Azure CosmosDB - update the property name - mongodb

Question

I am trying to update the property name of the json in mongodb document.
{
"_id" : ObjectId("1234556789"),
"apps" : [
{
"_id" : 101,
"regions" : [
"WANAE",
"WANAF"
]
},
{
"_id" : 102,
"regions" : [
"WANAE",
"WANAF"
]
}
]
}
in the above josn, I want to change apps regions to codes. Treid below queries but did not work
db.packs.updateMany( {}, { $rename: { 'apps.$.regions': 'apps.$.codes' } } );
db.packs.updateMany( {}, { $rename: { 'apps.$[].regions': 'apps.$[].codes' } } );
any help
Update: As Joe suggested, I have a aggregation that changes the document with the changes needed and I tried updating the entire collection like below with the aggregated result
db.packs.aggregate([
{
$addFields: {
apps: {
$map: {
input: "$apps",
as: "app",
in: {
_id: "$$app._id",
did: "$$app.did",
name: "$$app.name",
codes: "$$app.regions"
}
}
}
}
},
{
$project:{
"apps.regions":0
}
},
{
$out:"packs"
}
])
As per the documentation, $out should replace the existing collection if it is exists but I received an error that says I have to supply a new collection name Please supply a collection that does not already exist to the $out stage.. Isn't $Out replace the exiting packs with new aggregated results

Answer 1

When you reference a field in an array of objects, like "$apps.regions", the value is an array containing all of the values of that field from all of the elements.
If you set the value of regions directly, each sub document will contain an array of arrays, probably not what you want.
renaming the field in the entire array of objects will require iterating the array, perhaps with $map or $reduce.
If you are using MongoDB 4.2, you can do that with a pipeline in an update:
db.packs.updateMany( {}, [
{$set: {
"apps": {
$map: {
input: "$apps",
in: {
$mergeObjects: [
"$$this",
{
codes: "$$this.regions"
}
]
}
}
}
}},
{$unset: "apps.regions"}
]}
If you are using an earlier version, you'll need to do that with aggregation, perhaps with $out, and then replace the original collection with the updated one.