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Posted to github@arrow.apache.org by "irenjj (via GitHub)" <gi...@apache.org> on 2025/02/02 12:14:32 UTC
[PR] fix: first none in `ListArray` panics in `cast_with_options` [arrow-rs]
irenjj opened a new pull request, #7065:
URL: https://github.com/apache/arrow-rs/pull/7065
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Closes #7043
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Re: [PR] fix: first none in `ListArray` panics in `cast_with_options` [arrow-rs]
Posted by "irenjj (via GitHub)" <gi...@apache.org>.
irenjj commented on PR #7065:
URL: https://github.com/apache/arrow-rs/pull/7065#issuecomment-2639738016
Thanks @Jefffrey , I've made the requested changes. Could you help review it again?
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Re: [PR] fix: first none in `ListArray` panics in `cast_with_options` [arrow-rs]
Posted by "Jefffrey (via GitHub)" <gi...@apache.org>.
Jefffrey commented on code in PR #7065:
URL: https://github.com/apache/arrow-rs/pull/7065#discussion_r1946592305
##########
arrow-cast/src/cast/list.rs:
##########
@@ -88,6 +88,25 @@ where
let mut mutable = MutableArrayData::new(vec![&values], nullable, cap);
// The end position in values of the last incorrectly-sized list slice
let mut last_pos = 0;
+
+ // Need to flag when previous vector(s) are empty/None to distinguish from 'All slices were correct length' cases.
+ let is_prev_empty = if array.offsets().len() < 2 {
+ false
+ } else {
+ let first_offset = array
+ .offsets()
+ .first()
+ .ok_or_else(|| ArrowError::ComputeError("Failed to get the first offset".into()))?
+ .as_usize();
+ let second_offset = array
+ .offsets()
+ .get(1)
+ .ok_or_else(|| ArrowError::ComputeError("Failed to get the second offset".into()))?
+ .as_usize();
Review Comment:
```suggestion
let first_offset = array.offsets()[0].as_usize();
let second_offset = array.offsets()[1].as_usize();
```
nit: safe to use index as case where len < 2 is guarded above, so it can't panic
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Re: [PR] fix: first none in `ListArray` panics in `cast_with_options` [arrow-rs]
Posted by "Jefffrey (via GitHub)" <gi...@apache.org>.
Jefffrey commented on code in PR #7065:
URL: https://github.com/apache/arrow-rs/pull/7065#discussion_r1940758109
##########
arrow-cast/src/cast/list.rs:
##########
@@ -88,11 +88,16 @@ where
let mut mutable = MutableArrayData::new(vec![&values], nullable, cap);
// The end position in values of the last incorrectly-sized list slice
let mut last_pos = 0;
+ let mut null_first = false;
Review Comment:
I don't believe it's about nulls being first, rather about a potentially empty list being first. Consider this test case which also panics during cast:
```rust
#[test]
fn test456() {
let array = Arc::new(ListArray::from_iter_primitive::<Int64Type, _, _>(vec![
Some(vec![]),
Some(vec![Some(1), Some(2)]),
])) as ArrayRef;
let data_type =
DataType::FixedSizeList(FieldRef::new(Field::new("item", DataType::Int64, true)), 2);
let opt = CastOptions::default();
let r = cast_with_options(&array, &data_type, &opt).unwrap();
let fixed_array = Arc::new(FixedSizeListArray::from_iter_primitive::<Int64Type, _, _>(
vec![None, Some(vec![Some(1), Some(2)])],
2,
)) as ArrayRef;
assert_eq!(*fixed_array, *r);
}
```
This distinction is important as nullability isn't determined by the gap between offsets, rather it's determined by the null buffer.
##########
arrow-cast/src/cast/list.rs:
##########
@@ -112,16 +117,15 @@ where
}
}
- let values = match last_pos {
- 0 => array.values().slice(0, cap), // All slices were the correct length
- _ => {
- if mutable.len() != cap {
- // Remaining slices were all correct length
- let remaining = cap - mutable.len();
- mutable.extend(0, last_pos, last_pos + remaining)
- }
- make_array(mutable.freeze())
+ let values = if last_pos == 0 && !null_first {
+ array.values().slice(0, cap) // All slices were the correct length
+ } else {
+ if mutable.len() != cap {
+ // Remaining slices were all correct length
+ let remaining = cap - mutable.len();
+ mutable.extend(0, last_pos, last_pos + remaining)
}
+ make_array(mutable.freeze())
};
Review Comment:
```suggestion
let values = match last_pos {
0 if !null_first => array.values().slice(0, cap), // All slices were the correct length
_ => {
if mutable.len() != cap {
// Remaining slices were all correct length
let remaining = cap - mutable.len();
mutable.extend(0, last_pos, last_pos + remaining)
}
make_array(mutable.freeze())
}
};
```
nit: using guard in the match arm would reduce the diff happening here
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Re: [PR] fix: first none in `ListArray` panics in `cast_with_options` [arrow-rs]
Posted by "irenjj (via GitHub)" <gi...@apache.org>.
irenjj commented on code in PR #7065:
URL: https://github.com/apache/arrow-rs/pull/7065#discussion_r1942246993
##########
arrow-cast/src/cast/list.rs:
##########
@@ -88,11 +88,16 @@ where
let mut mutable = MutableArrayData::new(vec![&values], nullable, cap);
// The end position in values of the last incorrectly-sized list slice
let mut last_pos = 0;
+ let mut null_first = false;
Review Comment:
Thanks @Jefffrey for your review, in my local testing, `null_first` can identify both None and empty vec (the name `null_first` might be a bit misleading). My idea is to use `null_first` to prevent entering the `let values = match last_pos { 0 => }` situation.
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Re: [PR] fix: first none/empty list in `ListArray` panics in `cast_with_options` [arrow-rs]
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb merged PR #7065:
URL: https://github.com/apache/arrow-rs/pull/7065
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Re: [PR] fix: first none in `ListArray` panics in `cast_with_options` [arrow-rs]
Posted by "Jefffrey (via GitHub)" <gi...@apache.org>.
Jefffrey commented on code in PR #7065:
URL: https://github.com/apache/arrow-rs/pull/7065#discussion_r1944361803
##########
arrow-cast/src/cast/list.rs:
##########
@@ -88,11 +88,16 @@ where
let mut mutable = MutableArrayData::new(vec![&values], nullable, cap);
// The end position in values of the last incorrectly-sized list slice
let mut last_pos = 0;
+ let mut null_first = false;
Review Comment:
I think I understand what's happening now. It seems its an edge case of the algorithm used here, where a 0 sized list element precedes a list of the proper size, e.g.
```
Cast to fixed sized 2:
[
[],
[],
[1, 2],
]
```
Where `last_pos` is never updated from 0 because `end_pos` for the first two elements is `0` and `last_pos` doesn't get updated when the list element already matches the fixed size to cast to.
(Sorry if this was already obvious, just needed to air my thoughts out)
Whilst this fix is correct, I'd like some more documentation, and especially rename `null_first` to something more accurate (as the problem is with empty size lists too), to explain this edge case so it's obvious to anyone else modifying the code here in the future.
We could also look into moving the:
```rust
if start_pos == 0 && end_pos == 0 {
```
Check outside of the for loop as we only need to check it once upfront.
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Re: [PR] fix: first none/empty list in `ListArray` panics in `cast_with_options` [arrow-rs]
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #7065:
URL: https://github.com/apache/arrow-rs/pull/7065#issuecomment-2645826603
Thanks @irenjj and @Jefffrey
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