Ultrasphinx::UsageError (Invalid class name "Place")

Hi, all …

My application can run normally on development environment ,but when i change it to production, I got the problem below:

Ultrasphinx::UsageError (Invalid class name “Place”):
/vendor/plugins/ultrasphinx/lib/ultrasphinx/search/internals.rb:88:in
build _request_with_options' /vendor/plugins/ultrasphinx/lib/ultrasphinx/search/internals.rb:85:in map’
/vendor/plugins/ultrasphinx/lib/ultrasphinx/search/internals.rb:85:in
build _request_with_options' /vendor/plugins/ultrasphinx/lib/ultrasphinx/search.rb:333:in run’

The Ultrasphinx configure , index and daemon:start all seem to have gone.

Does anyone have an idea on this ?

Thanks in advance.