Acts_as_Taggable Tag Cloud

I am using the Acts_AS_Taggable plugin in one of my applications. the application is a forum where users can add tags to any thread.
The forum includes a set of forums which in turn include a set of threads.
When a user displays the forum/show.. he should see a tag cloud involving all the tags attached to the threads in this forum.
I found this link describing the code for the tag cloud; but it doesn't satisfy my need as it can be used only on the threads level.
I should confess that the performance was not my concern this time.
in the vendor/plugins/acts_as_taggable/lib/tag.rb file I added this code:

 def self.tags(options = {})
   query = " select tags.id, tags.name, t1.count"
   query << " from tags INNER JOIN"    
   query << " (select tag_id , count(*) as count FROM taggings, posts  "     
   query << " where"     
   query << " posts.forum_id=#{options[:forum]} and "if options[:forum] != nil  
   query << " taggings.taggable_type='Post' and taggings.taggable_id=posts.id"     
   query << " group by tag_id)AS t1 ON t1.tag_id=tags.id"     
   query << " order by #{options[:order]}" if options[:order] != nil     
   query << " limit #{options[:limit]}" if options[:limit] != nil     
   tags = Tag.find_by_sql(query)   
end 

Following the link, everything should be working well now.

OOPS...Don't forget to restart the server!!!