Return custom results using the Aggregate framework - mongodb

Question

I've the following Schemas in my Node.js app:
let CategorySchema = mongoose.Schema({
name: { type: String, required: true }
});
let UserSchema = mongoose.Schema({
firstName: { type: String, required: true },
lastName: { type: String, required: true }
});
let CustomerSchema = mongoose.Schema({
name: { type: String, required: true }
});
let VendorSchema = mongoose.Schema({
userID: { type: mongoose.Schema.Types.ObjectId, ref: 'User' },
category: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Category' }],
products: [ { type: mongoose.Schema.Types.ObjectId, ref: 'Product' } ],
name: { type: String, required: true }
});
let ProductSchema = mongoose.Schema({
vendorID: { type: mongoose.Schema.Types.ObjectId, ref: 'Vendor' },
name: { type: String, index: true, required: true },
customerReviews: [{
stars: { type: Number, required: false },
review: { type: String, required: false },
customerId: { type: mongoose.Schema.Types.ObjectId, ref: 'Customer', required: true }
}]
});
and I am trying to query the Vendors collection to return the following result:
{
_id: "dsi9dsik129dkdsdsds",
userData: {
_id: "dsa9dskd2kwd29dkkss",
firstName: "Michael",
lastName: "White"
},
categoryData: {
_id: "e9dids91i239dskds91",
name: "Category A"
},
productsData: [ {
_id: "3132139i31j32131",
vendorID: "dsi9dsik129dkdsdsds",
name: "Product ABC",
customerReviews [{
stars: "5",
review: "Good",
customerData: {
_id: "zds91i232131j2321j",
name: "John silver"
}
},
{
stars: "3",
review: "Bad",
customerData: {
_id: "ldso91232131j2321j",
name: "Mark Spenser"
}
}]
} ],
name: "Vendor XYZ"
}
I've built the following query on Vendors collection (meaning Vendors.aggregate(...) ) yet I am not sure how to format the returned results as well as retrieve Customers data in customers review, so I was wondering if anyone can help? Thanks.
(
{ $lookup: { from: "users", localField: "userID", foreignField: "_id", as: "userData" } },
{ $lookup: { from: "categories", localField: "category", foreignField: "_id", as: "categoryData" } },
{ $lookup: { from: "products", localField: "products", foreignField: "_id", as: "productsData" } },
{ $group: { _id: null, content: { $push: '$$ROOT' },count: { $sum: 1 } } },
{ $project: { content: { $slice: [ '$content', 0, 10 ] }, count: 1, _id: 0 } },
)
Test:
Category:
{
"_id" : ObjectId("5de7fc530ce9d05be4024170"),
"categoryName" : "Glass",
"__v" : 0
}
User:
{
"_id" : ObjectId("5d6671ae7be3be4e18ebe9bb"),
"firstName" : "Mark",
"lastName" : "Smith",
"__v" : 0
}
Customer:
{
"_id" : ObjectId("5dd7cb11f4b2544253368f24"),
"customerName" : "Michael White",
"__v" : 0
}
Vendor:
{
"_id" : ObjectId("5de7fc6a0ce9d05be4024171"),
"category" : [
ObjectId("5de7fc530ce9d05be4024170")
],
"products" : [
ObjectId("5de8474ccd0bbc05256db819")
],
"userID" : ObjectId("5d6671ae7be3be4e18ebe9bb"),
"vendorName" : "Michael White",
"__v" : 0
}
Product:
{
"_id" : ObjectId("5de8474ccd0bbc05256db819"),
"vendorID" : ObjectId("5de7fc6a0ce9d05be4024171"),
"name" : "Red Sause",
"customerReviews" : [
{
"moderated" : false,
"_id" : ObjectId("5de7fcf20ce9d05be4024175"),
"customerId" : ObjectId("5dd7cb11f4b2544253368f24"),
"stars" : 3,
"review" : "Didn't like it that much :( ",
"date" : ISODate("2019-12-04T18:37:38.253Z")
}
],
"__v" : 0
}
Note: I've added entity name before name in the test above, ex. vendorName / customerName just to avoid confusion between the field 'name' across multiple collections

Answer 1

You can try below aggregation from 3.6 version.
{"$lookup":{
"from": "users",
"localField": "userID",
"foreignField": "_id",
"as": "userData"
}},
{"$unwind":"$userData"},
{"$lookup":{
"from": "categories",
"localField": "category",
"foreignField": "_id",
"as": "categoryData"
}},
{"$lookup":{
"from":"products",
"let":{"products":"$products"},
"pipeline":[
{"$match":{"$expr":{"$in":["$_id","$$products"]}}},
{"$unwind":{"path":"$customerReviews", "preserveNullAndEmptyArrays":true}},
{"$lookup":{
"from":"customers",
"localField":"customerReviews.customerId",
"foreignField":"_id",
"as":"customerData"
}},
{"$unwind":{"path":"$customerData", "preserveNullAndEmptyArrays":true}},
{"$group":{
"_id":"$_id",
"vendorID": {"$first":"$vendorID"},
"name": {"$first":"$name"},
"customerReviews":{
"$push":{
"stars": "$customerReviews.stars",
"review": "$customerReviews.review",
"customerData":"$customerData"
}
}
}}
],
"as":"productsData"
}}