MongoDB remove objects from multiple nested arrays - mongodb

Question

I have a very complex json document in mongo like below:
{
"Category": [
{
"Name" : "",
"Description": "",
"SubCategory" : [
{
"Name": "",
"Description": "",
"Services": [
{"ServiceA": [
{
"Name": "",
"Description": "",
"CodeA": "1234"
}
]},
{"ServiceB" : [
{
"Name": "",
"Description": "",
"CodeBC": "ABCD",
"Key": ""
}
]},
{"ServiceC": [
{
"Name": "",
"Description": "",
"CodeBC": "ABCD",
"Section": [
{
"Name": "",
"Description": ""
}
]
}
]}
]
}
]
}
]
}
Now I want to retrieve the same document from Mongo but I want it to match only those objects inside ServiceA having CodeA = "1234" and those inside ServiceB and ServiceC having CodeBC = "ABCD".
I want it to remove all other objects inside ServiceA, ServiceB and ServiceC not matching the above condition and retrieve the document while maintaining the structure as it is.
Please Note : In the above example I just showed arrays containing single objects and fields that I want to retrieve but in real case it's very complex.

Answer 1

Try nested $map to iterate loop in your nested arrays, $mergeObjects to merge current object and new that we want to filter,
At the end in Services array filter documents on the base of condition in $filter, if filtered is null then that field will be removed using $ifNull
db.collection.aggregate([
{
$set: {
Category: {
$map: {
input: "$Category",
as: "c",
in: {
$mergeObjects: [
"$$c",
{
SubCategory: {
$map: {
input: "$$c.SubCategory",
as: "sc",
in: {
$mergeObjects: [
"$$sc",
{
Services: {
$map: {
input: "$$sc.Services",
as: "s",
in: {
$mergeObjects: [
"$$s",
{
ServiceA: {
$ifNull: [
{
$filter: {
input: "$$s.ServiceA",
cond: { $eq: ["$$this.CodeA", "1234"] }
}
},
"$$REMOVE"
]
},
ServiceB: {
$ifNull: [
{
$filter: {
input: "$$s.ServiceB",
cond: { $eq: ["$$this.CodeBC", "ABCD"] }
}
},
"$$REMOVE"
]
},
ServiceC: {
$ifNull: [
{
$filter: {
input: "$$s.ServiceC",
cond: { $eq: ["$$this.CodeBC", "ABCD"] }
}
},
"$$REMOVE"
]
}
}
]
}
}
}
}
]
}
}
}
}
]
}
}
}
}
}
])
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