Find Top rated product in mongoose - node.js

Question

I have a Review Model and Product Model such as:
const ProductReviewSchema = Schema({
rating: {
type: Number,
min: 1,
max: 5,
required: true,
},
product: {
type: mongoose.Types.ObjectId,
ref: 'ecommerce-product',
},
});
and
const ProductSchema = Schema({ name: String, price: Number });
and I want to display top-rated product I can do this using find method in reviewschema and using loops
const totalResult = await ProductReviewModel.find({}, 'rating _id');
let averageRatingNumerator = 0;
let averageRatingDenominator = 0;
if (totalResult) {
totalResult.forEach((eachRate) => {
averageRatingDenominator += 1;
averageRatingNumerator += eachRate.rating;
});
}
then find the average rating of each product and sort the result in ascending order. Can I do the exact same thing using mongoose aggregate, If yes what pipeline or operator should I use to achieve such a result:
My Expected result may be is:
[
{ product: 'abc', avgRating: 3.5 },
{ product: 'def', avgRating: 3.1 }
];

Answer 1

Search from the productReview Schema and populate the product,
$group by product and get average of rating
$sort by avgRating in descending order
$lookup and join product collection
$unwind deconstruct product
$project to show required fields
const totalResult = await ProductReviewModel.aggregate([
{
$group: {
_id: "$product",
avgRating: { $avg: "$rating" }
}
},
{ $sort: { avgRating: -1 } },
{
$lookup: {
from: "products", // update your actual product collection name
localField: "_id",
foreignField: "_id",
as: "product"
}
},
{ $unwind: "$product" },
{
$project: {
name: "$product.name",
avgRating: 1
}
}
]).exec();
Playground
Search from product Schema and populate productReview,
$lookup join products review collection
$size to get total reviews
$sum to calculate sum of return array of rating
$let to specify both (total, ratings) as variable
$cond check condition if total is not zero then $divide
$sort by avgRating in descending order
const totalResult = await Products.aggregate([
{
$lookup: {
from: "productsReview", // replace your actual review collection name here
localField: "_id",
foreignField: "product",
as: "review"
}
},
{
$project: {
name: 1,
avgRating: {
$let: {
vars: {
total: { $size: "$review" },
ratings: { $sum: "$review.rating" }
},
in: {
$cond: [{ $eq: ["$$total", 0] }, 0, { $divide: ["$$ratings", "$$total"] }]
}
}
}
}
},
{ $sort: { avgRating: -1 } }
]).exec();
Playground