Implement native interleave for ListView

arrow-select/src/interleave.rs

@@ -108,6 +108,8 @@ pub fn interleave(
         DataType::Struct(fields) => interleave_struct(fields, values, indices),
         DataType::List(field) => interleave_list::<i32>(values, indices, field),
         DataType::LargeList(field) => interleave_list::<i64>(values, indices, field),
+        DataType::ListView(field) => interleave_list_view::<i32>(values, indices, field),
+        DataType::LargeListView(field) => interleave_list_view::<i64>(values, indices, field),
         _ => interleave_fallback(values, indices)
     }
 }
@@ -411,6 +413,56 @@ fn interleave_list<O: OffsetSizeTrait>(
     Ok(Arc::new(list_array))
 }
 
+fn interleave_list_view<O: OffsetSizeTrait>(
+    values: &[&dyn Array],
+    indices: &[(usize, usize)],
+    field: &FieldRef,
+) -> Result<ArrayRef, ArrowError> {
+    let interleaved = Interleave::<'_, GenericListViewArray<O>>::new(values, indices);
+
+    // Build new offsets/sizes and compute total child capacity
+    let mut capacity = 0usize;
+    let mut offsets = Vec::with_capacity(indices.len());
+    let mut sizes = Vec::with_capacity(indices.len());
+    for &(array_idx, row_idx) in indices {
+        let list = interleaved.arrays[array_idx];
+        let size = list.sizes()[row_idx].as_usize();
+        offsets.push(
+            O::from_usize(capacity).ok_or_else(|| ArrowError::OffsetOverflowError(capacity))?,
+        );
+        sizes.push(O::from_usize(size).ok_or_else(|| ArrowError::OffsetOverflowError(size))?);
+        capacity += size;
+    }
+
+    // Bulk-copy child value ranges into a single flat child array
+    let child_data: Vec<_> = interleaved
+        .arrays
+        .iter()
+        .map(|list| list.values().to_data())
+        .collect();
+    let child_data_refs: Vec<_> = child_data.iter().collect();
+    let mut mutable_child = MutableArrayData::new(child_data_refs, false, capacity);
+    for &(array_idx, row_idx) in indices {
+        let list = interleaved.arrays[array_idx];
+        let start = list.offsets()[row_idx].as_usize();
+        let size = list.sizes()[row_idx].as_usize();
+        if size > 0 {
+            mutable_child.extend(array_idx, start, start + size);
+        }
+    }
+
+    let interleaved_values = make_array(mutable_child.freeze());
+    let list_view_array = GenericListViewArray::<O>::new(
+        field.clone(),
+        offsets.into(),
+        sizes.into(),
+        interleaved_values,
+        interleaved.nulls,
+    );
+
+    Ok(Arc::new(list_view_array))
+}
+
 /// Fallback implementation of interleave using [`MutableArrayData`]
 fn interleave_fallback(
     values: &[&dyn Array],
@@ -770,6 +822,61 @@ mod tests {
         test_interleave_lists::<i64>();
     }
 
+    fn test_interleave_list_views<O: OffsetSizeTrait>() {
+        // [[1, 2], null, [3]]
+        let mut a = GenericListBuilder::<O, _>::new(Int32Builder::new());
+        a.values().append_value(1);
+        a.values().append_value(2);
+        a.append(true);
+        a.append(false);
+        a.values().append_value(3);
+        a.append(true);
+        let a: GenericListViewArray<O> = a.finish().into();
+
+        // [[4], null, [5, 6, null]]
+        let mut b = GenericListBuilder::<O, _>::new(Int32Builder::new());
+        b.values().append_value(4);
+        b.append(true);
+        b.append(false);
+        b.values().append_value(5);
+        b.values().append_value(6);
+        b.values().append_null();
+        b.append(true);
+        let b: GenericListViewArray<O> = b.finish().into();
+
+        let values = interleave(&[&a, &b], &[(0, 2), (0, 1), (1, 0), (1, 2), (1, 1)]).unwrap();
+        let v = values
+            .as_any()
+            .downcast_ref::<GenericListViewArray<O>>()
+            .unwrap();
+
+        // [[3], null, [4], [5, 6, null], null]
+        let mut expected = GenericListBuilder::<O, _>::new(Int32Builder::new());
+        expected.values().append_value(3);
+        expected.append(true);
+        expected.append(false);
+        expected.values().append_value(4);
+        expected.append(true);
+        expected.values().append_value(5);
+        expected.values().append_value(6);
+        expected.values().append_null();
+        expected.append(true);
+        expected.append(false);
+        let expected: GenericListViewArray<O> = expected.finish().into();
+
+        assert_eq!(v, &expected);
+    }
+
+    #[test]
+    fn test_list_views() {
+        test_interleave_list_views::<i32>();
+    }
+
+    #[test]
+    fn test_large_list_views() {
+        test_interleave_list_views::<i64>();
+    }
+
     #[test]
     fn test_struct_without_nulls() {
         let fields = Fields::from(vec![