private int cmpFiltered(TableScanOperator o1, TableScanOperator o2) {
      if (o1.getConf().getFilterExpr() == null ^ o2.getConf().getFilterExpr() == null) {
            return (o1.getConf().getFilterExpr() == null) ? -1 : 1;
      }
      return 0;

    }
Orders TS operators in decreasing order by "weight".
ql/src/java/org/apache/hadoop/hive/ql/optimizer/SharedWorkOptimizer.java