mastodon/db/migrate/20200312185443_add_parent_id_to_email_domain_blocks.rb

class AddParentIdToEmailDomainBlocks < ActiveRecord::Migration[5.2]
  def change
    safety_assured { add_reference :email_domain_blocks, :parent, null: true, default: nil, foreign_key: { on_delete: :cascade, to_table: :email_domain_blocks }, index: false }
  end
end