mbutrovich opened a new pull request, #9692:
URL: https://github.com/apache/arrow-rs/pull/9692

   # Which issue does this PR close?
   
   - Closes #NNN.
   
   # Rationale for this change
   
   Several DataFusion PRs 
([#21464](https://github.com/apache/datafusion/pull/21464), 
[#21468](https://github.com/apache/datafusion/pull/21468), 
[#21471](https://github.com/apache/datafusion/pull/21471), 
[#21475](https://github.com/apache/datafusion/pull/21475), 
[#21477](https://github.com/apache/datafusion/pull/21477), 
[#21482](https://github.com/apache/datafusion/pull/21482), 
[#21532](https://github.com/apache/datafusion/pull/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`.
   
   For N inputs this means N-1 allocations. `NullBuffer::union_many` reduces 
this to 1 allocation (clone + in-place ANDs). For example, from 
[#21482](https://github.com/apache/datafusion/pull/21482):
   
   Before:
   ```rust
   [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:
   
   ```rust
   NullBuffer::union_many(&[
       array.nulls(),
       from_array.nulls(),
       to_array.nulls(),
       stride.and_then(|s| s.nulls()),
   ])
   ```
   
   # What changes are included in this PR?
   
   - `BooleanBuffer::bitand_many(&[&BooleanBuffer])`: bitwise AND of multiple 
buffers (1 clone + N-2 in-place ANDs = 1 allocation).
   - `NullBuffer::union_many(&[Option<&NullBuffer>])`: thin wrapper that 
filters `None`s and delegates to `bitand_many`.
   
   # Are these changes tested?
   
   Yes. 3 tests for `bitand_many`, 6 tests for `union_many`.
   
   # Are there any user-facing changes?
   
   Two new public methods on `BooleanBuffer` and `NullBuffer`.


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