docs: void setIndexRoots(Session session, String s) {
  
          if (!isCached) {
              throw Error.error(ErrorCode.X_42501, tableName.name);
          }
  
          ParserDQL p     = new ParserDQL(session, new Scanner(s));
          int[]     roots = new int[getIndexCount()];
  
          p.read();
  
          for (int i = 0; i < getIndexCount(); i++) {
              int v = p.readInteger();
  
              roots[i] = v;
          }
  
          setIndexRoots(roots);
      }