Altering the primary key in Rails to be a string

Question

So I've got two models, State and Acquisition. State has_many Acquisitions. I felt like an autoincrementing integer primary key for 51 records was rather silly. So I altered the model for the State to be the PK (State being the two letter abbreviation; I'm not storing the actual state name anywhere:

class State < ActiveRecord::Base  
    self.primary_key = "state"  
    has_many :acquisition_histories  
end

The problem is when I created my Acquisition model, it created the foreign key column state_id as an integer. More specifically, the script/generated migration did:

class CreateAcquisitions < ActiveRecord::Migration  
    def self.up  
        create_table :acquisitions do |t|  
          t.date :date  
          t.string :category  
          t.text :notes  
          t.references :state  
          t.timestamps  
    end
end

I'm assuming that t.references data type sets it to int. The problem is my create method on my Acquisition class is trying to put a state abbreviation into the state_id field on the table acquisitions (and yes, it's called state_id on the database, even though it says :state in the migration script). The method doesn't fail, but it does put a 0 in the state_id field and the records go into the ether.

Answer 1

You want to follow the Rails conventions. The extra primary key is not an issue in any way. Just use it.

Answer 2

I had a bit of experience with string used as primary keys and it's a pain in the ***. Remember that by default if you want to pass an object with the default :controller/:action/:id pattern, the :id will be a string and this will probably lead to routing problems if some ids get weirdly formatted ;)

Answer 3

I'm working on a project that uses UUIDs as primary keys, and honestly, I don't recommend it unless you're certain you absolutely need it. There are a ton of Rails plugins out there that will not work unmodified with a database that uses strings as primary keys.

Answer 4

I really need a long as a primary key, because my real primary key...is bigger than a breadbox. Is there really no sensible way to work around atleast having a non-default type?

Answer 5

Proper relational database theory in Rails? oh no no... that's bad. You will burn in the fiery pits of RoR hell!