Develop Reference

How to find key with type objectId , ref to <some model>

I have created a Notes model having schema as shown below
const notesschema = new Schema({
user :{
type : Schema.Types.ObjectId,
ref : 'User',
required : true
},
problem : {
type : Schema.Types.ObjectId,
ref : 'Problems',
required : true
},
content : {
type : 'string'
}
},{
timestamps : true
})
To show the User his notes for a particular task/problem I am trying to fetch notes and show to him and possibly update if he do some changes and save, The problem is with this schema I dont know how to write <model.findById >API to find notes from my notes model having particular user and specific task/problem.Which I would know the Id of.
With this particular schema , and my current knowledge i would have to write So much code. So if there is any easier way to do this task is welcomed, I was also thinking to change my schema and just placing my user id in my schema instead of whole user and finding notes from my database
edit : as suggested by all the answers we can simply find using user.id which I thought initially would not word as that was just the path, but which stores actually user.id

You create the notes' collection the same way you're doing it,
const notesSchema = new mongoose.Schema({
user: {
type: mongoose.Schema.Types.ObjectId,
ref: 'User', // # the name of the user model
required: true
},
problem: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Problem', // # the name of the user model
required: true
},
content: String
})
Then you'll create the model of the notesSchema as follows:
const NoteModel = mongoose.model('Note', notesSchema, 'notes')
export them so you can use them in your controllers:
module.exports = {
NoteModel,
notesSchema
}
or if you're using +es6 modules (think of, if you're using TypeScript):
export default {
NoteModel,
notesSchema
}
This will result in creating the following table (collection) in the database:
Let's think of the following challenges:
To get all the notes:
NoteModel.find({})
To get all the users:
UserModel.find({}) // you should have something like this in your code of course
To get all the problems:
ProblemModel.find({}) // you should have something like this in your code of course
To get all the notes of a user:
NotesModel.find({ user: USER_ID })
To search for notes by problems:
NotesModel.find({ problem: PROBLEM_ID })
Now, the above is how you do it in mongoose, now let's create a RESTFUL controller for all of that: (assuming you're using express)
const expressAsyncHandler = require('express-async-handler') // download this from npm if you want
app.route('/notes').get(expressAsyncHandler(async (req, res, next) => {
const data = await NotesModel.find(req.query)
res.status(200).json({
status: 'success',
data,
})
}))
The req.query is what's going to include the search filters, the search filters will be sent by the client (the front-end) as follows:
http://YOUR_HOST:YOUR_PORT/notes?user=TheUserId
http://YOUR_HOST:YOUR_PORT/notes?problem=TheProblemId
http://YOUR_HOST:YOUR_PORT/notes?content=SomeNotes

const notesschemaOfUser = await notesschema.findOne({user: user_id});

Mongoose: Count array elements

I have the following Schema with a array of ObjectIds:
const userSchema = new Schema({
...
article: [{
type: mongoose.Schema.Types.ObjectId,
}],
...
},
I will count the array elements in the example above the result should be 10.
I have tried the following but this doesn't worked for me. The req.query.id is the _id from the user and will filter the specific user with the matching article array.
const userData = User.aggregate(
[
{
$match: {_id: id}
},
{
$project: {article: {$size: '$article'}}
},
]
)
console.log(res.json(userData));
The console.log(article.length) give me currently 0. How can I do this? Is the aggregate function the right choice or is a other way better to count elements of a array?

Not sure why to use aggregate when array of ids is already with user object.
Define articles field as reference:
const {Schema} = mongoose.Schema;
const {Types} = Schema;
const userSchema = new Schema({
...
article: {
type: [Types.ObjectId],
ref: 'Article',
index: true,
},
...
});
// add virtual if You want
userSchema.virtual('articleCount').get(function () {
return this.article.length;
});
and get them using populate:
const user = await User.findById(req.query.id).populate('articles');
console.log(user.article.length);
or simply have array of ids:
const user = await User.findById(req.query.id);
console.log(user.article.length);
make use of virtual field:
const user = await User.findById(req.query.id);
console.log(user.articleCount);
P.S. I use aggregate when I need to do complex post filter logic which in fact is aggregation. Think about it like You have resultset, but You want process resultset on db side to have more specific information which would be ineffective if You would do queries to db inside loop. Like if I need to get users which added specific article by specific day and partition them by hour.

using prisma, how do you access newly created record from within a nested write (update first, then create within)

Using Prisma, I have a question about accessing a record that was newly created from within a nested write (update first, then create within).
I'm following along the examples on this page in the prisma docs.
In particular, I am looking at the following two items in the data model:
Note, I have slightly modified the example for the purposes of this question by adding a counter to User.
model User {
id Int #id #default(autoincrement())
email String #unique
posts Post[]
counter Int
}
model Post {
id Int #id #default(autoincrement())
title String
author User? #relation(fields: [authorId], references: [id])
authorId Int?
}
Now, let's say you want to create a new Post and connect it to the User and at the same time, you also want to increment the counter.
My assumption, after reading this section of the doc is that you would need to update the existing User and within that, create a new Post record.
i.e.
const user = await prisma.user.update({
where: { email: 'alice#prisma.io' },
data: {
// increment the counter for this User
counter: {
increment: 1,
},
// create the new Post for this User
posts: {
create: { title: 'Hello World' },
},
},
})
My question is this. In the above scenario, how do you access the newly created Post in the return of the query?
In particular, say you want to get the id of the new Post?
From what I can tell, the returned user object could possibly include the array of all associated Posts, i.e. if you added this to the update query...
include: {
posts: true,
}
But I can't yet see how, using Prisma, you get the individual Post that you just created as part of this update query.

I have found one way of achieving this that works.
It uses the tranaction api.
Basically, instead of trying to use a nested write that begins with an update on User and contains a nested create on Post...
I split the two operations out into separate variables and run them together using a prisma.$transaction() as follows.
const updateUser = prisma.user.update({
where: { email: 'alice#prisma.io' },
data: {
// increment the counter for this User
counter: {
increment: 1,
},
},
});
const createPost = prisma.post.create({
data: {
// create the new Post for this User
title: 'Hello World',
author: {
connect: {
email: 'alice#prisma.io',
},
},
},
});
const [ updateUserResult, createPostResult ] = await prisma.$transaction([updateUser, createPost ]);
// if createPostResult, then can access details of the new post from here...

How to make Mongoose not insert empty array or object fields into a document

Let's say we have a Mongoose schema in our Node.js project:
let coolSchema = new mongoose.Schema({
field_1 : Number,
field_2 : String,
field_3 : [ String ],
});
And let's we have an according object:
var data = {
field_1 : 123,
field_2 : 'blah',
field_3 : ['aa', 'bb'],
};
Now to save this data into MongoDB we can use this code:
let Model = require('mongoose').model('CoolModel', coolSchema);
(new Model(data)).save();
Ok, while it's all cool.
But if data does not contain field_3 (array field, and the same will be for an object field) Mongoose will anyway add this field into the being created document with empty value.
Can we somehow tell Mongoose not to create this field if it's not contained in the data object?

you can do it easily skip the array field and array of object field.. This will let you skip saving empty array in new documents.but you have to use pre hook for this .
var brandSchema = new Schema({
name : {type:String},
email:String,
check:[]
})
brandSchema.pre('save', function (next) {
if (this.isNew && 0 === this.check.length) {
this.check = undefined;
}
next();
})
when new document is inserted in your schema you have to use this middlware.this works fine so try this.
this is the response when we want to insert any document
"data": {
"__v": 0,
"name": "testing",
"email": "testing#gmail.com",
"_id": "5915b018e292833edda8837f"
}
so i have send only email and name but check(array) field is skipped(Not send any value).

The accepted answer is good. But if you wouldn't want to use pre-hook, then you can add default: undefined to the array fields. For example:
var schema = new Schema({
myArr: { type: [String], default: undefined }
});
Refer to this comment for more explanation.

Not particularly an answer to the question itself but some thought on the matter.
It's not clear exactly what you're trying to achieve here. You defined a schema that is supposed to contain a list of string. Mongoose correctly does so that the data saved in your schema is consistent with the definition of the schema.
In this case, the list is more of a structural part of the schema. If you have different behaviour, you'd have to handle special case in your code in case the list isn't present. Now, you can safely assume that you schema is always returning a list so fetching some data will always allow you to do:
coolData.field_3.forEach(function(x) {
do_cool_things(x)
})
What you're asking is to make the schema allow inconsistent data being returned from mongodb... In other words, you'd have to do this in order to prevent accessing attributes on undefined:
if (coolData.field_3) {
coolData.field_3.forEach(function(x) {
do_cool_things(x)
})
}
Also, I you were trying to optimize the size of you objects/database, you could fill a bug report so mongoose doesn't define empty values while saving the objects and autofill them with defaults when the field is missing from mongodb. (I could be wrong but did you actually check if the data in mongodb was containing empty values or you were just looking at data coming from mongoose?)

It's because you're not marking the fields as required in your schema definition.
Do this:
let coolSchema = new mongoose.Schema({
field_1 : { type: Number, required: true },
field_2 : { type: String, required: true },
field_3 : { type: [ String ], required: true },
});

Mongoose find/update subdocument

I have the following schemas for the document Folder:
var permissionSchema = new Schema({
role: { type: String },
create_folders: { type: Boolean },
create_contents: { type: Boolean }
});
var folderSchema = new Schema({
name: { type: string },
permissions: [ permissionSchema ]
});
So, for each Page I can have many permissions. In my CMS there's a panel where I list all the folders and their permissions. The admin can edit a single permission and save it.
I could easily save the whole Folder document with its permissions array, where only one permission was modified. But I don't want to save all the document (the real schema has much more fields) so I did this:
savePermission: function (folderId, permission, callback) {
Folder.findOne({ _id: folderId }, function (err, data) {
var perm = _.findWhere(data.permissions, { _id: permission._id });
_.extend(perm, permission);
data.markModified("permissions");
data.save(callback);
});
}
but the problem is that perm is always undefined! I tried to "statically" fetch the permission in this way:
var perm = data.permissions[0];
and it works great, so the problem is that Underscore library is not able to query the permissions array. So I guess that there's a better (and workgin) way to get the subdocument of a fetched document.
Any idea?
P.S.: I solved checking each item in the data.permission array using a "for" loop and checking data.permissions[i]._id == permission._id but I'd like a smarter solution, I know there's one!

So as you note, the default in mongoose is that when you "embed" data in an array like this you get an _id value for each array entry as part of it's own sub-document properties. You can actually use this value in order to determine the index of the item which you intend to update. The MongoDB way of doing this is the positional $ operator variable, which holds the "matched" position in the array:
Folder.findOneAndUpdate(
{ "_id": folderId, "permissions._id": permission._id },
{
"$set": {
"permissions.$": permission
}
},
function(err,doc) {
}
);
That .findOneAndUpdate() method will return the modified document or otherwise you can just use .update() as a method if you don't need the document returned. The main parts are "matching" the element of the array to update and "identifying" that match with the positional $ as mentioned earlier.
Then of course you are using the $set operator so that only the elements you specify are actually sent "over the wire" to the server. You can take this further with "dot notation" and just specify the elements you actually want to update. As in:
Folder.findOneAndUpdate(
{ "_id": folderId, "permissions._id": permission._id },
{
"$set": {
"permissions.$.role": permission.role
}
},
function(err,doc) {
}
);
So this is the flexibility that MongoDB provides, where you can be very "targeted" in how you actually update a document.
What this does do however is "bypass" any logic you might have built into your "mongoose" schema, such as "validation" or other "pre-save hooks". That is because the "optimal" way is a MongoDB "feature" and how it is designed. Mongoose itself tries to be a "convenience" wrapper over this logic. But if you are prepared to take some control yourself, then the updates can be made in the most optimal way.
So where possible to do so, keep your data "embedded" and don't use referenced models. It allows the atomic update of both "parent" and "child" items in simple updates where you don't need to worry about concurrency. Probably is one of the reasons you should have selected MongoDB in the first place.

In order to validate subdocuments when updating in Mongoose, you have to 'load' it as a Schema object, and then Mongoose will automatically trigger validation and hooks.
const userSchema = new mongoose.Schema({
// ...
addresses: [addressSchema],
});
If you have an array of subdocuments, you can fetch the desired one with the id() method provided by Mongoose. Then you can update its fields individually, or if you want to update multiple fields at once then use the set() method.
User.findById(userId)
.then((user) => {
const address = user.addresses.id(addressId); // returns a matching subdocument
address.set(req.body); // updates the address while keeping its schema
// address.zipCode = req.body.zipCode; // individual fields can be set directly
return user.save(); // saves document with subdocuments and triggers validation
})
.then((user) => {
res.send({ user });
})
.catch(e => res.status(400).send(e));
Note that you don't really need the userId to find the User document, you can get it by searching for the one that has an address subdocument that matches addressId as follows:
User.findOne({
'addresses._id': addressId,
})
// .then() ... the same as the example above
Remember that in MongoDB the subdocument is saved only when the parent document is saved.
Read more on the topic on the official documentation.

If you don't want separate collection, just embed the permissionSchema into the folderSchema.
var folderSchema = new Schema({
name: { type: string },
permissions: [ {
role: { type: String },
create_folders: { type: Boolean },
create_contents: { type: Boolean }
} ]
});
If you need separate collections, this is the best approach:
You could have a Permission model:
var mongoose = require('mongoose');
var PermissionSchema = new Schema({
role: { type: String },
create_folders: { type: Boolean },
create_contents: { type: Boolean }
});
module.exports = mongoose.model('Permission', PermissionSchema);
And a Folder model with a reference to the permission document.
You can reference another schema like this:
var mongoose = require('mongoose');
var FolderSchema = new Schema({
name: { type: string },
permissions: [ { type: mongoose.Schema.Types.ObjectId, ref: 'Permission' } ]
});
module.exports = mongoose.model('Folder', FolderSchema);
And then call Folder.findOne().populate('permissions') to ask mongoose to populate the field permissions.
Now, the following:
savePermission: function (folderId, permission, callback) {
Folder.findOne({ _id: folderId }).populate('permissions').exec(function (err, data) {
var perm = _.findWhere(data.permissions, { _id: permission._id });
_.extend(perm, permission);
data.markModified("permissions");
data.save(callback);
});
}
The perm field will not be undefined (if the permission._id is actually in the permissions array), since it's been populated by Mongoose.

just try
let doc = await Folder.findOneAndUpdate(
{ "_id": folderId, "permissions._id": permission._id },
{ "permissions.$": permission},
);