Create a Set only if value exists aggregate mongodb - mongodb

Question

I have a dataset:
[
{
"_id": 1,
"Data": {
"a": {
"levela": {
"fname": "fname",
"lname": "lname"
},
"levelfacility": []
}
}
},
{
"_id": 2,
"Data": {
"a": {
"levela": {},
"levelfacility": [
{
"facility": "facility"
}
]
}
}
},
{
"_id": 3,
"Data": {
"a": {
"levela": {},
"levelfacility": []
}
}
}
]
I want to apply an upper case to the values only if exists but when I apply a $set, it just is an empty string if it doesn't exist.
[
{
"_id": 1,
"Data": {
"a": {
"levela": {
"fname": "fname",
"fnameNORM": "FNAME",
"lname": "lname"
},
"levelfacility": []
}
}
},
{
"_id": 2,
"Data": {
"a": {
"levela": {},
"levelfacility": [
{
"facility": "facility",
"facilityNORM": "FACILITY"
}
]
}
}
},
{
"_id": 2,
"Data": {
"a": {
"levela": {},
"levelfacility": []
}
}
}
]
I want to apply something like a $conditional so I am not left with new fields with the original field doesnt exist
I have tried this for a string
{
$set: {
"Data.a.levela.fnameNORM": {
$cond: {
if: {
"$Data.a.levela.fname": {
$exist: true
}
},
then: {
$toUpper: "$Data.a.levela.fname"
},
else: "$$REMOVE"
}
}
}
}
I have tried this for an array
{
$set: {
"Data.a.levelfacility": {
$map: {
input: "$Data.a.levelfacility",
in: {
$mergeObjects: [
"$$this",
{
"facilityNORM": {
$cond: {
if: {
"$$this.FacilityName": {
$exist: true
}
},
then: {
$toUpper: "$$this.FacilityName"
},
else: "$$REMOVE"
}
}
}
]
}
}
}
}
}

Answer 1

You are actually on the right track. Just use $map to handle levelfacility array.
db.collection.aggregate([
{
"$addFields": {
"Data.a.levela": {
"$cond": {
"if": {
$ne: [
{
"$ifNull": [
"$Data.a.levela.fname",
null
]
},
null
]
},
"then": {
"fname": "$Data.a.levela.fname",
"fnameNORM": {
"$toUpper": "$Data.a.levela.fname"
}
},
"else": "$Data.a.levela"
}
}
}
},
{
"$addFields": {
"Data.a.levelfacility": {
"$map": {
"input": "$Data.a.levelfacility",
"as": "lf",
"in": {
"$cond": {
"if": {
$ne: [
{
"$ifNull": [
"$$lf.facility",
null
]
},
null
]
},
"then": {
"facility": "$$lf.facility",
"facilityNORM": {
"$toUpper": "$$lf.facility"
}
},
"else": "$$lf"
}
}
}
}
}
}
])
Here is the Mongo playground for your reference.