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MutableArrayData::try_extend_nulls panics on empty union input #11198
Description
Describe the bug
arrow-rs/arrow-data/src/transform/union.rs
Lines 80 to 84 in 83ebd72
arrow-rs/arrow-data/src/transform/union.rs
Lines 107 to 111 in 83ebd72
it assumes a non-empty unionfields, but an empty union is valid
To Reproduce
reproduction from codex:
// arrow-data/src/transform/mod.rs
#[test]
fn empty_union_extend_zero_nulls() {
use arrow_schema::UnionFields;
for mode in [UnionMode::Sparse, UnionMode::Dense] {
let mut builder = ArrayData::builder(DataType::Union(UnionFields::empty(), mode))
.len(0)
.add_buffer(Buffer::from_vec(Vec::<i8>::new()));
if mode == UnionMode::Dense {
builder = builder.add_buffer(Buffer::from_vec(Vec::<i32>::new()));
}
let source = builder.build().unwrap();
let mut mutable = MutableArrayData::new(vec![&source], true, 0);
mutable.try_extend_nulls(0);
}
}Expected behavior
this should not panic. need to consider what expected behaviour is though, as there are no child type ids to extend 🤔
Additional context
No response
Activity
fix: handle zero-length null extension for empty unions (apache#11209)