mongoose : Users who have not logged in since last 5 days - mongodb

Question

I have 2 schemas
userSchema:
const userSchema = new mongoose.Schema({
firstName: {
type: String,
},
lastName: {
type: String,
},
username: {
type: String,
required: true,
},
password: {
type: String,
required: true,
},
tokens: {
type: [
{
token: String,
},
],
},
});
useractivity:
const userActivitySchema = new mongoose.Schema({
ip: String,
ua: String,
date: {
type: Date,
default: Date.now,
},
user: {
type: mongoose.Schema.Types.ObjectId,
ref: "User",
},
});
I am adding a new entry in useractivity every time user logged into the system.
I wanted to featch list of users who haven't logIn in last 5 days for that I write query :
const dateToCheck = new Date();
dateToCheck.setDate(
dateToCheck.getDate() - process.env.LEASS_ACTIVE_USER_DAYS
);
const userActivity = await UserActivity.aggregate([
{ $match: { date: { $lt: dateToCheck } } },
{
$lookup: {
from: "users",
localField: "user",
foreignField: "_id",
as: "userdata",
},
},
{ $unwind: { path: "$userdata" } },
{
$project: {
date: 1,
"userdata.firstName": 1,
},
},
]);
with this, I am able to get date and firstName of users who haven't logged in last 5 days.
But the issue with this is as there are multiple records in useractivity, above query returns duplicate users in the result.
I tried using { $group: { _id: { user: "$user" } } } to group the result by foreign key but it returns [] in this case.
Any suggestions will be helpfull

Answer 1

Try this out, you already have access to the unique id of the user from your lookup, so use that to group your documents. Additionally, I am storing all the dates in an array from the grouping
UPDATE: Also attaching mongo playground link where I tried it
const userActivity = await UserActivity.aggregate([
{ $match: { date: { $lt: dateToCheck } } },
{
$lookup: {
from: "users",
localField: "user",
foreignField: "_id",
as: "userdata",
},
},
{ $unwind: { path: "$userdata" } },
{
$project: {
date: 1,
"userdata.firstName": 1,
"user_id": "$userdata._id"
},
},
{
$group: {
"_id": {
"user_id": "$user_id",
"user_name": "$userdata.firstName"
},
"dates": {
"$push": "$date"
}
}
}
]);