Develop Reference

MongoDB : - Merge object with same key into one

I am trying to merge an object inside an array with the same date but with a different key name for the status key.
I have 2 collections users and canteens
The query I am trying to get the result but am not able to figure out how to merge the object with the same Date
OUTPUT
User.aggregate([
{ $sort: { workerId: 1 } },
{
$lookup: {
from: "canteens",
localField: "_id",
foreignField: "employeeId",
pipeline: [
{
$match: {
Date: {
$gte: new Date(fromDate),
$lte: new Date(toDate),
},
},
},
{
$project: {
Date: 1,
status: 1,
},
},
],
as: "canteens",
},
},
{
$project: {
_id: 1,
workerId: 1,
workerFirstName: 1,
workerSurname: 1,
workerDepartment: 1,
workerDesignation: 1,
locationName: 1,
canteenData: "$canteens",
},
},
]);
[
{
"_id": "60e6fd3616dd663e84a925e2",
"workerFirstName": "Firstaname",
"workerSurname": "lastname",
"workerId": "1",
"locationName": "location",
"workerDesignation": "designation",
"workerDepartment": "department",
"canteenData": [
{
"_id": "63b285b9e92eee614feb7be1",
"status": "LUNCH",
"Date": "2023-01-02T00:00:00.000Z"
},
{
"_id": "63b2db8db10c24487201e0a2",
"status": "DINNER",
"Date": "2023-01-02T00:00:00.000Z"
},
{
"_id": "63b39b247adbeb50bfbe3503",
"status": "BREAK FAST",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b3d248c076184fb07ff2c4",
"status": "LUNCH",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b42b8ccb57a4cb7af34015",
"status": "DINNER",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b4ef71e038498fe6634506",
"status": "BREAK FAST",
"Date": "2023-01-04T00:00:00.000Z"
}
]
},
{
"_id": "60e6fd3616dd663e84a925e2",
"workerFirstName": "Firstaname1",
"workerSurname": "lastname1",
"workerId": "2",
"locationName": "location",
"workerDesignation": "designation",
"workerDepartment": "department",
"canteenData": [
{
"_id": "63b285b9e92eee614feb7be1",
"status": "LUNCH",
"Date": "2023-01-02T00:00:00.000Z"
},
{
"_id": "63b2db8db10c24487201e0a2",
"status": "DINNER",
"Date": "2023-01-02T00:00:00.000Z"
},
{
"_id": "63b39b247adbeb50bfbe3503",
"status": "BREAK FAST",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b3d248c076184fb07ff2c4",
"status": "LUNCH",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b42b8ccb57a4cb7af34015",
"status": "DINNER",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b4ef71e038498fe6634506",
"status": "BREAK FAST",
"Date": "2023-01-04T00:00:00.000Z"
}
]
}
]
The output I am trying to get
[
{
"_id": "60e6fd3616dd663e84a925e2",
"workerFirstName": "Firstanem",
"workerSurname": "lastname",
"workerId": "1",
"locationName": "location",
"workerDesignation": "designation",
"workerDepartment": "department",
"canteenData": [
{
"_id": "63b285b9e92eee614feb7be1",
"status1": "LUNCH",
"status2": "DINNER",
"Date": "2023-01-02T00:00:00.000Z"
},
{
"_id": "63b39b247adbeb50bfbe3503",
"status1": "BREAK FAST",
"status2": "LUNCH",
"status3": "DINNER",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b4ef71e038498fe6634506",
"status1": "BREAK FAST",
"Date": "2023-01-04T00:00:00.000Z"
}
]
},
{
"_id": "60e6fd3616dd663e84a925e2",
"workerFirstName": "Firstanem1",
"workerSurname": "lastname1",
"workerId": "2",
"locationName": "location",
"workerDesignation": "designation",
"workerDepartment": "department",
"canteenData": [
{
"_id": "63b285b9e92eee614feb7be1",
"status1": "LUNCH",
"status2": "DINNER",
"Date": "2023-01-02T00:00:00.000Z"
},
{
"_id": "63b39b247adbeb50bfbe3503",
"status1": "BREAK FAST",
"status2": "LUNCH",
"status3": "DINNER",
"Date": "2023-01-03T00:00:00.000Z"
},
{
"_id": "63b4ef71e038498fe6634506",
"status1": "BREAK FAST",
"Date": "2023-01-04T00:00:00.000Z"
}
]
}
]

One option is to add 2 steps into your $lookup pipeline aggregation:
{$group: {
_id: "$Date",
_idVal: {$first: "$_id"},
data: {$addToSet: "$status"}
}},
{$replaceRoot: {
newRoot: {
$mergeObjects: [
{_id: "$_idVal", Date: "$_id"},
{$arrayToObject: {
$reduce: {
input: "$data",
initialValue: [],
in: {$concatArrays: [
"$$value",
[{k: {$concat: [
"status",
{$toString: {$add: [{$size: "$$value"}, 1]}}
]},
v: "$$this"}]
]}
}
}}
]
}
}}
See how it works on the playground example

It's not easy to create status1, status2, ... variables dynamically + how do we know BREAK FAST should be status1 and not status2.
Alternative solution: We $group inside correlated subqueries and push all status values into an array
db.users.aggregate([
{
"$lookup": {
"from": "canteens",
"localField": "_id",
"foreignField": "employeeId",
pipeline: [
{
// Put your custom filters here
$match: {}
},
{
$group: {
_id: "$Date",
//pick "first" canteens _id
id: {
$first: "$_id"
},
status: {
$push: "$status"
}
}
},
{
$project: {
_id: "$id",
Date: "$_id",
status: 1
}
},
],
as: "canteenData",
}
}
])
MongoPlayground

How to return single object (mongoose/mongoDB)

I have this data stored in database.
{
"_id": "62fa5aa25778ec97bc6ee231",
"user": "62f0eb5ebebd0f236abcaf9d",
"name": "Marketing Plan",
"columns": [
{
"name": "todo",
"_id": "62fa5aa25778ec97bc6ee233",
"tasks": [
{
"title": "Task Four testing 2",
"description": "This is task four",
"subtasks": [
{
"name": "wash dshes test",
"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
}
I want to be able to return a single object with the id equal to the req.params.id, in this case that would be 62ff74bfe80b11ade2d34455.
{
"title": "Task Four testing 2",
"description": "This is task four",
"subtasks": [
{
"name": "wash dshes test",
"completed": false,
"_id": "62ff74bfe80b11ade2d34456"
},
{
"name": "do homework",
"completed": false,
"_id": "62ff74bfe80b11ade2d34457"
}
],
"_id": "62ff74bfe80b11ade2d34455"
}
I researched stackoverflow and came across this potential solution: Mongoose retrieve one document from nested array which implemented the aggregate framework. But when I test this in postman, the request isn't made.
const getTask = asyncHandler(async (req, res) => {
const task = await Board.aggregate([
{
$match: {
"columns.tasks._id": req.params.id,
},
},
{
$project: {
columns: {
$first: {
$filter: {
input: "$columns.tasks",
cond: {
$eq: ["$$this._id", req.params.id],
},
},
},
},
},
},
{
$replaceRoot: {
newRoot: "$columns",
},
},
]);
});

Having an array inside an array complicates the query a bit, but here's one way to retrieve the data you want.
db.Board.aggregate([
{
$match: {
"columns.tasks._id": req.params.id
}
},
{"$unwind": "$columns"},
{
$match: {
"columns.tasks._id": req.params.id
}
},
{
"$project": {
"task": {
"$first": {
"$filter": {
"input": "$columns.tasks",
"cond": {"$eq": ["$$this._id", req.params.id]}
}
}
}
}
},
{"$replaceWith": "$task"}
])
Try it on mongoplayground.net. [The mongoplayground.net example uses "62ff74bfe80b11ade2d34455" rather than req.params.id.]

MongoDB - Structure an array without using key field in Aggregration

I'm having an issue with making count for items returned from an array without assuming or using those fields in my aggregration.
Data structure looks like this:
[
{
"_id": "1",
"title": "Vanella Icream",
"contain": "sugar",
"details": [
{
"flavour": "Vanella"
},
{
"weight": "10KG"
},
{
"sugar": "15KG"
}
]
},
{
"_id": "2",
"title": "Pretzels",
"contain": "salt",
"details": [
{
"flavour": "Wheat"
},
{
"weight": "10KG"
},
{
"sugar": "15KG"
}
]
},
{
"_id": "3",
"title": "Rasmalai Icream",
"contain": "sugar",
"details": [
{
"flavour": "Vanella"
},
{
"weight": "15KG"
},
{
"sugar": "12KG"
}
]
},
{
"_id": "4",
"title": "Vanella Icream",
"contain": "sugar",
"details": [
{
"flavour": "Vanella"
},
{
"weight": "15KG"
},
{
"sugar": "12KG"
}
]
}
]
Output I want:
[
{
"details": {
"flavour": {
"Vanella": 3, //Number of times Vanella present in each document.
"Wheat": 1,
},
"weight": {
"10KG": 2,
"15KG": 2
},
"sugar": {
"12KG": 2,
"15KG": 2
}
}
}
]
Query:
db.collection.aggregate([
{
"$unwind": {
"path": "$details"
}
},
{
"$replaceRoot": {
"newRoot": {
"$mergeObjects": [
"$details",
"$$ROOT"
]
}
}
},
{
"$facet": {
"flavour": [
{
"$group": {
"_id": "$flavour",
"sum": {
"$sum": 1
}
}
},
{
"$addFields": {
"flavour": "$_id"
}
},
{
"$project": {
"_id": 0
}
}
],
"weight": [
{
"$group": {
"_id": "$weight",
"sum": {
"$sum": 1
}
}
},
{
"$addFields": {
"weight": "$_id"
}
},
{
"$project": {
"_id": 0
}
}
]
}
},
{
"$addFields": {
"flavour": {
"$reduce": {
"input": {
"$filter": {
"input": {
"$map": {
"input": "$flavour",
"as": "w",
"in": {
"$cond": [
{
"$ne": [
"$$w.flavour",
null
]
},
{
"$let": {
"vars": {
"o": [
[
"$$w.flavour",
"$$w.sum"
]
]
},
"in": {
"$arrayToObject": "$$o"
}
}
},
null
]
}
}
},
"as": "f",
"cond": {
"$ne": [
"$$f",
null
]
}
}
},
"initialValue": {},
"in": {
"$let": {
"vars": {
"d": "$$value",
"p": "$$this"
},
"in": {
"$mergeObjects": [
"$$d",
"$$p"
]
}
}
}
}
},
"weight": {
"$reduce": {
"input": {
"$filter": {
"input": {
"$map": {
"input": "$weight",
"as": "w",
"in": {
"$cond": [
{
"$ne": [
"$$w.weight",
null
]
},
{
"$let": {
"vars": {
"o": [
[
"$$w.weight",
"$$w.sum"
]
]
},
"in": {
"$arrayToObject": "$$o"
}
}
},
null
]
}
}
},
"as": "f",
"cond": {
"$ne": [
"$$f",
null
]
}
}
},
"initialValue": {},
"in": {
"$let": {
"vars": {
"d": "$$value",
"p": "$$this"
},
"in": {
"$mergeObjects": [
"$$d",
"$$p"
]
}
}
}
}
}
}
},
{
"$project": {
"details": "$$ROOT"
}
}
])
Here I'm trying to get the flavour and weight with their count, with manually adding those fields in $filter stage. I want to do it without assuming those keys. So, even if there is 20 items present in array details it will map those items and shows me output with their counts respectively.
I hope you guys understand.
Playground:https://mongoplayground.net/p/j1mzgWvcmvd

You need to change the schema, the thing you want to do is easy, and both those queries are so complicated and slow, even the second that is much smaller has 2 $unwind and 3 $group with 3 $arrayToObject and 8 stages total because of the schema and the schema of the answer.
Don't store data in the keys of the documents, people that are new to MongoDB do those, i was doing it also, but it makes all things harder.(i can't say like never do it but you dont need it here)
Your schema should be something like
{
"_id": "2",
"title": "Pretzels",
"contain": "salt",
"details": [
{
"type" : "flavour",
"value" : "Wheat"
},
{
"type" : "weight",
"value" : "10KG"
},
{
"type" : "sugar",
"value" : "15KG"
}
]
}
See this example
Converts your schema, to the new schema and produce the results you
want but without data in keys (the first part you wouldnt need it you would need only the bellow query if you had that schema from start)
Query with the new Schema (no data in keys)
[{"$unwind": { "path": "$details"}},
{"$replaceRoot": {"newRoot": "$details"}},
{
"$group": {
"_id": {
"type": "$type",
"value": "$value"
},
"sum": {"$sum": 1}
}
},
{
"$replaceRoot": {
"newRoot": {"$mergeObjects": ["$_id","$$ROOT"]}
}
},
{"$project": {"_id": 0}},
{
"$group": {
"_id": "$type",
"values": {
"$push": {
"value": "$value",
"sum": "$sum"
}
}
}
},
{"$addFields": {"type": "$_id"}},
{"$project": {"_id": 0}}
]
MongoDB operators are not made to support for data in keys or dynamic keys(uknown keys) (to do it you do complicated things like the above)
If you want to change your schema, either do it with update in the database,
Or take the documents to the application and do it with javascript, and re-insert.
Even if you solve this question in the next one, you will have again problems.

I'm the guy from Mongodb Forum:
Try this out https://mongoplayground.net/p/tfyfpIkHilQ

How to add a condition inside $lookup in MongoDb .aggregate()?

persons collection:
{
"_id": ObjectId("5f3258cfbaaccedaa5dd2c96"),
"gender": "male",
"name": {
"title": "mr",
"first": "victor",
"last": "pedersen",//... more properties
}
persondetails collection:
{
"_id": ObjectId("5f3a91e68b1c26e68f9ed3ad"),
"country": "India",
"personid": ObjectId("5f3258cfbaaccedaa5dd2c96")
}
Get documents from persons along with associated persondetails where associated country in persondetails is "India
So if out of 10 persons only 3 are from India. I should get 3 person documents in resultset along with their associated persondetails
Query:
[
{
"$match": {
"$or": [
{
"$expr": {
"$eq": [
"$gender",
"male"
]
}
}
]
}
},
{
"$facet": {
"totalCount": [
{
"$count": "value"
}
],
"data": [
{
"$project": {
"_id": "$_id",
"fname": "$name.first",
"lname": "$name.last",
"dobage": "$dob.age",
"registeredAge": "$registered.age"
}
},
{
"$sort": {
"name.first": 1
}
} ,
{
"$lookup": {
"from": "persondetails",
"localField": "_id",
"foreignField": "personid", // how to add where clause in this lookup?
"as": "persondetail"
}
}
]
}
}
]
EDIT:
https://mongoplayground.net/p/3vBs6Frt-aK
Expected Result:
[
{
"data": [
{
"_id": ObjectId("5f3258cfbaaccedaa5dd2c96"),
"fname": "victor",
"lname": "pedersen",
"persondetail": [
{
"_id": ObjectId("5f3a91e68b1c26e68f9ed3ad"),
"country": "India",
"personid": ObjectId("5f3258cfbaaccedaa5dd2c96")
}
]
}],
"totalCount": [
{
"value": 1
}
]
}
]

There is a second $lookup syntax which allows you to specify custom filtering condition:
{
"$lookup": {
"from": "persondetails",
"let": { person_id: "$_id" },
"pipeline": [
{
$match: {
$expr: {
$and: [
{ $eq: [ "$$person_id", "$personid" ] },
{ $eq: [ "$country", "India" ] },
]
}
}
}
],
"as": "persondetail"
}
}
EDIT:
You also need to add $match to filter out people with empty persondetail and if you want this to be included in your count then you need to run $facet as the last operation:
[
{
"$match": {
"$or": [ {"$expr": { "$eq": [ "$gender", "male" ] } } ]
}
},
{
"$project": {
"_id": "$_id",
"fname": "$name.first",
"lname": "$name.last",
"dobage": "$dob.age",
"registeredAge": "$registered.age"
}
},
{
"$lookup": {
"from": "persondetails",
"let": { person_id: "$_id" },
"pipeline": [
{
$match: {
$expr: {
$and: [
{ $eq: [ "$$person_id", "$personid" ] },
{ $eq: [ "$country", "India" ] },
]
}
}
}
],
"as": "persondetail"
}
},
{
$match: {
persondetail: { $ne: [] }
}
},
{
$facet: {
totalCount: [ { $count: "value" } ],
data: [ { $sort: { "name.first": 1 } }, ]
}
}
]
Mongo Playground

How to compare two arrays and get matching output?

In my collection I have a category array as below.
I receive another array to my API like below
array = ['Chess','Rugby'];
I want to add a condition to my database query such that catName field from category objects exists in array.
currently I'm using the below code to get the results:
postSchemaModel.aggregate([{
"$geoNear": {
"near": { "type": "Point", "coordinates": [parseFloat(long), parseFloat(lat), ] },
"distanceField": "dist.calculated",
"maxDistance": parseInt(maxDistance),
"includeLocs": "dist.location",
"spherical": true
}
},
{ "$match": { "$or": [{ "typology": "post" }, { "typology": "chat_group" }] } },
{
"$match": {
"createdAt": {
"$gte": '2020-07-15 23:54:38.673665',
"$lt": '2020-06-15 23:54:38.673665'
}
}
},
{ "$limit": limit },
{ "$skip": startIndex },
{ "$sort": { "createdAt": -1 } },
{
"$lookup": {
"from": userSchemaModel.collection.name,
"localField": "user_id",
"foreignField": "_id",
"as": "user_id"
}
},
{
"$project": {
"post_data": 1,
"likes": 1,
"commentsCount": 1,
"post_img": 1,
"isUserLiked": 1,
"usersLiked": 1,
'exp_date': 1,
"has_img": 1,
"user_id": {
"img": "$user_id.img",
"_id": "$user_id._id",
"user_name": "$user_id.user_name",
"bday": "$user_id.bday",
"imagesource": "$user_id.imagesource",
"fb_url": "$user_id.fb_url",
},
"typology": 1,
"geometry": 1,
"category": 1,
"created": 1,
"createdAt": 1,
"updatedAt": 1,
}
},
]).then(async function(posts) {
//some code here
}
});
UPDATE : Sample Output
{
"_id": "5f0bd1b7d6ed4f0017e5177c",
"post_data": "bitch boy sudesh",
"likes": 2,
"commentsCount": 1,
"post_img": null,
"isUserLiked": true,
"usersLiked": [
"5f0bfa296ee76f0017f13787",
"5ef60bba10e9090017e2c935"
],
"exp_date": "2020-07-16T00:00:00.000Z",
"has_img": false,
"user_id": [
{
"img": [
"default-user-profile-image.png"
],
"_id": [
"5ef9a7a2922eba0017ce47e0"
],
"user_name": [
"Sudesh"
],
"bday": [
"1997-05-02T00:00:00.000Z"
],
"imagesource": [
"fb"
],
"fb_url": [
"https://platform-lookaside.fbsbx.com/platform/profilepic/?asid=1846836948784193&width=400&ext=1596011605&hash=AeRsB0QJQH7edpRT"
]
}
],
"typology": "post",
"geometry": {
"pintype": "Point",
"_id": "5f0bd1b7d6ed4f0017e5177d",
"coordinates": [
79.9200017,
6.7088167
]
},
"category": [
{
"_id": "5f0bd1b7d6ed4f0017e5177e",
"catID": "5eef80cc5de48230887f3aa8",
"catName": "Chess"
},
{
"_id": "5f0bd1b7d6ed4f0017e5177e",
"catID": "5eef80cc5de48230887f3aa8",
"catName": "Rugby"
}
],
"created": 1594610103626,
"createdAt": "2020-07-13T03:15:03.629Z",
"updatedAt": "2020-07-18T14:02:35.080Z"
}

You can use some method if you only want to get true/false result:
category.some(element => array.includes(element.catName))
If you want to get an array of all the category objects with cat names that also exist in the array then you can filter method:
category.filter(element => array.includes(element.catName))
If you have an object called array in your code and you want to find at array of categories where cat names are in the array then you can add the condition to your $match stage:
{ "$match": { "$or": [{ "typology": "post" }, { "typology": "chat_group" }] }, "category.catName": { $in: array } }

Using another $match with "$elemMatch" solved the problem
"$match": {
"category": { "$elemMatch": { "catName": "Rugby", "catName": "Carrom" } },
}