I'm trying to build some sort of a social media app using node.js and mongoDB.
I have a mongoose schema for 'User', and when i render some user page on the app, it needs to also show all of his posts/images/list of friends and etc...
right now i have a mongoose schema for 'UserPost' and also for 'Image', and when i save an image for example, it has a field which keeps the username of the user who uploaded it, so when i render the user page it finds all of his images.
It is the first time i'm dealing with db's so i heard that i might have to use a reference data instead of embedded data.
can someone explain to how should i organize the data model for my app?
It's very handful to use mongoose population for handling db references
Define your schemas like these:
var mongoose = require('mongoose')
, Schema = mongoose.Schema
var userSchema = Schema({
name : String,
posts : [{ type: Schema.Types.ObjectId, ref: 'Post' }]
});
var postSchema = Schema({
title : String,
images : [{ url: String, filename: String }]
});
var User = mongoose.model('User', userSchema);
var Post = mongoose.model('Post', postSchema);
According to mongoose population docs, you can get all your data:
User.findOne().populate('posts').exec(function(error, user) {
console.log(user.posts) // there are populated posts objects inside array
})
Not sure, is it a good idea to use separated collection for image uploads, it's simpier to embed it inside Post (or User), but you may always add { type: Schema.Types.ObjectId, ref: 'Image' } for images
MongoDB is a NoSql DBMS. It means, you schould not create references between data fields, because the performance coming from NoSql will be killed: https://en.wikipedia.org/wiki/NoSQL
But, if you are really thinking you need references, checkout this: http://docs.mongodb.org/master/reference/database-references/
You can reference to a data document in the mongoDB by the _id ("Page"=>"createdBy" = "User"=>"_id" for example).
It depends of what kind of data you want to embed. MongoDB has object size limits according to the storage engine you use. Thus you should predict or estimate the the size of the object you want to embed.
See more about limits here: http://docs.mongodb.org/master/reference/limits/
See more about references here: http://docs.mongodb.org/master/reference/database-references/
Related
i am trying to create group chat system using mongoDB but in mongoose object type is supported how can i create model like this(inserting image below)? and also query this data? i've tried to create schema but didnt work
sample of model (dummy)
const chatSchema = new mongoose.Schema({ users: Array, texts:[{ user: String, text: String, time: Date, }] });
Try this schema. Users who will be in group chat will added in users field. The text will have author(user), text(text) and date(time).
Trying to design a Form Entry web app and i've rarely used MongoDB before.
Wondering if this is the best practice for storing form (document) data inside a collection.
const mongoose = require('mongoose');
// Create Schema and Model
const documentSchema = mongoose.Schema({
nps: [{ // New Promotion Submission
documentId: Number,
orgid: Number,
documentFields: [{ // Form Fields
id: Number,
dateTimeSubmitted: Date,
title: String,
productDescription: String,
productUnitSize: Number,
productCartonQty: Number
}]
}]
})
const documents = mongoose.model('documents', documentSchema);
module.exports = documents;
This is absolutely fine design, couple of things to look at:
Make sure you introduce validation on your schema fields, mirror the same validation pattern on the frontend form fields also.
Be consistent with your naming: if you use camelCase in documentId make sure to also origId
Convention says you name a model in singular form, i.e. "Document" not "documents".
If you're going to re-use the documentFields schema anywhere else in other models, make sure to store it as a separate schema and import as needed.
In my application I have a User Collection. Many of my other collections have an Author (an author contains ONLY the user._id and the user.name), for example my Post Collection. Since I normally only need the _id and the name to display e.g. my posts on the UI.
This works fine, and seems like a good approach, since now everytime I deal with posts I don`t have to load the whole user Object from the database - I can only load my post.author.userId/post.author.name.
Now my problem: A user changes his or her name. Obviously all my Author Objects scattered around in my database still have the old author.
Questions:
is my approuch solid, or should I only reference the userId everywhere I need it?
If I'd go for this solution I'd remove my Author Model and would need to make a User database call everytime I want to display the current Users`s name.
If I leave my Author as is, what would be a good way to implement a solution for situations like the user.name change?
I could write a service which checks every model which has Authors of the current user._id and updates them of course, but this sounds very tedious. Although I'm not sure there's a better solution.
Any pro tipps on how I should deal with problems like this in the future?
Yes, sometime database are good to recorded at modular style. But You shouldn't do separating collection for user/author such as
At that time if you use mongoose as driver you can use populate to get user schema data.
Example, I modeling user, author, post that.
var UserSchema = new mongoose.Schema({
type: { type: String, default: "user", enum: ["user", "author"], required: true },
name: { type: String },
// Author specific values
joinedAt: { type: Date }
});
var User = mongoose.model("User", UserSchema);
var PostSchema = new mongoose.Schema({
author: { type: mongoose.Scheam.Types.ObjectId, ref: "User" },
content: { type: String }
});
var Post = mongoose.model("Post", PostSchema);
In this style, Post are separated model and have to save like that. Something like if you want to query a post including author's name, you can use populate at mongoose.
Post.findOne().populate("author").exce(function(err, post) {
if(err)
// do error handling
if(post){
console.log(post.author.type) // author
}
});
One solution is save only id in Author collection, using Ref on the User collection, and populate each time to get user's name from the User collection.
var User = {
name: String,
//other fields
}
var Author = {
userId: {
type: String,
ref: "User"
}
}
Another solution is when updating name in User collection, update all names in Author collection.
I think first solution will be better.
I have a product model, it has many fields. Some of them are dedicated to front-end application, ex:
var GameSchema = new Schema({
likes: {
type: [{
type: Schema.ObjectId,
ref: 'User'
}]
},
likes_count: {
type: Number
}
});
I don't need likes_count field in Db, but controller returns only fields that model have, so i add likes_count field to db model
exports.some_method = function(req, res){
var game = req.game;
game.likes_count = game.likes.length
res.json(game);
}
Is there a way to add extra data to db model when sending request without having them in db?
Please note, problem is not in likes_count field itself, i have different models, but the point is having extra data on db model.
For those who still interested, mongo_db mongoose(#robertklep) has virtual fields, that can be used as temporary data field, that doesn't exist in database
GameSchema.virtual('likes_count').get(function () {
return this.likes.length;
});
And note, your model must have permission for virtuals like this, so that you can use it inside controllers
var UserSchema = new Schema({
username: {
type: String
}
}, {
toObject: { virtuals: true },
toJSON: { virtuals: true }
});
"Is there a way to add extra data to db model when sending request without having them in db?"
You may be able to do so from a driver's perspective and I'll leave that to those who know abut such things. Check out the following post Mapping a private backing field with MongoDB C#.
I can answer from the MongoDB engine & server processes aspect; if you are looking for a way to flag a field in the JSON document to make it private when sent to the actual CRUD request the MongoDB engine receives then no.
However, you could intercept the JSON prior to the actual CRUD request and transform it. The JSON you are generating is not inserted until you execute one of the INSERT, Modify, or Update statements. The pseudo steps would be to generate a JSON document, send it to a broker\wrapper etc in front of MongoDB, and then transform it by removing the fields in question, then send the new object as a CRUD request to the MongoDB engine.
I have the following schema in my Node js / express app where each warehouse can optionally have a parent warehouse. I wrote the code to save warehouse, but can't figure out how to retrieve any warehouse (which has a parent) and get its parent warehouse name...so was wondering if there is any way I can do that in one call? Thanks
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var warehouseSchema = new Schema({
name: { type: String, required: true },
parentID: { type: String, ref: 'Warehouse' }
});
module.exports = mongoose.model('Warehouse', warehouseSchema);
Just as Philipp said, you can't do it with a single MongoDB auery.
But you can do it with single Mongoose command, using its Query Population feature:
Warehouse.findById(warehouse_id).populate('parentID').exec(function(err, doc) {
if (err) {
// something get wrong
} else {
// doc.parentID is a parrent Warehouse here
}
})
Internally, Mongoose will make two separate queries to MongoDB (one for the child document, and then another for its parent), bu for you it'll look like a single command.
MongoDB can't do JOINs on the database. As long as the parent is a reference in the warehouse object, you can not retrieve both with one query. You first have to query the warehouse(s) and then resolve the reference(s) with a second query.
To avoid the second query you might want to look into embedding the required information about the parent-document in the child-document. Duplicate information in MongoDB isn't as abnormal as in a relational database.