Correct data structure for storing an array of objects

Question

I want to store latitude and longitude coordinates for a user. They may have more than one so I am making it an array of objects. I just wanted to ask if this structure is okay for storing an array of objects for a user or should it be changed to something different/better?

In my User mongoose schema:

  places: [
    {
      location: {
        latitude: {
          type: Number,
        },
        longitude: {
          type: Number,
        },
      },
    },
  ],

My controller:

exports.addLocation = async (req, res) => {
  const { latitude, longitude, userId } = req.body;

  const user = await User.findById(userId);
  if (!user) {
    return res.status(404).send("No user found");
  }

  user.places.push({ location: { longitude: longitude, latitude: latitude } });
  await user.save();
  res.status(201).send(user);
};

When I look in Mongo DB Atlas I can see that each object in the array has its own _id.

{
    "_id": {
        "$oid": "5f2d9ec5053d4a754d6790e8"
    },
    "name": "Bob",
    "email": "[email protected]",
    "__v": 31,
    "places": [{
        "_id": {
            "$oid": "5f3577d511d3f56b7082d320"
        },
        "location": {
            "longitude": 48.137565,
            "latitude": 11.575502
        },
        "saved_at": {
            "$date": "2020-08-13T17:26:45.312Z"
        }
    }, {
        "_id": {
            "$oid": "5f3577ee11d3f56b7082d321"
        },
        "location": {
            "longitude": 48.863129,
            "latitude": 2.294873
        },
        "saved_at": {
            "$date": "2020-08-13T17:27:10.594Z"
        }
    }]
}

Better is to have different collection called places where you will store lat/long with User id. It would be much easier to query and update if needed — Andrey Sherman
– Andrey Sherman, Commented Aug 12, 2020 at 18:28
I did think about that. But isn't that then like a sql database? — user8463989
– user8463989, Commented Aug 12, 2020 at 18:41
Yes, it's more sql approach to do such relations, but you still have free structure to use, like nosql. And in case if you need to delete or update place data, it's for sure easy to do using sql relation approach(especially with deleting) — Andrey Sherman
– Andrey Sherman, Commented Aug 12, 2020 at 18:44
In most cases, if I want to use complicated arrays, I'm separating it to another collection and it works perfectly — Andrey Sherman
– Andrey Sherman, Commented Aug 12, 2020 at 18:46
If the number of locations a person can add is not limited, you should store them in a separate collection. Also consider your indexing strategy since an index can only include 1 array per document. — Joe
– Joe, Commented Aug 13, 2020 at 2:22

fadil eldin · Accepted Answer · 2020-08-13 18:12:59Z

1

Both options, depend on your use-case. In any NoSQL modeling, the data dictates if it better to embed repeated data in the same document or split into more documents.
If you are tracking your users, for example, and your "places" array will store destinations where a user stayed more than 10 minutes, then your array may keep growing beyond the max document size of 16MB.
Even when it is much smaller than that zise, querying your array with several hundred elements will become a nightmare.
For such a use-case, you better split those visits into separate documents. e.g. add "day" after "email" and store each day's places in a separate document, where each array element is another diestination visited on that day.
But if the "places" array is not expected to grow, then keep it embedded in a sigle user document, same as in your example.

edited Aug 13, 2020 at 18:12

answered Aug 13, 2020 at 18:07

fadil eldin

1531 silver badge8 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Andrey Sherman · Accepted Answer · 2020-08-13 18:03:18Z

0

Here are questions, that we have:

Do we need to store places in array as long as it's should be NoSQL
approach?
Isn't the point of a NoSql database to not have to normalise the database and create tables that require multiple joins etc.

With current data, normalization approach will look like this:

As for normalization approach we don't want to have any duplications and have many-to-many relation. In this case it's not suitable for NoSQL database.

Here is an other example with separating places to another collection, but more with NoSQL-suitable approach

NOTE: example for MongoDB is provided in table view just as showcase. For sure it should be JSON-format

Json Structure

Users collection:

{
    "_id" : ObjectId("5f0b0540c0c721d9f87ded50"),
    "name":"Bob",
    "email": "[email protected]"
}

Places collection:

[{
    "_id": ObjectId("5f3577d511d3f56b7082d320")
    "location": {
        "longitude": 48.137565,
        "latitude": 11.575502
    },
    "saved_at": "2020-08-13T17:26:45.312Z",
    "user_id": ObjectId("5f0b0540c0c721d9f87ded50")
},
{
    "_id": ObjectId("5f3577d5098gh56b7082d410")
    "location": {
        "longitude": 43.137565,
        "latitude": 12.575502
    },
    "saved_at": "2020-08-13T19:26:45.312Z",
    "user_id": ObjectId("5f0b0540c0c721d9f87ded50")
}]

As you could see here we will have data duplication and in NoSQL world we don't care of it. We choose this 2 collections separating, to increase and simplify queries to database.

Just to sum up - We don't use SQL normalization in this case. We are separating data, duplicating data, so it would be easy to query, setting several indexes(if needed), updating and deleting documents, etc.

edited Aug 13, 2020 at 18:03

answered Aug 13, 2020 at 14:43

Andrey Sherman

3601 silver badge7 bronze badges

2 Comments

user8463989 Over a year ago

Thanks for this, Andrey. I am not 100% sure I follow your mongo db example so I have edited my original question to post my structure in json format with some dummy data. So, I just want to confirm that I should still rather use a separate collection for the locations?

Andrey Sherman Over a year ago

@user8463989 just updated answer with json structure example. And yes, I suggest to use places in separate collection in this case

Collectives™ on Stack Overflow

Correct data structure for storing an array of objects

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related