MongoDB update query for nest array - node.js

Question

Having collection Measurement such as shown below:
{
"Data" : [ [-5, [[1, 1023.0], [2, 694.0]]], [-1, [[1, 0.0], [2, 20.0]]], [-3, [[1, 30.75], [2, 30.75]]] ]
}
it reflects c# structure of Dictionary<int, Dictionary<int, double>> - what I'd need to do is to write an update script which will add 5 to all the parental dictionary keys. How could this be done via mongo update script? So it would turn the object to look as follows:
{
"Data" : [ [0, [[1, 1023.0], [2, 694.0]]], [4, [[1, 0.0], [2, 20.0]]], [2, [[1, 30.75], [2, 30.75]]] ]
}

Answer 1

The only way to do this is programatically, i.e., looping over the Data array and updating each individually.

Answer 2

This is probably not the structure that you really want if you need to update things in this way. The problem lies with the ability to match elements in a nested array in that the current limitation is that you can only match the first position and reference that index only when doing an update.
We can't tell much about your purpose based on what you have presented, but what you probably need is something like this:
{
"Data" : [
{
"pos": 0,
"ref": -5,
"A": { "x": 1, "y": 1023.0 },
"B": { "x": 2, "y": 694.0 }
},
{
"pos": 1,
"ref": -1,
"A": { "x": 1, "y": 0.0},
"B": { "x": 2, "y": 20.0 }
},
{
"pos": 2,
"ref": -3,
"A": { "x": 1, "y": 30.75 },
"B": { "x": 2, "y": 30.75 }
}
]
}
Yet even that does not allow you to update in a single query. You can do it with one for each element though:
db.collection.update({"_id": id, "Data.pos": 0}, {"$inc":{"Data.$.ref": 5}});
db.collection.update({"_id": id, "Data.pos": 1}, {"$inc":{"Data.$.ref": 5}});
db.collection.update({"_id": id, "Data.pos": 3}, {"$inc":{"Data.$.ref": 5}});
And your current schema would not allow you to do even that. And at least all of the elements could be accessed in this way, which again they could not before.
In any case, updating all of the array elements at once is not possible other than in a loop:
db.collection.find({ "_id": id }).forEach(function(doc) {
doc.Data.forEach(function(data) {
data.ref += 5;
});
db.collection.update(
{ "_id": doc._id },
{ "$set": { "Data": doc.Data } }
);
})
Or some variant that might even do something like the first example rather that just replacing the whole array as this does. Your current structure would rely on looping through several nested arrays to do the same thing.
Of course if you regularly have to update all elements in this way, then consider something other than an array. Or live with how you have to update, according to what your data access needs are.
Read the documentation on how things can be handled and make you decisions from there.