change_column_null for existing column

Question

I'm attempting to change the nil possibility of a boolean attribute on the existing column :access_titles on the :profiles table. That column exists because of this migration:

class AddAccessItemsToProfiles < ActiveRecord::Migration
  def self.up
    add_column :profiles, :access_items, :boolean, :default => true
  end

  def self.down
    remove_column :profiles, :access_items, :boolean, :default => nil
  end
end

To change nil, I tried generating a migration as I always have:

rails g migration ChangeColumnNull :profiles :access_items :null => false

But that did nothing, so I did a standalone migration:

rails g migration AddChangeColumnNullToAccessItems

And within that I added:

class AddChangeColumnNullToAccessItems < ActiveRecord::Migration
  def self.up
    change_column_null :profiles, :access_items, :boolean, false
  end

  def self.down
    change_column_null :profiles, :access_items, :boolean, true
  end
end

I then ran rake db:migrate, restarted my server and saw no changes. So I tried:

class AddChangeColumnNullToAccessItems < ActiveRecord::Migration
  def self.up
    change_column_null :profiles, :access_items, false
  end

  def self.down
    change_column_null :profiles, :access_items, true
  end
end

Then did the same thing: rake db:migrate, restarted the server, and nothing changed.

What am I doing wrong? I was hoping to only have the boolean value of :access_items be true and false without having to dump the database.

UPDATE: Trying change_column_null :profiles, :access_items, false I got an error:

-- change_column_null(:profiles, :access_items, false)
rake aborted!
An error has occurred, this and all later migrations canceled:

PGError: ERROR:  column "access_items" contains null values
: ALTER TABLE "profiles" ALTER "access_items" SET NOT NULL

So, per the advice below I had to insert change_column_null :profiles, :access_items, false, true into my migration.

Answer 1

You can use:

change_column_null :profiles, :access_items, false, 1

The fourth parameter is optional and allows you to set the default value for the column. This is required when you have nulls in a column and you're setting the null value to false.