Mongoose adds _id to all nested objects - mongodb

Question

When creating a document with nested objects (e.g. an array of objects), each object is given its own _id. For example, my schema looks like this:
mongoose = require "mongoose"
Schema = mongoose.Schema
schema = new Schema
name:
type: String
required: true
unique: true
trim: true
lists: [
list:
type: Schema.Types.ObjectId
required: true
ref: "List"
allocations: [
allocation:
type: Number
required: true
]
]
createdAt:
type: Date
default: Date.now
updatedAt:
type: Date
# Ensure virtual fields are serialised.
schema.set "toJSON",
virtuals: true
exports = module.exports = mongoose.model "Portfolio", schema
Every object in the lists array is given an _id, as is every allocation object in the lists.allocations array, when documents are eventually created. This seems like overkill and bloats the document, but is there a reason MongoDB (or Mongoose) needs the document to contain this additional information? If not, I'd like to prevent it from happening so that the only _id is on the root document.
Furthermore, Mongoose automatically creates a virtual id for _id, which I need because my client code expects a field id. This is why I'm having virtuals returned with JSON. However, because there are _id fields all throughout the document, not just at the root, this virtual duplicates all of them. If there is no way to prevent the additional _id fields, how can I get a virtual to only apply only to the root document _id? Or if there is a better way to do what I'm trying to do with it, what would it be?

Answer 1

I have figured out a way to solve both issues with the same technique: by using explicit schemas for each nested object type and setting their _id and id options to false. It seems that when nesting objects that you define "inline", Mongoose creates schemas for each of those objects behind the scenes. Since the default for a schema is _id: true and id: true, they will get an _id as well as have a virtual id. But by overriding this with an explicit schema, I can control the _id creation. More code, but I get what I want:
mongoose = require "mongoose"
Schema = mongoose.Schema
AllocationSchema = new Schema
allocation:
type: Number
required: true
,
_id: false
id: false
mongoose.model "Allocation", AllocationSchema
ListsSchema = new Schema
list:
type: Schema.Types.ObjectId
required: true
ref: "List"
allocations: [AllocationSchema]
,
_id: false
id: false
mongoose.model "Lists", ListsSchema
PortfolioSchema = new Schema
name:
type: String
required: true
unique: true
trim: true
lists: [ListsSchema]
createdAt:
type: Date
default: Date.now
updatedAt:
type: Date

Answer 2

#neverfox thanks for info, I just adding the code for Nodejs
var _incidents = mongoose.Schema({
name : {type : String},
timestamp: {type : Number},
_id : {id:false}
});
_schema = mongoose.Schema({
_id: {type: String, required: true},
user_id: {type: String, required: true},
start_time: {type: Number, required: true},
incidents : [_incidents],
});