Proposed solution to the AR includes problem

I would like to propose the following solution to the AR includes problem (see 'Known Issue' at the end of the README), and to open a discussion with Alex and the geocoder community.

Proposed solution:

1. Remove the :select from the AR query.
2. Instead, add distance and bearing instance methods to the AR model, to be calculated application-side. The formulae would translate easily into pure Ruby code.

This would primarily enable the includes scope to work correctly, but would also improve performance:

• The bearing is currently always calculated, but may not be required.
• The database must currently calculate the distance twice per row: once for the SELECT and again for the ORDER BY.
• When used in conjunction with pagination, many of the calculated distances and bearings are discarded if they don't appear on the current page, only to be recalculated when the page changes.

Comments welcome.

Start with the Known Issue in README and the Active Record query in lib/geocoder/stores/active_record.rb around lines 160-162. Review the discussion and determine whether the proposed query and model-method changes have community agreement. Done requires an agreed design and a verified solution for the includes scope.