MongoDB addFields based on condition (array of array) - mongodb

Question

Let's say I have a sample object as below
[
{
"status": "ACTIVE",
"person": [
{
"name": "Jim",
"age": "2",
"qualification": [
{
"type": "education",
"degree": {
"name": "bachelor",
"year": "2022"
}
},
{
"type": "certification",
"degree": {
"name": "aws",
"year": "2021"
}
}
]
}
]
}
]
Now, I need to add a field "score" only when the qualification.type == bachelor
This is the query I tried but could not get the proper result. Not sure what mistake I am doing. Any help is highly appreciated. Thank you in advance.
db.collection.aggregate([
{
$addFields: {
"person.qualification.score": {
$reduce: {
input: "$person.qualification",
initialValue: "",
in: {
$cond: [
{
"$eq": [
"$$this.type",
"bachelor"
]
},
"80",
"$$REMOVE"
]
}
}
}
}
}
])

Answer 1

$set - Set person array field.
1.1. $map - Iterate person array and return a new array.
1.1.1. $mergeObjects - Merge current iterate (person) document and the document with qualification.
1.1.1.1. $map - Iterate the qualification array and return a new array.
1.1.1.1.1. $cond - Match type of current iterate qualification document. If true, merge current iterate qualification document and the document with score field via $mergeObjects. Else remain the existing document.
db.collection.aggregate([
{
$set: {
person: {
$map: {
input: "$person",
as: "p",
in: {
$mergeObjects: [
"$$p",
{
qualification: {
$map: {
input: "$$p.qualification",
in: {
$cond: {
if: {
$eq: [
"$$this.type",
"education"
]
},
then: {
$mergeObjects: [
"$$this",
{
score: "80"
}
]
},
else: "$$this"
}
}
}
}
}
]
}
}
}
}
}
])
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