presto-main/src/main/java/io/prestosql/operator/aggregation/DecimalSumAggregation.java/DecimalSumAggregation/accumulateValueInState
class DecimalSumAggregation:    private static void accumulateValueInState(Slice unscaledDecimal, LongDecimalWithOverflowState state)
    {
        initializeIfNeeded(state);
        Slice sum = state.getLongDecimal();
        long overflow = UnscaledDecimal128Arithmetic.addWithOverflow(sum, unscaledDecimal, sum);
        state.setOverflow(state.getOverflow() + overflow);
    }