Is your feature request related to a problem or challenge? Please describe what you are trying to do.

The partition_validity method looks like it could be more efficient, the current code does not pre-allocate the vectors with the correct capacity based on the known null counts. It also calls Array::is_valid via dynamic dispatch, instead of first getting the NullBuffer and calling NullBuffer::is_valid, which could be inlined.

Describe the solution you'd like

Try to improve it and run the sort_kernels microbenchmark.

Describe alternatives you've considered

Additional context