presto-main/src/main/java/io/prestosql/operator/aggregation/LongSumAggregation.java/LongSumAggregation/sum
class LongSumAggregation:    @InputFunction
    public static void sum(@AggregationState LongLongState state, @SqlType(StandardTypes.BIGINT) long value)
    {
        state.setFirst(state.getFirst() + 1);
        state.setSecond(BigintOperators.add(state.getSecond(), value));
    }