Paste document without knowing _id in Mongoose / Mongodb

Question

I know that there are no "unions" in MongoDB. I am trying to link a large number of documents with 40,000 places in my collection of places.

My place collection has user (read: not under my control) location identifiers and their corresponding lat / lng coordinates.

var Locations = new Schema({
    location_id: String, 
    loc: { //lng, lat: as per mongodb documents
         type: [Number], 
         index: '2d'
    } 
});

There are several collections that have a field that references this user identifier to match latitude and longitude.

var MyCollection = new Schema({
    location: String,
    otherFields: Strings...
});

I lost a little what is the best way to do this. Many posts offer a link through a Scheme, but I have only seen this with help Schema.Types.ObjectId. This seems impractical to me, because the data I import has only its own identifier.

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Answer 1

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1. "[...], if the mongod receives a document to insert that does not contain an _id field, mongod will add the _id field that holds an ObjectId. [...]" 

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Locations.find({location_id: <the_location_id>})

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- :

Locations.find({lat: {$gt: <x>-a, $lt: <x>+a}, lon: {$gt: <y>-b, $lt: <y>+b}}, function(locations){ ... });

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