Modeling data on a many-to-many join in Mongo?

问题

So in a relational DB I might have 2 tables, 'User' and 'Event', which have a many-to-many relationship, and thus a join table 'UsersEvents' say. Now I have some data that I want to store on this table other than the 2 IDs, something like a boolean called 'Enjoyed'.

I understand that in Mongo you would create embedded links between the tables e.g. using Mongoose

var Person = new Schema({
    email: String,
    events: [EventFeedback]
})

var Event = new Schema({ ... });

var EventFeedback = new Schema({
    person: Schema.ObjectId,
    event: Schema.ObjectId,
    enjoyed: Boolean
});

but is this really the best way to model this? I would have thought that everything in EventFeedback could be in Person.events, which would be indexed by the Event._id? Or perhaps this is just a limitation of Mongoose?

回答1:

You would be better off using an Embedded Document rather than a link.

var Person = { 
   email: "joe.user@users.mongodb.org",
   events: [ 
        {code: "MONGONY2012", name: "Mongo NY", date: "5/23/2012", link: "http://www.10gen.com/events/mongo-nyc", enjoyed: true}, 
        {code: "MONGOPHL2012", name: "Mongo Philly", date: "4/9/2012", link: "http://www.10gen.com/events/mongodb-philly", enjoyed: true}
   ]
}

You can query Mongo for an event easily, using dot notation:

db.people.find({"events.code": "MONGONY2012"})

回答2:

Try this way

var EventScheme = new Schema({ ... });  
mongoose.model('Event', EventScheme);

var PersonScheme = new Schema({
  email: String,
  events: [{
    event: {
      type: mongoose.Schema.ObjectId,
      ref: 'Event'
    },
    enjoyed: Boolean
  }]
});

来源：https://stackoverflow.com/questions/9720464/modeling-data-on-a-many-to-many-join-in-mongo

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mongodb

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database