presto-main/src/main/java/io/prestosql/sql/planner/plan/AggregationNode.java/AggregationNode/hasNonEmptyGroupingSet
class AggregationNode:    public boolean hasNonEmptyGroupingSet()
    {
        return groupingSets.getGroupingSetCount() > groupingSets.getGlobalGroupingSets().size();
    }