westonpace commented on code in PR #7366:
URL: https://github.com/apache/arrow-rs/pull/7366#discussion_r2026949053
##########
arrow-array/src/array/struct_array.rs:
##########
@@ -294,10 +294,34 @@ impl StructArray {
impl From<ArrayData> for StructArray {
fn from(data: ArrayData) -> Self {
+ let parent_offset = data.offset();
+ let parent_len = data.len();
+
let fields = data
.child_data()
.iter()
- .map(|cd| make_array(cd.clone()))
+ .map(|cd| {
+ let child_offset = cd.offset();
+ let child_len = cd.len();
+ assert!(
+ child_len >= parent_len + parent_offset,
+ "struct array has offset {} and len {} but child array
only has {} items",
+ parent_offset,
+ parent_len,
+ child_len
+ );
+ // SAFETY: We have already checked that the child array has
enough items and the
+ // only thing we are changing is the offset and length. As
long as the child data
+ // was previously valid, then the new child data is also valid.
+ let cd = unsafe {
+ cd.clone()
+ .into_builder()
+ .offset(child_offset + parent_offset)
Review Comment:
We do not need to consider `child_offset`. The `child_len` is "number of
items in the underlying array, after skipping any `child_offset`."
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