CODEWITHSUNDEEP
mongodbdata-modeling
Chase Thorpe
Chase Thorpe

Reputation: 45

Is this the correct way to model data in MongoDB?

I am new to data modelling and am working on a personal project in which users can upload photos to containers. These containers can be nested (for example: "Japan" container may have a sub container called "Cats" in which you can store pictures of all the cats you saw in Japan).

I am imagining 3 entities: Users, Containers, and Photos structured in the following way:

Users Collection:

{
  User_id: userId101,
  userName: “Chase”,
  Email: “[email protected]”,
  Containers: [{name: “Thailand”, parentContainer: null}, {name: “Food”, parentContainer:
                     “Thailand”],
}

Containers Collection:

{
  Id: cont_01,
  Name: “Thailand”,
  ownedBy: userId101
  parentContainer: null,
  Photos: [“photoId1”, “photoId2”, etc.]
{

Photos Collection:

{
  Id: photo_01,
  userRef: userId101
  Url: “www.unsplash.com/1279178298”
}

I just want to know if I am missing any major detail that will break this before I spend weeks building this out.

Thank you very much :)

Upvotes: 2

Views: 38

Answers (1)

mickl
mickl

Reputation: 49985

There's really multiple factors that can be taken into consideration here. First of all you don't need to think that every "entity" should have a separate collection (like in SQL) BSON can handle nested arrays like below:

{
    Id: cont_01,
    Name: "Thailand",
    ownedBy: userId101
    parentContainer: null,
    Photos: [ { id: "photo_01", "www.unsplash.com/1279178298" }]
}

"Joining" ($lookup) the data in MongoDB is an additional overhead so keep it merged unless you have a good reason to divide into multiple collections.

Having the data modeled like above gives you a possibility to use $graphLookup to get a tree of parent-child relationships.

This is what I would start with. As a next step you can consider embedding user data into each container (denormalized) to avoid using $lookups or having single user document with an array of containers having embedded photos - more difficult to maintain (updates are a bit more complicated like here) but better read performance since you don't need lookups.

The drawback of having extremely large documents is also 16MB document size limitation which is a lot but it's good to keep that in mind.

Upvotes: 3

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