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@murali-db murali-db commented Nov 14, 2025

⚠️ REVIEW ORDER: This PR depends on #1479 and should be reviewed AFTER it.

This PR is stacked on #1479#1478#1477. Once those merge, GitHub will automatically update to show only this PR's changes.


This is part 4 of 5 PRs that implement schema diffing for Delta Kernel Rust.

What's in this PR

Array tests covering:

  • Array element struct field changes
  • Doubly nested array type changes (array<array<int>>array<array<string>>)
  • Nested array nullability changes (loosened/tightened)
  • Inner array element nullability changes (loosened/tightened)
  • Simple array nullability changes (loosened/tightened)

Key Point

This PR is test-only. The array implementation (in classify_data_type_change and collect_fields_from_datatype) was already included in PR 2.

What's NOT in this PR

  • Map tests (PR 5)
  • NO implementation changes

Feature Gating

Inherits feature gate from PR #1477. Gate will be removed in PR 5.

Part of #1346

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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codecov bot commented Nov 14, 2025

Codecov Report

❌ Patch coverage is 96.68349% with 46 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.35%. Comparing base (fe01172) to head (fa43ac0).

Files with missing lines Patch % Lines
kernel/src/schema/diff.rs 96.67% 39 Missing and 7 partials ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #1480      +/-   ##
==========================================
+ Coverage   84.84%   85.35%   +0.51%     
==========================================
  Files         120      121       +1     
  Lines       32103    33490    +1387     
  Branches    32103    33490    +1387     
==========================================
+ Hits        27238    28587    +1349     
- Misses       3542     3573      +31     
- Partials     1323     1330       +7     

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murali-db and others added 6 commits November 14, 2025 13:48
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
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.
Extends schema diffing to handle nested structures:
- Recursive field collection through struct hierarchies
- Ancestor filtering to report only LCA changes
- Type change classification for struct containers
- Support for arbitrarily deep nesting

Arrays and maps support coming in follow-up PRs.

This is part 3/5 of the schema diffing feature implementation.

Related to delta-io#1346

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>
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 8 comprehensive array tests:
- Array element struct field changes
- Doubly nested array type changes
- Nested array nullability (loosened/tightened)
- Inner array nullability (loosened/tightened)
- Simple array nullability (loosened/tightened)

All array implementation code was already present from PR 2.
This PR only adds tests to verify array functionality.

This is part 4/5 of the schema diffing feature implementation.

Related to delta-io#1346

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>
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