How do I reverse a Postgresql unique index constraint in a rails migration?

Question

I created a unique index on my model like so:

add_index(:courses, :name, unique: true)

I no longer require the name to be unique. I think I have the same problem as this person , so I worked through those suggestions to no avail.

I receive errors like "ActiveRecord::RecordNotUnique: PG::UniqueViolation: ERROR: duplicate key value violates unique constraint "index_courses_on_name" when I try to add a record with the same name.

To remove the unique constraint I've tried:

1. remove_index :courses, :name

   (migration succeeds, but later I get the same error suggesting there is still a uniqueness constraint)

2. execute "ALTER TABLE courses DROP CONSTRAINT unique_index_courses_on_name"
3. execute "ALTER TABLE courses DROP CONSTRAINT index_courses_on_name"
4. execute "ALTER TABLE courses DROP CONSTRAINT unique_name"
5. execute "ALTER TABLE courses DROP CONSTRAINT name"
6. execute "ALTER TABLE courses DROP INDEX index_courses_on_name"
7. execute "ALTER TABLE courses DROP INDEX courses_on_name"
8. execute "DROP INDEX unique_courses_name"

(PG::UndefinedObject: ERROR: index "unique_courses_name" does not exist)

9. execute "ALTER TABLE courses disable CONSTRAINT unique_courses_name"

(PG::SyntaxError: ERROR: syntax error at or near "CONSTRAINT" LINE 1: ALTER TABLE courses disable CONSTRAINT unique_courses_name)

10. execute "ALTER TABLE courses DROP INDEX unique_courses_name"

I'm on psql 9.4.4, Rails 4.2, and my last ounce of sanity. Thanks everyone.

Answer 1

I think unique will be removed if you remove the old index and add it again

class RemoveUniqueFromCoursesName < ActiveRecord::Migration
  def change
    remove_index(:courses, :name)
    add_index(:courses, :name)
  end
end