activity duplicate check

create trigger activity_duplicate_check before insert on activities
  for each row begin
    set @activity_id=new.activity_id;
    set @poll_result_id=new.poll_result_id;
    set @created_at=new.created_at;
    set @data_collector_id=new.data_collector_id;
    begin
      declare found_ids int default 0;
      declare found_created_at datetime default 0;

      declare j int default 0;
      while j < 5 and (found_created_at = '0000-00-00 00:00:00' or found_created_at is null)
        do
          select count(1), created_at into found_ids, found_created_at
            from activities use index(index_activities_on_data_collector_id_and_activity_id)
            where activity_id = @activity_id
              and data_collector_id = @data_collector_id
              and created_at > date_sub( date_format(@created_at, '%Y/%m/%d 00:00:00'), interval j day)
              and created_at < date_sub( date_format(@created_at, '%Y/%m/%d 23:59:59'), interval j day);
        set j = j + 1;
      end while;

      if found_ids = 0 then
        update poll_results set updated_at = @created_at,
          poll_results.new_item_count = poll_results.new_item_count + 1
        where poll_results.id = @poll_result_id
          and data_collector_id = @data_collector_id;
      else
        set new.created_at=found_created_at;
      end if;
    end;
  end;