looks like:
{friends:[ObjectId('12345'),ObjectId('12345')]}

Suggested Fix

Enhance the schema model to allow unique attribute for an array, which internally uses the Set() object in Mongoose. Then once save() is called, mongoose will convert the set to an array and use the "$addToSet" mongodb operator that will ensure values are unique in the array. Something like the following code snippet would be desired:

var schema = mongoose.Schema({
friends : [{type : mongoose.Schema.Types.ObjectId, ref : 'User', unique: true }]
})
model = new mongoose.model('User')

model['friends'].push(ObjectId('12345'))
model['friends'].push(ObjectId('12345'))

model.save()

Mongo document now looks like:
{friends:[ObjectId('12345')]}

Current Method

Currently it is being suggested to create a seperate update() function with the "$addToSet" parameter, which seems to be more work and burden on the developer than it should be. Please refer to the following:

https://groups.google.com/forum/#!topic/mongoose-orm/QSpr_7rtEYY
http://stackoverflow.com/questions/15921700/mongoose-unique-values-in-nested-array-of-objects

plugin

Source

ccravens

👍30 ❤3 🎉1

Most helpful comment

Check out http://thecodebarbarian.com/whats-new-in-mongoose-4.10-unique-in-arrays.html if you're eager to get started :+1:

vkarpov15 on 20 May 2017

🎉5 👍1

All 35 comments

filfat on 25 Feb 2016

👍3

+1
Also, just wondering but how difficult would it be to implement this?

BlueAccords on 25 Feb 2016

👍2

Pretty difficult actually, mongoose would have to do a lot to make this work, because $addToSet doesn't work well with document arrays. For example, there is no good way to, say, $addToSet a user object to an array called users while enforcing that the username property should be unique. This would make the API a bit unwieldy, because unique would only work as expected for regular arrays, but not work right for document arrays.

vkarpov15 on 25 Feb 2016

👍2

+1
I can imagine it would be a bit complex and inefficient on the querying side but it still would be nice to have.

yonib05 on 7 Mar 2016

👍1

+1
It would be very nice to do it

trycontrolmymind on 7 Mar 2016

👍3

+1
Nice feature to have!

forl on 12 Mar 2016

👍4

+1

 That'd be a really awesome feature, especially for use with sub-schemas /documents such that each has it's own distinct scope.  
 Somebody please add it.