Refactor JdbcAdmin #3121

brfrn169 · 2025-11-06T04:36:34Z

Description

This PR refactors JdbcAdmin to improve maintainability and extensibility.

Related issues and/or PRs

N/A

Changes made

Extracted table metadata operations from JdbcAdmin into TableMetadataService
Extracted namespace metadata operations from JdbcAdmin into NamespaceMetadataService
Updated tests to reference the new service classes for metadata constants and methods

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)

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Release notes

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gemini-code-assist · 2025-11-06T04:36:58Z

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 focuses on a significant refactoring of the JdbcAdmin class within the JDBC storage implementation. The primary goal is to enhance modularity and maintainability by extracting metadata management responsibilities into two specialized service classes: TableMetadataService and NamespaceMetadataService. This change centralizes metadata-related logic, simplifies the JdbcAdmin class, and ensures a clearer separation of concerns, making the codebase easier to understand and extend.

Highlights

Refactoring JdbcAdmin: The core JdbcAdmin class has been significantly refactored to improve modularity and separation of concerns. Metadata management logic has been extracted into new dedicated service classes.
New Metadata Services: Two new classes, TableMetadataService and NamespaceMetadataService, have been introduced. TableMetadataService handles operations related to table metadata (e.g., creating, deleting, retrieving table schemas), while NamespaceMetadataService manages namespace-specific metadata (e.g., creating, dropping, and checking namespace existence).
Code Simplification and Delegation: The JdbcAdmin class is now much leaner, delegating all metadata-related SQL query generation and execution to the newly created services. This reduces the complexity of JdbcAdmin and centralizes metadata logic.
Test Updates: All relevant integration and unit tests have been updated to reflect the refactoring, ensuring that the new metadata services are correctly utilized and the functionality remains robust.

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gemini-code-assist

Code Review

This pull request refactors the JdbcAdmin class by extracting metadata management logic into new TableMetadataService and NamespaceMetadataService classes. This is a good improvement for separation of concerns. The review has identified a few potential issues with the refactored logic, including missing checks in corner cases like upgrading a fresh environment or dropping the last namespace, which could lead to unexpected behavior or metadata loss. There is also a minor issue where a schema is assumed to exist before a table is created, which could make the code more fragile.

core/src/main/java/com/scalar/db/storage/jdbc/JdbcAdmin.java

core/src/main/java/com/scalar/db/storage/jdbc/NamespaceMetadataService.java

core/src/main/java/com/scalar/db/storage/jdbc/TableMetadataService.java

Copilot

Pull Request Overview

This PR refactors the JDBC admin code by extracting table and namespace metadata management logic into dedicated service classes (TableMetadataService and NamespaceMetadataService), improving code organization and separation of concerns.

Extracted table metadata operations from JdbcAdmin into TableMetadataService
Extracted namespace metadata operations from JdbcAdmin into NamespaceMetadataService
Updated tests to reference the new service classes for metadata constants and methods

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
`JdbcAdmin.java`	Refactored to use new metadata service classes, reducing class size and improving modularity
`TableMetadataService.java`	New service class handling all table metadata operations
`NamespaceMetadataService.java`	New service class handling all namespace metadata operations
`JdbcAdminTest.java`	Updated test to reference new service classes and removed unused test helper and variables
`JdbcOperationCheckerTest.java`	Removed unused import and mock variable
`JdbcAdminTestUtils.java`	Updated to reference metadata constants from new service classes
`MultiStorageAdminTestUtils.java`	Updated to reference metadata constants from new service classes

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core/src/main/java/com/scalar/db/storage/jdbc/JdbcAdmin.java

core/src/main/java/com/scalar/db/storage/jdbc/TableMetadataService.java

brfrn169 · 2025-11-06T06:58:10Z

/gemini review

gemini-code-assist

Code Review

This pull request refactors the JdbcAdmin class by extracting metadata management logic into new TableMetadataService and NamespaceMetadataService classes. This is a significant improvement in terms of code organization and separation of concerns. The changes are well-executed, and the tests have been updated to match. I have a couple of suggestions for minor improvements related to code duplication and a small inefficiency, which I've detailed in the comments. Overall, this is a solid and beneficial refactoring.

core/src/main/java/com/scalar/db/storage/jdbc/NamespaceMetadataService.java

Copilot

Pull Request Overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.

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core/src/main/java/com/scalar/db/storage/jdbc/TableMetadataService.java

komamitsu · 2025-11-07T02:08:56Z

core/src/main/java/com/scalar/db/storage/jdbc/NamespaceMetadataService.java

+      int count = 0;
+      while (results.next()) {
+        namespaces.add(results.getString(COL_NAMESPACE_NAME));
+        // Only need to fetch the first two rows


The order of the records is always guaranteed? SELECT * FROM tbl WHERE namespace_name != $metadataSchema LIMIT 1 might be more robust?

Actually, this logic doesn’t depend on the order. To determine whether the namespaces table is empty, we need to verify that it contains only the row for the system namespace (metadataSchema). So I think the current logic is robust enough.
BTW, this refactoring does not change the original behavior.

komamitsu · 2025-11-07T02:18:29Z

core/src/main/java/com/scalar/db/storage/jdbc/NamespaceMetadataService.java

+            + encloseFullTableName(metadataSchema, TABLE_NAME)
+            + " WHERE "
+            + enclose(COL_NAMESPACE_NAME)
+            + " = ?";


[minor] It might depend on the underlying RDBMS, but adding LIMIT 1 might optimize the scan.

Yes, I think so too. However, I’d rather not do that now because we need the SELECT query to work across all supported JDBC databases. For example, Oracle doesn’t support the LIMIT clause, so we’d need database-specific SQL. So let’s add that optimization later if it becomes truly necessary. Thanks!

komamitsu · 2025-11-07T02:35:20Z

core/src/main/java/com/scalar/db/storage/jdbc/TableMetadataService.java

+
+  private boolean isMetadataTableEmpty(Connection connection) throws SQLException {
+    String selectAllTables =
+        "SELECT DISTINCT "


[trivial] In this case, SELECT full_table_name FROM tbl LIMIT 1 might be a bit better?

Yes. However, as I mentioned in the following, let’s add that optimization later if it becomes truly necessary. Thanks!
https://github.com/scalar-labs/scalardb/pull/3121/files#r2506970881

Torch3333

LGTM, thank you!

KodaiD

LGTM. Thank you!

brfrn169 self-assigned this Nov 6, 2025

Copilot AI review requested due to automatic review settings November 6, 2025 04:36

brfrn169 added the improvement label Nov 6, 2025

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Refactor JdbcAdmin

6a5289c

brfrn169 force-pushed the refactor-JdbcAdmin branch from 5095fcb to 6a5289c Compare November 6, 2025 06:56

brfrn169 requested a review from Copilot November 6, 2025 06:58

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brfrn169 requested review from KodaiD, Torch3333, feeblefakie and komamitsu November 6, 2025 07:18

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brfrn169 requested a review from KodaiD November 6, 2025 08:31

Rename constants

dc4f3bb

komamitsu reviewed Nov 7, 2025

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Torch3333 approved these changes Nov 7, 2025

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KodaiD approved these changes Nov 7, 2025

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brfrn169 requested a review from komamitsu November 8, 2025 15:12

Refactor JdbcAdmin #3121

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Refactor JdbcAdmin #3121

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brfrn169 commented Nov 6, 2025 •

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