appending to rake db:seed in rails and running it without duplicating data

Question

Rake db:seed populates your db with default database values for an app right? So what if you already have a seed and you need to add to it(you add a new feature that requires the seed). In my experience, when I ran rake db:seed again, it added the existing content already so existing content became double.

What I need is to add some seeds and when ran, it should just add the newest ones, and ignore the existing seeds. How do I go about with this? (the dirty, noob way I usually do it is to truncate my whole db then run seed again, but that's not very smart to do in production, right?)

Answer 1

A cleaner way to do this is by using find_or_create_by, as follows:

User.find_or_create_by_username_and_role(
  :username => "admin",
  :role => "admin",
  :email => "[email protected]")

Here are the possible outcomes:

1. A record exists with username "admin" and role "admin". This record will NOT be updated with the new e-mail if it already exists, but it will also NOT be doubled.
2. A record does not exist with username "admin" and role "admin". The above record will be created.
3. Note that if only one of the username/role criteria are satisfied, it will create the above record. Use the right criteria to ensure you aren't duplicating something you want to remain unique.