presto-spi/src/main/java/io/prestosql/spi/block/AbstractVariableWidthBlock.java/AbstractVariableWidthBlock/getLong
class AbstractVariableWidthBlock:    @Override
    public long getLong(int position, int offset)
    {
        checkReadablePosition(position);
        return getRawSlice(position).getLong(getPositionOffset(position) + offset);
    }