Mongo Error: Duplicate Key error makes no sense

Question

Hi fellow developers! I've got this error showing up in my console when I try to save two identical documents in a collection in MongoDB that has nothing to do with the index shown in the error.

Here's the error: E11000 duplicate key error collection: Bohemian.orders index: user.email_1 dup key: { user.email: null }

Now this makes no sense, because I'm trying to save an Order document in a separate collection, which has nothing to do with the user router I had set up previously.

Here is the schema and model code:

const mongoose = require('mongoose');

const orderSchema = new mongoose.Schema({
    amountToPay: Number,
});

const Order = mongoose.model("Order", orderSchema);

module.exports.Order = Order;

As shown here, I am only trying to save the amount to be payed into the database in a separate collection.

Here is the router file:

const express = require('express');
const router = express.Router();
const { Order } = require('../models/Order');

router.get("/", async (req, res, next) => {
    try {
        const orders = await Order.find();
        if (orders.length === 0) return res.status(404).send("There are currently no orders");
        res.send(orders);
    } catch (ex) {
        console.error(ex);
        next();
    }
});

router.post("/", async (req, res, next) => {
    try {
        const order = new Order({
            amountToPay: req.body.amountToPay
        });
        await order.save();
        res.send(order);
    } catch (ex) {
        console.error(ex);
        next();
    }
});

module.exports = router;

As you can see there is nothing relative to the error that I'm getting and I have no clue why I'm getting a duplicate user.email = null key , when I haven't made any reference to the User model or router.

Here is the POST call I'm making from POSTMAN to test:

Pretty straight forward, nothing extreme, nothing tangled, right? Well the first ever POST call saves the document in the Database, but from then on I keep getting the same error. The only thing I can take from that is that when I save the first document, Mongo looks for the user.email property when I'm creating the new instance of Order and when it doesnt find it, it creates it with a value of null and then the next document would naturally be a duplicate, hence the error. But I'm confused, because this model and router should not absolutely nothing to do with the user ones.

Here is the error:

So please if anyone can help me understand why MongoDB is screwing with me or where I'm making a mistake, I would really appreciate it.

Check the indexes on the orders collection. In cli use db.orders.getIndexes() or something like that. It looks to me that you might have created an index on user.email in the past. — Molda

Unknown Unknown · Accepted Answer · 2020-05-30T12:06:36

I found out what the problems was, thanks to Molda: At some point I had created these indexes, which I'm still unsure when and how, but I did. Which essentially lead to this error, when I tried to save the second document. A simple quick console log of the indexes in the collection showed that I had that index in there.

const indexes = await Order.collection.getIndexes();
console.log(indexes);

Then I removed them using this method:

await Order.collection.dropIndexes("user.email_1");

And everything worked flawlessly from there. I hope this helps anyone in this situation in the future and thanks Molda! :)

Mongo Error: Duplicate Key error makes no sense

1 Answers