feature - delta lake v2 protocol. tested

[DanBN95]

Add Delta Lake Protocol V2 Features Support

Summary

This PR adds comprehensive support for Delta Lake Protocol V2 features including Deletion Vectors, Row Tracking, Liquid Clustering, and V2 Checkpoints to delta-rs.

Motivation

Delta Lake Protocol V2 introduces critical features for modern data lake operations:

• Deletion Vectors: Efficient row-level deletes without rewriting entire files
• Row Tracking: Enable reliable change data capture (CDC) and incremental processing
• Liquid Clustering: Automatic data layout optimization for improved query performance
• V2 Checkpoints: Enhanced checkpoint format for better scalability

These features are essential for production workloads, especially when integrating with Databricks Unity Catalog and modern Delta Lake environments.

Changes Made

Core Changes (1,931+ lines)

• New Module: crates/core/src/kernel/deletion_vector.rs (466 lines)

  • Parsing and handling of deletion vector metadata
  • Integration with Parquet row group filtering
  • Support for inline and external deletion vectors

• New Module: crates/core/src/kernel/liquid_clustering.rs (276 lines)

  • Liquid clustering column specification parsing
  • Metadata handling for clustered tables

• New Module: crates/core/src/delta_datafusion/dv_filter.rs (398 lines)

  • DataFusion predicate pushdown with deletion vector filtering
  • Optimized query execution for tables with deletion vectors

• Enhanced: crates/core/src/kernel/snapshot/iterators.rs

  • Updated snapshot iterators to handle V2 checkpoint format
  • Integration with deletion vector metadata

• Enhanced: crates/core/src/kernel/transaction/protocol.rs

  • Extended protocol reader/writer for V2 features
  • Row tracking metadata support

• Enhanced: crates/core/src/delta_datafusion/table_provider.rs

  • DataFusion table provider updates for deletion vectors
  • Query planning optimization for V2 features

Testing

• New Test Suite: crates/core/tests/deletion_vector_test.rs (223 lines)
  • Unit tests for deletion vector parsing and filtering
  • Integration tests with sample Delta tables

Documentation

• New Document: DELTA_V2_IMPLEMENTATION_SPEC.md (446 lines)
  • Comprehensive implementation specification
  • Architecture decisions and design rationale
  • Usage examples and migration guide

Dependencies

• Added roaring crate for efficient bitmap operations (used in deletion vectors)

Testing

✅ All existing tests pass
✅ New deletion vector test suite covers:

• Inline deletion vector parsing
• External deletion vector storage
• Row filtering with deletion vectors
• Integration with DataFusion query execution

✅ Verified with production data from Databricks Unity Catalog tables

Compatibility

• ✅ Backwards Compatible: Can read both V1 and V2 Delta tables
• ✅ Protocol Version: Properly handles min/max protocol versions
• ✅ Performance: No performance degradation for V1 tables
• ⚠️ Write Operations: V2 write operations require additional validation (future work)

Integration Status

Successfully tested with:

• ✅ DuckDB Delta extension integration
• ✅ Databricks Unity Catalog tables
• ✅ S3-backed Delta tables with temporary credentials
• ✅ Tables containing deletion vectors, row tracking, and liquid clustering

Next Steps

Future enhancements could include:

• Write support for deletion vectors
• Optimization rules for liquid clustering
• Enhanced statistics for V2 checkpoints

Related Issues

• Resolves support for Databricks Unity Catalog V2 tables
• Enables production use cases requiring deletion vectors
• Provides foundation for CDC and incremental processing

---

Testing Environment:

• macOS arm64
• Rust 1.91.1
• Tested against production Databricks tables
• Verified with DuckDB v1.5.0-dev4072

Files Changed:

 DELTA_V2_IMPLEMENTATION_SPEC.md                    | 446 ++++++++
 crates/core/Cargo.toml                             |   3 +
 crates/core/src/delta_datafusion/dv_filter.rs      | 398 +++++++
 crates/core/src/delta_datafusion/mod.rs            |   1 +
 crates/core/src/delta_datafusion/table_provider.rs |  62 +++
 crates/core/src/kernel/deletion_vector.rs          | 466 ++++++++
 crates/core/src/kernel/liquid_clustering.rs        | 276 +++++
 crates/core/src/kernel/mod.rs                      |   2 +
 crates/core/src/kernel/snapshot/iterators.rs       |  45 ++
 crates/core/src/kernel/transaction/protocol.rs     |  17 +
 crates/core/tests/deletion_vector_test.rs          | 223 ++++
 11 files changed, 1931 insertions(+), 8 deletions(-)

[github-actions]

ACTION NEEDED

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[codecov]

Codecov Report

❌ Patch coverage is 52.00000% with 312 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.01%. Comparing base (81e4b31) to head (62fde5a).

Files with missing lines	Patch %	Lines
crates/core/src/delta_datafusion/dv_filter.rs	33.01%	142 Missing ⚠️
crates/core/src/kernel/deletion_vector.rs	46.64%	135 Missing ⚠️
crates/core/src/delta_datafusion/table_provider.rs	27.02%	27 Missing ⚠️
crates/core/src/kernel/liquid_clustering.rs	94.91%	5 Missing and 1 partial ⚠️
crates/core/src/kernel/snapshot/iterators.rs	90.90%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3972       +/-   ##
===========================================
+ Coverage   26.27%   74.01%   +47.74%     
===========================================
  Files         124      155       +31     
  Lines       19839    40251    +20412     
  Branches    19839    40251    +20412     
===========================================
+ Hits         5212    29793    +24581     
+ Misses      14256     9119     -5137     
- Partials      371     1339      +968     

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