update object in an array if exists Push if not exists - mongodb

Question

Here my example document
{
"_id" : "1",
"principal" : "Joe",
"classroom" : [
{
"grade" : "1",
"class" : "A",
"totalStudent" : 10.0
},
{
"grade" : "1",
"class" : "B",
"totalStudent" : 20.0
}
]
}
my goal is
increment TotalStudent when filter match ex.
principal : "Joe", classroom.grade: "1" classroom.class: "A"
push new object into classroom if object isn't exists ex. classroom.grade: "1" classroom.class: "C"
my current query (this work fine with increment into exists object)
db.getCollection("classsroom").updateOne(
{
pricipal: "Joe",
"classroom": {$elemMatch: {"grade":"1","class": "A"}}
},
{ $inc: { "classroom.$.totalStudent": 5 } },
{upsert: true}
)
expect result
{
"_id" : "1",
"principal" : "Joe",
"classroom" : [
{
"grade" : "1",
"class" : "A",
"totalStudent" : 10.0
},
{
"grade" : "1",
"class" : "B",
"totalStudent" : 20.0
},
{
"grade" : "1",
"class" : "c",
"totalStudent" : 5.0
}
]
}

Answer 1

Maybe something like this using update/aggregation ( 4.2+ ):
db.collection.update({ "principal":"Joe" },
[
{
$addFields: {
x: {
$size: {
$filter: {
input: "$classroom",
as: "c",
cond: {
$and: [
{
$eq: [
"$$c.grade",
"1"
]
},
{
$eq: [
"$$c.class",
"A"
]
}
]
}
}
}
}
}
},
{
$addFields: {
classroom: {
$cond: [
{
"$ne": [
"$x",
0
]
},
{
$map: {
input: "$classroom",
in: {
$mergeObjects: [
"$$this",
{
$cond: [
{
$and: [
{
$eq: [
"$$this.grade",
"1"
]
},
{
$eq: [
"$$this.class",
"A"
]
}
]
},
{
totalStudent: {
$add: [
"$$this.totalStudent",
5
]
}
},
{}
]
}
]
}
}
},
{
$concatArrays: [
"$classroom",
[
{
"class": "C",
"grade": "1",
"totalStudent": 5
}
]
]
}
]
}
}
},
{
$unset: "x"
}
],
{
multi: true
})
Explained:
Add temporary variable x that contain count of elements matching the criteria (grade="1",class="A")
Use the temporary variable x to check if array contain the matching element , if x=0 ( no elements matching ) perform concatArrays[] to add the new element. If x>0 (there is at least 1x element matching ) update the totalStudent value adding the needed increment amount.
Remove with $unset the temporary variable.
Add multi:true to perform the operation in all matching documents in collection
Playground
Improved version ( using $let for the temporary x variable ):
Playground2