HIVE-29453: Separate create/drop catalog from HMSHandler

[rtrivedi12]

What changes were proposed in this pull request?

Extract catalog CRUD operations from HMSHandler into three dedicated handler classes ( CreateCatalogHandler, DropCatalogHandler, AlterCatalogHandler) following the existing @RequestHandler / AbstractRequestHandler pattern used across HIVE-29402.

Why are the changes needed?

HMSHandler Refactoring work - HIVE-29402

Does this PR introduce any user-facing change?

No

How was this patch tested?

mvn test -pl standalone-metastore/metastore-server
-Dtest=org.apache.hadoop.hive.metastore.client.TestCatalogs
-Dtest.groups=org.apache.hadoop.hive.metastore.annotation.MetastoreCheckinTest

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
1.3% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

This PR continues the HMSHandler refactoring (HIVE-29402 lineage) by moving catalog CRUD logic out of HMSHandler into dedicated @RequestHandler-based classes, aligning catalog operations with the existing AbstractRequestHandler pattern used across the standalone metastore server.

Changes:

• Refactors create_catalog, alter_catalog, and drop_catalog in HMSHandler to delegate work to AbstractRequestHandler implementations.
• Introduces CreateCatalogHandler, AlterCatalogHandler, and DropCatalogHandler to encapsulate catalog-specific logic and listener/event handling.
• Removes the inlined dropCatalogCore implementation from HMSHandler.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/HMSHandler.java	Delegates catalog CRUD RPCs to the request-handler framework and removes inlined drop core logic.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/handler/CreateCatalogHandler.java	New request handler encapsulating catalog creation, directory setup, and event/listener notifications.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/handler/AlterCatalogHandler.java	New request handler encapsulating catalog alteration and event/listener notifications.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/handler/DropCatalogHandler.java	New request handler encapsulating catalog drop behavior (including default DB handling) and notifications.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Suppressed comments (1)

standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/handler/DropCatalogHandler.java:127

• afterExecute() always notifies listeners, even when ifExists=true and the catalog did not exist (so cat remains null). In that path this emits a successful DropCatalogEvent with a null catalog, which can break listeners that assume a non-null catalog for successful DROP events. Consider skipping the non-transactional listener notification when cat is null (no drop actually happened).

  protected void afterExecute(DropCatalogResult result) throws TException, IOException {
    if (!handler.getListeners().isEmpty()) {
      MetaStoreListenerNotifier.notifyEvent(handler.getListeners(),
          EventType.DROP_CATALOG,
          new DropCatalogEvent(result != null && result.success(), handler, cat),