Add mutable bitwise operations to BooleanArray and NullBuffer::union_many

[mbutrovich]

Which issue does this PR close?

• Closes [Arrow] Add bitwise operations BooleanArray that potentially reuse the underlying allocation #8809.

Rationale for this change

Several DataFusion PRs (#21464, #21468, #21471, #21475, #21477, #21482, #21532) optimize NULL handling in scalar functions by replacing row-by-row null buffer construction with bulk NullBuffer::union. When 3+ null buffers need combining, they chain binary union calls, each allocating a new BooleanBuffer.

NullBuffer::union_many reduces this to 1 allocation (clone + in-place ANDs). For example, from #21482:

Before:

[array.nulls(), from_array.nulls(), to_array.nulls(), stride.and_then(|s| s.nulls())]
    .into_iter()
    .fold(None, |acc, nulls| NullBuffer::union(acc.as_ref(), nulls))

After:

NullBuffer::union_many([
    array.nulls(),
    from_array.nulls(),
    to_array.nulls(),
    stride.and_then(|s| s.nulls()),
])

Per @alamb's suggestion, this PR also implements the general-purpose mutable bitwise operations on BooleanArray from #8809, following the PrimitiveArray::unary / unary_mut pattern. This builds on the BitAndAssign/BitOrAssign/BitXorAssign operators added to BooleanBuffer in #9567.

What changes are included in this PR?

NullBuffer::union_many(impl IntoIterator<Item = Option<&NullBuffer>>): combines multiple null buffers in a single allocation (clone + in-place &=). Used by DataFusion for bulk null handling.

BooleanArray bitwise operations (6 new public methods):

Unary (op: FnMut(u64) -> u64):

• bitwise_unary(&self, op) — always allocates a new array
• bitwise_unary_mut(self, op) -> Result<Self, Self> — in-place if uniquely owned, Err(self) if shared
• bitwise_unary_mut_or_clone(self, op) — in-place if uniquely owned, allocates if shared

Binary (op: FnMut(u64, u64) -> u64):

• bitwise_bin_op(&self, rhs, op) — always allocates, unions null buffers
• bitwise_bin_op_mut(self, rhs, op) -> Result<Self, Self> — in-place if uniquely owned, Err(self) if shared, unions null buffers
• bitwise_bin_op_mut_or_clone(self, rhs, op) — in-place if uniquely owned, allocates if shared, unions null buffers

Note: #8809 proposed the binary variants take a raw buffer and right_offset_in_bits. This PR takes &BooleanArray instead, which encapsulates both and matches existing patterns like BooleanArray::from_binary.

Are these changes tested?

Yes. 23 tests for the BooleanArray bitwise methods and 6 tests for union_many, covering:

• Basic correctness (AND, OR, NOT)
• Null handling (both nullable, one nullable, no nulls, null union)
• Buffer ownership (uniquely owned → in-place, shared → Err / fallback)
• Edge cases (empty arrays, sliced arrays with non-zero offset, misaligned left/right offsets)

Are there any user-facing changes?

Six new public methods on BooleanArray and one new public method on NullBuffer.

[neilconway]

Nice! I noticed this as well, should be a nice win.

[alamb]

Thnak you @mbutrovich and @neilconway

Instead of a new kernel, would you be wiling to implement this intead?

• [Arrow] Add bitwise operations BooleanArray that potentially reuse the underlying allocation #8809

I think ti would take a little more work, but would be more general

[mbutrovich]

Thnak you @mbutrovich and @neilconway

Instead of a new kernel, would you be wiling to implement this intead?

• [Arrow] Add bitwise operations BooleanArray that potentially reuse the underlying allocation #8809

I think ti would take a little more work, but would be more general

I'll take a look!

[alamb]

Tank you for this PR -- I plan to review it more carefully today

[alamb]

Thank you so much @mbutrovich -- this is so nice ❤️

I pushed a small commit to this PR to

1. add a few other test cases
2. verified that buffers are actually the same/different

[alamb]

This might be more generic if we had it take the iterator so it wouldn't require a slice

    pub fn union_many(nulls: impl IntoIterator<Item=Option<&NullBuffer>)) -> Option<NullBuffer> {

[mbutrovich]

IIRC I tried this at one point, but the current design seemed more idiomatic to the codebase. Happy to go with whatever makes sense to you.

[mbutrovich]

I'll make the change real fast.

[alamb]

I also think a slice is fine

[alamb]

I should probably note that the BooleanArray API additions are in addition to NullBuffer:union_many -- they are not required to be in the same PR

[alamb]

(I am not asking for changes here I am just observing)

[alamb]

Looks great -- thanks again @mbutrovich