Reuse null comparison helper in single-column sorting

[PointKernel]

Description

This PR reuses null_compare in simple_comparator to remove duplicate null-ordering logic in single-column sorting.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[copy-pr-bot]

Auto-sync is disabled for draft pull requests in this repository. Workflows must be run manually.

Contributors can view more details about this message here.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 80bccaf8-7e00-404d-9baf-06230db8fc3e

📥 Commits

Reviewing files that changed from the base of the PR and between a07a985 and a03921f.

📒 Files selected for processing (1)

• cpp/src/sort/sort_column_impl.cuh

Included review availability: Your plan provides up to 12 included reviews per hour; 11 remain after this review.

---

📝 Summary

Summary by CodeRabbit

• Bug Fixes
  • Corrected null-value ordering during sorting, including descending sorts.
  • Preserved existing ordering behavior for non-null values.

Walkthrough

Changes

Sort null ordering

Layer / File(s)	Summary
Comparator null ordering cpp/src/sort/sort_column_impl.cuh	simple_comparator now uses null_compare and weak_ordering for null ordering. Non-null comparison behavior remains unchanged.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Refactor

Merge Risk: ⚪ Minimal · up to a0392

The null-ordering refactor is mergeable with no material residual risk identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description accurately explains that simple_comparator reuses null_compare to remove duplicate null-ordering logic.
Title check	✅ Passed	The title clearly summarizes the main change: reusing the null comparison helper in single-column sorting.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands.}