feat: Implement schema diffing for flat schemas (2/5) #1478
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Introduces core data structures for schema diffing: - SchemaDiff, FieldChange, FieldUpdate types - FieldChangeType enum for classifying changes - SchemaDiffError for validation errors - ColumnName::parent() helper method This is part 1/5 of the schema diffing feature implementation. The actual diffing algorithm will be added in PR 2. Note: This PR includes a temporary stub for compute_schema_diff() to allow basic tests to compile. The full implementation from the original PR delta-io#1346 will be copied exactly in PR 2. Related to delta-io#1346
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## main #1478 +/- ##
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+ Coverage 84.84% 84.92% +0.08%
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This was referenced Nov 14, 2025
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Adds a comprehensive unit test that exercises the filtering logic by manually constructing a SchemaDiff with both top-level and nested field changes. This test verifies that the methods correctly filter fields by path depth (length 1 vs length > 1). The test improves code coverage for these methods from 0% to full coverage of the filtering logic, addressing CI coverage requirements.
Adds complete diffing functionality for non-nested schemas: - Field collection and ID-based matching - Detection of adds, removes, renames, nullability changes - Physical name validation for column mapping - Breaking change classification - Full type classification including arrays and maps - Ancestor filtering for LCA reporting Currently supports flat schemas (top-level fields only). The collect_all_fields_with_paths() function has a commented-out recursive call that will be enabled in PR 3 to support nested fields. All other functions are copied exactly from the original PR delta-io#1346 (murali-db/schema-evol) with no logic changes. This is part 2/5 of the schema diffing feature implementation. Tests included (9 tests): - test_identical_schemas - test_change_count - test_top_level_added_field - test_added_required_field_is_breaking - test_added_nullable_field_is_not_breaking - test_physical_name_validation - test_multiple_change_types - test_multiple_with_breaking_change - test_duplicate_field_id_error Related to delta-io#1346
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OussamaSaoudi
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Nov 17, 2025
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| // Construct parent path by removing the last component | ||
| let parent_path = ColumnName::new(&path_parts[..path_parts.len() - 1]); |
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This is part 2 of 5 PRs that implement schema diffing for Delta Kernel Rust.
What's in this PR
What's NOT in this PR
Feature Gating
Inherits feature gate from PR #1477. Gate will be removed in PR 5.
Part of #1346