A typical stacktrace.log

[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:192:in `add_sphinx_index'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:193:in `add_sphinx_index'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:193:in `each'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:193:in `add_sphinx_index'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:159
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:174:in `call'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:174:in `define_indexes'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:173:in `each'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/active_record.rb:173:in `define_indexes'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/context.rb:15:in `define_indexes'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/context.rb:14:in `each'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/context.rb:14:in `define_indexes'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/search.rb:71:in `initialize'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/search_methods.rb:368:in `new'
[PROJECT_ROOT]/vendor/gems/thinking-sphinx-1.3.16/lib/thinking_sphinx/search_methods.rb:368:in `search'

thinking_sphinx_classloading_fix.rb

# You've been a very bad girl, Thinking Sphinx. A very, very, bad, bad girl, Sphinx.

module ActiveRecord
  class Base
    def self.add_sphinx_index(index)
      if self.sphinx_indexes
        self.sphinx_indexes << index
      end
      subclasses.each { |klass| klass.add_sphinx_index(index) }
    end
  end
end