How to remove item in nested collection by id - mongoose - mongodb

Question

I want to remove a topic by id from the following collection. Here is the hierarchy of the collection - Area.
Area ---
|
---Subjects---
|
Courses---
|
Chapters----
|
Topics
The Area example is as following.
{
"_id" : ObjectId("607f7c67f64e993a5c9b9793"),
"name" : "Automatic Engineering",
"description" : "this is the description.",
"created" : ISODate("2021-04-21T01:14:15.736Z"),
"subjects" : [
{
"description" : "dddd",
"name" : "Transfer Function",
"_id" : ObjectId("607f7c7af64e993a5c9b9794"),
"created" : ISODate("2021-04-21T01:14:34.943Z"),
"courses" : [
{
"description" : "dddd",
"name" : "conception",
"_id" : ObjectId("607f7c9af64e993a5c9b9796"),
"created" : ISODate("2021-04-21T01:15:06.696Z"),
"chapters" : [
{
"description" : "chapter 1",
"name" : "Chapter 1",
"_id" : ObjectId("607f7cb4f64e993a5c9b9798"),
"created" : ISODate("2021-04-21T01:15:32.855Z"),
"topics" : [
{
"description" : "1",
"name" : "Topic 1",
"_id" : ObjectId("607f7ccef64e993a5c9b979b"),
"created" : ISODate("2021-04-21T01:15:58.064Z")
},
{
"description" : "2",
"name" : "Topic 2",
"_id" : ObjectId("607f7cd5f64e993a5c9b979c"),
"created" : ISODate("2021-04-21T01:16:05.663Z")
},
{
"description" : "3",
"name" : "Topic 3",
"_id" : ObjectId("607f7cdcf64e993a5c9b979d"),
"created" : ISODate("2021-04-21T01:16:12.336Z")
}
]
},
{
"description" : "chapter2",
"name" : "Chapter 2",
"_id" : ObjectId("607f7cbcf64e993a5c9b9799"),
"created" : ISODate("2021-04-21T01:15:40.231Z"),
"topics" : []
},
{
"description" : "chapter 3",
"name" : "Chapter 3",
"_id" : ObjectId("607f7cc5f64e993a5c9b979a"),
"created" : ISODate("2021-04-21T01:15:49.000Z"),
"topics" : []
}
]
},
{
"description" : "dddd",
"name" : "exercise",
"_id" : ObjectId("607f7ca6f64e993a5c9b9797"),
"created" : ISODate("2021-04-21T01:15:18.465Z"),
"chapters" : []
}
]
},
{
"description" : "this is the example",
"name" : "State Space Equation",
"_id" : ObjectId("607f7c8ef64e993a5c9b9795"),
"created" : ISODate("2021-04-21T01:14:54.056Z"),
"courses" : []
}
],
"__v" : 0
}
And I need to remove topic object in chapters array. So this is what I have done.
areaModel.findOneAndUpdate({
'_id': req.body.area_id,
'subjects._id': req.body.subject_id,
'courses._id': req.body.course_id,
'chapter._id': req.body.chapter_id
}, {
"$pull": {
"subjects.$.courses.$.chapters.$.topics": {
_id: req.body.topic_id
}
}
}, (err, result) =>{
if (err) {
return res.json({success: false, msg: err});
} else {
return res.json({success: true, msg:"successfully removed" });
}
});
By using $pull method of mongoose, I could remove the course from the area easily. But it was impossible for me to remove the more nested items like chapters and topics.
How can I solve this issue?

Answer 1

you can do so with the use of arrayFilters like so:
db.collection.updateOne(
{
_id: ObjectId("607f7c67f64e993a5c9b9793")
},
{
$pull: {
"subjects.$[s].courses.$[c].chapters.$[ch].topics": {
_id: ObjectId("607f7ccef64e993a5c9b979b")
}
}
},
{
arrayFilters: [
{
"s._id": { $eq: ObjectId("607f7c7af64e993a5c9b9794") }
},
{
"c._id": { $eq: ObjectId("607f7c9af64e993a5c9b9796") }
},
{
"ch._id": { $eq: ObjectId("607f7cb4f64e993a5c9b9798") }
}
]
})
https://mongoplayground.net/p/kVyV27nnkII

Answer 2

Try it:
areaModel.findOneAndUpdate(
{ _id: req.body.area_id },
{
$pull: {
"subjects.$[].courses.$[].chapters.$[].topics": {
_id: req.body.topic_id,
},
},
}
);