Getting error "ThinkingSphinx::SphinxError (unknown local index '' in search request):"

We define index for Sphinx in model in blocks as such:
define_index do
      indexes :name, :sortable => true
      indexes description
...
...
    end

Whenever we do some changes in such type of index and start ThinkingSphinx it gives us error as :
ThinkingSphinx::SphinxError (unknown local index '<delta_name>' in search request):

To solve such type of issues, run
rake ts:rebuild
It will first do changes in config file and then will do indexing as per the changes done, then you will be able to run Thinking Sphinx.