Add isConsistentVirtualTableReadGuaranteed() to StorageInfo

[brfrn169]

Description

This PR introduces a new method isConsistentVirtualTableReadGuaranteed() method to the StorageInfo interface to indicate whether a storage guarantees consistent reads for virtual tables.

Implementation:

• Cassandra: Returns false (doesn't support virtual tables)
• Cosmos DB: Returns false (doesn't support virtual tables)
• DynamoDB: Returns false (doesn't support virtual tables)
• JDBC: Dynamically determines based on the database's transaction isolation level:
  • MySQL/MariaDB/TiDB: true if isolation level is REPEATABLE READ or SERIALIZABLE
  • PostgreSQL/YugabyteDB/AlloyDB: true if isolation level is REPEATABLE READ or SERIALIZABLE
  • Oracle: true if isolation level is SERIALIZABLE
  • SQL Server: true if isolation level is REPEATABLE READ or SERIALIZABLE
  • SQLite: true if isolation level is READ COMMITTED, REPEATABLE READ, or SERIALIZABLE
  • DB2: true if isolation level is REPEATABLE READ or SERIALIZABLE

Related issues and/or PRs

N/A

Changes made

• Added StorageInfo#isConsistentVirtualTableReadGuaranteed() method to indicate whether a storage guarantees consistent reads for virtual tables

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

Added isConsistentVirtualTableReadGuaranteed() method to the StorageInfo interface to indicate whether a storage guarantees consistent reads for virtual tables.

[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 enhances the StorageInfo interface by adding a new method to explicitly communicate whether a given storage backend provides consistent reads for virtual tables. This allows the system to adapt its behavior based on the underlying storage's capabilities, particularly for JDBC-based databases where consistency depends on the configured transaction isolation level. The change ensures that the system can accurately reflect the consistency guarantees offered by different data sources when dealing with virtualized data.

Highlights

• New Method for Virtual Table Read Consistency: Introduced isConsistentVirtualTableRead() to the StorageInfo interface, allowing storage backends to declare whether they guarantee consistent reads for virtual tables.
• JDBC Dynamic Consistency Check: For JDBC-based storages, the isConsistentVirtualTableRead() status is dynamically determined based on the current transaction isolation level and the specific RDB engine's capabilities (e.g., REPEATABLE READ for MySQL/PostgreSQL, SERIALIZABLE for Oracle).
• Storage-Specific Implementations: Cassandra, Cosmos DB, DynamoDB, and Object Storage implementations of StorageInfo now explicitly return false for isConsistentVirtualTableRead(), as they do not support virtual tables.
• Internal API Note: Added a Javadoc note to DistributedStorageAdmin clarifying that StorageInfo is primarily for internal use and may be subject to breaking changes.

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[gemini-code-assist]

Code Review

This PR introduces a new method isConsistentVirtualTableRead() to the StorageInfo interface. The implementation looks good, especially the dynamic check for JDBC storages. I've found a few issues, including a potential bug in StorageInfoImpl where equals() and hashCode() are not updated, and an incorrect isolation level for SQLite. I've also suggested a refactoring for the new tests in JdbcAdminTest to reduce duplication.

Also, please note there is an inconsistency in the method name between the PR description/release notes (isConsistentReadGuaranteed) and the actual implementation (isConsistentVirtualTableRead). It would be good to make them consistent.

[Copilot]

Pull Request Overview

This PR adds a new isConsistentVirtualTableRead() method to the StorageInfo interface to indicate whether a storage backend guarantees consistent reads for virtual tables. The implementation is storage-specific: most storage backends (Cassandra, Cosmos DB, DynamoDB, Object Storage) return false as they don't support virtual tables, while JDBC implementations dynamically determine the value based on the database's transaction isolation level.

Key changes:

• Added isConsistentVirtualTableRead() method to StorageInfo interface with appropriate documentation
• Implemented the method in StorageInfoImpl with a new boolean field
• Updated all storage implementations (Cassandra, Cosmos, DynamoDB, Object Storage, JDBC, MultiStorage) to provide the new parameter
• Added database-specific logic in each RdbEngine implementation to determine minimum isolation levels for consistent reads

Reviewed Changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
core/src/main/java/com/scalar/db/api/StorageInfo.java	Added new isConsistentVirtualTableRead() method to interface
core/src/main/java/com/scalar/db/api/DistributedStorageAdmin.java	Added documentation note that getStorageInfo is for internal use
core/src/main/java/com/scalar/db/common/StorageInfoImpl.java	Added new boolean field and getter implementation
core/src/main/java/com/scalar/db/storage/jdbc/RdbEngineStrategy.java	Added getMinimumIsolationLevelForConsistencyReads() method to interface
core/src/main/java/com/scalar/db/storage/jdbc/RdbEngine*.java	Implemented isolation level logic for MySQL, PostgreSQL, Oracle, SQL Server, SQLite, and DB2
core/src/main/java/com/scalar/db/storage/jdbc/JdbcAdmin.java	Changed getStorageInfo() to dynamically determine consistent read guarantee based on isolation level
core/src/main/java/com/scalar/db/storage/cassandra/CassandraAdmin.java	Updated to pass false for consistent virtual table reads
core/src/main/java/com/scalar/db/storage/cosmos/CosmosAdmin.java	Updated to pass false for consistent virtual table reads
core/src/main/java/com/scalar/db/storage/dynamo/DynamoAdmin.java	Updated to pass false for consistent virtual table reads
core/src/main/java/com/scalar/db/storage/objectstorage/ObjectStorageAdmin.java	Updated to pass false for consistent virtual table reads
core/src/main/java/com/scalar/db/storage/objectstorage/ObjectStorageWrapper.java	Enhanced documentation for close() method (unrelated to main feature)
core/src/main/java/com/scalar/db/storage/multistorage/MultiStorageAdmin.java	Updated to forward the new field from underlying storage
Test files	Updated all test instantiations of StorageInfoImpl to include the new boolean parameter and added comprehensive tests for isolation level behavior

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[feeblefakie]

Overall, looking good! Thank you!
Left some comments and suggestions.

[feeblefakie]

LGTM! Thank you!
But, I left one suggestion. PTAL!

[Torch3333]

LGTM, thank you!

[komamitsu]

LGTM! 👍