presto-spi/src/main/java/io/prestosql/spi/block/AbstractSingleMapBlock.java/AbstractSingleMapBlock/getLong
class AbstractSingleMapBlock:    @Override
    public long getLong(int position, int offset)
    {
        position = getAbsolutePosition(position);
        if (position % 2 == 0) {
            return getRawKeyBlock().getLong(position / 2, offset);
        }
        else {
            return getRawValueBlock().getLong(position / 2, offset);
        }
    }