Purpose

Some actions, such as moving a page, can take a long time when the page has a very large number of child pages. For this reason it can be useful to identify pages with a very large number of children and, if necessary, break up the page hierarchy into smaller page trees. 

Solution

The following query will return details of the 50 pages with the most direct child pages. 

select contentid, title, count from content join (select parentid, count(*) from content 
where contenttype = 'PAGE' and content_status = 'current' 
group by parentid 
order by count desc limit 50) 
top on top.parentid = content.contentid;

This query has been tested with PostgreSQL, and may need to be adapted for your database.