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How to update nested object in array (Mongoose/MongoDB)

I've been struggling to get my around how to update a object in a nested array with a particular id. I've attempted to implement $set as shown below. I want to be able to update the task with an _id of 62ff74bfe80b11ade2d34455 with the data from the request body.
{
"_id": "62fa5aa25778ec97bc6ee231",
"user": "62f0eb5ebebd0f236abcaf9d",
"name": "Marketing Plan",
"columns": [
{
"name": "todo",
"_id": "62fa5aa25778ec97bc6ee233",
"tasks": [
{ ====> here
"title": "Task Four",
"description": "This is task four",
"subtasks": [
{
"name": "wash dshes",
"completed": false,
"_id": "62ff74bfe80b11ade2d34456"
},
{
"name": "do homework",
"completed": false,
"_id": "62ff74bfe80b11ade2d34457"
}
],
"_id": "62ff74bfe80b11ade2d34455"
}
]
},
{
"name": "doing",
"_id": "62fa5aa25778ec97bc6ee234",
"tasks": []
},
{
"name": "done",
"_id": "62fa5aa25778ec97bc6ee235",
"tasks": []
}
],
"__v": 0
}
const updatedTask = await Board.findOneAndUpdate(
{
"columns.tasks._id": req.params.id,
},
{ $set: { "columns.$.tasks": req.body } },
{ new: true }
);

You can use the positional operator in combination with an arrayfilter. Here's an example how you'd update a specific field of the relevant task:
db.collection.update({
"columns.tasks._id": req.params.id
},
{
"$set": {
"columns.$[].tasks.$[t].title": "it works"
}
},
{
"arrayFilters": [
{
"t._id": req.params.id
}
]
})
You can also try this on mongoplayground.
If you're looking for a way to replace the matching task object itself you can do:
db.collection.update({
"columns.tasks._id": req.params.id
},
{
"$set": {
"columns.$[].tasks.$[t]": req.body
}
},
{
"arrayFilters": [
{
"t._id": req.params.id
}
]
})

mongodb fetch records if array exists

I have 2 collections:
Vehicles:
[
{
"_id": "a1",
"type:": "car",
"make": "Honda",
"specifications": ["1", "2"]
},
{
"_id": "a2",
"type:": "car",
"make": "Toyota",
"specifications": ["3", "4"]
},
{
"_id": "a3",
"type:": "car",
"make": "Honda",
"specifications": []
},
{
"_id": "a4",
"type:": "car",
"make": "Toyota"
}
]
Specifications:
[
{
"_id": "1",
"color": "Black"
},
{
"_id": "2",
"sunroof": "yes"
},
{
"_id": "3",
"engine": "1800 CC"
},
{
"_id": "4",
"bodyType": "Sedan"
}
]
I want to fetch those records which has at least one specification.
And also the details from specifications collections should appear in Vehicles collections somewhere.
Expected response:
[
{
"_id": "a1",
"make": "Honda",
"type:": "car",
"carSpecifications": [
{
"color": "Black"
},
{
"sunroof": "yes"
}
],
},
{
"_id": "a2",
"make": "Toyota",
"type:": "car",
"specifications": [
{
"engine": "1800 CC"
},
{
"bodyType": "Sedan"
}
]
}
]
Now what I tried so far is:
db.vehicles.find({type: "car", "specifications": {$exists: true}}, {fields: {"specifications.$": 1}}).fetch()
this query is returning all the records from Vehicles.
After getting all the records I put a loop on the records I get and check manually if specifications.length > 0 than I query from Specifications collection accordingly.
Can I achieve all this with a single query?

You should look for an aggregation query.
$match - Filter documents with "type:" "car" and specifications is not an empty array (with $ifNull, default as [] when specifications field is null or not existed).
$lookup - Vehicles collection join specifications collection (Refer to Use $lookup with an Array). Work with pipeline to return the array without the _id field (Refer to Correlated Subqueries Using Concise Syntax).
MongoDB v5 query
db.vehicles.aggregate({
$match: {
$and: [
{
"type:": "car"
},
{
$expr: {
$ne: [
{
$ifNull: [
"$specifications",
[]
]
},
[]
]
}
}
]
}
},
{
$lookup: {
from: "specifications",
localField: "specifications",
foreignField: "_id",
pipeline: [
{
$project: {
_id: 0
}
}
],
as: "specifications"
}
})
Sample Mongo Playground (v5)
MongoDB v4 query
db.vehicles.aggregate({
$match: {
$and: [
{
"type:": "car"
},
{
$expr: {
$ne: [
{
$ifNull: [
"$specifications",
[]
]
},
[]
]
}
}
]
}
},
{
$lookup: {
from: "specifications",
let: {
specifications: "$specifications"
},
pipeline: [
{
$match: {
$expr: {
$in: [
"$_id",
"$$specifications"
]
}
}
},
{
$project: {
_id: 0
}
}
],
as: "specifications"
}
})
Sample Mongo Playground (v4)

MongoDB aggregate conditional - hide object based on conditional

From the database:
_id: "123123123123123"
question: "Question1"
answer: "some answer"
by: "user1"
__v: 0
There is a conditional I am trying to implement here. It does not work. If by is empty, then do not display _id: "$question",
let answers = await Answer.aggregate([
{ $match: { $or: [{ by: user.email }, { by: user2[0].email }] } },
{
$cond: {
if: {
$eq: ["$by", ""],
},
then: 0,
else: 1,
},
},
{
$group: {
_id: "$question",
data: {
$push: "$$ROOT",
},
},
}
]);
Outcome (wrong):
{
"_id": "Question1",
"data": [
{
"answer": "some answer",
"by": "user1"
},
{
"answer": "some answer",
"by": "user2"
}
]
},
{
"_id": "Question2",
"data": [
{
"answer": "some answer",
"by": "user1",
}
]
},
Expected outcome:
I want to display only Question1 because user2 does not have an answer (there is no user2 by). So display Question only if there are 2 by.
{
"_id": "Question1",
"data": [
{
"answer": "some answer",
"by": "user1"
},
{
"answer": "some answer",
"by": "user2"
}
]
},

You have to remove $orcondition and use $all in
{ $match: { $or: [{ by: user.email }, { by: user2[0].email }] } },
changed to
{ $match: { $all: [{ by: user.email }, { by: user2.email }] } },

How to findOneAndUpdate single field with multi nested array documents

I'm stuck on how to update single value in multi nested array documents value with findOneAndUpdate.
My condition goes like this:
Update warehouse amount where the productCode is "abc123", size "41" in warehouse "Hamburg".
I just get back null or bot sizes 41 and 42.
Here is the part of the doc:
{
"_id": ObjectId("xxxx636309f84479ec0c7b"),
"productCode": "abc123",
"brand": "Nike",
"name": "aaa",
"model": "Runner",
"color": "Brown",
"image": "shoe.jpg",
"sizes": [{
"_id": ObjectId("xxxxc636309f84479ec0c7e"),
"size": "41",
"wares": [{
"_id": ObjectId("xxxx2c636309f84479ec0c80"),
"ware": "Hamburg",
"amount": 7
},
{
"_id": ObjectId("5db72c636309f84479ec0c7f"),
"ware": "Berlin",
"amount": 7
}
]
},
{
"_id": ObjectId("5db72c636309f84479ec0c7c"),
"size": "42",
"wares": [{
"_id": ObjectId("5db72c636309f84479ec0c7d"),
"ware": "Hamburg",
"amount": 16
}]
}
],
"__v": 0
}
This is what I've tried:
Product.findOneAndUpdate({
"productCode": "abc123",
"sizes.size": 41,
"sizes.wares.ware": "Hamburg"
}, {
"$set": {
"sizes.0.wares.amount": 99
}
}, {
useFindAndModify: false
},
(err, products) => {
if (err) {
return res.status(422).send(err)
}
return res.json(products)
}
);
How can I solve this?

And to fulfill #ambianBeing, this is how it would be done with findOneAndUpdate:
Product.findOneAndUpdate({
"productCode": "abc123",
"sizes": {
$elemMatch: {
$and: [
{ size: "41" },
{
wares: {
$elemMatch: {
ware: "Hamburg"
}
}
}]
}
}
}, {
$set: {
"sizes.$[theSize].wares.$[theWare].amount": 99
}
}, {
arrayFilters: [{
"theSize.size": "41"
}, {
"theWare.ware": "Hamburg"
}]
})

Can be done using filtered positional operator $[<identifier>] which is nifty in use cases of nested array updation.
Query (Mongo Shell):
db.collection.update(
{ productCode: "abc123" },
{ $set: { "sizes.$[outer].wares.$[inner].amount": 99 } },
{
arrayFilters: [{ "outer.size": "41" }, { "inner.ware": "Hamburg" }],
multi: false
}
);
Query with Mongoose Model:
Product.update(
{ productCode: "abc123" },
{ "sizes.$[outer].wares.$[inner].amount": 99 },
{
arrayFilters: [{ "outer.size": "41" }, { "inner.ware": "Hamburg" }],
multi: false
},
(err, rawDoc) => {
if (err) {
console.error(err);
}
console.info(rawDoc);
}
);

Aggregate array occourances

I have a set of documents (posts) which have an array of users mentioned in each post.
{
"title": "Some post title",
[ ... ]
"mentions": ["johnsmith", "johndoe", "paul"]
}
I want to aggregate a list of unique mentions, and the number of times they've been mentioned across all posts. For example:
[{ user: "johnsmith", count: 5 }, { user: "benlewis", count: 9 }, { user: "johndoe", count: 1 }]
With Mongo, I'd do something like:
"mentions": [{
"$unwind": "$mentions"
}, {
"$group": {
"_id": "$mentions",
"count": { "$sum": 1 }
}
}]
What's the equivalent in Elasticsearch?

You can use a Terms aggregation for that. A small (5.x) example:
PUT test
{
"mappings": {
"test" : {
"properties": {
"title": {
"type": "text"
},
"mentions": {
"type": "keyword"
}
}
}
}
}
POST test/test/1
{
"title": "Some post title",
"mentions": [
"johnsmith",
"johndoe",
"paul"
]
}
POST test/test/2
{
"title": "Some post title 2",
"mentions": [
"johnsmith"
]
}
GET test/_search
{
"size": 0,
"aggs": {
"test": {
"terms": {
"field": "mentions",
"size": 10
}
}
}
}
Gives the following response:
"aggregations": {
"test": {
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0,
"buckets": [
{
"key": "johnsmith",
"doc_count": 2
},
{
"key": "johndoe",
"doc_count": 1
},
{
"key": "paul",
"doc_count": 1
}
]
}
}
}
Hope this helps :)