MongoDB filter recursively nested Array by object field - mongodb

Question

I want to filter a nested object array by a field in mongoDb Compass.
Here is an example collection.
{
"_id": "MENU_ORDER_POS_1",
"menuVersion": "MENU_ORDER",
"menuType": "MAIN",
"status": "ENABLED",
"children": [
{
"_id": "MENU_ORDER_CHILD_1",
"menuVersion": "MENU_ORDER",
"status": "ENABLED",
"children": [
{
"_id": "MENU_ORDER_CHILD_1.1",
"menuVersion": "MENU_ORDER",
"status": "ENABLED",
"children": []
},
{
"_id": "MENU_ORDER_CHILD_1.2",
"menuVersion": "MENU_ORDER",
"status": "DISABLED",
"children": []
}
]
},
{
"_id": "MENU_ORDER_CHILD_2",
"menuVersion": "MENU_ORDER",
"status": "DISABLED",
"children": []
},
{
"_id": "MENU_ORDER_CHILD_3",
"menuVersion": "MENU_ORDER",
"status": "DISABLED",
"children": []
}
]
},
{
"_id": "MENU_ORDER_POS_2",
"menuVersion": "PANEL",
"menuType": "",
"defaultPath": "",
"eventNameToNavigate": "",
"status": "ENABLED",
"children": []
}
Expected output:
{
"_id": "MENU_ORDER_POS_1",
"menuVersion": "MENU_ORDER",
"menuType": "MAIN",
"status": "ENABLED",
"children": [
{
"_id": "MENU_ORDER_CHILD_1",
"menuVersion": "MENU_ORDER",
"status": "ENABLED",
"children": [
{
"_id": "MENU_ORDER_CHILD_1.1",
"menuVersion": "MENU_ORDER",
"status": "ENABLED",
"children": []
}
]
}
]
}
Aggregate stages
First I need to get all the documents with menuVersion = "MENU_ORDER" and status = "ENABLED".
Then I need to filter all nested items in the children Array, note that this array is recursive and can have multiple children object inside an item. I need to get all the children items that matches status = "ENABLED"
Note The children array can have elements with the children object and this can be infinite, it is multilevel and all the items in the nested array must meet the filter criteria
I figure aggregate is the best choice here, using match and filter should do the job but I can't figure how to make it infinite recursive to filter all N child in the array.
So far I have written the filter part.
{
children: {
$filter: {
input: "$children",
as: "children",
cond: {
$eq: "children.status", "ENABLED" }
}
}
}

Answer 1

Your approach of using $filter is correct. You just need to refer the variable you set (i.e. children) using $$. Repeat it again with the inner array.
db.collection.aggregate([
{
$set: {
children: {
"$filter": {
"input": "$children",
"as": "c",
"cond": {
$and: [
{
$eq: [
"$$c.menuVersion",
"MENU_ORDER"
]
},
{
$eq: [
"$$c.status",
"ENABLED"
]
}
]
}
}
}
}
},
{
$set: {
children: {
"$map": {
"input": "$children",
"as": "c",
"in": {
"$mergeObjects": [
"$$c",
{
"children": {
"$filter": {
"input": "$$c.children",
"as": "innerChild",
"cond": {
$eq: [
"$$innerChild.status",
"ENABLED"
]
}
}
}
}
]
}
}
}
}
}
])
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