presto-main/src/main/java/io/prestosql/operator/aggregation/histogram/SingleTypedHistogram.java/SingleTypedHistogram/addNewGroup
class SingleTypedHistogram:    private void addNewGroup(int hashPosition, int position, Block block, long count)
    {
        hashPositions.set(hashPosition, values.getPositionCount());
        counts.set(values.getPositionCount(), count);
        type.appendTo(block, position, values);

        // increase capacity, if necessary
        if (values.getPositionCount() >= maxFill) {
            rehash();
        }
    }