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TaylorMac
TaylorMac

Reputation: 9002

Node, MongoDB, Mongoose Design Choice - Creating two collections or one collection

I'm struggling with a large design choice for my applications' mongo collections and mongoose schemas.

My applications calls for two account types: Students and Teachers.

The only similarity between the two account types is that they both require the fields: firstName, lastName, email, and password. Other than that, they are different (teachers have "assignments", "tests", students have "homework", etc.)

I have pondered my options extensively, and considered the following design choices:

  1. Use mongoose-schema-extend, and create an "abstract" schema for all accounts. Then, extend this schema to create the Teacher and Student schemas. This implies two collections, and therefore some redundant fields. There are also issues with logging in and account creation (checking to see if the email used to log in is a student email or teacher email, etc.)

  2. Create one collection "accounts", and add a type field to indicate if the account is a "student" or a "teacher". This implies that entries in the "accounts" collection will be dissimilar. This also requires that I have two mongoose schemas for a single collection.

  3. Create an "accounts" collection, have a "type" field and an "accountId" field. In addition to a "student" collection and a "teacher" collection -- the "type" field will indicate which collection the student-specific or teacher-specific fields reside within, and the "accountId" field will indicate exactly which entry the account is matched with.

I appreciate all input, criticism or suggestions.

Upvotes: 3

Views: 681

Answers (2)

TaylorMac
TaylorMac

Reputation: 9002

@jibsales has an excellent solution.

One more solution to consider is using Population with references http://mongoosejs.com/docs/populate.html from the Users collection to the Student and Teacher collections. Some benefits are:

  • Entries in each of the three collections (Users, Teachers, Students) are similar in storage.

  • Allows you to obtain the fields for the "User" independently of obtaining the fields for the referenced collection.

This would require that the schema is modified before an instance is created (and a model is created from the schema), where refType is the desired collection:

var userSchema = new Schema({
  _id     : Number,
  name    : String,
  age     : Number,
  stories : [{ type: Schema.Types.ObjectId, ref: refType}]
});

Upvotes: 0

srquinn
srquinn

Reputation: 10481

I've been down a similar road and I eventually landed on a mix of option 1 and 2.

mongoose-schema-extend simply modifies the prototype of Schema with an #extend() method which when invoked performs a deep copy of the passed schema. Most helpful. However, you can control which collection mongoose saves to in MongoDB by adding a collections property to the Schema:

var schema = new Schema({
  foo: String,
  bar: Boolean
}, { collection: "FooBarBaz" });

Remember: Mongoose understands the concept of a Schema but MongoDB does not. This means you can store dissimilar data and use your custom business logic to control the mess. With that said, you can create a base model called User, force mongoose to use the same collection by using the collection option and then extend off this base model to make your Teachers and Students models.

Make sure you add a type flag in the base model as you suggested in option 2. Not only is this convenient for quick lookups, but it will be critical when working commando with raw MongoDB data.

Upvotes: 3

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