EllisLab/CodeIgniter — pull request #1612 by borgir (2012-07-12 23:37:27+00:00)
Title: FIX - Ignores SQL functions on the SELECT statement. 

SQL functions can result on unexpected results when there are , (commas) inside.
Thats because the select method (DB_query_builder.php) processes its arguments (the selects - $select) with an explode by , (commas) regardless of the content.

My solution, simply ignores the functions and its parameters. So it won't check the validity of the parameters nor add the database prefix when needed.

Based on this thread:
http://codeigniter.com/forums/viewthread/220573/