Update name of a key in nested mongo document - mongodb

Question

I did check on multiple platforms for the solution, however did not get the answer. Here is my problem:
I have a nested Mongo Document of the format:
{
_id: "xxxx",
"Type": <value>,
"Data" : {
"1": { <<< this key might differ for diff documents
"00": { <<< this key might differ for diff documents
"cont": "India"
},
"05": {
"cont": "India"
},
....
}
"32": {
"41": {
"cont": "India"
},
"44": {
"cont": "India"
},
....
}
}
}
I want to rename the key cont to country in all the documents in the collection, however as mentioned above the key 1, 00, 32 might differ for different documents hence I could not reach to a solution for this.
Is there something like:
db.collection.updateMany({Type: "abc"}, { $rename: { "Data.*.*.cont": "Data.*.*.country" }})
because the key cont resides at the third level after the key Data
Can someone please help me out here?
Thanks!

Answer 1

Using dynamic value as field name is generally considered as an anti-pattern. Nevertheless, you can still use $objectToArray to convert the nested objects into k-v tuples and manipulate them. Then converted it back using $arrayToObject
db.collection.update({},
[
{
"$addFields": {
"arr": {
// first conversion
"$objectToArray": "$Data"
}
}
},
{
"$addFields": {
"arr": {
// second conversion
"$map": {
"input": "$arr",
"as": "a",
"in": {
k: "$$a.k",
v: {
"$objectToArray": "$$a.v"
}
}
}
}
}
},
{
"$addFields": {
"arr": {
"$map": {
"input": "$arr",
"as": "a",
"in": {
k: "$$a.k",
v: {
"$map": {
"input": "$$a.v",
"as": "a2",
"in": {
k: "$$a2.k",
// rename the field `country`
v: {
country: "$$a2.v.cont"
}
}
}
}
}
}
}
}
},
{
"$addFields": {
"arr": {
"$map": {
"input": "$arr",
"as": "a",
"in": {
k: "$$a.k",
v: {
// 1st backward conversion
"$arrayToObject": "$$a.v"
}
}
}
}
}
},
{
"$project": {
_id: 1,
Type: 1,
"Data": {
// 2nd backward conversion
"$arrayToObject": "$arr"
}
}
}
])
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