The examples I listed were cut and pasted from developer support. They are actual queries, with timing, from a random user accessing his MySpace on SloanSpace this morning.
The numbers you see are a list of package_ids supplied by the portal package that indicate which communities this particular user is a member of.
The code that generates the query for the news portlet for example can be viewed at
http://cvs.openacs.org/cvs/news-portlet/www/news-portlet-oracle.xql?rev=1.7&content-type=text/x-cvsweb-markup&cvsroot=dotlrn
The snippet that generates the long list of numbers is:
and news_items_approved.package_id in ([join $list_of_package_ids ", "])
This is pretty typical of the dotLRN portlets.