Fix index-based Get/Scan to filter out results whose index key no longer matches after lazy recovery rollback

[brfrn169]

Description

When a PREPARED record is found via the normal secondary index during an index-based Get/Scan, and lazy recovery rolls back the transaction, the index column value reverts to its before-image value. If this reverted value no longer matches the queried index key, the result should be filtered out. Previously, such results were returned incorrectly.

For example:

1. Transaction T1 updates col_idx from "B" to "A" (PREPARED state)
2. Transaction T2 queries col_idx = "A" via index-based Get/Scan
3. The PREPARED record is found via the normal index (col_idx = "A")
4. Lazy recovery rolls back T1, reverting col_idx to "B"
5. Bug: The record with col_idx = "B" was returned for the col_idx = "A" query

This PR addresses this issue.

Related issues and/or PRs

N/A

Changes made

• Added index key validation after lazy recovery rollback in CrudHandler.read() (Get) and CrudHandler.processScanResult() (Scan). When recoveryResult.rolledBack is true and the operation uses a secondary index, the recovered result is filtered using resultMatchesIndexKey().
• Added resultMatchesIndexKey() private method in CrudHandler that compares the result's index column value against the queried index key.
• Added unit tests in CrudHandlerTest covering rollback with matching/non-matching index keys for both Get and Scan operations.
• Added integration tests in ConsensusCommitSpecificIntegrationTestBase for Get, Scan, and getScanner that verify rolled-back PREPARED records are correctly filtered out when the index key matches the after-image.

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)

• The filtering is only applied when rolledBack is true because roll-forward (commit) preserves the after-image value, which already matches the queried index key by definition — the record was found via the normal index because its after-image matched the query.

Release notes

Fixed a bug where index-based Get and Scan operations could return incorrect results after lazy recovery rolled back a PREPARED record whose after-image index value matched the query but whose before-image (restored) value did not.

[gemini-code-assist]

Code Review

This pull request introduces logic to filter out records that no longer match a secondary index key after a lazy recovery (rollback) in the CrudHandler. This ensures consistency when querying via secondary indexes. Feedback suggests deduplicating the filtering logic between the read and processScanResult methods and adding a safety check when accessing partition key columns in the resultMatchesIndexKey helper to prevent potential IndexOutOfBoundsException.

[Copilot]

Pull request overview

Fixes an inconsistency in index-based reads under Consensus Commit where a record found via the (after-image) secondary index could be lazily recovered (rolled back) to a different index value but still be returned to the caller.

Changes:

• Added post-recovery index-key validation for index-based Get and Scan paths in CrudHandler.
• Introduced resultMatchesIndexKey() to compare the recovered row’s indexed column value against the requested index key.
• Added unit + integration coverage for rolled-back PREPARED records whose restored (before-image) index value no longer matches the queried index key.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
core/src/main/java/com/scalar/db/transaction/consensuscommit/CrudHandler.java	Filters recovered results for index-based reads when the returned view is effectively “rolled back” to before-image values.
core/src/test/java/com/scalar/db/transaction/consensuscommit/CrudHandlerTest.java	Adds unit tests validating filtering behavior for index-based Get/Scan after rollback.
integration-test/src/main/java/com/scalar/db/transaction/consensuscommit/ConsensusCommitSpecificIntegrationTestBase.java	Adds integration tests for Get/Scan/getScanner ensuring rolled-back rows are not returned when the index key no longer matches.

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[brfrn169]

/gemini review

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

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[gemini-code-assist]

Code Review

This pull request implements filtering for secondary index results after a lazy recovery (rollback) in the consensus commit transaction protocol. It ensures that if a record's index column value reverts to an original value that no longer matches the query criteria after a rollback, the record is filtered out of the result set. Additionally, the logic prevents caching these filtered-out results as empty in the transaction snapshot to avoid incorrect subsequent reads. I have no feedback to provide as no review comments were submitted.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

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[komamitsu]

LGTM! 👍

[feeblefakie]

LGTM! Thank you!

[KodaiD]

LGTM. Thank you!

[Torch3333]

LGTM, thank you!