MongoDB / Node: Insert part of a doc in a collection into a doc in another collection

Question

thanks for reading. I am trying to get a big list of data I have stored in a mongodb database, to display on a frontend, using the mongoose module in NodeJS. I am wondering what's the best way to tackle this problem? My data looks like this...

Collection 1: caves

{ 
    "_id" : ObjectId("564d2f6eb0896138247ff791"), 
    "name" : "ACME Cave", 
    "slug" : "acme-cave",
    "timeCreated" : ISODate("2015-11-19T02:09:50.492+0000"), 
    "address" : {
        "county" : "Somewhere", 
        "state" : "CA", 
        "country" : "USA"
    }
}

Collection 2: locations

{ 
    "_id" : ObjectId("564d2f6fb0896138247ff855"), 
    "latitude" : 54.5793621, 
    "longitude" : -74.9669167, 
    "parent_id" : ObjectId("564d2f6eb0896138247ff791"), <-- matches collection 1
    "timeCreated" : ISODate("2015-11-19T02:09:51.413+0000"),
}
{ 
    "_id" : ObjectId("564d2f6fb0896138247ff855"), 
    "latitude" : 48.5783611, 
    "longitude" : -72.9669167, 
    "parent_id" : ObjectId("564d2f6eb0896138247ff791"), <-- matches collection 1
    "timeCreated" : ISODate("2015-11-19T02:09:51.413+0000"),
}

I would like to merge some of the children fields into the parent like so...

{ 
    "_id" : ObjectId("564d2f6eb0896138247ff791"), 
    "name" : "ACME Cave", 
    "slug" : "acme-cave",
    "timeCreated" : ISODate("2015-11-19T02:09:50.492+0000"), 
    "address" : {
        "county" : "Somewhere", 
        "state" : "NY", 
        "country" : "USA"
    },
    locations: [
    { 
            "_id" : ObjectId("564d2f6fb0896138247ff855"), 
            "latitude" : 54.5793621, 
            "longitude" : -74.9669167, 
            "parent_id" : ObjectId("564d2f6eb0896138247ff791"), <-- matches doc collection 1
            "timeCreated" : ISODate("2015-11-19T02:09:51.413+0000"),
    },
    { 
            "_id" : ObjectId("564d2f6fb0896138247ff855"), 
            "latitude" : 48.5783611, 
            "longitude" : -72.9669167, 
            "parent_id" : ObjectId("564d2f6eb0896138247ff791"), <-- matches doc collection 1
            "timeCreated" : ISODate("2015-11-19T02:09:51.413+0000"),
    }
    ]
}

I have this snippet below which accomplishes this, but it doesn't seem right. Does anyone have any insight into doing this right?

Parent.find({}, {'locations': 1}).stream().on('data', function(parent) {
    // add the location to the parent doc
    Child.find({parent_id: {$in: parent._id}}, {'latitude': 1, 'longitude': 1}, function(err, child) {
      parent.locations = child;
      console.log(parent);
    });
});

This returns the follwing JSON, which is the same as my output..

{ 
    "_id" : ObjectId("564d2f6eb0896138247ff791"), 
    "name" : "ACME Cave", 
    "slug" : "acme-cave",
    "timeCreated" : ISODate("2015-11-19T02:09:50.492+0000"), 
    "address" : {
        "county" : "Somewhere", 
        "state" : "NY", 
        "country" : "USA"
    },
    locations: [
    { 
            "_id" : ObjectId("564d2f6fb0896138247ff855"), 
            "latitude" : 54.5793621, 
            "longitude" : -74.9669167, 
            "parent_id" : ObjectId("564d2f6eb0896138247ff791"), <-- matches doc collection 1
            "timeCreated" : ISODate("2015-11-19T02:09:51.413+0000"),
    },
    { 
            "_id" : ObjectId("564d2f6fb0896138247ff855"), 
            "latitude" : 48.5783611, 
            "longitude" : -72.9669167, 
            "parent_id" : ObjectId("564d2f6eb0896138247ff791"), <-- matches doc collection 1
            "timeCreated" : ISODate("2015-11-19T02:09:51.413+0000"),
    }
    ]
}

I have thought about rolling up these Schemas into 1 collection, but I cannot due to other features I'll be adding to the code, like storing pictures, and edits per children. I don't think using a single collection is wise, because I'll be storing too much information in a document.

Thanks for your help!

hecnabae · Accepted Answer · 2015-11-20 07:49:59Z

1

I think that you can use one-to-many with document references model. That is to say, store the location reference (only _id) inside the cave document.

{ 
    "_id" : ObjectId("564d2f6eb0896138247ff791"), 
    "name" : "ACME Cave", 
    "slug" : "acme-cave",
    "timeCreated" : ISODate("2015-11-19T02:09:50.492+0000"), 
    "address" : {
        "county" : "Somewhere", 
        "state" : "NY", 
        "country" : "USA"
    },
    locations: [ 564d2f6fb0896138247ff855, 564d2f6fb0896138247ff855 ]
}

answered Nov 20, 2015 at 7:49

hecnabae

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3 Comments

devinception Over a year ago

This isn't a bad idea! I was thinking somewhere along the lines of this, but I kept thinking to myself, what if I have a random location document and I need to get the parent? I could store the parent_id still, I guess. I think this is a bad way to go about it, or maybe it's common to store both in each collection? I come from a strong relational database background and getting my head out of that is been rough.

hecnabae Over a year ago

In MongoDB there are different solutions to your problem . I recommend the following series of articles: 6 Rules of thumb for MongoDB Schema Design.

devinception Over a year ago

Thanks for all your help, I've decided to follow your example and store the ObjectIds in the cave documents.

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