[neelesh]

I used a slightly different approach of combining acts_as_tree (for faster updates/inserts) and added a dotted_id for faster reads. The dotted id is a string,as in 0001.0002.0007. Index this column and its fairly fast. The obvious limitation this approach creates is the depth of your comment tree. approx =dotted id col size/#of digits in max pk -1. Not an issue for many. When Im updating the hierarchy , I update root of the hierarchy being moved and then a single UPDATE to update the dotted ids in that subtree. If you are using MySQL, then the max length of a column that can be indexed is also limited. Don't remember the exact length.