HIVE-29877: HMSCatalogAdapter fails to route Iceberg REST endpoints containing an optional {prefix}

[Aggarwal-Raghav]

What changes were proposed in this pull request?

HIVE-29877
Previously, the router expected URLs to match an exact length and crashed if an Iceberg client sent a {prefix} (like my_catalog). This PR introduces a mathematical offset that dynamically calculates the length of any prefix, allowing the server to gracefully accept and route multi-segment prefixes.

Why are the changes needed?

• To comply with the OpenAPI specification and HMS Rest catalog exposes {prefix} in ../iceberg/v1/config
• Databricks Unity IRC follows the following standard where catalogs/<uc_catalog_name> can be prefix https://docs.databricks.com/aws/en/external-access/iceberg#rest-api-curl-example

https://<workspace-instance>/api/2.1/unity-catalog/iceberg-rest/v1/catalogs/<uc_catalog_name>/namespaces/<uc_schema_name>/tables/<uc_table_name>

• Spark client can inject prefix using --conf spark.sql.catalog.local.prefix=my_test_prefix

Does this PR introduce any user-facing change?

Yes (Positive Impact): Users can now successfully connect strict Iceberg REST clients that inject custom multi-segment prefixes into the HTTP paths without hitting HTTP 400 errors.

How was this patch tested?

Write Junit test and spark docker image testing (Screenshot attached below)

[Aggarwal-Raghav]

BEFORE:

spark-sql ()> show databases;
26/09/01 19:21:04 ERROR SparkSQLDriver: Failed in [show databases]
org.apache.iceberg.exceptions.BadRequestException: Malformed request: No route for request: GET v1/my_test_prefix/namespaces
        at org.apache.iceberg.rest.ErrorHandlers$NamespaceErrorHandler.accept(ErrorHandlers.java:276)
        at org.apache.iceberg.rest.ErrorHandlers$NamespaceErrorHandler.accept(ErrorHandlers.java:266)
        at org.apache.iceberg.rest.HTTPClient.throwFailure(HTTPClient.java:242)
        at org.apache.iceberg.rest.HTTPClient.execute(HTTPClient.java:347)
        at org.apache.iceberg.rest.HTTPClient.execute(HTTPClient.java:299)
        at org.apache.iceberg.rest.BaseHTTPClient.get(BaseHTTPClient.java:77)
        at org.apache.iceberg.rest.RESTSessionCatalog.listNamespaces(RESTSessionCatalog.java:776)
        at org.apache.iceberg.catalog.BaseSessionCatalog$AsCatalog.listNamespaces(BaseSessionCatalog.java:139)
        at org.apache.iceberg.rest.RESTCatalog.listNamespaces(RESTCatalog.java:256)
        at org.apache.iceberg.catalog.SupportsNamespaces.listNamespaces(SupportsNamespaces.java:74)
        at org.apache.iceberg.spark.SparkCatalog.listNamespaces(SparkCatalog.java:383)
        at org.apache.spark.sql.execution.command.ShowNamespacesCommand.run(ShowNamespacesCommand.scala:44)
        at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult$lzycompute(commands.scala:79)

AFTER:

HTTP request fired from spark -> HMS IRC: GET /iceberg/v1/my_test_prefix/namespaces?pageToken= HTTP/1.1

[sonarqubecloud]

Quality Gate passed

Issues
18 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud