Mongodb multiple aggregation match and group - node.js

Question

I am fetching for category and subcategory i am using the following pipeline
Category:
{
"$match": {
"category": {
"$in": ["list of my categories"]
}
}
},
{
"$group": {
"category": "$category",
"count": {
"$sum": 1
}
}
},
This gives me:
{category: category name,
count: totalcount}
Subcategory pipeline
{
"$match": {
"category": {
"$in": ["list of my categories"]
}
}
},
{
"$group": {
"_id": { subCategory: "$subCategory", category: "$category" },
"count": {
"$sum": 1
}
}
},
{
"$group": {
"_id": "$_id.category",
"counts": {
"$push": {
"k": "$_id.subCategory",
"v": "$count"
},
},
"count":{
$sum: "$counts"
}
}
},
{
"$project": {
"counts": { "$arrayToObject": "$counts" },
}
},
This gives me
category: name {
subcategory1 : total count,
...
}
How do I join the two to get a single call to return something like
{category: categoryname,
count: totalcountforcategory,
subcategories: {
subcategory: totalcount,
subcategory2:totalcount}
Update
Here is my sample JSON
{
"category": "Category one",
"name": "Sample name",
"subCategory": "subCategory one",
},
{
"category": "Category one",
"name": "Sample name",
"subCategory": "subCategory two",
},
{
"category": "Category two",
"name": "Sample name",
"subCategory": "subCategory one",
},
{
"category": "Category one",
"name": "Sample name",
"subCategory": "subCategory two",
}
Expected OutPut
{
"Category one": 3,
subCategories: {
"subCategoryone": 2,
"subCategorytwo":3,
}
}
{
"Category two": 5,
subCategories: {
"subCategoryone": 2,
"subCategorytwo":3,
}
}

Answer 1

db.collection.aggregate([
{
"$group": {
"_id": {
cat: "$category",
sub: "$subCategory"
},
"count": {
"$sum": 1
},
"subCategory": {
$push: "$$ROOT"
}
}
},
{
"$group": {
"_id": "$_id.cat",
"counts": {
"$push": {
"k": "$_id.sub",
"v": "$count"
},
},
"count": {
$sum: "$counts"
}
}
},
{
"$project": {
"counts": {
"$arrayToObject": "$counts"
},
}
},
])
Playground

Answer 2

I used $facet to join pipelines i don't know if it is best practice or not
const pipeline = [
{
"$facet": {
"GroupAll":
[{ $project: { name: 1, category: 1,subCategory:1,votes:1 } }]
,
"GroupTotal": [
{
"$match": {
"nominationYear": {
"$eq": "2022"
}
}
},
{
$count: "total"
}
],
"GroupCategories": [
{
"$match": {
"category": {
"$in": ["Categories"]
}
}
},
{
"$group": {
"_id": { category: "$category" },
"count": {
"$sum": 1
}
}
},
],
"GroupSubCategories": [
{
"$match": {
"category": {
"$in": ["Categories"]
}
}
},
{
"$group": {
"_id": { subCategory: "$subCategory", category: "$category" },
"count": {
"$sum": 1
}
}
},
{
"$group": {
"_id": "$_id.category",
"counts": {
"$push": {
"k": "$_id.subCategory",
"v": "$count"
},
},
"count": {
$sum: "$counts"
}
}
},
{
"$project": {
"counts": { "$arrayToObject": "$counts" },
}
},
]
}
}
]
And here is my output
{
"nominations": [
{
"GroupAll": [""],
"GroupTotal": [""],
"GroupCategories": [""],
"GroupSubCategories":[""]
}
],
"total": ""
}
I achieved it using $facet to join multiple pipelines