At the moment ’m building a web app using Ruby on Rails. I try to get my head around the data model and database part. To make it easy to understand I’ll use IFTTT as an analogy:
In the app, the user can add different recipes, for example:
Facebook — Twitter
Weather — Send email
You name it...
Of course every recipe has its own fields and options. So the user can choose multiple recipes from the library and set options to every recipe. The library of recipes is defined in code.
I have a few questions regarding this setup and would be happy if I could get some directions:
Is it smart to serialize the options of a recipe into a single database field? Every recipe has different fields and I don‘t want a database table for every recipe type.
Or is it better to create a ‘key-value’ table with all the options of all the recipes?
How to handle validation? Can Virtus come in handy?
Is a NoSQL database a good fit for these kinds of applications?
Are there best practices for these kinds of applications/data models? Any help is welcome.
Thanks!
Rens
Not sure if SO is the best place for really general questions like this but I'll take a swing
1 && 2) Personally I'd give the recipe table an action_taken field, probably as a string, and fields for all the available, resulting actions as booleans. Then the only thing you really need to be careful of is making sure the action_taken field remains uniform
3) ActiveRecord has a pretty fleshed out validation suite built in. You can validate based on presence, uniqueness, inclusion in a set of elements, etc. You can also extra validations on the database if you feel like being extra safe
4) I would use PostgreSQL, seems to be the community standard so probably the easiest to get support with if you need it
Hope this helps
Related
Ive been working on an app for table-top RPG games that is meant to be universal for all games. Currently the way im doing this is with a combination of a specific tables for each game (with columns for each attribute) and also making universal tables for things like equipment, attacks, etc. This is working but the tables are getting a little complex and hard to handle with multiple nested relationships.
I stumbled upon rails ActiveRecord Store and think this is a better option as I could serialize the attributes into a single column and the views would handle saving and loading the right variables from the serialized column.
Im wondering if I am missing something or is this a valid option?
It sounds like a great option. Write lots of tests. Try it out.
There's nothing wrong with hundreds of tables. It can help in terms of organization to separate models into namespaces.
First time posting in Stack Overflow, hope I'm doing this right.
I'm writing an app with Ruby on Rails right now. Without disclosing too much, the premise is that we have organizations and normal users. Organizations have events, which require users to answer a questionnaire before participating.
I'm pretty sure about these models / relationships that I will be using (this isn't really that important/pertinent to my question i think, but just wanted to give background):
organization (one to many) events
event (one to one) quesitonnaire)
questionnaire (one to many) users
(specific) response (one to one) user
The part I have a question about is how to implement the questionnaire. I want to give the ability to Organizations to essentially write / build their own forms. I'd like to stay away from them using code if that's possible (ie any DSL and whatnot).
I suppose the easiest way to do this is to give them a set number of text-area responses, so that I can consistently store the data and don't have to hassle around with how to configure storing this data (for example, maybe each event can only have exactly 5 responses to be filled in by textfield response by the user).
My ideal would be for the organization to be able to dynamically generate the forms on their own - maybe one questionnaire will have 1 text input, followed by 3 multiple choices, and maybe 2 short answers at the end; another one may have 5 multiple choices, and 1 short answer; yet another questionnaire might only have 1 text input...you get the idea.
So I see two parts of this problem - the first is the user interface for the organization to create the questionnaire. i'm imagining this wouldn't be terribly hard - ask them how many of each response type (MC, short answer) they would like to put into the form, give them the ability to rearrange them, etc.
The second part of the problem (what I'm more concenred about) is how to store/access this data. I'm guessing there's no dynamic-attribute sort of deal in ruby - storing some field with an unspecified number of parts and whatnot. i suppose i could make them all individual models (ie a question_response model, with :question, :response_type, :response, etc), but I'm fairly certain that's probably inefficient.
My initial guess is probably to serialize the data / use json; I worked briefly with Drupal 6 and this seems to be the way they did it. I was wondering if anyone else had any experience / suggestions though? I'm pretty new to Ruby so I was wondering if there's a gem out there or something that would help with what I'm trying to do.
Thanks!
You might want to look at the Surveyor gem
http://vimeo.com/7051279
*slightly old how-to video
https://github.com/breakpointer/surveyor
Surveyor does come with it's own DSL which is relatively easy to use (although can be abit restrictive at times). The data is saved as a set of question - answer values, so there is no actual specific model (beyond Surveys -> Questions (question_groups) -> Answers).
Originally I did look at having people submit their own Surveyor DSL specs - which would then be used to generate the actual survey via a Rake command.
I think if you need to build a dynamic model (and save the data) it is possible, although I am not not sure if you'll be able to get the Rake tasks to run to build the actual tables in a dynamic way due to permission restrictions.
Have a look at http://ruby-metaprogramming.rubylearning.com/ and Metaprogramming Ruby: Program Like the Ruby Pros by Paolo Perrotta, for some starters.
Considering models in Rails:
class Organization < ActiveRecord::Base
belongs_to :OrgType
end
Does it bother you that models in Rails don't include the fields that made the entity?
I know this is done for DRY's sake but you have to check the data base tables schema every time you want to check model's fields.
If you prefer a declarative style of ORM model, you might want to check out DataMapper or Sequel, both of which are easy to plug in to Rails 3.
Not annoying for me... ever since I started using the annotate-models gem to automatically add comments to the top of my model files, listing the fields associated with that model.
I was listening to a podcast a few months ago where the guy hosting the cast and the guest were advocating that Rails should take this path, and do away with migrations. The guy kept repeating "migrations must die", suggesting there be a way to specify your schema on the model instead.
I cannot disagree more, and I hope Rails never takes this path. Not only is it not DRY, but I like the fact that Rails encourages you to be aware of your own databases schema and structure.
In addition, there would be no way to keep a history of your schema if models were what controlled it, without having them be extremely cluttered. Migrations are essentially version control for your database that evolves with your application...and I wouldn't want to not have that.
Let's assume that OrgType has a field called position. This is common when you want to present a select list to the users who will be choosing a type. It's highly unlikely that your Organization will ever care about this field. Now extrapolate this to other related models with fields that other models don't care about, and add in the fact that if you ever wanted to change one of these fields you'd then have to hunt down each declaration of them, not just each place where they are used.
It's a mess.
Open up your db tool and look at your fields when you want to know what they are. Keep your models clean and readable. If you see code like this:
organization.org_type.name
It's pretty obvious that OrgType has a name field, without having to look it up, and without having to wade through configuration clutter in each model.
I'm learning Rails, and the target of my experiments is to realize something similar to Zoho Creator, Flexlist or Mytaskhelper, i.e. an app where the user can create his own database schema and views. What's the best strategy to pursue this?
I saw something about the Entity-Attribute-Value (EAV) but I'm not sure whether it's the best strategy or if there is some support in Rails for it.
If there was any tutorial in Rails about a similar project it would be great.
Probably it's not the easiest star for learning a new language and framework, but it would be something I really plan to do since a long time.
Your best bet will be MongoDB. It is easy to learn (because the query language is JavaScript) and it provides a schema-less data store. I would create a document for each form that defines the structure of the form. Then, whenever a user submits the data, you can put the data into a generic structure and store it in a collection based on the name of the form. In MongoDB collections are like tables, but you can create them on the fly. You can also create indexes on the fly to speed searches.
The problem you are trying to solve is one of the primary use cases for document oriented databases which MongoDB is. There are several other document oriented databases out there, but in my opinion MongoDB has the best API at the moment.
Give the MongoDB Ruby tutorial a read and I am sure you will want to give it a try.
Do NOT use a relational database to do this. Creating tables on the fly will be miserable and is a security hazard, not just for your system, but for the data of your users as well. You can avoid creating tables on the fly by creating a complex schema that tracks the form structures and each field type would require its own table. Rails makes this less painful with polymorphic associations, but it definitely is not pretty.
I think it's not exactly what you want, but this http://github.com/LeonB/has_magic_columns_fork but apparently this does something similar and you may get some idea to get started.
Using a document store like mongodb or couchdb would be the best way forward, as they are schema-less.
It should be possible to generate database tables by sending DDL-statements directly to the server or by dynamical generating a migration. Then you can generate the corresponding ActiveRecord models using Class.new(ActiveRecord::Base) do ... end. In principle this should work, but it has to be done with some care. But this definitely no job for a beginner.
A second solution could be to use MongoMapper and MongoDB. My idea is to use a collection to store the rows of your table and since MongoDB is schema less you can simply add attributes.
Using EntryAttributeValue allows you to store any schema data in a set amount of tables, however the performance implications and maintenance issues this creates may very well not be worth it.
Alternately you could store your data in XML and generate an XML schema to validate against.
All "generic" solutions will have issues with foreign keys or other constraints, uless you do all of that validation in memory before storage.
Scenario: I have a users table in my application. I also have two subclasses of users, lets say contributors and viewers. Each user group must have an entirely different set of attributes but they both share certain user properties (login, password, name).
What is the best way to implement this using Ruby on Rails?
I think single table inheritance would leave me with too many null fields.
I think linking three tables (users, viewers, contributors) would work fine, but then when wanting to edit any information i have to do: #user.viewer, while i would love to be able to just do #viewer.
Any ideas of the best solution?
I would probably go with the three tables approach. Data integrity is king over code cleanliness.
If you want to make it look neater, put virtual attributes on the Viewer and Contributor models that make it look like the User attributes are local. You can make it a module and include it in both Viewer and Contributor models.
You can also set up an :include => :user on the default finders so that you don't get an extra query when using those fields.
I'm extremely caffeinated right now, so comment back if that doesn't make sense :)
don't compromise the database schema, make it fit best. I like the three table method. If you do the database bad, the application will have very hard to fix issues later, run slow, etc.