anchor.diff:          skip = SkipCount,
           start_docid = StartDocId
       } = QueryArgs,
  +    validate_map_query(QueryArgs),
       CurrentEtag = view_group_etag(Group, Keys),
       couch_httpd:etag_respond(Req, CurrentEtag, fun() ->     
           {ok, RowCount} = couch_view:get_row_count(View),
  
positive.code:         start_key = StartKey,
          start_docid = StartDocId
      } = QueryArgs,
      CurrentEtag = view_group_etag(Group),
      couch_httpd:etag_respond(Req, CurrentEtag, fun() -> 
          {ok, RowCount} = couch_view:get_row_count(View),
  
negative.code:             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{
  