Mongoose Unique index not working!

Question

Oops! You just have to restart mongo.

Oops! You just have to restart mongo.

And re-index too, with:

mongo <db-name>
> db.<collection-name>.reIndex()

In testing, since I don't have important data, you can also do:

mongo <db-name>
> db.dropDatabase()

I ran into the same issue: I added the unique constraint for the email field to our UserSchema after already having added users to the db, and was still able to save users with dupe emails. I resolved this by doing the following:

1) Remove all documents from the users collection.

2) From the mongo shell, execute the command: db.users.createIndex({email: 1}, {unique: true})

Regarding step 1, note that from Mongo's docs:

MongoDB cannot create a unique index on the specified index field(s) if the collection already contains data that would violate the unique constraint for the index.

https://docs.mongodb.com/manual/core/index-unique/

I've done something like this:

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const FooSchema = new Schema({
   name: { type: String, required: true, index: true, unique: true }
});

const Foo = mongoose.model('Foo', FooSchema);

Foo.createIndexes();

module.exports = Foo

I added the Foo.createIndexes() line b.c. I was getting the following deprecation warning when the code was being ran:

(node:21553) DeprecationWarning: collection.ensureIndex is deprecated. Use createIndexes instead.

I'm not sure if Foo.createIndexes() is asynchronous, but AFAIK things seem to be working fine

This behavior happen also if you have left some duplicates in Mongo. Mongoose will try to create them in Mongo when your application starts up.

To prevent this, you can handle this error this way :

yourModel.on('index', function(err) {
  if (err?) {
    console.error(err)
  }
);

Ok, i was able to resolve this from the mongoshell by adding the index on the field and setting the unique property:

db.<collectionName>.ensureIndex({fieldName: 1}, {unique: true});

Shell should respond in this way:

{
    "createdCollectionAutomatically" : false,
    "numIndexesBefore" : 1,
    "numIndexesAfter" : 2,
    "ok" : 1
}

Now to test quickly from the mongoshell:

var doc = {fieldName: 'abc'};
db.<collectionName>.insert(doc)

Should give: WriteResult({ "nInserted" : 1 })

But when repeating again:

db.<collectionName>.insert(doc)

Will give:

WriteResult({
    "nInserted" : 0,
    "writeError" : {
        "code" : 11000,
        "errmsg" : "insertDocument :: caused by :: 11000 E11000 duplicate key error index: fuelConsumption.users.$email_1  dup key: { : \"[email protected]\" }"
    }
})