search without query

Hi, I`m just getting into the grips of hacking vB (2.9). My latest effort is to modify the search so that you can search by hours, and without a query. I got the hours part finnished, but I`m stuck on the query part after lots of trials and errors.
I don`t think I need to explain much for you to help, me. I think it would help alot if someone explained "postids" in the context of search.php at line 521 :

PHP Code:

  // insert query into db
  $DB_site->query("INSERT INTO search (searchid,query,postids,dateline,querystring,showposts,userid,ipaddress) VALUES (NULL,'".addslashes($wheresql)."','".addslashes($goodpostlist)."',".time().",'".addslashes($query)."','".intval($showposts)."',$bbuserinfo[userid],'".addslashes($ipaddress)."')");
  $searchid=$DB_site->insert_id(); 


The $goodpostlist variable is inputted, but I can`t figure out the meaning of it, an example would be great.

Thanks!
Haakon