Fokko opened a new pull request, #9430:
URL: https://github.com/apache/arrow-rs/pull/9430

   
   # Which issue does this PR close?
   
   - Closes #9429
   
   I'm doing some performance optimization, and noticed that we have a loop 
adding one value to the null mask at a time. Instead, I'd suggest adding 
`append_non_nulls` to do this at once.
   
   ```
   append_non_nulls(n) vs append(true) in a loop (with bitmap allocated)
   
   ┌───────────┬───────────────────┬─────────────────────┬─────────┐
   │     n     │ append(true) loop │ append_non_nulls(n) │ speedup │
   ├───────────┼───────────────────┼─────────────────────┼─────────┤
   │ 100       │ 251 ns            │ 73 ns               │ ~3x     │
   ├───────────┼───────────────────┼─────────────────────┼─────────┤
   │ 1,000     │ 2.0 µs            │ 94 ns               │ ~21x    │
   ├───────────┼───────────────────┼─────────────────────┼─────────┤
   │ 10,000    │ 19.3 µs           │ 119 ns              │ ~162x   │
   ├───────────┼───────────────────┼─────────────────────┼─────────┤
   │ 100,000   │ 191 µs            │ 348 ns              │ ~549x   │
   ├───────────┼───────────────────┼─────────────────────┼─────────┤
   │ 1,000,000 │ 1.90 ms           │ 3.5 µs              │ ~543x   │
   └───────────┴───────────────────┴─────────────────────┴─────────┘
   ```
   
   
   # Rationale for this change
   
   It adds a new public API in favor of performance improvements.
   
   # What changes are included in this PR?
   
   A new public API
   
   # Are these changes tested?
   
   Yes, with new unit-tests.
   
   # Are there any user-facing changes?
   
   Just a new convient API.


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