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Shiva Venkatesh

JavaScript Hacker

Nov 12, 2017

Storing and querying relational data in mongoDB using Mongoose

Hi Sandeep, I read in a post on Hashnode that you guys use mongoDB as your primary database. Features like follows and feeds would require storing and querying heavily relational data. Assuming I have a users collection, what would be the best way to implement follows in mongoDB?

#mongodb #mongoose #nodejs

Responses(1)

Sandeep Panda

co-founder, Hashnode

Nov 16, 2017

Hi Shiva!

For architecting "Follow/Following" system in MongoDB, your best bet is probably creating a junction collection (Many-Many table in relational DBs). For example, you could have a collection with documents that have the following schema:

{
  from: { type: ObjectId }, // Indicates who's is following
  to: { type: ObjectId } , // Who's being followed
  dateAdded: 'Date',
  isActive: 'Boolean'
}

Or if you need a more sophisticated approach, use a graph database that gives you more freedom and flexibility. The only downside is that you will introduce another moving part into your app and you should have enough knowledge of the graph DB.

IMO, if you are just starting out go with MongoDB (assuming this is the DB of your choice), and once you hit any bottlenecks or limitations, start searching for other solutions.

Hey Sandeep Panda ,

What would be the downside of storing it in the user details or if required in a separate collection in form or array?

{
    .
    .
    . // other user details
    followers: [ObjectId],
    follows: [ObjectId], 
}

This would eliminate aggregation query in a junction collection. Every time user_1 follows user_2 :

Add id of user_2 in follows of user_1
Add id of user_1 in followers if user_2.

If you also want to maintain the date-time of following, you can add

{
    id: ObjectId,
    dateAdded: 'Date'
}

as the object in the array.

If required to kept out of user collection, it can be made a standalone collection of its own with reference to user id:

{
    userId: ObjectId,
    followers: [ObjectId], // or [{id: ObjectId, dateAdded: 'Date'}]
    follows: [ObjectId], // or [{id: ObjectId, dateAdded: 'Date'}]
}

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Storing and querying relational data in mongoDB using Mongoose

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