Thinking Sphinx - Showing the right record from the association - ruby-on-rails

Question

I have successfully got Thinking Sphinx working with Geolocation on an associated model. Happy days!
But I now need it to show the right associated record on a Google map.
The scenario is a Company with has_many offices. Offices have got the lng,lat values. I am searching on the Company and associating the offices to it.
E.g.
define_index do
indexes :name, :sortable => true
indexes offices(:city), :as => :city
indexes offices(:postal_code), :as => :postal_code
has "RADIANS(offices.lat)", :as => :lat, :type => :float
has "RADIANS(offices.lng)", :as => :lng, :type => :float
has created_at
has updated_at
set_property :latitude_attr => 'lat'
set_property :longitude_attr => 'lng'
set_property :field_weights => { 'name' => 10,
'service_name' => 9,
'city' => 8 }
end
Searching for x company in y location / postcode works perfectly, showing the correct companies that have got offices in the desired location within the #geodist radius.
E.g.
{:geo=>[0.9283660690549609, -0.050527407508941975], :sort_mode=>:expr, :sort_by=>"#weight * #weight / #geodist", :with=>{"#geodist"=>0.0..120700.8}, :conditions=>{:service_name=>"Business strategies"}, :page=>1, :per_page=>12, :star=>true}
The resulting records are company object, not the offices, which is fine for the list view but I want to show icons on a google map of the relevant associated office.
What is the best way to find the relevant associated office record to show within the radius bounds?

Answer 1

Sphinx only reliably handles single-value float attributes - and it has no concept of paired lat/lng values. This means that you can't have a solid search across objects with more than one lat/lng pair.
The best workaround is to actually search on Office instead - and perhaps pull in each office's company information:
define_index do
indexes company.name, :as => :name, :sortable => true
indexes city, postal_code
has "RADIANS(offices.lat)", :as => :lat, :type => :float
has "RADIANS(offices.lng)", :as => :lng, :type => :float
has company.created_at, :as => :created_at
has company.updated_at, :as => :updated_at
has company_id
set_property :field_weights => {
'name' => 10,
'service_name' => 9,
'city' => 8
}
end
And then when searching, you can group by company_id to ensure only one result for any company (if that's what you'd prefer):
Office.search 'foo',
:geo => [lat, lng],
:with => {'#geodist' => 0.0..120700.8}
:group_function => :attr
:group_by => 'company_id'
If it's important as to which Office gets returned for a given company_id, then you'll probably want to use the :group_clause option as well. The docs cover this.