Prod Deployment Preparation
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alembic/README
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alembic/README
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Generic single-database configuration.
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alembic/README.md
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# Alembic Database Migrations
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This directory contains **Alembic** database migrations for the LOAF membership platform.
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## What is Alembic?
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Alembic is a lightweight database migration tool for SQLAlchemy. It allows you to:
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- Track database schema changes over time
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- Apply migrations incrementally
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- Roll back changes if needed
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- Auto-generate migration scripts from model changes
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## Directory Structure
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```
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alembic/
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├── versions/ # Migration scripts (KEEP IN VERSION CONTROL)
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│ └── *.py # Individual migration files
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├── env.py # Alembic environment configuration
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├── script.py.mako # Template for new migration files
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└── README.md # This file
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```
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## Quick Start
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### 1. Create a New Migration
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After making changes to `models.py`, generate a migration:
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```bash
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cd backend
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alembic revision --autogenerate -m "add_user_bio_field"
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```
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This will create a new file in `alembic/versions/` like:
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```
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3e02c74581c9_add_user_bio_field.py
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```
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### 2. Review the Generated Migration
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**IMPORTANT:** Always review auto-generated migrations before applying them!
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```bash
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# Open the latest migration file
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cat alembic/versions/3e02c74581c9_add_user_bio_field.py
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```
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Check:
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- ✅ The `upgrade()` function contains the correct changes
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- ✅ The `downgrade()` function properly reverses those changes
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- ✅ No unintended table drops or data loss
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### 3. Apply the Migration
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```bash
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# Apply all pending migrations
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alembic upgrade head
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# Or apply migrations one at a time
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alembic upgrade +1
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```
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### 4. Rollback a Migration
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```bash
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# Rollback the last migration
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alembic downgrade -1
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# Rollback to a specific revision
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alembic downgrade 3e02c74581c9
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```
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## Common Commands
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| Command | Description |
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|---------|-------------|
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| `alembic current` | Show current migration revision |
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| `alembic history` | Show migration history |
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| `alembic heads` | Show head revisions |
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| `alembic upgrade head` | Apply all pending migrations |
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| `alembic downgrade -1` | Rollback last migration |
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| `alembic revision --autogenerate -m "message"` | Create new migration |
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| `alembic stamp head` | Mark database as up-to-date without running migrations |
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## Migration Workflow
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### For Development
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1. **Make changes to `models.py`**
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```python
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# In models.py
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class User(Base):
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# ...existing fields...
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bio = Column(Text, nullable=True) # New field
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```
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2. **Generate migration**
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```bash
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alembic revision --autogenerate -m "add_user_bio_field"
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```
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3. **Review the generated file**
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```python
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# In alembic/versions/xxxxx_add_user_bio_field.py
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def upgrade():
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op.add_column('users', sa.Column('bio', sa.Text(), nullable=True))
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def downgrade():
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op.drop_column('users', 'bio')
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```
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4. **Apply migration**
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```bash
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alembic upgrade head
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```
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5. **Commit migration file to Git**
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```bash
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git add alembic/versions/xxxxx_add_user_bio_field.py
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git commit -m "Add user bio field"
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```
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### For Production Deployment
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**Fresh Database (New Installation):**
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```bash
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# 1. Create database
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createdb membership_db
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# 2. Run initial schema SQL (creates all 17 tables)
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psql -U username -d membership_db -f ../migrations/000_initial_schema.sql
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# 3. Mark database as up-to-date with Alembic
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alembic stamp head
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# 4. Verify
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alembic current # Should show: 001_initial_baseline (head)
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```
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**Existing Database (Apply New Migrations):**
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```bash
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# 1. Pull latest code
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git pull origin main
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# 2. Apply migrations
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alembic upgrade head
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# 3. Verify
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alembic current
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# 4. Restart application
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systemctl restart membership-backend
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```
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## Configuration
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### Database Connection
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Alembic reads the `DATABASE_URL` from your `.env` file:
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```env
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DATABASE_URL=postgresql://user:password@localhost:5432/membership_db
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```
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The connection is configured in `alembic/env.py` (lines 29-36).
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### Target Metadata
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Alembic uses `Base.metadata` from `models.py` to detect changes:
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```python
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# In alembic/env.py
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from models import Base
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target_metadata = Base.metadata
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```
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## Important Notes
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### ✅ DO:
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- Always review auto-generated migrations before applying
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- Test migrations in development before production
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- Commit migration files to version control
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- Write descriptive migration messages
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- Include both `upgrade()` and `downgrade()` functions
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### ❌ DON'T:
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- Don't edit migration files after they've been applied in production
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- Don't delete migration files from `alembic/versions/`
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- Don't modify the `revision` or `down_revision` values
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- Don't commit `.pyc` files (already in .gitignore)
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## Migration History
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| Revision | Description | Date | Type |
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|----------|-------------|------|------|
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| `001_initial_baseline` | Baseline marker (empty migration) | 2026-01-02 | Baseline |
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**Note:** The actual initial schema is created by running `backend/migrations/000_initial_schema.sql`. The baseline migration is an empty marker that indicates the starting point for Alembic tracking.
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## Troubleshooting
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### "Target database is not up to date"
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```bash
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# Check current revision
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alembic current
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# Check pending migrations
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alembic history
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# Apply missing migrations
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alembic upgrade head
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```
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### "FAILED: Can't locate revision identified by 'xxxxx'"
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The database thinks it's at a revision that doesn't exist in your `alembic/versions/`.
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**Solution:**
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```bash
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# Mark database at a known good revision
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alembic stamp head
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```
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### Migration conflicts
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If you get merge conflicts in migration files:
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1. Resolve conflicts in the migration file
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2. Ensure `revision` and `down_revision` chain is correct
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3. Test the migration locally
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### Fresh database setup
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For a completely new database:
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```bash
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# Step 1: Run initial schema SQL
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psql -U username -d membership_db -f ../migrations/000_initial_schema.sql
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# Step 2: Mark as up-to-date
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alembic stamp head
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# Step 3: Verify
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alembic current # Should show: 001_initial_baseline (head)
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```
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## Legacy Migrations
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Old numbered SQL migrations (`000_initial_schema.sql` through `011_wordpress_import_enhancements.sql`) are preserved in `backend/migrations/` for reference. These have been consolidated into the initial Alembic migration.
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**Going forward, all new migrations must use Alembic.**
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## Additional Resources
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- [Alembic Documentation](https://alembic.sqlalchemy.org/)
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- [SQLAlchemy Documentation](https://docs.sqlalchemy.org/)
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- [PostgreSQL Documentation](https://www.postgresql.org/docs/)
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alembic/env.py
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alembic/env.py
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import os
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import sys
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from logging.config import fileConfig
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from sqlalchemy import engine_from_config, pool
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from alembic import context
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from dotenv import load_dotenv
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# Add the parent directory to the path so we can import our models
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sys.path.insert(0, os.path.dirname(os.path.dirname(__file__)))
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# Load environment variables from .env file
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load_dotenv()
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# Import all models so Alembic can detect them
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from models import Base
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import models # This ensures all models are imported
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# this is the Alembic Config object, which provides
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# access to the values within the .ini file in use.
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config = context.config
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# Interpret the config file for Python logging.
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# This line sets up loggers basically.
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if config.config_file_name is not None:
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fileConfig(config.config_file_name)
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# Set the SQLAlchemy URL from environment variable
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database_url = os.getenv("DATABASE_URL")
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if database_url:
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config.set_main_option("sqlalchemy.url", database_url)
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else:
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raise ValueError(
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"DATABASE_URL environment variable not set. "
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"Please create a .env file with DATABASE_URL=postgresql://user:password@host:port/dbname"
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)
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# Add your model's MetaData object here for 'autogenerate' support
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target_metadata = Base.metadata
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def run_migrations_offline() -> None:
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"""Run migrations in 'offline' mode.
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This configures the context with just a URL
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and not an Engine, though an Engine is acceptable
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here as well. By skipping the Engine creation
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we don't even need a DBAPI to be available.
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Calls to context.execute() here emit the given string to the
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script output.
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"""
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url = config.get_main_option("sqlalchemy.url")
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context.configure(
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url=url,
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target_metadata=target_metadata,
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literal_binds=True,
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dialect_opts={"paramstyle": "named"},
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compare_type=True, # Detect type changes
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compare_server_default=True, # Detect default value changes
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)
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with context.begin_transaction():
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context.run_migrations()
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def run_migrations_online() -> None:
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"""Run migrations in 'online' mode.
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In this scenario we need to create an Engine
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and associate a connection with the context.
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"""
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connectable = engine_from_config(
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config.get_section(config.config_ini_section, {}),
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prefix="sqlalchemy.",
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poolclass=pool.NullPool,
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)
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with connectable.connect() as connection:
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context.configure(
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connection=connection,
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target_metadata=target_metadata,
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compare_type=True, # Detect type changes
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compare_server_default=True, # Detect default value changes
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)
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with context.begin_transaction():
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context.run_migrations()
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if context.is_offline_mode():
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run_migrations_offline()
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else:
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run_migrations_online()
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alembic/script.py.mako
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alembic/script.py.mako
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"""${message}
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Revision ID: ${up_revision}
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Revises: ${down_revision | comma,n}
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Create Date: ${create_date}
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"""
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from typing import Sequence, Union
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from alembic import op
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import sqlalchemy as sa
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${imports if imports else ""}
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# revision identifiers, used by Alembic.
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revision: str = ${repr(up_revision)}
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down_revision: Union[str, None] = ${repr(down_revision)}
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branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
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depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
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def upgrade() -> None:
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${upgrades if upgrades else "pass"}
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def downgrade() -> None:
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${downgrades if downgrades else "pass"}
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59
alembic/versions/001_initial_baseline.py
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alembic/versions/001_initial_baseline.py
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"""initial_baseline - Use 000_initial_schema.sql for fresh deployments
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Revision ID: 001_initial_baseline
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Revises:
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Create Date: 2026-01-02 16:45:00.000000
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IMPORTANT: This is a baseline migration for existing databases.
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For FRESH deployments:
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1. Run: psql -U user -d dbname -f backend/migrations/000_initial_schema.sql
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2. Run: alembic stamp head
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For EXISTING deployments (already have database):
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1. Run: alembic stamp head (marks database as up-to-date)
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This migration intentionally does NOTHING because:
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- Fresh deployments use 000_initial_schema.sql to create all tables
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- Existing deployments already have all tables from 000_initial_schema.sql
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- Future migrations will be incremental changes from this baseline
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"""
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from typing import Sequence, Union
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from alembic import op
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import sqlalchemy as sa
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# revision identifiers, used by Alembic.
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revision: str = '001_initial_baseline'
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down_revision: Union[str, None] = None
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branch_labels: Union[str, Sequence[str], None] = None
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depends_on: Union[str, Sequence[str], None] = None
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def upgrade() -> None:
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"""
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This migration does nothing.
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It serves as a baseline marker that indicates:
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- All 17 tables exist (users, events, subscriptions, etc.)
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- All 8 enums are defined (UserStatus, UserRole, etc.)
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- All indexes and constraints are in place
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The actual schema is created by running:
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backend/migrations/000_initial_schema.sql
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"""
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pass
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def downgrade() -> None:
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"""
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Cannot downgrade below baseline.
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If you need to completely reset the database:
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1. dropdb dbname
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2. createdb dbname
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3. psql -U user -d dbname -f backend/migrations/000_initial_schema.sql
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4. alembic stamp head
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"""
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pass
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Reference in New Issue
Block a user