Aggregate Function Mongoose - Node - node.js

Question

I have a schema
const membershipsSchema = new Schema({
spaceId: {
type: Schema.Types.ObjectId,
ref: 'Space',
},
member: {
type: Schema.Types.ObjectId,
ref: 'User',
},
....
);
mongoose.model('Membership', membershipsSchema);
I want to use join statement like
Select * from membershipPlans as plans join User as users on plans.member=users._id
where plans.spaceId=id and users.status <> 'archived'; // id is coming from function arguments
I tried the aggregate pipeline like
const memberships = await Memberships.aggregate([
{
$match: {
spaceId: id
}
},
{
$lookup: {
from: 'User',
localField: 'member',
foreignField: '_id',
as: 'users',
},
},
{
$match: {
'users.status': {$ne: 'archived'}
}
},
]);
But on console.log(memberships); I am getting an empty array. If I try return Memberships.find({ spaceId: id }) it returns populated memberships of that space. But when I try
const memberships = await Memberships.aggregate([
{
$match: {
spaceId: id
}
},
]}
It still returns an empty array. Not sure if I know how to use an aggregate pipeline.

Answer 1

There are two things that you need to do:
Cast id to ObjectId.
Instead of using $match, just filter the contents of the users array using $filter.
Try this:
const memberships = await Memberships.aggregate([
{
$match: {
spaceId: new mongoose.Types.ObjectId(id)
}
},
{
$lookup: {
from: 'User',
localField: 'member',
foreignField: '_id',
as: 'users',
},
},
{
$project: {
users: {$filter: {
input: "$users",
as: "user",
cond: {
$ne: ["$$user.status", "archived"]
}
}}
}
},
]);