How to turn off auto_increment in Rails Active Record

Question

Is it possible to create primary key without auto_increment flag in ActiveRecord?

I can\'t do

create table :blah, :id          


        

Answer 1

  def change
    create_table :tablename do |t|
      # t.string :fieldname
    end

   change_column :tablename, :id, :bigint, auto_increment: false
 end

Notice: Since Rails 5.1 default primary keys are bigint. http://www.mccartie.com/2016/12/05/rails-5.1.html

If you want 4-byte key change :bigint to :integer