presto-main/src/main/java/io/prestosql/operator/aggregation/state/LongDecimalWithOverflowStateSerializer.java/LongDecimalWithOverflowStateSerializer/serialize
class LongDecimalWithOverflowStateSerializer:    @Override
    public void serialize(LongDecimalWithOverflowState state, BlockBuilder out)
    {
        if (state.getLongDecimal() == null) {
            out.appendNull();
        }
        else {
            Slice slice = Slices.allocate(Long.BYTES + UnscaledDecimal128Arithmetic.UNSCALED_DECIMAL_128_SLICE_LENGTH);
            SliceOutput output = slice.getOutput();

            output.writeLong(state.getOverflow());
            output.writeBytes(state.getLongDecimal());

            VARBINARY.writeSlice(out, slice);
        }
    }