Display only select nested fields of object in MongoDB Compass aggregation - mongodb

Question

I have the following data model:
{
"_id": {
"$oid": "63b6da81661f0ecd23cd9830"
},
"Plan": [
{
"_id": {
"$oid": "63b6311e0871625f7ceb85ad"
},
"Name": "Straight ankle lock",
"Date": {
"$date": {
"$numberLong": "1672725600000"
}
},
"Notes": "Christian taught ankle locks",
"TeamId": {
"$oid": "63a291ebb60592854e23b8fb"
}
}
],
"User": [
{
"_id": {
"$oid": "6240fd2ee1335b45680bee9d"
},
"FirstName": "Test",
"LastName": "User",
"TeamId": {
"$oid": "639fd03bb31c7995a9d4b28c"
}
}
]
}
And I'd like to show a new object via aggregation that looks like:
{
"_id": {
"$oid": "63b6da81661f0ecd23cd9830"
},
"PlanName": "Straight ankle lock",
"UserName": "Test User"
}
I've been trying to figure this out for a few days, but at this point not sure if it is even possible. Any ideas?
Thanks.
Newer model based on Ray's input using project:
{
"_id": {
"$oid": "63b6da81661f0ecd23cd9830"
},
"InsertDate": {
"$date": {
"$numberLong": "1672927873507"
}
},
"Plan": {
"Name": "Straight ankle lock"
},
"User": {
"FirstName": "Adam",
"LastName": "Gusky"
},
"Team": {
"TeamName": "GB2 No Gi"
}
}
The query I'm using to get the above data:
[
{
$lookup: {
from: "Plans",
localField: "PlanId",
foreignField: "_id",
as: "Plan",
},
},
{
$lookup: {
from: "Teams",
localField: "TeamId",
foreignField: "_id",
as: "Team",
},
},
{
$lookup: {
from: "Users",
localField: "UserId",
foreignField: "_id",
as: "User",
},
},
{
$project: {
Plan: {
$first: "$Plan",
},
User: {
$first: "$User",
},
Team: {
$first: "$Team",
},
InsertDate: 1,
},
},
{
$project: {
"Plan.Name": 1,
"User.FirstName": 1,
"User.LastName": 1,
"Team.TeamName": 1,
InsertDate: 1,
},
},
]

Answer 1

You can simply set the value you want in the $project stage.
db.collection.aggregate([
{
$project: {
_id: 1,
PlanName: {
$first: "$Plan.Name"
},
UserName: {
"$concat": [
{
"$first": "$User.FirstName"
},
" ",
{
"$first": "$User.LastName"
}
]
}
}
}
])
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