validates_uniqueness_of - how did I get two users?

I have the following in my user model:

  validates_uniqueness_of :login, :email, :case_sensitive => false

yet somehow I ended up with two users with the same email. Does this line mean that the COMBINATION is unique (I didn't think it did).

Should I have this instead:

validates_uniqueness_of :login, :case_sensitive => false validates_uniqueness_of :email, :case_sensitive => false

Any ideas?

No, it doesn't mean that the combination is unique, it means that :login and :email are going to be unique.

There are two possible reasons, the user was added manually at the database (which is bad, as the database should have a unique index at both columns) or you got into a racing condition, where the two selects hit the database at the same time and thus both returned false.

Best thing to do is to improve you database schema by creating some unique indexes that reflect your validations.

The odd thing is that the users were created through the website two months apart!

In ActiveRecord::Base, the save method takes a flag called perform_validation, which you can set to false. Check your controller code to make sure someone didn't decide to skip the validations somewhere.