compute::binary_mut returns Err(PrimitiveArray<T>) only with certain arrays

[MaxenceMaire]

Describe the bug
compute::binary_mut returns Err(PrimitiveArray<T>) in cases when the underlying buffer is not shared (as described in the documentation). It only happens when passing certain arrays.

To Reproduce

• Err case:

let a = Int32Array::from(vec![
    Some(3),
    Some(4),
    Some(5),
    Some(6),
    None,
]);

let b = Int32Array::from(vec![
    Some(10),
    Some(11),
    Some(12),
    Some(13),
    Some(14),
]);

let a = binary_mut(a, &b, |a, b| a + b);

produces

Err(PrimitiveArray<Int32>
[
  3,
  4,
  5,
  6,
  null,
])

• Ok case:

let a = Int32Array::from(vec![
    Some(3),
    Some(4),
    Some(5),
    Some(6),
    None,
]);

let b = Int32Array::from(vec![
    Some(10),
    Some(11),
    None,
    Some(13),
    Some(14),
]);

let a = binary_mut(a, &b, |a, b| a + b);

produces

Ok(Ok(PrimitiveArray<Int32>
[
  13,
  15,
  null,
  19,
  null,
]))

Expected behavior
I would have expected the first case to produce

Ok(Ok(PrimitiveArray<Int32>
[
  13,
  15,
  17,
  19,
  null,
]))

Additional context

Additional cases

• Err case:

let a = Int32Array::from(vec![
    Some(3),
    Some(4),
    Some(5),
    Some(6),
    None,
    Some(8)
]);

let b = Int32Array::from(vec![
    Some(10),
    Some(11),
    Some(12),
    Some(13),
    Some(14),
    Some(15),
]);

let a = binary_mut(a, &b, |a, b| a + b);

produces

Err(PrimitiveArray<Int32>
[
  3,
  4,
  5,
  6,
  null,
  8,
])

• Ok case:

let a = Int32Array::from(vec![
    Some(3),
    Some(4),
    Some(5),
    Some(6),
    None,
    Some(8)
]);

let b = Int32Array::from(vec![
    Some(10),
    Some(11),
    Some(12),
    Some(13),
    Some(14),
    None,
]);

let a = binary_mut(a, &b, |a, b| a + b);

produces

Ok(Ok(PrimitiveArray<Int32>
[
  13,
  15,
  17,
  19,
  null,
  null,
]))

The errors seem to be associated with an uneven number of null values.

[MaxenceMaire]

Note that I get the expected result when constructing the array with a separate null buffer:

let a = Int32Array::new(
    vec![3, 4, 5, 6, 7].into(),
    Some(vec![true, true, true, true, false].into()),
);

let b = Int32Array::new(
    vec![10, 11, 12, 13, 14].into(),
    Some(vec![true, true, true, true, true].into()),
);

let a = binary_mut(a, &b, |a, b| a + b);

produces:

Ok(Ok(PrimitiveArray<Int32>
[
  13,
  15,
  17,
  19,
  null,
]))

Unfortunately I haven't had time to dig deeper into it yet, but it would seem to indicate that the null buffer references the scalar buffer when using the From<Vec<Option<T>>> trait to construct the array, which in turns causes the shared buffer error on binary_mut?

[alamb]

this sounds like a good find. Perhaps @viirya has some thoughts / ideas on this (as I think Comet uses binary_mut a lot)

[viirya]

Looking into this.

[alamb]

label_issue.py automatically added labels {'arrow'} from #6396