presto-main/src/main/java/io/prestosql/operator/aggregation/ChecksumAggregationFunction.java/ChecksumAggregationFunction/input
class ChecksumAggregationFunction:    public static void input(Type type, NullableLongState state, Block block, int position)
    {
        state.setNull(false);
        if (block.isNull(position)) {
            state.setLong(state.getLong() + PRIME64);
        }
        else {
            state.setLong(state.getLong() + type.hash(block, position) * PRIME64);
        }
    }