Possible to specify unique index with NULLs allowed in Rails/ActiveRecord?

Question

I want to specify a unique index on a column, but I also need to allow NULL values (multiple records can have NULL values). When testing with PostgreSQ

Answer 1

Your migration will work and will allow multiple null values (for the most database engines).

But your validation for the user class should look like below.

validates :email, uniqueness: true, allow_nil: true