@Override
  public RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
    assert inputs.isEmpty();
    return this;
  }
Creates a HiveTableScan.

@param cluster
         Cluster
@param traitSet
         Traits
@param table
         Table
@param table
         HiveDB table
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/reloperators/HiveTableScan.java