Mongoose: Schema option {_id: false} will trigger error 'document must have an _id before saving'

[MauroJr]

I tried to run the code below, which I picked up from Mongoose documentation, and the execution not occur like expect. If I set schema option _id to false, mongoose must let me save without _id and then Mongodb will generate the _id for me, but instead, mongoose is throwing the following error "document must have an _id before saving".

var assert = require("assert");
var mongoose = require("mongoose");
var Schema = mongoose.Schema;

mongoose.connect('mongodb://localhost/noIDTest');

// disabled _id
var schema = new Schema({ name: String }, { _id: false });

var Page = mongoose.model('Page', schema);
var p = new Page({ name: 'mongodb.org' });
console.log(p); // { name: 'mongodb.org' }

// MongoDB will create the _id when inserted
p.save(function (err) {
  assert.ifError(err);
  Page.findById(p, function (err, doc) {
    assert.ifError(err); // instead is printing this: Error: document must have an _id before saving
    console.log(doc); // should print this: { name: 'mongodb.org', _id: '50341373e894ad16347efe12' }
  })
});

[vkarpov15]

Hmm where did you get this example from in the docs? Mongoose explicitly doesn't support saving documents without a top-level _id, because there's no other way for us to know what document we're updating...

[juanmi108]

I have the same issue, I implemented a schema similar to the one found in http://mongoosejs.com/docs/guide.html#_id

var listSchema = new schema({

    _name: {type: String, unique: true, required: true, index: true},
    owner: {type: String, required: true, index: true},
    visibility: {type: String, default: 'private'},
    color: {type: String, default: '#e95e01'},
    activ: {type: Boolean, default: true},
    todos: []

    }, {_id: false});

[vkarpov15]

More of an issue with the docs than anything, mongoose doesn't really support saving a doc that doesn't have an _id defined, because then we don't know how to update the doc.

[juanmi108]

oh ok, thanks for the clarification :)

[mattbontrager]

I know this is old but, I stumbled across it with the same issue. I think the part of the explanation that is lacking is this:

The _id option exists to prevent one being created and assigned to every sub-document within your document.

So, it's not for this:

var Schema = mongoose.Schema,
    ThingSchema = new Schema({
    name: String,
    categories: [{
        label: {
            type: String,
            uppercase: true
        },
        value: String
    }]
    }, {_id: false});
    //   ^^^^^^^^^
    // this won't work

It's for this:

var Schema = mongoose.Schema,
    ThingSchema = new Schema({
        name: String,
        categories: [{
            label: {
                type: String,
                uppercase: true
           },
           value: String,
           _id: false // <--- this works
        }]
    });

Took me a while but, after running into the same problem, I found the documentation here.

[pouriamoosavi]

I really cant understand the "_because then we don't know how to update the doc_" sentence. The program will give mongoose enough criteria to update a document so mongoose should update document base on my first input in update query. Then what is the problem with update what I say and ignore _id? Like the original update in mongodb does.

[vkarpov15]

This issue is about save(), not update(). save() doesn't take a query filter as a parameter.