def clear_extended_doc_fresh_cache
      ::CouchRest::ExtendedDocument.subclasses.each{|klass| klass.req_design_doc_refresh if klass.respond_to?(:req_design_doc_refresh)}
    end
def clear_extended_doc_fresh_cache
      ::CouchRest::ExtendedDocument.subclasses.each{|klass| klass.req_design_doc_refresh if klass.respond_to?(:req_design_doc_refresh)}
    end
If the database is deleted, ensure that the design docs will be refreshed.