aggregate nested array of objects using mongoose - node.js

Question

I have the following model and I want to query a specific user on _id field and populate the inbox.messages array with the necessary data that matches the corresponding _id field in the users model and more importantly i also want to group each message by the 'from' field and return that result
const UserSchema = new Schema({
username: {
type: String,
required: true,
},
blockedUsers: {
users: [
{
userId: {type: Schema.Types.ObjectId, ref: 'User', required: true },
}
]
},
favorites: {
users: [
{
userId: {type: Schema.Types.ObjectId, ref: 'User', required: true },
}
]
},
profileViews: {
views: [
{
userId: {type: Schema.Types.ObjectId, ref: 'User', required: true },
date: {type: Date}
}
]
},
inbox: {
messages: [
{
messageId: {type: Schema.Types.ObjectId},
from: {type: Schema.Types.ObjectId, ref: 'User', required: true },
content: {type: String, required: true},
date: {type: Date}
}
]
},
images: {
"imagePaths": [
{
imageId: {type: Schema.Types.ObjectId},
path: { type: String, required: true},
date: {type: Date}
}
],
}
})
what I have so far
let incomingId = '5e29fd75fdfd5320d0e42bc4';
let myUser = await User.aggregate([
{ $match: {"_id": mongoose.Types.ObjectId(incomingId) }},
{ $lookup: { }}
])
Not sure exactly what to put in the $lookup field or if this is even correct.
As a sample I would like the documents to look like:
[
{
"from": "5e240f7480a24e07d832c7bd",
"username":"hable0",
"images": {
imagePaths: [
'images/2020-09-24-Z_34234342_12.jpg'
],
},
"inbox": {
"messages": [
{
"messageId": "5e2a110a21c64d63f451e39e",
"content": "Message content",
"date": "2020-01-23T21:32:58.126Z"
},
{
"messageId": "5e2a111321c64d63f451e3a0",
"content": "Message content",
"date": "2020-01-23T21:33:07.378Z"
},
{
"messageId": "5e2a112321c64d63f451e3a2",
"content": "Message content",
"date": "2020-01-23T21:33:23.036Z"
}
]
}
}
]

Answer 1

You could try the following pipeline with aggregate().
Find the document that matches the id
Unwind inbox.messages
Group by from field
Perform a $lookup to get another document
Perform a $unwind to destruct the array
Specify fields to be included in the output
let myUser = await User.aggregate([
{
$match: { "_id": mongoose.Types.ObjectId(incomingId) }
},
{
$unwind: "$inbox.messages"
},
{
$group: {
_id: { from: "$inbox.messages.from" },
messages: {
$push: {
messageId: "$inbox.messages.messageId"
// Add more info of the message here as needed
}
}
},
},
{
$lookup: {
from: "User",
localField: "_id.from",
foreignField: "_id",
as: "extraUserInfo"
}
},
{
$unwind: "$extraUserInfo"
},
{
$project: {
_id: 0,
from: "$_id.from",
inbox: { messages: "$messages" },
username: "$extraUserInfo.username",
images: "$extraUserInfo.images"
}
}
]);
Sample output:
{
"from": "user1",
"inbox": {
"messages": [{
"messageId": "message1-from-user1"
}]
},
"username": "user1-username",
"images": {
"imagePaths": ["image-path-user1"]
}
} {
"from": "user2",
"inbox": {
"messages": [{
"messageId": "message1-from-user2"
}, {
"messageId": "message2-from-user2"
}, {
"messageId": "message3-from-user2"
}]
},
"username": "user2-username",
"images": {
"imagePaths": ["image-path-user2"]
}
} {
"from": "user3",
"inbox": {
"messages": [{
"messageId": "message1-from-user3"
}, {
"messageId": "message2-from-user3"
}]
},
"username": "user3-username",
"images": {
"imagePaths": ["image-path-user3"]
}
}
Hope this answers part of your question. Though I'm not very clear how you would like to populate the messages array with the user info who sent the messages. But you can perform a $lookup() with a pipeline after $group() operation to attach additional info from the sender to the result.
Read more about $unwind, $group, $project and $lookup.