This post tells you how to using the thinking sphinx rails plugin to search a bunch of records that have a specific tag (acts_as_taggable_on).
class Photo < ActiveRecord::Base ... acts_as_taggable_on :keywords define_index do indexes :caption indexes keywords.name, :as => :keywords end ... end
Now lets assign some tags to our Photo
>> photo = Photo.create :user_id => 1, :caption => 'BMW M7', :keyword_list => 'BMW, Car' >> photo.keywords => [#<Tag id: 1, name: "BMW">, #<Tag id: 3, name: "Car">]