GH-47252: [C++][Compute] Fix sort_indices for temporal types in arrow::Table

[nfrmtk]

Rationale for this change

I was unable to use compute::SortIndices with timestamp type because of crash.

What changes are included in this PR?

Fix. The issue was that comparator for merging record batches was not converting timestamp type to its physical variant.
so it crashed on null pointer reference on checked_cast result

Are these changes tested?

yes

Are there any user-facing changes?

This PR contains a "Critical Fix". (If the changes fix either (a) a security vulnerability, (b) a bug that caused incorrect or invalid data to be produced, or (c) a bug that causes a crash (even when the API contract is upheld), please provide explanation. If not, you can remove this.)
i've already provided, i suppose

• GitHub Issue: Segmentation fault upon multi-key sorting of concatenated tables #47252

[github-actions]

⚠️ GitHub issue #47252 has been automatically assigned in GitHub to PR creator.

[Copilot]

Pull request overview

Fixes a crash in compute::SortIndices / Table::sort_by when sorting arrow::Table columns with temporal logical types (e.g., timestamp), by ensuring per-batch sort-key arrays are converted to their physical representation before comparator-based merges.

Changes:

• Convert flattened per-record-batch sort-key arrays to the physical type (GetPhysicalType + GetPhysicalArray) when constructing ResolvedTableSortKey chunks.
• Add a regression test covering Table multi-key sorting on timestamp columns across multiple JSON chunks (record batches).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
cpp/src/arrow/compute/kernels/vector_sort_internal.h	Ensure table sort-key chunks use physical array types to prevent comparator downcast crashes for temporal logical types.
cpp/src/arrow/compute/kernels/vector_sort_test.cc	Add regression coverage for Table sort indices on timestamp keys across multiple chunks and null placement variants.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[pitrou]

Thanks for diagnosing and fixing this @nfrmtk . I'll wait for CI and then merge.

[pitrou]

(just another review to add a suggestion)

[Copilot]

Copilot was unable to review this pull request because the user who requested the review is ineligible. To be eligible to request a review, you need a paid Copilot license, or your organization must enable Copilot code review.

[pitrou]

CI failures are unrelated, I'll merge.

[github-actions]

⚠️ GitHub issue #47252 has been automatically assigned in GitHub to PR creator.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit bf108d4.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 2 possible false positives for unstable benchmarks that are known to sometimes produce them.

[nfrmtk]

Thanks for diagnosing and fixing this @nfrmtk

welcome