MongoDB how to filter in nested array - mongodb

Question

I have below data. I want to find value=v2 (remove others value which not equals to v2) in the inner array which belongs to name=name2. How to write aggregation for this? The hard part for me is filtering the nestedArray which only belongs to name=name2.
{
"_id": 1,
"array": [
{
"name": "name1",
"nestedArray": [
{
"value": "v1"
},
{
"value": "v2"
}
]
},
{
"name": "name2",
"nestedArray": [
{
"value": "v1"
},
{
"value": "v2"
}
]
}
]
}
And the desired output is below. Please note the value=v1 remains under name=name1 while value=v1 under name=name2 is removed.
{
"_id": 1,
"array": [
{
"name": "name1",
"nestedArray": [
{
"value": "v1"
},
{
"value": "v2"
}
]
},
{
"name": "name2",
"nestedArray": [
{
"value": "v2"
}
]
}
]
}

Answer 1

You can try,
$set to update array field, $map to iterate loop of array field, check condition if name is name2 then $filter to get matching value v2 documents from nestedArray field and $mergeObject merge objects with available objects
let name = "name2", value = "v2";
db.collection.aggregate([
{
$set: {
array: {
$map: {
input: "$array",
in: {
$mergeObjects: [
"$$this",
{
$cond: [
{ $eq: ["$$this.name", name] }, //name add here
{
nestedArray: {
$filter: {
input: "$$this.nestedArray",
cond: { $eq: ["$$this.value", value] } //value add here
}
}
},
{}
]
}
]
}
}
}
}
}
])
Playground

Answer 2

You can use the following aggregation query:
db.collection.aggregate([
{
$project: {
"array": {
"$concatArrays": [
{
"$filter": {
"input": "$array",
"as": "array",
"cond": {
"$ne": [
"$$array.name",
"name2"
]
}
}
},
{
"$filter": {
"input": {
"$map": {
"input": "$array",
"as": "array",
"in": {
"name": "$$array.name",
"nestedArray": {
"$filter": {
"input": "$$array.nestedArray",
"as": "nestedArray",
"cond": {
"$eq": [
"$$nestedArray.value",
"v2"
]
}
}
}
}
}
},
"as": "array",
"cond": {
"$eq": [
"$$array.name",
"name2"
]
}
}
}
]
}
}
}
])
MongoDB Playground