MongoDB - How to $inc in a double nested array - json

Question

I'm trying to increment c every time a user choose a label.
My sample dataset has two nested arrays:
{
"id": 123,
"labels": [
{
"label": "orange",
"hitCount": 2,
"hits": [
{
"who": "bob",
"c": "2"
}
]
},
{
"label": "red",
"hitCount": 6,
"hits": [
{
"who": "bob",
"c": "5"
},
{
"who": "alice",
"c": "1"
}
]
}
]
}
For example bob choose again red so I want to increment the c inside bob's object inside red's object from 5 to 6.
I can't use $ two times to navigate inside more than one array per https://docs.mongodb.com/manual/reference/operator/update/positional/#nested-arrays
So anyone knows how to traverse more than one level of array and obtain a reference for $inc?

Answer 1

I suggest you to change you data model to:
{
"id": 123,
"labels": [
{
"label": "orange",
"hitCount": 2,
"hits": {
"bob": 2
}
},
{
"label": "red",
"hitCount": 6,
"hits": {
"bob":5,
"alice":1
}
}
]
}
Then you could update hits using this command:
db.hits.update(
{ 'labels.label': 'red' },
{ '$inc': { 'labels.$.hitCount': 1, 'labels.$.hits.bob': 1 } }
);
If you need to construct update with dynamic username, you can do it:
var userName = 'bob';
var updateCommand = {
$inc: {
'labels.$.hitCount': 1
}
};
updateCommand.$inc['labels.$.hits.' + userName] = 1;
db.hits.update({ 'labels.label': 'red' }, updateCommand);