presto-spi/src/main/java/io/prestosql/spi/type/LongDecimalType.java/LongDecimalType/getObjectValue
class LongDecimalType:    @Override
    public Object getObjectValue(ConnectorSession session, Block block, int position)
    {
        if (block.isNull(position)) {
            return null;
        }
        Slice slice = getSlice(block, position);
        return new SqlDecimal(decodeUnscaledValue(slice), getPrecision(), getScale());
    }