refactor(index): remove dead segment commit branch

[ddupg]

Summary

• Remove the dead segment-commit branch from CreateIndexBuilder::execute.
• Remove helpers used solely by that branch and rename the stale IVF-RQ test.
• The branch became redundant in #6889, which replaced its segment metadata conversion with the same CreateIndex transaction as the fallback branch but left the guard in place.

Testing

• cargo fmt --all -- --check
• cargo clippy --all --tests --benches -- -D warnings
• Focused index::create vector, IVF-RQ, and BTree tests

[coderabbitai]

📝 Walkthrough

Walkthrough

CreateIndexBuilder::execute now builds create-index transactions with new_idx.dataset_version through a single path. Obsolete segment-commit selection helpers are removed, and the related IVF-RQ test is renamed without changing its assertions.

Changes

Index transaction construction

Layer / File(s)	Summary
Unify index transaction construction rust/lance/src/index/create.rs	CreateIndexBuilder::execute uses one TransactionBuilder path with the dataset version and transaction properties; obsolete path-selection helpers are removed and the affected test is renamed.

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

Possibly related PRs

• lance-format/lance#6806: Changes the staged index-segment transaction API involved in index transaction handling.
• lance-format/lance#7244: Modifies CreateIndexBuilder::execute transaction-path selection in the same file.

Suggested labels: A-index

Suggested reviewers: xuanwo, jackye1995, wjones127

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%.
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.
Title check	✅ Passed	The title clearly reflects the main change: removing the dead segment-commit branch in index creation.
Description check	✅ Passed	The description matches the changeset and explains the removed branch, helper cleanup, and test rename.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[coderabbitai]

Note

Quiet mode is enabled, so only the most important comments were posted inline. Other review comments are grouped below.

🟡 Other comments (1)

rust/lance/src/index/create.rs-1831-1834 (1)

1831-1834: 🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Assert the concrete error variant as well as the message.

These tests only check to_string(), so an incorrect error type with the same text would still pass. Assert the expected Error variant and retain the message assertion.

As per coding guidelines, tests must assert both the error variant and message content.

Also applies to: 3121-3124

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@rust/lance/src/index/create.rs` around lines 1831 - 1834, Update the affected
error tests around the merge-error assertion and the corresponding assertion at
the other reported location to match the concrete expected Error variant before
retaining the existing “future dataset version” message check. Ensure both
assertions validate the error type and message content, using the project’s
established variant-matching pattern.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Other comments:
In `@rust/lance/src/index/create.rs`:
- Around line 1831-1834: Update the affected error tests around the merge-error
assertion and the corresponding assertion at the other reported location to
match the concrete expected Error variant before retaining the existing “future
dataset version” message check. Ensure both assertions validate the error type
and message content, using the project’s established variant-matching pattern.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: QUIET

Plan: Pro Plus

Run ID: 941b7c73-892b-4749-b4a5-e52d6bbd4814

📥 Commits

Reviewing files that changed from the base of the PR and between ef796d0 and a8e243f.

📒 Files selected for processing (1)

• rust/lance/src/index/create.rs