MongoDB $pop element which is in 3 time nested array - mongodb

Question

Here is the data structure for each document in the collection. The datastructure is fixed.
{
'_id': 'some-timestamp',
'RESULT': [
{
'NUMERATION': [ // numeration of divisions
{
// numeration of producttypes
'DIVISIONX': [{'PRODUCTTYPE': 'product xy', COUNT: 100}]
}
]
}
]
}
The query result should be in the same structure but only contain producttypes matching a regular expression.
I tried using an nested $elemMatchoperator but this doesn't get me any closer. I don't know how I can iterate each value in the producttypes array for each division.
How can I do that? Then I could apply $pop, $in and $each.
I looked at:
Querying an array of arrays in MongoDB
https://docs.mongodb.com/manual/reference/operator/update/each/
https://docs.mongodb.com/manual/reference/operator/update/pop/
... and more
The solution I want to avoid is writing something like this:
collection.find().forEach(function(x) { /* more for eaches */ })
Edit:
Here is an example document to copy:
{"_id":"5ab550d7e85d5930b0879cbe","RESULT":[{"NUMERATION":[{"DIVISION":[{"PRODUCTTYPE":"Book","COUNT":10},{"PRODUCTTYPE":"Giftcard","COUNT":"300"}]}]}]}
E.g. the query result should only return the entry with the giftcard:
{"_id":"5ab550d7e85d5930b0879cbe","RESULT":[{"NUMERATION":[{"DIVISION":[{"PRODUCTTYPE":"Giftcard","COUNT":"300"}]}]}]}

Answer 1

Using the forEach approach the result is in the correct format. I'm still looking for a better way which does not involve the use of that function - therefore I will not mark this as an answer.
But for now this works fine:
db.collection.find().forEach(
function(wholeDocument) {
wholeDocument['RESULT'].forEach(function (resultEntry) {
resultEntry['NUMERATION'].forEach(function (numerationEntry) {
numerationEntry['DIVISION'].forEach(function(divisionEntry, index) {
// example condition (will be replaced by regular expression evaluation)
if(divisionEntry['PRODUCTTYPE'] != 'Giftcard'){
numerationEntry['DIVISION'].splice(index, 1);
}
})
})
})
print(wholeDocument);
}
)
UPDATE
Thanks to Rahul Raj's comments I have read up the aggregation with the $redact operator. A prototype of the solution to the issue is this query:
db.getCollection('DeepStructure').aggregate( [
{ $redact: {
$cond: {
if: { $ne: [ "$PRODUCTTYPE", "Giftcard" ] },
then: "$$DESCEND",
else: "$$PRUNE"
}
}
}
]
)

Answer 2

I hope you're trying to update nested array.
You need to use positional operators $[] or $ for that.
If you use $[], you will be able to remove all matching nested array elements.
And if you use $, only the first matching array element will get removed.
Use $regex operator to pass on your regular expression.
Also, you need to use $pull to remove array elements based on matching condition. In your case, its regular expression. Note that $elemMatch is not the correct one to use with $pull as arguments to $pull are direct queries to the array.
db.collection.update(
{/*additional matching conditions*/},
{$pull: {"RESULT.$[].NUMERATION.$[].DIVISIONX":{PRODUCTTYPE: {$regex: "xy"}}}},
{multi: true}
)
Just replace xy with your regular expression and add your own matching conditions as required. I'm not quite sure about your data set, but I came up with the above answer based on my assumptions from the given info. Feel free to change according to your requirements.