gistfile1.rb

ev=Event.find 33701
parent_problematic = []
# get parent registrations
ev.event_registrations.where("parent_registration_id IS NOT NULL").map{|r|
r.parent_registration_id}.uniq.each do |parent_registration_id|
  parent_registration = nil
  begin
    parent_registration = EventRegistration.find(parent_registration_id)
  rescue
    #break
  end
  if !parent_registration.nil? and (parent_registration.status == 'Complete' || parent_registration.status == 'rm_pending') and parent_registration.processed == true
    children_registrations = parent_registration.children_registrations.where("processed = false AND status='Expired' AND cost IS NOT NULL")
   if children_registrations.size > 0
    parent_problematic << parent_registration_id
   end
  end
  puts "PARENTS OF PROBLEMATIC REGISTRATIONS \n"
  puts parent_problematic.join(', ')
  puts "========================================================="
end

Step 1 for identifying parent (primary registration) of problematic piggyback registration