presto-main/src/main/java/io/prestosql/operator/aggregation/histogram/GroupedTypedHistogram.java/GroupedTypedHistogram/processEntry
class GroupedTypedHistogram:        private boolean processEntry(long groupId, Block block, int position, long count)
        {
            if (isEmpty()) {
                addNewGroup(groupId, block, position, count);
                return true;
            }
            else {
                valueNode.add(count);
                return false;
            }
        }