Question

MongoDB, and mongoose.js specifically, allows tuples as attributes. For instance, the MongoDB documentation has this example where the attribute comments is itself an array of objects with the attributes [{body: String, date: Date}]. Yay!

var blogSchema = new Schema({
  title:  String,
  author: String,
  body:   String,
  comments: [{ body: String, date: Date }],
  date: { type: Date, default: Date.now },
  hidden: Boolean,
  meta: {
    votes: Number,
    favs:  Number
  }
})

Now when i persist that to MongoDB, not only does each instance of blogSchema get its own value for _id (e.g. 502efea0db22660000000002) but each individual value of comment gets its own _id field.

For the most part I don’t care, but in my app the analog to comments may have thousands of values. Each of which gets its own huge value of _id.

Can I prevent that? I’ll never need to refer to them individually. Or should I learn to stop worrying and love the unique identifier? I grew up programming the Vic20 and TRS80 as a kid, so may be overly paranoid about wasting memory/storage.

Answer 1

The _id can be disabled by setting the noId schema option to true. To pass the option you need to pass an instance of schema instead of using the object literal:

// instead of this...
comments: [{ body: String, date: Date }]

// do this...
var commentSchema = new Schema({ body: String, date: Date }, { noId: true });
var blogSchema = new Schema({
  ..
  comments: [commentSchema]
})