Phil Skentelbery
2b2849a58d
Documents the diagnosis and resolution of database migration detection conflicts
123 lines
5.1 KiB
Markdown
123 lines
5.1 KiB
Markdown
# ADR-041: Database Migration Conflict Resolution
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## Status
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Accepted
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## Context
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The v1.0.0-rc.2 container deployment is failing with the error:
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```
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Migration 002_secure_tokens_and_authorization_codes.sql failed: table authorization_codes already exists
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```
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The production database is in a hybrid state:
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1. **v1.0.0-rc.1 Impact**: The `authorization_codes` table was created by SCHEMA_SQL in database.py
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2. **Missing Elements**: The production database lacks the proper indexes that migration 002 would create
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3. **Migration Tracking**: The schema_migrations table likely shows migration 002 hasn't been applied
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4. **Partial Schema**: The database has tables/columns from SCHEMA_SQL but not the complete migration features
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### Root Cause Analysis
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The conflict arose from an architectural mismatch between two database initialization strategies:
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1. **SCHEMA_SQL Approach**: Creates complete schema upfront (including authorization_codes table)
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2. **Migration Approach**: Expects to create tables that don't exist yet
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In v1.0.0-rc.1, SCHEMA_SQL included the `authorization_codes` table creation (lines 58-76 in database.py). When migration 002 tries to run, it attempts to CREATE TABLE authorization_codes, which already exists.
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### Current Migration System Logic
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The migrations.py file has sophisticated logic to handle this scenario:
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1. **Fresh Database Detection** (lines 352-368): If schema_migrations is empty and schema is current, mark all migrations as applied
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2. **Partial Schema Handling** (lines 176-211): For migration 002, it checks if tables exist and creates only missing indexes
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3. **Smart Migration Application** (lines 383-410): Can apply just indexes without running full migration
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However, the production database doesn't trigger the "fresh database" path because:
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- The schema is NOT fully current (missing indexes)
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- The is_schema_current() check (lines 89-95) requires ALL indexes to exist
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## Decision
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The architecture already has the correct solution implemented. The issue is that the production database falls into an edge case where:
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1. Tables exist (from SCHEMA_SQL)
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2. Indexes don't exist (never created)
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3. Migration tracking is empty or partial
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The migrations.py file already handles this case correctly in lines 383-410:
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- If migration 002's tables exist but indexes don't, it creates just the indexes
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- Then marks the migration as applied without running the full SQL
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## Rationale
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The existing architecture is sound and handles the hybrid state correctly. The migration system's sophisticated detection logic can:
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1. Identify when tables already exist
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2. Create only the missing pieces (indexes)
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3. Mark migrations as applied appropriately
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This approach:
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- Avoids data loss
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- Handles partial schemas gracefully
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- Maintains idempotency
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- Provides clear logging
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## Consequences
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### Positive
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1. **Zero Data Loss**: Existing tables are preserved
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2. **Graceful Recovery**: System can heal partial schemas automatically
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3. **Clear Audit Trail**: Migration tracking shows what was applied
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4. **Future-Proof**: Handles various database states correctly
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### Negative
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1. **Complexity**: The migration logic is sophisticated and must be understood
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2. **Edge Cases**: Requires careful testing of various database states
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## Implementation Notes
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### Database State Detection
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The system uses multiple checks to determine database state:
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```python
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# Check for tables
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table_exists(conn, 'authorization_codes')
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# Check for columns
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column_exists(conn, 'tokens', 'token_hash')
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# Check for indexes (critical for determining if migration 002 ran)
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index_exists(conn, 'idx_tokens_hash')
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```
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### Hybrid State Resolution
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When a database has tables but not indexes:
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1. Migration 002 is detected as "not needed" for table creation
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2. System creates missing indexes individually
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3. Migration is marked as applied
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### Production Fix Path
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For the current production issue:
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1. The v1.0.0-rc.2 container should work correctly
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2. The migration system will detect the hybrid state
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3. It will create only the missing indexes
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4. Migration 002 will be marked as applied
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If the error persists, it suggests the migration system isn't detecting the state correctly, which would require investigation of:
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- The exact schema_migrations table contents
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- Which tables/columns/indexes actually exist
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- The execution path through migrations.py
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## Alternatives Considered
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### Alternative 1: Remove Tables from SCHEMA_SQL
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**Rejected**: Would break fresh installations
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### Alternative 2: Make Migration 002 Idempotent
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Use CREATE TABLE IF NOT EXISTS in the migration.
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**Rejected**: Would hide partial application issues and not handle the DROP TABLE statement correctly
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### Alternative 3: Version-Specific SCHEMA_SQL
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Have different SCHEMA_SQL for different versions.
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**Rejected**: Too complex to maintain
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### Alternative 4: Manual Intervention
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Require manual database fixes.
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**Rejected**: Goes against the self-healing architecture principle
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## References
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- migrations.py lines 176-211 (migration 002 detection)
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- migrations.py lines 383-410 (index-only creation)
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- database.py lines 58-76 (authorization_codes in SCHEMA_SQL)
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- Migration file: 002_secure_tokens_and_authorization_codes.sql |