@Override
    public void visit(RelNode node, int ordinal, RelNode parent) {
      if (node instanceof Project ||
          node instanceof Filter ||
          node instanceof TableScan) {
        // We can continue
        super.visit(node, ordinal, parent);
      } else {
        throw new ReturnedValue(false);
      }
    }
Whether the execution of the query below this jdbc converter
can be split by Hive.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/reloperators/jdbc/HiveJdbcConverter.java