Group by date in mongoDB while counting other fields - mongodb

Question

I've been using MongoDB for just a week and I have problems achieving this result: I want to group my documents by date while also keeping track of the number of entries that have a certain field set to a certain value.
So, my documents look like this:
{
"_id" : ObjectId("5f3f79fc266a891167ca8f65"),
"recipe" : "A",
"timestamp" : ISODate("2020-08-22T09:38:36.306Z")
}
where recipe is either "A", "B" or "C". Right now I'm grouping the documents by date using this pymongo query:
mongo.db.aggregate(
# Pipeline
[
# Stage 1
{
"$project": {
"createdAt": {
"$dateToString": {
"format": "%Y-%m-%d",
"date": "$timestamp"
}
},
"progressivo": 1,
"temperatura_fusione": 1
}
},
# Stage 2
{
"$group": {
"_id": {
"createdAt": "$createdAt"
},
"products": {
"$sum": 1
}
}
},
# Stage 3
{
"$project": {
"label": "$_id.createdAt",
"value": "$products",
"_id": 0
}
}])
Which gives me results like this:
[{"label": "2020-08-22", "value": 1}, {"label": "2020-08-15", "value": 2}, {"label": "2020-08-11", "value": 1}, {"label": "2020-08-21", "value": 5}]
What I'd like to have is also the counting of how many times each recipe appears on every date. So, if for example on August 21 I have 2 entries with the "A" recipe, 3 with the "B" recipe and 0 with the "C" recipe, the desired output would be
{"label": "2020-08-21", "value": 5, "A": 2, "B":3, "C":0}
Do you have any tips?
Thank you!

Answer 1

You can do like following, what have you done is excellent. After that,
In second grouping, We just get total value and value of each recipe.
$map is used to go through/modify each objects
$arrayToObject is used to covert the array what we have done via map (key : value pair) to object
$ifNull is used for, sometimes your data might not have "A" or "B" or "C". But you need the value should be 0 if there is no name as expected output.
Here is the code
[
{
"$project": {
"createdAt": {
"$dateToString": {
"format": "%Y-%m-%d",
"date": "$timestamp"
}
},
recipe: 1,
"progressivo": 1,
"temperatura_fusione": 1
}
},
{
"$group": {
"_id": {
"createdAt": "$createdAt",
"recipeName": "$recipe",
},
"products": {
$sum: 1
}
}
},
{
"$group": {
"_id": "$_id.createdAt",
value: {
$sum: "$products"
},
recipes: {
$push: {
name: "$_id.recipeName",
val: "$products"
}
}
}
},
{
$project: {
"content": {
"$arrayToObject": {
"$map": {
"input": "$recipes",
"as": "el",
"in": {
"k": "$$el.name",
"v": "$$el.val"
}
}
}
},
value: 1
}
},
{
$project: {
_id: 1,
value: 1,
A: {
$ifNull: [
"$content.A",
0
]
},
B: {
$ifNull: [
"$content.B",
0
]
},
C: {
$ifNull: [
"$content.C",
0
]
}
}
}
]
Working Mongo playground