Extend applicability of one-phase commit optimization in Consensus Commit

[brfrn169]

Description

This PR extends the applicability of one-phase commit optimization in the Consensus Commit protocol.

Previously, one-phase commit optimization was not available when the isolation level is SERIALIZABLE. This change enables one-phase commit even in SERIALIZABLE isolation level when validation is not actually needed. This change will improve transaction performance in SERIALIZABLE isolation level for read-modify-write workloads.

Related issues and/or PRs

N/A

Changes made

• Moved validation logic from Snapshot to CommitHandler: The toSerializable() method and related validation logic have been relocated to CommitHandler, making the validation process more centralized and easier to manage.
• Introduced ValidationInfo class: This new class encapsulates the information needed for validation and provides the isActuallyValidationRequired() method to determine if validation is truly necessary.
• Updated canOnePhaseCommit() logic: The method now uses ValidationInfo.isActuallyValidationRequired() instead of TransactionContext.isValidationRequired(), enabling one-phase commit when validation is configured but not actually needed.

Checklist

The following is a best-effort checklist. If any items in this checklist are not applicable to this PR or are dependent on other, unmerged PRs, please still mark the checkboxes after you have read and understood each item.

• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes.
• I have considered whether similar issues could occur in other products, components, or modules if this PR is for bug fixes.
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.).
• Tests (unit, integration, etc.) have been added for the changes.
• My changes generate no new warnings.
• Any dependent changes in other PRs have been merged and published.

Additional notes (optional)

N/A

Release notes

Extended the applicability of one-phase commit optimization in the Consensus Commit protocol. This allows one-phase commit to be used even in SERIALIZABLE isolation level when the transaction only reads records that it subsequently updates, improving performance for read-modify-write workloads.

[gemini-code-assist]

Summary of Changes

Hello @brfrn169, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant refactoring of the transaction commit and validation process. The primary goal is to extend the applicability of the one-phase commit optimization, allowing it to be utilized more broadly, especially for transactions operating under SERIALIZABLE isolation. By moving and refining the validation logic, the system can now intelligently determine when a full validation phase is truly necessary, thereby optimizing performance for transactions that don't inherently require it, without compromising correctness.

Highlights

• Refactored Validation Logic: The transaction validation logic, previously residing in the Snapshot class, has been moved to the CommitHandler. This includes methods for validating read sets, scan sets, and indexed operations.
• Extended One-Phase Commit Applicability: The one-phase commit optimization can now be applied to transactions under SERIALIZABLE isolation, provided that the transaction's read set does not actually require validation (e.g., if all read records are also modified by the same transaction). A new ValidationInfo class helps determine this.
• Improved Performance for SERIALIZABLE Transactions: By allowing one-phase commit for certain SERIALIZABLE transactions, the number of storage operations during commit can be reduced, leading to potential performance improvements.
• Updated Snapshot Class: The Snapshot class has been simplified by removing its direct dependency on Isolation level and ParallelExecutor, as well as the validation methods that were moved to CommitHandler.
• Comprehensive Test Coverage: Extensive unit and integration tests have been added or updated to cover the new validation logic in CommitHandler and to verify the extended applicability of the one-phase commit optimization across various storage atomicity units.

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[gemini-code-assist]

Code Review

This pull request extends the applicability of the one-phase commit optimization to SERIALIZABLE transactions, provided that the read set only contains records that are also part of the write set. This is a significant performance improvement. The implementation involves refactoring the validation logic out of the Snapshot class and into the CommitHandler, using a new ValidationInfo helper class. The changes are well-structured and accompanied by thorough unit and integration tests. My review includes a few suggestions to improve robustness and maintainability, such as addressing a potential StackOverflowError from tail recursion, fixing a bug in an equals method used in tests, and refactoring test code to reduce duplication.

[Copilot]

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[brfrn169]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a valuable optimization for one-phase commits in SERIALIZABLE isolation level, specifically for read-modify-write workloads. The refactoring of moving validation logic from Snapshot to CommitHandler is a great design improvement, enhancing separation of concerns and making the code easier to maintain. The introduction of the ValidationInfo class further cleans up the validation process. The accompanying unit and integration tests are comprehensive and provide good coverage for these critical changes.

I have found one potential issue regarding a recursive method call that could lead to a StackOverflowError under certain data patterns. My review includes a specific comment and suggestion to address this. Overall, this is a high-quality contribution.

[Copilot]

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