Duplicate key error collection with unique field

Question

I am getting a MongoDB error when trying to insert a document without nickname second time. The document already have unique field and non required.

Here is my Mongoose model:

var schema = new Schema ({

        username: {
            type: String,
            required: false
        },

        nickname: {
            type: String,
            required: false,
            unique: true,
            trim: true
        },

        status: {
            type: String,
            required: false,
            trim: true,
            minlength: 1,
            maxlength: 100
        },

        avatar: String,

        online: {
            type: Boolean,
            default: false
        },

        created: {
            type: Date,
            default: Date.now
        },

        device: {
            type: ObjectId,
            ref: 'Device',
            required: false
        },

        createdRooms:[{
            type: Schema.Types.ObjectId,
            ref: 'Room'
        }],

        facebook: {
            facebookToken: {
                type: String,
                required: false,
                trim: true,
                unique: false
            },

            facebookId: {
                type: String,
                required: false,
                trim: true,
                unique: false
            }
        }
    },

    {
        toObject: {
            virtuals: true
        },
        toJSON: {
            virtuals: true
        }

});

For the first time, the document without a nickname is added to the database, but when I want to save another document without a nickname, I get an error:

MongoError: E11000 duplicate key error collection: grooptag.users index: nickname_1 dup key: { : null }

Isn't the problem that nickname is not required but is unique? — Nadia Cerezo, Sep 26 '16 at 08:58
@NadiaCerezo yes, but how to make sure that the field be unique and not required? — nickheck, Sep 26 '16 at 09:00

score 1 · Answer 1 · edited May 23 '17 at 11:48

1

So I looked up "MongoDB not required but unique" and I found this: mongoDB/mongoose: unique if not null

It seems you need to use sparse: true instead of required: false to get what you want.

Edit: Reading up the MongoDB documentation on sparse indexes, however, I was redirected to partial indexes which seem to be the way to go from MongoDB 3.2 onward: https://docs.mongodb.com/manual/core/index-partial/#index-type-partial

The problem is that while the documentation clearly states:

Partial indexes represent a superset of the functionality offered by sparse indexes and should be preferred over sparse indexes.

It does not seem to be true for sparse and unique indexes, since they also state on the same page:

A partial index with a unique constraint does not prevent the insertion of documents that do not meet the unique constraint if the documents do not meet the filter criteria.

Way to contradict themselves... :/

edited May 23 '17 at 11:48

Community

1
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answered Sep 26 '16 at 09:02

Nadia Cerezo

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Thanks, I'll check and let you know. – nickheck Sep 26 '16 at 09:09
This is not working for me. It seems "sparse" is only for the reference type fields. – nickheck Sep 26 '16 at 09:28
Strange, the documentation here https://docs.mongodb.com/manual/core/index-sparse/ states: An index that is both sparse and unique prevents collection from having documents with duplicate values for a field but allows multiple documents that omit the key. And that sounds like precisely what you want, right? – Nadia Cerezo Sep 26 '16 at 09:30
True, but I just checked on my model and it does not work. And the link that you have attached, in the comments said that it is not working. One commentator said: "Does not work with missing fields Maybe behavior was changed in later versions of mongodb Answer should be updated." It now looks my field: `nickname: { type: String, sparse: true, index: true, unique: true, trim: true }` – nickheck Sep 26 '16 at 09:39
You're right, it seems sparse indexes have been somewhat deprecated... shame. – Nadia Cerezo Sep 26 '16 at 09:48

Duplicate key error collection with unique field

1 Answers1