let input_vec = input.flat_vector(0);
let mut option_raw = input_vec.as_slice_with_len::<duckdb_string_t>(input.len())[0];

// TODO: duckdb-rs doesn't prvide a way to get string from a FlatVector.
// (DuckString::new() is pub(crate) so unavailable).
let option = unsafe {
    let len = duckdb_string_t_length(option_raw);
    let c_ptr = duckdb_string_t_data(&mut option_raw);
    let string = String::from_utf8_lossy(std::slice::from_raw_parts(
        c_ptr as *const u8,
        len as usize,
    ));

    // This is very important. Cow refers to DuckDB's memory, which
    // might can be erased. So, it needs to be copied into Rust.
    string.to_string()
};