MongoDB: Find a document that matches a condition in all its subdocument - mongodb

Question

I am trying to write a mongo query to fetch the result that satisifes a condition on all its subdocument,
1. {
"_id" : 1,
"data" : [
{
"Id" : "513",
"Nom" : "alouale pfouga",
}
],
"campaigns" : [
{
"user" : "1",
"latest" : NumberInt(0),
"postcode" : [
[
]
],
},
{
"user" : "2",
"latest" : NumberInt(1),
"postcode" : [
{
"id" : "772",
"name" : "xxx",
}
],
}
],
}
2. {
"_id" : 2,
"data" : [
{
"Id" : "514",
"Nom" : "pfouga remi",
}
],
"campaigns" : [
{
"user" : "1",
"latest" : NumberInt(0),
"postcode" : [
[
]
],
},
],
}
I need to find the record that has "Postcode" array is empty.
As far as I understand query like this: db.users.find({"campaigns.postcode":[]}) gives me both records, but i need only record 2 , because record 1 has postcode node in one sub documents, Please anyone help me !!!

Answer 1

This would give you the answer:
db.test.find({ 'campaigns.postcode': { $size: 0 } } )
but in your case 'campaigns.postcode' has an empty array in it and that means the size is not 0, its 1
You should remove your empty array
"postcode" : [
[
]
],
should be
"postcode" : []
Updated:
After spending some time on the question I realized the problem
For converting "postcode" : [[]] to "postcode" : [] you can use this code:
db.test.find({ 'campaigns.postcode': []} ).forEach(function(item){
for(var i0 = 0; i0 < item.campaigns.length; i0++)
{
if(item.campaigns[i0].postcode[0].length == []) item.campaigns[i0].postcode = [];
}
db.test.update({'_id' : item._id}, item);
});
after that you can find your proper result with:
db.test.find({ 'campaigns.postcode': { $size: 0 }, 'campaigns': { $size: 1 } } )

Answer 2

In your json structure it contains
"postcode" : [
[
]
],
So I tried some but not found exact what you want in expected results I found postcode data where all postcode was empty using following aggregation
db.collectionName.aggregate({"$unwind":"$campaigns"},
{"$unwind":"$campaigns.postcode"},
{"$match":{"campaigns.postcode":{"$size":0}}})