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Akshat Singhania
Akshat Singhania

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Mongoose Unique Not Working

You have a user schema and you want the email field to be unique

import { Schema } from 'mongoose';

const userSchema = new Schema({
    password: { type: String, required: true },
    email: { type: String, required: true, unique: true },

export default user schema;
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but it doesn't work! , here are some reasons because which this wouldn't work

1. Duplicate documents already created in DB before defining this property

You might have already added some duplicate data in the database so mongoose and MongoDB simply doesn't check unique field because it's already messed up

Delete the messed data from the MongoDB collections page to solve it

2. Auto Indexing or Create index is false

If you wouldn't have specified to auto index the data
which means to check for uniqueness, mongoose wouldn't do that

Simply make them to true while connecting to the database

    .connect('connection url', {
        useUnifiedTopology: true,
        useNewUrlParser: true,
        useCreateIndex: true, //make this true
        autoIndex: true, //make this also true
    .then(() => {
        console.log('Connected to mongoDB');
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Top comments (3)

gravy17 profile image
Tofi Agbaje • Edited

Hi from Nov 2022... neither of these worked for me, and it was because the indexes were being created in the background and I was seeding data as soon as a connection was established. This meant the data was added before the indexes were created, and apparently even though there was no duplicate, the indexes would not be created once this happens. There are two ways I know of to solve this:

  1. The first- and best imho- is to use mongoose.connection.syncIndexes() to reconstruct the indexes of all collections to match all schemas (it will even create collections for you in the process), and only when this is complete (.then() or await) do you seed data or process requests.

  2. An alternative is to use mongoose.model.createIndexes() to create indexes for the specific models you want to ensure indexes for; you also have to do this before seeding/processing.

Apparently there was an ensureIndexes() method to similar effect that was deprecated.

javadsh profile image

maybe I find a better way.
there is a package that can help easily.

sulaimanaminubarkindo profile image
Sulaiman Aminu Barkindo

Thanks it worked for me. the DB already have duplicate data that was why it was not working