Using Mongoose's findAndUpdate method along with discriminators

Question

Using Mongoose's findAndUpdate method along with discriminators

My inventory consists of various products like smartphones, laptops, headphones, etc. However, in the end, all these products are represented as a single generalized ProductsModel

ProductsModel

import { Schema, model } from 'mongoose'

export const productsDiscriminatorKey = 'productKind'

const ProductsSchema = new Schema(
    {
        name: { type: String },
    },
    { productsDiscriminatorKey, timestamps: true }
)

export default model('Products', ProductsSchema)

PhoneModel

import mongoose, { Schema } from 'mongoose'

import ProductsModel, { productsDiscriminatorKey } from './ProductsModel.js'

const PhoneSchema = new Schema(
    {
        name: { type: String, required: true },
        price: { type: String, required: true },
        color: { type: String, required: true },
        memory: { type: String, required: true },
        screen: { type: String, required: true },
        fps: { type: String, required: true },
        sim: { type: String, required: true },
        preview: { type: String, required: true },
        images: [{ type: String, required: true }],
        category: {
            type: mongoose.Schema.ObjectId,
            ref: 'Category',
        },
        type: {
            type: mongoose.Schema.ObjectId,
            ref: 'Type',
        },
        count: { type: Number },
    },
    { productsDiscriminatorKey }
)

const PhoneModel = ProductsModel.discriminator('Phones', PhoneSchema)
export default PhoneModel

I have implemented a method for removing products from the database based on quantity rather than deleting the entire model at once. The logic works correctly when used in specific models like PhoneModel, but not when tried from ProductsModel. The count field remains unchanged.

Delete logic

    async delete(req, res) {
        try {
            const { id } = req.params
            const { count } = req.body

            const candidate = await ProductsModel.findById(id)

            if (candidate.count < count) {
                return res.status(500).json({ message: 'More than count in base' })
            }

            if (candidate.count === count || !count) {
                await ProductsModel.findByIdAndDelete(id)
                return res.status(200).json({ message: 'All deleted' })
            }

            if (candidate.count > count) {
                await ProductsModel.findByIdAndUpdate({ _id: id }, { count: candidate.count - count })

                return res.status(200).json({ message: `${count} successfully deleted` })
            }
        } catch (error) {
            return res.status(500).json({ message: 'Server error' })
        }
    }

In certain scenarios, only a specific quantity (count) needs to be deleted and not all at once. This is achieved by adjusting the count field using findByIdAndUpdate. Despite implementing this logic, it does not function as expected without any error messages.

javascript mongodb express mongoose

Answer 1

Answer №1

There is an issue because the base schema does not have access to keys in an inherited schema. The problem arises when the base schema attempts to retrieve the key count from the inherited schema. In this scenario, ProductsModel represents the base schema and PhoneModel represents the inherited schema. The key 'count' belongs to the PhoneModel schema and not the ProductsModel schema. As a result, Mongoose will disregard the update document { count: candidate.count - count }.

await ProductsModel.findByIdAndUpdate({ _id: id }, { count: candidate.count - count })

On the other hand, queries that involve the key _id work correctly since it exists in both schemas.

const candidate = await ProductsModel.findById(id)
await ProductsModel.findByIdAndDelete(id)

The provided code showcases this issue with references to line 1, line 2, and line 3. Verification of these lines confirms that the base schema lacks access to keys in an inherited schema.

const mongoose = require('mongoose');
const { Schema } = mongoose;
const asserts = require('assert');

const options = { discriminatorKey: 'kind' };

const parentSchema = new Schema({ parentkey1: String }, options);
const Parent = mongoose.model('Parent', parentSchema);

const childSchema = new Schema({ childkey1: String }, options);
const Child = Parent.discriminator('Child', childSchema, options);

let parentdoc = new Parent({
  parentkey1: 'parentkey1',
});

let childdoc = new Child({
  parentkey1: 'parentkey1',
  childkey1: 'childkey1',
});

// document objects
asserts.ok(parentdoc._id);
asserts.ok(childdoc._id);

asserts.ok(parentdoc.parentkey1);
asserts.ok(!parentdoc.childkey1);  // line 1
asserts.ok(childdoc.parentkey1);
asserts.ok(childdoc.childkey1);

run().catch((err) => console.log(err));
async function run() {
  await mongoose.connect('mongodb://127.0.0.1:27017/test');
  await Parent.deleteMany();
  await Child.deleteMany();
  await parentdoc.save();
  await childdoc.save();

  parentdoc = await Parent.findById(parentdoc._id);
  childdoc = await Child.findById(childdoc._id);

  asserts.ok(parentdoc._id);
  asserts.ok(childdoc._id);

  asserts.ok(parentdoc.parentkey1);
  asserts.ok(!parentdoc.childkey1); // line 2
  asserts.ok(childdoc.parentkey1);
  asserts.ok(childdoc.childkey1);

  parentdoc = await Parent.findByIdAndUpdate(parentdoc._id, {
    childkey1: 'new value',
  });
  asserts.ok(parentdoc.parentkey1);
  asserts.ok(!parentdoc.childkey1);  // line 3
}

Answer 2

There is an issue because the base schema does not have access to keys in an inherited schema. The problem arises when the base schema attempts to retrieve the key count from the inherited schema. In this scenario, ProductsModel represents the base schema and PhoneModel represents the inherited schema. The key 'count' belongs to the PhoneModel schema and not the ProductsModel schema. As a result, Mongoose will disregard the update document { count: candidate.count - count }.

await ProductsModel.findByIdAndUpdate({ _id: id }, { count: candidate.count - count })

On the other hand, queries that involve the key _id work correctly since it exists in both schemas.

const candidate = await ProductsModel.findById(id)
await ProductsModel.findByIdAndDelete(id)

The provided code showcases this issue with references to line 1, line 2, and line 3. Verification of these lines confirms that the base schema lacks access to keys in an inherited schema.

const mongoose = require('mongoose');
const { Schema } = mongoose;
const asserts = require('assert');

const options = { discriminatorKey: 'kind' };

const parentSchema = new Schema({ parentkey1: String }, options);
const Parent = mongoose.model('Parent', parentSchema);

const childSchema = new Schema({ childkey1: String }, options);
const Child = Parent.discriminator('Child', childSchema, options);

let parentdoc = new Parent({
  parentkey1: 'parentkey1',
});

let childdoc = new Child({
  parentkey1: 'parentkey1',
  childkey1: 'childkey1',
});

// document objects
asserts.ok(parentdoc._id);
asserts.ok(childdoc._id);

asserts.ok(parentdoc.parentkey1);
asserts.ok(!parentdoc.childkey1);  // line 1
asserts.ok(childdoc.parentkey1);
asserts.ok(childdoc.childkey1);

run().catch((err) => console.log(err));
async function run() {
  await mongoose.connect('mongodb://127.0.0.1:27017/test');
  await Parent.deleteMany();
  await Child.deleteMany();
  await parentdoc.save();
  await childdoc.save();

  parentdoc = await Parent.findById(parentdoc._id);
  childdoc = await Child.findById(childdoc._id);

  asserts.ok(parentdoc._id);
  asserts.ok(childdoc._id);

  asserts.ok(parentdoc.parentkey1);
  asserts.ok(!parentdoc.childkey1); // line 2
  asserts.ok(childdoc.parentkey1);
  asserts.ok(childdoc.childkey1);

  parentdoc = await Parent.findByIdAndUpdate(parentdoc._id, {
    childkey1: 'new value',
  });
  asserts.ok(parentdoc.parentkey1);
  asserts.ok(!parentdoc.childkey1);  // line 3
}

Using Mongoose's findAndUpdate method along with discriminators

Answer №1

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