Iceberg CDC streaming source

[ahmedabu98]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @ahmedabu98, 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 delivers a robust Iceberg Change Data Capture (CDC) streaming source for Apache Beam. It allows Beam pipelines to consume a continuous stream of changes from an Iceberg table, including inserts, deletes, and updates. The implementation intelligently handles different types of change events, processing straightforward additions or removals directly, while employing a sophisticated reconciliation step for complex update scenarios. This significantly expands Beam's capabilities for real-time data integration with Iceberg.

Highlights

• New CDC Streaming Source: Introduced a comprehensive Change Data Capture (CDC) streaming source for Iceberg tables, enabling continuous processing of data modifications (inserts, deletes, updates) within Apache Beam pipelines.
• Changelog Task Processing: Implemented a mechanism to scan incremental Iceberg snapshots and categorize changelog tasks into 'uniform' (all inserts or all deletes) and 'mixed' (both inserts and deletes for the same record) for optimized processing.
• Data Reconciliation for Updates: Developed a reconciliation process for 'mixed' changelog tasks, using co-grouping by record ID to accurately identify and emit 'UPDATE_BEFORE' and 'UPDATE_AFTER' records, alongside pure inserts and deletes.
• Enhanced Read Utilities: Extended ReadUtils with new methods and classes (DeleteReader, BeamDeleteFilter, BeamDeleteReader) to support reading and filtering based on Iceberg delete files, crucial for CDC functionality.
• Serialization of Iceberg Metadata: Added new serializable classes (SerializableDeleteFile, SerializableChangelogTask, ChangelogDescriptor) to efficiently transfer Iceberg metadata and task information across Beam workers.
• Increased Component Visibility: Adjusted the visibility of key classes and methods in IncrementalScanSource and SerializableDataFile to public or protected, facilitating their reuse and extension within the new CDC framework.

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[ahmedabu98]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a significant new feature: an Iceberg CDC (Change Data Capture) streaming source. The overall design is solid, leveraging Beam's splittable DoFns and CoGroupByKey for reconciling changes. The code is well-structured into different components for scanning, reading, and reconciling changelogs.

I've identified a few areas for improvement, mainly around cleaning up TODO comments and debugging statements. My specific comments are below.

There is one critical issue I couldn't comment on directly due to tooling limitations: in SerializableDataFile.java, the equals and hashCode methods have not been updated to include the newly added fields (dataSequenceNumber, fileSequenceNumber, firstRowId). This violates the Object contract and can lead to subtle bugs. Please ensure this is fixed.

[ahmedabu98]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a new Iceberg CDC (Change Data Capture) streaming source, which is a significant and valuable addition. The overall architecture is well-designed, with a clear separation of concerns for scanning changelogs, reading data, and reconciling changes to identify updates. The implementation of serializable classes for Iceberg objects is also a good approach.

However, there are a few critical issues that need to be addressed before this can be merged. The most important is that the output of the CDC source does not include any metadata about the type of change (INSERT, DELETE, UPDATE), which is fundamental for a CDC stream. Additionally, there are several leftover debugging statements and some dead code that should be cleaned up. I've left specific comments with suggestions on how to address these points.