protected void newAggregateRel(RelBuilder relBuilder,
      Aggregate oldAggregate, List<AggregateCall> newCalls) {
    relBuilder.aggregate(
        relBuilder.groupKey(oldAggregate.getGroupSet(),
            oldAggregate.getGroupSets()),
        newCalls);
  }
Do a shallow clone of oldAggRel and update aggCalls. Could be refactored
into Aggregate and subclasses - but it's only needed for some
subclasses.

@param relBuilder Builder of relational expressions; at the top of its
                  stack is its input
@param oldAggregate LogicalAggregate to clone.
@param newCalls  New list of AggregateCalls
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveAggregateReduceFunctionsRule.java