GH-34529: [C++][Compute] Replace explicit checking with DCHECK for invariants in row segmenter

[zanmato1984]

Rationale for this change

As #34529 described.

What changes are included in this PR?

Change the if checking for invariants in row segmenter to DCHECK.

Are these changes tested?

No need.

Are there any user-facing changes?

None.

• GitHub Issue: [C++] Clean up invariant checks in RowSegmenter to be DCHECK #34529

[github-actions]

⚠️ GitHub issue #34529 has been automatically assigned in GitHub to PR creator.

[zanmato1984]

I found a remaining trivial enhancement request regarding to row segmenter, hence filing this trivial PR. @pitrou Mind to take a look? Thanks.

[mapleFU]

So they would not get error in these scenrio?

[zanmato1984]

Moved down into the next anonymous namespace enclosing Grouper because this function is for Grouper to use.

[zanmato1984]

So they would not get error in these scenrio?

The errors touched in this PR are all internal invariants, that are not breakable by user inputs. In other words, these errors can only occur on bad implementation, so DCHECK should be sufficient.

As a comparison, some checking, e.g.

arrow/cpp/src/arrow/compute/row/grouper.cc

Lines 65 to 68 in 80622fa

	if (values.size() != key_types.size()) {
	return Status::Invalid("expected batch size ", key_types.size(), " but got ",
	values.size());
	}

can be triggered by user's (invalid) input, so it is kept as is.

[kou]

+1

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit ac6d7e8.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 10 possible false positives for unstable benchmarks that are known to sometimes produce them.