ForeverAngry opened a new pull request, #2434:
URL: https://github.com/apache/iceberg-python/pull/2434
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# Rationale for this change
This PR adds comprehensive branch merge strategies to PyIceberg, bringing
Git-like branch merging capabilities to Iceberg table operations. This
enhancement enables users to merge branches with different strategies depending
on their workflow needs.
**Feature Overview:**
Apache Iceberg supports branch operations (create, delete, tag), but lacked
merge capabilities between branches. This PR implements 5 standard merge
strategies commonly used in version control systems:
1. **MERGE**: Classic three-way merge creating a merge commit that preserves
history of both branches
2. **SQUASH**: Condenses all commits from source branch into a single clean
commit on target branch
3. **REBASE**: Creates linear history by replaying commits from source
branch on top of target branch
4. **CHERRY_PICK**: Selects and applies specific individual commits from one
branch to another
5. **FAST_FORWARD**: Moves target branch pointer forward when no divergent
commits exist (no merge commit needed)
**Implementation Details:**
- **Strategy Pattern**: Clean, extensible architecture with abstract base
class and concrete implementations
- **Automatic Detection**: Fast-forward possibility automatically detected
and validated
- **Robust Utilities**: Common ancestor finding, branch validation, and
snapshot traversal utilities
- **Flexible API**: Optional source branch deletion after successful merge
- **Error Handling**: Comprehensive validation with clear error messages for
invalid operations
**Use Cases:**
- **Development Workflows**: Feature branch integration with different merge
policies
- **Data Pipeline Management**: Merging experimental data processing
branches back to production
- **Schema Evolution**: Combining schema changes from different development
branches
- **Multi-tenant Environments**: Merging tenant-specific changes while
maintaining isolation
## Are these changes tested?
Yes, extremely comprehensive test coverage with **35 tests** across multiple
categories:
**Core Functionality Tests:**
- **Strategy Implementation**: All 5 merge strategies individually tested
with various scenarios
- **Utility Methods**: Common ancestor finding, fast-forward detection,
branch validation
- **Integration Tests**: End-to-end testing through ManageSnapshots API
**Edge Cases & Error Handling:**
- Missing snapshots and branches with proper error messages
- Circular reference detection (prevents infinite loops)
- Self-merge prevention and validation
- Empty/invalid branch names
- No common ancestor scenarios
**Behavioral Validation:**
- Fast-forward validation specific to FastForwardStrategy
- Strategy selection and factory method testing
- Source branch preservation vs. deletion options
- Consistent return types across all strategies
**Quality Assurance:**
- All existing functionality preserved (no regressions)
- Comprehensive type hints and documentation
- All linting checks pass (ruff, mypy, pydocstyle)
- Mock-based testing for isolation and reliability
## Are there any user-facing changes?
**Yes - New Feature Addition (No Breaking Changes)**
**New Public API:**
```python
from pyiceberg.table.update.snapshot import BranchMergeStrategy
# New enum with 5 merge strategies
BranchMergeStrategy.MERGE
BranchMergeStrategy.SQUASH
BranchMergeStrategy.REBASE
BranchMergeStrategy.CHERRY_PICK
BranchMergeStrategy.FAST_FORWARD
# New method on ManageSnapshots
table.manage_snapshots().merge_branch(
source_branch="feature",
target_branch="main",
strategy=BranchMergeStrategy.SQUASH,
delete_source_branch=False # Optional: preserve or delete source branch
).commit()
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