bulk_update_account_manager.rb

# For example,
# mappings = [["actualgeek","david.jones@freeagent.com"]]
ap = AccountancyPractice.find xxxx

mappings.each do |map|
  subdomain = map[0]
  email = map[1]

  company = ap.companies.find_by_subdomain(subdomain)
  old_manager = company.account_manager
  new_manager = ap.account_managers.find_by_email(email)

  if old_manager != new_manager
    puts "Changing company #{company.subdomain}(#{company.id}) from AccountManager##{old_manager.id} to AccountManager##{new_manager.id}"
    company.account_manager = new_manager
    company.save!
  else
    puts "Skipping company #{company.subdomain}(#{company.id}) as account manager is already correct"
  end
end;nil