Abhayla Claude Best Practices Fastapi DB Migrate

Database Migration Helper (FastAPI + Alembic)

Automates Alembic migration creation and model import location updates.

Scope: New model creation with migration generation. For modifying existing models, manually edit the model file and run alembic revision --autogenerate. For stack-neutral migration support (Prisma, Knex, Django, etc.), use /db-migrate. After any migration, verify with /db-migrate-verify.

Note: The backend/ path is a convention. If your project uses a different layout, adjust paths accordingly.

Request: $ARGUMENTS

Modes

STEP 1: New Model Mode

1. Create the Model File

Create backend/app/models/{model_name_snake}.py following existing patterns:

from sqlalchemy import Column, String, DateTime, ForeignKey, func
from sqlalchemy.dialects.postgresql import UUID
from app.db.base import Base
import uuid

class ModelName(Base):
    __tablename__ = "table_name"
    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), server_default=func.now(),

2. Update Import Locations

Find all locations where models are imported and add the new one:

cd backend && grep -rn "from app.models" app/db/ app/models/__init__.py tests/conftest.py

Update each location to include the new model import.

3. Generate Migration

cd backend && alembic revision --autogenerate -m "add {model_name} table"

4. Run Migration

cd backend && alembic upgrade head

5. Verify

cd backend && PYTHONPATH=. python -c "from app.models import *; print('All imports OK')"

STEP 2: Check Mode

Verify all model imports are in sync across required locations:

1. List all model files:

   ls backend/app/models/*.py | grep -v __init__ | grep -v __pycache__
   

2. For each model file, check it's imported in:
   • backend/app/models/__init__.py
   • backend/app/db/base.py (or equivalent base import file)
   • backend/tests/conftest.py (if test fixtures reference models)
3. Report mismatches:

   Import Sync Check:
   - model_name.py: ✓ __init__.py | ✓ base.py | ✗ conftest.py (MISSING)
   

STEP 3: Status Mode

cd backend && alembic current && alembic history --verbose | head -20

Report current head, pending migrations, and any branch divergence.

Output Summary

After any mode, report:

Migration Summary:
  Mode: <new-model|migrate|status|check>
  Model: <name or N/A>
  Files changed: <list>
  Migration: <generated|applied|checked|N/A>
  Import sync: <all OK|N mismatches>

CRITICAL RULES

• MUST NOT skip any import location — missing imports cause silent failures at runtime
• MUST run sync check (Step 2) after adding a model — Why: partial imports break Alembic autogenerate
• MUST follow existing naming conventions (snake_case files, PascalCase classes) — Why: inconsistent naming causes import confusion
• MUST NOT modify existing migrations — generate new ones instead
• After migration, verify with /db-migrate-verify if available

Source: abhayla/claude-best-practices — distributed by TomeVault.