Removing a specific attribute in an array of nested documents - json

Question

Excuse my English, I'm from Russia.
I asked this question in the Russian version SO, but they still haven't answered it.
There is a record collection that stores archival files. Here is its simplified structure (I omitted most of the attributes):
{
"_id": 1,
"tomes": [
{
"number":1,
"archive_number":1
},
{
"number":2,
"archive_number":1
}
]
}
{
"_id": 2,
"tomes": [
{
"number":1,
"archive_number":1
},
{
"number":2,
"archive_number":1
},
{
"number":3,
"archive_number":1
}
]
}
I need to remove the archive_number attribute from each of the nested documents of the tomes array for all documents in the record collection.
After deletion, the structure should look like this:
{
"_id": 1,
"tomes": [
{
"number":1,
},
{
"number":2,
}
]
}
{
"_id": 2,
"tomes": [
{
"number":1,
},
{
"number":2,
},
{
"number":3,
}
]
}
I was able to write a query like this:
db.record.update(
{
"tomes": {
$elemMatch:{
"archive_number":{$exists:true}
}
}
},
{
$unset: {
"tomes.$.archive_number":1
}
},
false, true
)
But this query only removes the archive_number attribute on one volume per archive case. I.e., after launch, we will see the following picture:
{
"_id": 1,
"tomes": [
{
"number":1,
},
{
"number":2,
"archive_number":1
}
]
}
{
"_id": 2,
"tomes": [
{
"number":1,
},
{
"number":2,
"archive_number":1
},
{
"number":3,
"archive_number":1
}
]
}
Can you please tell me how to delete all volumes? I don’t know how to correct the request, but my head doesn’t understand anymore.

Answer 1

Solution 1
With $[<indentifier>] (filtered positional operator) and arrayFilters to update the document(s) in the array.
db.collection.update({
"tomes": {
$elemMatch: {
"archive_number": {
$exists: true
}
}
}
},
{
$unset: {
"tomes.$[tome].archive_number": 1
}
},
{
arrayFilters: [
{
"tome.archive_number": {
$exists: true
}
}
],
multi: true
})
Sample Mongo Playground (Solution 1)
Solution 2
With $[] (all positional operator).
The all positional operator $[] indicates that the update operator should modify all elements in the specified array field.
db.collection.update({
"tomes": {
$elemMatch: {
"archive_number": {
$exists: true
}
}
}
},
{
$unset: {
"tomes.$[].archive_number": 1
}
},
{
multi: true
})
Sample Mongo Playground (Solution 2)
References
How the arrayFilters Parameter Works in MongoDB