I'm trying to figure out how to create a very complex data model in Firebase database. The whole app is like a network. There are users with profiles, there are posts, comments, likes, reblogs, etc.
Now, my goal is to outline my database before I start coding it all. But here's the thing - I know that the database should be (or it's advisable to be) as flat as possible, structure should be based on the views (UIViewControllers) and it should use referencing.
The thing is that it gets very complex, especially because there's not just 1 type of a post but 9 of them. Meaning - normal text post, video post, audio post, poll post, etc. And I'm not sure how to structure those, because each post would also have comments, likes, reblogs etc. Currently, I have a global Posts object that stores ALL types of posts, but based on the post type the user has created, it's stored into each specific post type. Then I reference that in the user object so I can easily pull them out and sort them by type. But I'm not convinced this is the right way to do it or if there's a better way. I'm starting to see some nesting and that's why I'm not sure.
Here's a screenshot of the database structure (it's easier to illustrate it that way):
Related
I am creating a new application that allow the users to either create content in the local application database or directly on Facebook.
Imagine the user have a CRUD interface for a Post. I have a created a model for Post that sub classes ActiveRecord::Base. Objects of this class has methods for saving the post to the local database.
However, the user is also able to "tick" and option in my application that says "connect to Facebook". When it is checked the content will not be stored in my local database but it will go directly to Facebook Graph API.
The service layer and controller layer is not aware of where the data actually goes. At least this is my idea.
My question is if I can use the same Post class for both local data and Facebook data? Some of the methods in the Post class would not make sense when the post object contains data from Facebook; such as the save method.
Does that design seem stupid? Should I create another Post class that is just a normal Ruby class without sub classing ActiveRecord::Base? Or are there other better ways?
When designing a class you should make it as lean as possible. A good way to look at it is counting the nouns and verbs that are included in your model. A post can be saved or deleted, but if your save and delete start having logic related to Facebook it's a good sign that this should belong to a different class altogether.
One more note related to Facebook: the new guidelines don't allow posting 'pre-written' posts for a user. Meaning that you won't be able to make a post to a users wall without prompting him with Facebook either way.
I don't see any problems with having Post < ActiveRecord::Base - that is the standard Rails way and it does look like you should implement the standard ways of storing data to your DB and look into the Facebook posting from another angle.
There are some definite problems with that approach - the first is that you will end up with alot of tight couplings to the Facebook API. I have had tons of grief from the FB API's changing without warning or not working as documented.
Another issue is performance - loading data from FB is often painfully slow even compared to reading from a DB across the wire. It is also prone to outrages (at least in my experience).
I would definitely use "proxy objects" which are stored in your database and regularly hydrated from Facebook instead.
I have already read Rails - How do I temporarily store a rails model instance? and similar questions but I cannot find a successful answer.
Imagine I have the model Customer, which may contain a huge amount of information attached (simple attributes, data in other tables through has_many relation, etc...). I want the application's user to access all data in a single page with a single Save button on it. As the user makes changes in the data (i.e. he changes simple attributes, adds or deletes has_many items,...) I want the application to update the model, but without committing changes to the database. Only when the user clicks on Save, the model must be committed.
For achieving this I need the model to be kept by Rails between HTTP requests. Furthermore, two different users may be changing the model's data at the same time, so these temporary instances should be bound to the Rails session.
Is there any way to achieve this? Is it actually a good idea? And, if not, how can one design a web application in which changes in a model cannot be retained in the browser but in the server until the user wants to commit them?
EDIT
Based on user smallbutton.com's proposal, I wonder if serializing the model instance to a temporary file (whose path would be stored in the session hash), and then reloading it each time a new request arrives, would do the trick. Would it work in all cases? Is there any piece of information that would be lost during serialization/deserialization?
As HTTP requests are stateless you need some kind of storeage between requests. The session is the easiest way to store data between requests. As for you the session will not be enough because you need it to be accessed by multiple users.
I see two ways to achive your goal:
1) Get some fast external data storage like a key-value server (redis, or anything you prefer http://nosql-database.org/) where you put your objects via serializing/deserializing (eg. JSON).
This may be fast depending on your design choices and data model but this is the harder approach.
2) Just store your Objects in the DB as you would regularly do and get them versioned: (https://github.com/airblade/paper_trail). Then you can just store a timestamp when people hit the save-button and you can always go back to this state. This would be the easier approach i guess but may be a bit slower depending on the size of your data model changes ( but I think it'll do )
EDIT: If you need real-time collaboration between users you should probably have a look at something like Firebase
EDIT2: Anwer to your second question, whether you can put the data into a file:
Sure you can do that. But you would need some kind of locking to prevent data loss if more than one person is editing. You will need that aswell if you go for 1) but tools like redis already include locks to achive your goal (eg. redis-semaphore). Depending on your data you may need to build some logic for merging different changes of different users.
3) Another aproach that came to my mind would be doing all editing with Javascript and save it in one db-transaction. This would go well with synchronization tools like firebase (or your own synchronization via Rails streaming API)
I have some data that needs to be loaded from the server (backend). For example, let's just say I have an entities of user and event. The relationship between them is many-to-many (user can attend many events and event can have many attendees). All the data is stored remotely on backend and locally in Core Data. When I download data from backend I convert it into NSManagedObjects and store it in NSManagedObjectContext. Everything's very simple, but...
When I download a list of events I want to know, how many attendees this event has. But I cannot download a list of users in the same request, because it's totally overkill. What I need is to download, let's say, a list of users' unique ids so that I can have two things: total number of attendees and means to download detailed data of concrete users (via unique id). Or there's another example: I need to know total number of attendees and download a limited set of them, so I can create some entities in CoreData, but not all of them.
So the main question is how am I supposed to store such information in my CoreData? Meaning I need to know that for some entity there are some related entities in relationship that are not actually currently present in CoreData, but I know how many of them there should be. The first thing that came in my mind is to have a attribute called something like usersCount in my event entity, but that seems to be kind of dirty. What is the best practice for such situation?
Please comment if the question is not clear enough so I can maybe add some more specifics.
When you download an event with a list of corresponding user ids, then you can create
the Event object and also the related User objects, but you fill only the "userId"
attribute in the user object.
Later, when you download the complete user info, you update the existing (incomplete) objects
or create new user objects. Implementing Find-or-Create Efficiently in the "Core Data Programming Guide"
describes a pattern that might be useful.
So the idea is to create Core Data objects with incomplete information first and update the
objects with detailed information later. The advantage is that you can set up all relationships immediatly, and e.g. counting related users works even if the user information
is yet incomplete.
There is nothing dirty about having an attribute to store the count, especially if those entities are retrieved and paged via separate requests.
I have an application that has different data sets depending on which company the user has currently selected (dropdown box on sidebar currently used to set a session variable).
My client has expressed a desire to have the ability to work on multiple different data sets from a single browser simultaneously. Hence, sessions no longer cut it.
Googling seems to imply get or post data along with every request is the way, which was my first guess. Is there a better/easier/rails way to achieve this?
You have a few options here, but as you point out, the session system won't work for you since it is global across all instances of the same browser.
The standard approach is to add something to the URL that identifies the context in which to execute. This could be as simple as a prefix like /companyx/users instead of /users where you're fetching the company slug and using that as a scope. Generally you do this by having a controller base class that does this work for you, then inherit from that for all other controllers that will be affected the same way.
Another approach is to move the company identifying component from the URL to the host name. This is common amongst software-as-a-service providers because it makes sharding your application much easier. Instead of myapp.com/companyx/users you'd have companyx.myapp.com/users. This has the advantage of preserving the existing URL structure, and when you have large amounts of data, you can partition your app by customer into different databases without a lot of headache.
The answer you found with tagging all the URLs using a GET token or a POST field is not going to work very well. For one, it's messy, and secondly, a site with every link being a POST is very annoying to work with as it makes navigating with the back-button or forcing a reload troublesome. The reason it has seen use is because out of the box PHP and ASP do not have support routes, so people have had to make do.
You can create a temporary database table, or use a key-value database and store all data you need in it. The uniq key can be used as a window id. Furthermore, you have to add this window id to each link. So you can receive the corresponding data for each browser tab out of the database and store it in the session, object,...
If you have an object, lets say #data, you can store it in the database using Marshal.dump and get it back with Marshal.load.
I am using embedded documents in MongoDB for a Rails 3 app. I like that I can use embedded documents and the values are all returned with one query and there is less load on the database server. But what happens if I want my users to be able to update properties that really should be shared across documents. Is this sort of operation feasible with MongoDB or would I be better off using normal id based relations? If ID based relations are the way to go would it affect performance to a great degree?
If you need to know anything else about the application or data I would be happy to let you know what I am working with.
Document that has many properties that all documents share.
Person
name: string
description: string
Document that wants to use these properties:
Post
(references many people)
body: string
This all depends on what are you going to do with your Person model later. I know of at least one working example (blog using MongoDB) where its developer keeps user data inside comments they make and uses one collection for the entire blog. Well, ok, he uses second one for his "tag cloud" :) He just doesn't need to keep centralized list of all commenters, he doesn't care. His blog contains consolidated data from all his previous sites/blogs?, almost 6000 posts total. Posts contain comments, comments contain users, users have emails, he got "subscribe to comments" option for every user who comments some post, authorization is handled by the external OpenID service aggregator (Loginza), he keeps user email got from Loginza response and their "login token" in their cookies. So the functionality is pretty good.
So, the real question is - what are you going to do with your Users later? If really feel like you need a separate collection (you're going to let users have centralized control panels, have site-based registration, you're going to make user-centristic features and so on), make it separate. If not - keep it simple and have fun :)
It depends on what user info you want to share acrross documents. Lets say if you have user and user have emails. Does not make sence to move emails into separate collection since will be not more that 10, 20, 100 emails per user. But if user say have some big related information that always growing, like blog posts then make sence to move it into separate collection.
So answer depend on user document structure. If you show your user document structure and what you planning to move into separate collection i will help you make decision.