Move Iceberg-only API classes to iceberg-api module

[andygrove]

Summary

Move classes that are exclusively used by Iceberg (not used by any non-@IcebergApi Comet code) from common into the new iceberg-api module, added in #3240. This will improve the separation of concerns and make the Iceberg API boundary clearer.

Classes to Move

The following 4 classes are only referenced by other @IcebergApi classes and exist purely for Iceberg integration:

Class	Current Location	Purpose
ParquetColumnSpec	common/src/main/java/org/apache/comet/parquet/	Bridge class to pass column descriptors between Comet and Iceberg (since Iceberg shades Parquet)
RowGroupReader	common/src/main/java/org/apache/comet/parquet/	PageReadStore implementation for row group reading
WrappedInputFile	common/src/main/java/org/apache/comet/parquet/	Wraps Iceberg's InputFile to implement Parquet's InputFile interface
AbstractCometSchemaImporter	common/src/main/java/org/apache/arrow/c/	Base class for schema import functionality

Important Considerations

Packaging/Shading Concerns

⚠️ This change requires careful attention to packaging and shading:

1. Iceberg shades Parquet - ParquetColumnSpec exists specifically because Iceberg uses shaded Parquet classes. Any module structure changes must preserve this compatibility.

2. JAR structure - Ensure the classes remain accessible to Iceberg after the move. The final packaged JAR must include these classes in a location Iceberg can access.

3. Maven shade plugin configuration - Review and update shade plugin configuration if needed to ensure:

   • Classes are included in the shaded JAR
   • Package relocations don't break Iceberg's access
   • No duplicate classes across modules

4. Dependency direction - The iceberg-public-api module currently only contains tests. If we move source classes there, we need to:

   • Update module dependencies
   • Ensure common module can still depend on these classes if needed
   • Consider if a separate iceberg-api module (non-test) is more appropriate

Testing Requirements

• Verify Iceberg integration tests pass after the move
• Verify shaded JAR contains all necessary classes
• Test with actual Iceberg to ensure no classloader issues
• Run iceberg-public-api module tests

Alternative Approaches

1. Keep in common, just document - Leave classes in common but document they're Iceberg-specific
2. New iceberg-api source module - Create a separate source module (not test-only) for Iceberg API classes
3. Subpackage organization - Move to org.apache.comet.iceberg.* package within common

Related

• PR test: Add Iceberg API stability tests #3240 - Added iceberg-public-api test module
• PR chore: Annotate classes/methods/fields that are used by Apache Iceberg #3237 - Added @IcebergApi annotation