Jefffrey commented on code in PR #9176:
URL: https://github.com/apache/arrow-rs/pull/9176#discussion_r2704583580
##########
arrow-row/src/list.rs:
##########
@@ -323,3 +316,180 @@ pub unsafe fn decode_fixed_size_list(
builder.build_unchecked()
}))
}
+
+/// Computes the encoded length for a single list element given its child rows.
+///
+/// This is used by list types (List, LargeList, ListView, LargeListView) to
determine
+/// the encoded length of a list element. For null elements, returns 1 (null
sentinel only).
+/// For valid elements, returns 1 + the sum of padded lengths for each child
row.
+#[inline]
+fn list_element_encoded_len(rows: &Rows, range: Option<Range<usize>>) -> usize
{
+ match range {
+ None => 1,
+ Some(range) => {
+ 1 + range
+ .map(|i|
super::variable::padded_length(Some(rows.row(i).as_ref().len())))
+ .sum::<usize>()
+ }
+ }
+}
+
+/// Computes the encoded lengths for a `GenericListViewArray`
+///
+/// `rows` should contain the encoded child elements
+pub fn compute_lengths_list_view<O: OffsetSizeTrait>(
+ lengths: &mut [usize],
+ rows: &Rows,
+ array: &GenericListViewArray<O>,
+ shift: usize,
+) {
+ let offsets = array.value_offsets();
+ let sizes = array.value_sizes();
+
+ lengths.iter_mut().enumerate().for_each(|(idx, length)| {
+ let start = offsets[idx].as_usize() - shift;
+ let size = sizes[idx].as_usize();
+ let range = array.is_valid(idx).then_some(start..start + size);
+ *length += list_element_encoded_len(rows, range);
+ });
+}
+
+/// Encodes the provided `GenericListViewArray` to `out` with the provided
`SortOptions`
+///
+/// `rows` should contain the encoded child elements
+pub fn encode_list_view<O: OffsetSizeTrait>(
+ data: &mut [u8],
+ out_offsets: &mut [usize],
+ rows: &Rows,
+ opts: SortOptions,
+ array: &GenericListViewArray<O>,
+ shift: usize,
+) {
+ let offsets = array.value_offsets();
+ let sizes = array.value_sizes();
+
+ out_offsets
+ .iter_mut()
+ .skip(1)
+ .enumerate()
+ .for_each(|(idx, offset)| {
+ let start = offsets[idx].as_usize() - shift;
+ let size = sizes[idx].as_usize();
+ let range = array.is_valid(idx).then_some(start..start + size);
+ let out = &mut data[*offset..];
+ *offset += encode_one(out, rows, range, opts)
+ });
+}
+
+/// Decodes a `GenericListViewArray` from `rows` with the provided `options`
+///
+/// # Safety
+///
+/// `rows` must contain valid data for the provided `converter`
+pub unsafe fn decode_list_view<O: OffsetSizeTrait>(
+ converter: &RowConverter,
+ rows: &mut [&[u8]],
+ field: &SortField,
+ validate_utf8: bool,
+) -> Result<GenericListViewArray<O>, ArrowError> {
+ let opts = field.options;
+
+ let mut values_bytes = 0;
+
+ let mut child_count = 0usize;
+ let mut list_sizes: Vec<O> = Vec::with_capacity(rows.len());
+
+ // First pass: count children and compute sizes
+ for row in rows.iter_mut() {
+ let mut row_offset = 0;
+ let mut list_size = 0usize;
+ loop {
+ let decoded = super::variable::decode_blocks(&row[row_offset..],
opts, |x| {
+ values_bytes += x.len();
+ });
+ if decoded <= 1 {
+ list_sizes.push(O::usize_as(list_size));
+ break;
+ }
+ row_offset += decoded;
+ child_count += 1;
+ list_size += 1;
+ }
+ }
+ O::from_usize(child_count).expect("overflow");
Review Comment:
Personally I feel it makes more sense to return an error here since the
function already supports that
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