Function string_view_substr

datafusion/functions/src/unicode/substr.rs:271–320

(
    string_view_array: &StringViewArray,
    args: &[ArrayRef],
)

}

fn string_view_substr(
    string_view_array: &StringViewArray,
    args: &[ArrayRef],
) -> Result<ArrayRef> {
    let start_array = as_int64_array(&args[0])?;
    let count_array_opt = args.get(1).map(|a| as_int64_array(a)).transpose()?;

    let is_ascii =
        enable_ascii_fast_path(&string_view_array, start_array, count_array_opt);

    // Combine null bitmaps from all inputs in bulk.
    let nulls = NullBuffer::union_many([
        string_view_array.nulls(),
        start_array.nulls(),
        count_array_opt.and_then(|a| a.nulls()),
    ]);

    let mut views_buf = Vec::with_capacity(string_view_array.len());

    for (i, raw_view) in string_view_array.views().iter().enumerate() {
        if nulls.as_ref().is_some_and(|n| n.is_null(i)) {
            views_buf.push(0);
            continue;
        }

        let string = string_view_array.value(i);
        let start = start_array.value(i);
        let count = count_array_opt.map(|a| a.value(i));

        let (byte_start, byte_end) = get_true_start_end(string, start, count, is_ascii)?;
        let substr = &string[byte_start..byte_end];

        append_view(&mut views_buf, raw_view, substr, byte_start as u32);
    }

    let views_buf = ScalarBuffer::from(views_buf);

    // Safety:
    // (1) The blocks of the given views are all provided
    // (2) Each of the range `view.offset+start..end` of view in views_buf is within
    // the bounds of each of the blocks
    unsafe {
        let array = StringViewArray::new_unchecked(
            views_buf,
            string_view_array.data_buffers().to_vec(),
            nulls,
        );
        Ok(Arc::new(array) as ArrayRef)
    }
}

fn values_fit_in_i32<T: OffsetSizeTrait>(string_array: &GenericStringArray<T>) -> bool {
    // The Arrow spec defines StringView offset fields as signed 32-bit