public void visit(
          RelNode node,
          int ordinal,
          RelNode parent) {
        if (node instanceof JdbcHiveTableScan && tmpJdbcHiveTableScan [0] == null) {
          tmpJdbcHiveTableScan [0] = (JdbcHiveTableScan) node;
        } else {
          super.visit(node, ordinal, parent);
        }
      }
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