anchor.diff:      return this;
     }
     SelectorBuilder sortBy(String fieldName, {bool descending: false}){
  -    _query;
  -    if (!map.containsKey("orderby")){
  -      map["orderby"] = new LinkedHashMap();
  -    }
  +    _ensureOrderBy();
       int order = 1;
       if (descending){
         order = -1;
  
positive.code:     }
    }
  
    SelectorBuilder eq(String fieldName,value){
      _addExpression(fieldName,value);
      return this;
  
negative.code:     return this;
    }
  
    SelectorBuilder metaTextScore(String fieldName) {
      _ensureParamFields();
      paramFields[fieldName] = {'\$meta' : "textScore"};
    }
  
    SelectorBuilder fields(List<String> fields) {
      _ensureParamFields();
      for (var field in fields) {
        paramFields[field] = 1;
      }
      return this;
    }
  
    SelectorBuilder excludeFields(List<String> fields) {
      _ensureParamFields();
      for (var field in fields) {
        paramFields[field] = 0;
      }
  