I have to manage 1 million geo-points localized all over the earth.
For performance reason, I need to group the points which are in the same "cells". I have implemented an algorithm wich computes for each point, its geohash value, so that it is quite easy, using the aggregate framework and functions like $substr, to group and count the points which are in the same cell.

But the documentation says Mongo already computes geoHash values from geo points given as [lon, lat].

It would be nice if this internally computed geoHash value could be returned (as a readonly attribute ?) with the documents.