ActiveRecord: delete duplicate entries.rb

def delete_dups_for(model, collect_by)
  keep_array = Hash.new { |h,k| h[k] = [] }
  delete_array = []
  model_name = model.name
  all_objects = model.all.reverse #so we add newest first, sort of
  pbar = ProgressBar.new(model_name.pluralize, all_objects.count)
  all_objects.each do |obj|
    if detect_dup((keep_array[obj.send(collect_by)]), obj).nil?
      keep_array[obj.send(collect_by)] << obj
    else
      delete_array << obj.id
    end
  pbar.inc
  end
  sql = ActiveRecord::Base.connection();
  sql.execute "DELETE FROM #{model.table_name} WHERE id IN(#{delete_array.join(',')})" unless delete_array.empty?
  pbar.finish
end