how to query mongodb nested query three level？ - json

Question

I have three collections (docs example struct see below :)
my mongodb version is 4.4
section
{
_id: ObjectId('62b131211331e0e9ba284187'),
name: 'name1',
},
{
_id: ObjectId('62b131211331e0e9ba284187'),
name: 'name2',
}
...
2.problems
{
_id: ObjectId('62b13d5f1331e0e9ba2841e6'),
title: 'title1',
score: 10,
section_id: ObjectId('62b131211331e0e9ba284188')
},
{
_id: ObjectId('62b13d5f1331e0e9ba2841e6'),
title: 'title2',
score: 20,
section_id: ObjectId('62b131211331e0e9ba284188')
},
{
_id: ObjectId('62b13d5f1331e0e9ba2841e6'),
title: 'title3',
score: 30,
section_id: ObjectId('62b131211331e0e9ba284188')
}
...
3.choices
{
_id: ObjectId('62b164ae1331e0e9ba284236'),
text: 'text1',
value: 0,
checked: false,
problem_id: ObjectId('62b13d5f1331e0e9ba2841ed')
},
{
_id: ObjectId('62b164ae1331e0e9ba284236'),
text: 'text2',
value: 0,
checked: false,
problem_id: ObjectId('62b13d5f1331e0e9ba2841ed')
},
{
_id: ObjectId('62b164ae1331e0e9ba284236'),
text: 'text3',
value: 0,
checked: false,
problem_id: ObjectId('62b13d5f1331e0e9ba2841ed')
},
...
the relationship of those collections
sections has many problems
problems has many choices
My question is :
Now I have an array of sections's id like below:
[
ObjectId('62b131211331e0e9ba284188'),
ObjectId('62b131211331e0e9ba28418a'),
ObjectId('62b131211331e0e9ba28418c')
]
I want to perform one query get the result like below:
[
{
_id: ObjectId('62b131211331e0e9ba284187'),
name: 'name1',
problems: [
{
_id: ObjectId('62b13d5f1331e0e9ba2841e6'),
title: 'title1',
score: 10,
section_id: ObjectId('62b131211331e0e9ba284188')，
choices: [
{}, // choice doc
]
},
{
_id: ObjectId('62b13d5f1331e0e9ba2841e6'),
title: 'title2',
score: 10,
section_id: ObjectId('62b131211331e0e9ba284188')，
choices: [
{}, // choice doc
]
},
...
]
},
{
_id: ObjectId('62b131211331e0e9ba284187'),
name: 'name1',
problems: [
{},
]
},
{
_id: ObjectId('62b131211331e0e9ba284187'),
name: 'name1',
problems: [
{}，
]
}
]
I have try run this query in my mongoexpress but it didn't work:
// match stage (ps: start with sections collection)
{
"_id": {
$in: [
ObjectId('62b131211331e0e9ba284188'),
ObjectId('62b131211331e0e9ba28418a'),
ObjectId('62b131211331e0e9ba28418c')
]
}
// lookup stage
{
from: 'problems',
let: {"sid": "$_id"},
pipeline: [
{
"$match": {
"$expr": {
"$eq": ["$section_id", "$$sid"]
},
},
},
{
"$lookup": {
from: "choices",
let: {"chid": "$_id"},
pipeline: [
{
"$match": {
"$expr": {},
},
},
],
as: "choices"
},
},
],
as: "problems"
}