[krishanth7]

Summary

Phase 6.5 delivers the Schema Snapshot & Deterministic Fingerprints Subsystem (dera.reverse_engineering.snapshots) for the DERA Database Engineering Platform.

Building upon Phase 5.5 Canonical Metadata & ObjectIds, Phase 6.1 Canonical Schema Representation, Phase 6.2 Structural Reconstruction, Phase 6.3 Relationship Graphs, and Phase 6.4 Dependency Analysis, this milestone provides:

• Strongly typed, immutable snapshot representations (SchemaSnapshot).
• Strict separation of intrinsic structural payload from volatile operational envelope metadata.
• Deterministic RFC 8785 canonical JSON serialization with unescaped Unicode and explicit nulls.
• Domain-separated cryptographic SHA-256 structural fingerprints (DERA:SCHEMA:STRUCTURAL:V1).
• Stable snapshot record identity (snap_<hex32>) independent of structural digests.
• Standalone cryptographic integrity verification (verify_snapshot_integrity).
• Pluggable storage architecture with content-addressable deduplication and atomic filesystem writes.
• Retention management with tag protection and structural iteration preservation.
• Comprehensive protection against path traversal, credential leakage, and payload DoS.
• Zero external AI/LLM/ML models, zero database mutations, and zero customer database connections.

Change Type

• Feature (feat)
• Bug fix (fix)
• Documentation (docs)
• Refactor (refactor)
• Performance (perf)
• Test improvement (test)
• CI/CD or Build (ci, build)
• Security enhancement (security)
• Breaking change (!)

Related Issues

Closes #51

Implementation Details

1. Base Commit SHA

5b665c86cae22f05505dabc17bd6d8fd1c14b591

2. Architecture & Pipeline

Phase 5 Canonical Metadata
          │
          ▼
Phase 6.1 Schema Representation
          │
          ▼
Phase 6.2 Structural Reconstruction
          │
          ▼
Phase 6.3 Foreign Key Relationship Graph
          │
          ▼
Phase 6.4 Dependency Analysis & Cycle Detection
          │
          ▼
Phase 6.5 Schema Snapshot Builder
    ├── Immutable Structural Payload (SnapshotStructuralPayload)
    ├── RFC 8785 Canonical JSON Serialization
    ├── SHA-256 Fingerprint (Domain: DERA:SCHEMA:STRUCTURAL:V1)
    ├── Operational Envelope (SnapshotEnvelope) & Provenance
    ├── Metadata Completeness Preservation
    ├── Cryptographic Integrity Verification
    └── Secure Workspace-Isolated Storage (InMemory / FileSystem)
          │
          ▼
Versioned Schema Snapshot (`dera.schema.snapshot.v1`)

3. Canonicalization & Fingerprinting

• Lexicographical Tables & Constraints: Namespaces and tables sorted alphabetically.
• Column Ordinals: Columns sorted strictly by ordinal position to preserve database semantics.
• RFC 8785 JSON: Canonical formatting with UTF-8 unescaped characters, compact delimiters (,, :), UTC 'Z' timestamps, and rejection of non-finite numbers.
• Cryptographic Test Vectors:
  • empty_db: 5a341218a5a6965a5c1c4e03720510e0d67d558e56abbb69528634b91017d8df (349 bytes)
  • single_tbl_db: 0f37c68ee6534cb98f678e6bb57331ed09b898419546a06b25d2113804f12680 (1668 bytes)
  • composite_db: e63982b1804665c416a0b71d6d129bd97b222ec70eedc616dabef0640a739eb9 (3211 bytes)
  • unicode_db: d70235206edeebcfc5fb2566ae09162eb9c897d3c9c98ec10e87cbe399246de4 (1463 bytes)

Testing

• Relevant tests passed (python scripts/development/dev.py all or test)
• Tests not applicable — explanation below (e.g., documentation, typo fix, governance)
• Tests not run / blocked — explanation below

Test evidence & notes:

• pytest tests/reverse_engineering/phase_6_5: 58 passed in 1.25s
• pytest tests/reverse_engineering/: 264 passed in 2.47s
• python -m unittest discover tests/reverse_engineering/: 154 passed in 0.83s
• Tested against PostgreSQL, SQLite, MySQL, and MariaDB schemas.
• Performance tests confirm snapshot construction < 5ms (budget < 500ms), serialization < 2ms (budget < 200ms), verification < 1ms (budget < 100ms).

Documentation Impact

• Documentation in docs/ updated or verified where required
• Documentation validation passed (npm run docs:check)
• No documentation updates required for this change

17 dedicated documentation and audit artifacts created under docs/reverse-engineering/ and docs/audit/.

Security Impact & Deterministic Engineering

• Strict Non-AI Policy: Verified zero generative AI, LLM, or external inference APIs are introduced.
• Database Safety: Verified all database connector operations enforce read-only introspection without data modification.
• Credential Protection: Confirmed that no production credentials, passwords, or .env secrets are committed.
• Least Privilege: Validated that permissions and access boundaries are minimized.
• No Security Impact: Change does not affect database connections, security boundaries, or credentials.

Breaking Changes

• No breaking changes.
• Breaking change introduced (detailed explanation and migration path below):

Contributor Checklist

• My code follows the code style and guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings or lint errors.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published in downstream modules.

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