Documentation states: "For regular expressions of the form /^''normalchars''.*/, the database will use an index when available and appropriate."

However, the definition of "normal chars" as space, ascii letters and digits is hugely restrictive. For instance, our ids are URL paths. All of them of course starting with a /, making the indexes totally useless for our purposes.

Please have a look at:

http://github.com/kali/mongo/commit/d1664437ef4b1c0dab490522f55521bcb6b04cc1