Using OR query in rails devise omniauth for multiple users - mysql

Question

I would like to be able to sign a user in with omniauth and devise from multiple accounts. In my user model I have set the twitter user's uid to equal uid and the provider = twitter. For the user's Facebook uid would equal uid2 and provider2 = Facebook.
I currently use this query to either sign a user in if auth.slice = provider, uid or register them if not.
where(auth.slice(:provider, :uid)).first_or_create do |user|
However now I want to run something similar to:
where(auth.slice(:provider, :uid || :provider2, :uid2 )).first_or_create do |user|
I.e where auth.slice = :provider, :uid OR :provider2, :uid2
essentially I need to be able to run an OR query.
Any help will be much appreciated.

Answer 1

Firstly, the auth.slice(:provider, :uid) is referring to keys in the auth hash from omniauth but provider2 and uid2 are only columns in your db, so they can't be used in the slice in any way as they aren't keys in the auth hash (though I realise that was only an illustration/example of yours). You'd need to extract the hash entries and compare with provider and uid columns and provider2 and uid2 columns separately. Also, to do an OR, you could either use the old-school approach of SQL snippets:
Users.where('(provider = :provider AND uid = :uid) OR (provider2 = :provider AND uid2 = :uid', {provider: auth[:provider], uid: auth[:uid]})
or use AREL, as the bog-standard where can't handle OR. The AREL readme is quite readable https://github.com/rails/arel -- you could do something like:
prov = auth[:provider]
uid = auth[:uid]
users = Arel::Table.new(:users)
users.where(users[:provider].eq(prov).and(users[:uid].eq(uid))).or(users[:provider2].eq(prov).and(users[:uid2].eq(uid)))).project(Arel.sql('*'))
However, I think the long-windedness of both of these highlights that the approach of adding sets of columns per-provider makes things a bit of a pain and it would get worse if, for example, you add login via google, yahoo or whatever, resulting in provider3, uid3 and provider4, uid4... An alternative is to have another model/table which stores these different identities, with a has_many relationship with users. For example:
class User < ActiveRecord::Base
has_many :identities
...
end
class Identity < ActiveRecord::Base
belongs_to :user
...
end
Then you could look up by identities using a simple
Identity.where(auth.slice(:provider, :uid))
like you do now, and not have to worry about adding new providers. They would just result in another row in the identies table related to the relevant user. You could join with users or however you want to handle getting the associated user.