@Override
    protected SqlFunction getFloorSqlFunction(TimeUnitRange flag) {
      return HiveRelBuilder.getFloorSqlFunction(flag);
    }
This PROGRAM will be executed when there is a partial rewriting
(using union operator) to pull up the projection expressions
on top of the input that executes the modified query. The goal
of the program is to expose all available expressions below
the root of the plan.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/views/HiveMaterializedViewRule.java