Rails 3.2.5 was released today. I tried to upgrade my application from 3.2.3 to 3.2.5, but I encountered uniqueness validation failure problem.
This problem reported at #5853. I read the discussion of this issue. I'm about understood about this problem. I also read the commit, but, unfortunately, I coundn't understand why this commit effects a query that checking for uniqueness.
My workaround is using
allow_blank: true option at uniqueness validation. I'm afraid that this workaround is proper or not.
Thank you for this stackoverflow topic about describing how
allow_blank option works.