I would expect that most models do not require information about when they were created and updated as a necessary feature of the model. Indeed, the getting started guide doesn't use or mention them. So what is the reasoning behind creating created_at/updated_at fields for models by default?
You may disable them from being created in your migrations if you would like. But to answer your question, you may be surprised how many models tend to have some sort of need to use data from the time stamps in some way, whether thats setting the default scope of that table, using the data to expire certain things, etc... They are included by default because they are useful and convenient to a lot of people, but if you are positive you don't need those feilds, feel free to get rid of them.
A timestamp is added to make it easier for user. A timestamp can be used to understand when what model was created and also to distinguish between different databases
Related
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
I am looking for a way to add a lot of records at ones in ActiveAdmin. To be more specific, I have 2 models: Stores and Programs. Stores have many Programs.
I don't mind adding a Store using standard ActiveAdmin create view. But I would like a faster way to add programs in a spreadsheet-like way. I looked into best_in_place (https://github.com/bernat/best_in_place) but it doesn't do do adding records, just editing them.
Any suggestions? I would really appreciate it.
The short answer is Rails has nothing to help you do this. Rails has a defined convention for editing multiple objects if they belong to another object that can accept nested attributes for a few reasons, the most important of which is that there's a place to aggregate validation, as well as a standard way to differentiate each set of fields (the id). Neither of these are true during creation.
You can, however, manually work around this a couple of ways.
would be to simply write out the forms yourself, and put the logic to loop through them in your controller. This is going to be fragile, and you'll have issues getting validation to work properly, however.
would be to either create a new class that handles this single case, or try and adapt your existing Store class to handle nested attributes. There's a very solid explanation of how to do this here.
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 have been tasked with developing a new retail e-commerce storefront for my current job, and I am considering tackling it with RoR to A) Build a "real" project with my limited Rails knowledge, and B) Give management quick turnaround and feedback (they are wanting to get this done ASAP and their deadlines are rather unrealistic - I'm talking a couple of weeks to go from nothing to working model so they can start to market it with SEO/SEM and, I kid you not, "video blogging" because my boss heard that's the future).
We do have a database structure in place but it's absolutely terrible and was thrown together without rhyme nor reason, so I'm going to largely ignore it and create a new database from scratch; however, I have existing data that I need to load into the application (like I said, it's an e-commerce app and we have the product data). I need to massage this data into a usable format because our supplier provides it to us with cryptic, abbreviated column names and it's highly denormalized, especially in the categories (I've posted a question regarding it before - basically the categories table has six fields, one for each category/subcategory, with some of them being blank if that category doesn't apply).
There are two main issues that are giving me second thoughts:
As I said the data needs to be put into a "proper" database schema; I can't just load it as-is. I have some thoughts as to a good data model for it, but my analysis is not completed yet. There would end up being a large amount of joins tables to link various things together (e.g. products_categories, products_attributes, products_prices) etc and these tables would link products not via an ID but by their SKU (see below).
Everything already has an ID that's generated for it, but anything new I add needs to have one autogenerated; I doubt this will be a problem with any mature RDBMS, but I know Rails likes to generate IDs itself. Also, almost all of the product-related tables are linked by SKUs (and in the data provided by the supplier are actually a composite key consisting of the prefix and stock number, which combined make up the full SKU), not by IDs and I'm not sure if this will be a performance issue (of course, I could always manually create indexes on these columns to speed it up). It does mean that I'll need to break away from the Rails conventions, however.
In short, I think that Rails might be a good choice as far as time-to-market and ease-of-development, but having to work with the existing data content might turn into a pain because the application will need to be developed around that, instead of the "traditional" Rails app, and that factor is giving me major doubts about using Rails. There are also some other issues (having to set up a Linux server, and the fact that the area I live in has very few Rails developers so if I left the company I'd basically be holding them hostage as far as updates/modifications). I'm really unsure as to the best path to proceed.
I would develop the app as if you didn't have the data. Use the ORM and make your database the best it can be, but of course keep in mind what data you have to populate it with (eg: don't make crazy new constraints for things that will leave you going through old data record by record).
When you're done and tested, write an import script that pulls your real data onto your new database.
It's not that different from the conventional design/development model... Apart from you can do your data-input in a semi-automated fashion.
I was in the same situation not too long ago — a crappy PHP app that held ten years worth of all company data.
What I did was simply create a Migration model and added methods to import each resource.
class Migration
def migration_all
self.jobs
end
def self.jobs
...
end
end
The cool thing about this is that you can arrange which order resources are imported as one will likely reference another. I also added methods that directly modified the db schema. One nice trick if you have to keep an existing primary key is to create a field named 'legacy_id', copy over your existing primary key, and when you're done, simply remove the 'id' field, rename the 'legacy_id' field to 'id', then add the primary_key constraint on the new 'id' field.
Don't use the SKU as the unique key for each product - use the standard Rails incremented id.
SKU could change as it may be misentered, etc and that would make it a nightmare to change all of the references from other tables. Put your current id in a sku column, index it and update the references in your other tables to the Rails ids.
You'd be able to do Product.find_by_sku(params[:sku]) in your controllers, set up a /products/:sku route, etc. I don't see what you'd gain (other than a headache) by using your non generated ids as the database primary keys.
I'd also suggest running your old data through your app's validations to make sure you are not loading up a bunch of inconsistencies and erros. It will help your app run smoothly and highlight existing data errors at a point where you can fix them.
Don't assume the existing data is valid just because it is already there.
I'm working on an "analytics" page for a rails app. The analytics page does not persist any data of its own (it's very primitive at this point) but does utilize metrics that I'm grabbing from the DB (via the aggregate expressions built into ActiveRecord). Aside from gathering and presenting the metrics the only other requirement I have is to allow the user to provide a date range to filter the data. Up to this point I have been using instance variables and the like to store the metrics information...as the number of metrics grow along with the need to manage the start and end filter dates I begin thinking that I should put this data into its own model. If I do move all of my "data" into a model should I just use a plain object with attr_accessors or is there a more appropriate base class I could use for non-persistent data? I'm familiar enough with a MVC architecture to know that my controller is getting to bloated but no familiar enough with rails to determine how I should organize my data/logic in this case.
Any insight would be greatly appreciated!
It sounds like you could use a Rails non active-record model. There's a good Railscast about that :
http://railscasts.com/episodes/121-non-active-record-model
Hope that helps,
You're on the right track here. Many applications have classes inside app/models that do not inherit from ActiveRecord::Base. Any time you find yourself managing lots of arbitrary variables inside controller actions, it's a good place to consider abstracting that data into a non-persistent model.
This is an area that's not well documented at present, probably because the ActiveRecord stuff is sexier?
I went through the same process, finding my controller actions were becoming uncomfortably large and full of logic as I strove to construct my derived data from ActiveRecord-based models, which in turn started to acquire additional responsibilities that they didn't really want or need.
Once I got the same advice you're getting now the whole thing simplified magnificently.