anchor.diff:              end, {ok, FoldAccInit}, Keys),
           finish_view_fold(Req, RowCount, FoldResult)
       end).
  +
  +validate_map_query(QueryArgs) ->
  +    case QueryArgs#view_query_args.group_level of
  +    0 -> ok;
  +    _ ->
  +        throw({query_parse_error, <<"Query parameter \"group\" and/or \"group_level\" are invalid for map views.">>})
  +    end.
   
   output_reduce_view(Req, View, Group, QueryArgs, nil) ->
       #view_query_args{
  
positive.code:         skip = SkipCount,
          start_docid = StartDocId
      } = QueryArgs,
      CurrentEtag = view_group_etag(Group, Keys),
      couch_httpd:etag_respond(Req, CurrentEtag, fun() ->     
          {ok, RowCount} = couch_view:get_row_count(View),
  
negative.code:         start_key = StartKey,
          start_docid = StartDocId
      } = QueryArgs,
      validate_map_query(QueryArgs),
      CurrentEtag = view_group_etag(Group),
      couch_httpd:etag_respond(Req, CurrentEtag, fun() -> 
          {ok, RowCount} = couch_view:get_row_count(View),
  