# BREEDR Database Migrations

## Automatic Migration System

BREEDR now includes an **automatic migration system** that runs on every startup to ensure your database schema is always correct and up-to-date.

## How It Works

### On Every Startup

1. **Initialize Database** - Creates tables if they don't exist
2. **Run Migrations** - Automatically fixes schema issues
3. **Validate Schema** - Verifies everything is correct
4. **Start Application** - Server begins accepting requests

You don't need to do anything manually!

---

## Migrations Included

### Migration 001: Remove Old Parent Columns

**Problem**: Old schema had `sire` and `dam` columns in the `dogs` table causing "no such column: sire" errors.

**Solution**: 
- Creates `parents` table for relationships
- Migrates existing sire/dam data to `parents` table
- Recreates `dogs` table without sire/dam columns
- Preserves all existing dog data

**Automatic**: Runs only if old schema detected

### Migration 002: Add Litter ID Column

**Problem**: Dogs table missing `litter_id` column for linking puppies to litters.

**Solution**:
- Adds `litter_id` column to `dogs` table
- Creates foreign key to `litters` table

**Automatic**: Runs only if column is missing

---

## Schema Version Tracking

The migration system uses a `schema_version` table to track which migrations have been applied:

```sql
CREATE TABLE schema_version (
  version INTEGER PRIMARY KEY,
  applied_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  description TEXT
);
```

Each migration runs only once, even if you restart the server multiple times.

---

## Correct Schema (Current)

### Dogs Table (No sire/dam columns!)

```sql
CREATE TABLE dogs (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  name TEXT NOT NULL,
  registration_number TEXT,
  microchip TEXT,
  sex TEXT CHECK(sex IN ('male', 'female')),
  birth_date DATE,
  breed TEXT,
  color TEXT,
  weight REAL,
  height REAL,
  notes TEXT,
  litter_id INTEGER,
  photo_urls TEXT,
  is_active INTEGER DEFAULT 1,
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (litter_id) REFERENCES litters(id) ON DELETE SET NULL
);
```

### Parents Table (Relationships)

```sql
CREATE TABLE parents (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  dog_id INTEGER NOT NULL,
  parent_id INTEGER NOT NULL,
  parent_type TEXT NOT NULL CHECK(parent_type IN ('sire', 'dam')),
  FOREIGN KEY (dog_id) REFERENCES dogs(id) ON DELETE CASCADE,
  FOREIGN KEY (parent_id) REFERENCES dogs(id) ON DELETE CASCADE,
  UNIQUE(dog_id, parent_type)
);
```

---

## How to Use

### Normal Startup (Automatic)

Just start your application normally:

```bash
# With Docker
docker-compose up -d

# Without Docker
cd server && npm start
```

Migrations run automatically!

### Check Migration Logs

Look at the server console output:

```
============================================================
BREEDR Database Migration System
============================================================
Database: /app/data/breedr.db

Current schema version: 0

[Migration 001] Checking for old sire/dam columns...
[Migration 001] Found old schema with sire/dam columns
[Migration 001] Migrating to parents table...
[Migration 001] Backed up 15 dogs
[Migration 001] Migrated 8 sire relationships
[Migration 001] Migrated 8 dam relationships
[Migration 001] Dropped old dogs table
[Migration 001] Created new dogs table
[Migration 001] Restored 15 dogs
[Migration 001] ✓ Migration complete!

[Migration 002] Checking for litter_id column...
[Migration 002] litter_id column already exists, skipping

[Validation] ✓ Dogs table exists
[Validation] ✓ Dogs table has no sire/dam columns
[Validation] ✓ Parents table exists
[Validation] ✓ Litter_id column exists
[Validation] ✓ Litters table exists
[Validation] ✓ All schema checks passed!

============================================================
Schema version: 0 → 2
Migration system complete!
============================================================
```

### Manual Migration (If Needed)

You can also run migrations manually:

```bash
node server/db/migrations.js
```

---

## Fresh Install

For a fresh installation:

1. **No database file exists** → `init.js` creates correct schema
2. **Migrations check schema** → Everything already correct, no migration needed
3. **Application starts** → Ready to use!

**Result**: Fresh installs automatically have the correct schema.

---

## Upgrading from Old Version

For existing installations with old schema:

1. **Old database detected** → Migration system kicks in
2. **Data is backed up** → Safety first!
3. **Schema is updated** → Sire/dam data moved to parents table
4. **Data is restored** → All your dogs are preserved
5. **Application starts** → Now using correct schema!

**Result**: Existing data is preserved and schema is fixed automatically.

---

## Docker Integration

### Dockerfile

No changes needed! Migrations run automatically when the container starts.

### docker-compose.yml

No changes needed! Just restart:

```bash
docker-compose restart
```

Or rebuild:

```bash
docker-compose down
docker-compose up --build -d
```

---

## Troubleshooting

### Migration Failed

If you see an error:

```
⚠️  Database migration failed!
Error: [error message]
```

1. **Check the error message** - It will tell you what went wrong
2. **Check database file permissions** - Make sure the file is writable
3. **Check disk space** - Ensure you have enough space
4. **Try manual migration**:
   ```bash
   node server/db/migrations.js
   ```

### Database is Locked

If migrations fail with "database is locked":

1. Stop all running instances of BREEDR
2. Check for zombie processes: `ps aux | grep node`
3. Kill any old processes: `kill <PID>`
4. Restart BREEDR

### Migration Keeps Running

If the same migration runs every time:

1. Check `schema_version` table:
   ```sql
   SELECT * FROM schema_version;
   ```
2. If empty, migration isn't being recorded
3. Check for database transaction issues
4. Manually add version:
   ```sql
   INSERT INTO schema_version (version, description) VALUES (1, 'Manual fix');
   ```

### Want to Start Fresh

To completely reset the database:

1. **Stop BREEDR**
2. **Backup your data** (optional):
   ```bash
   cp data/breedr.db data/breedr.db.backup
   ```
3. **Delete database**:
   ```bash
   rm data/breedr.db
   ```
4. **Restart BREEDR** - Fresh database will be created

---

## Validation Checks

The migration system validates your schema:

- ✓ Dogs table exists
- ✓ Dogs table has no sire/dam columns  
- ✓ Parents table exists
- ✓ Litter_id column exists
- ✓ Litters table exists

If any check fails, you'll see a warning.

---

## Adding New Migrations

If you need to add a new migration:

1. **Edit `server/db/migrations.js`**
2. **Add new migration function**:
   ```javascript
   migration003_yourNewMigration() {
     console.log('[Migration 003] Doing something...');
     // Your migration code here
   }
   ```
3. **Add to runMigrations()**:
   ```javascript
   if (currentVersion < 3) {
     this.migration003_yourNewMigration();
     this.recordMigration(3, 'Description of migration');
   }
   ```
4. **Test thoroughly** before deploying

---

## Best Practices

1. **Let migrations run automatically** - Don't skip them
2. **Check logs on startup** - Verify migrations succeeded
3. **Backup before major updates** - Safety first
4. **Test in development** - Before deploying to production
5. **Monitor schema_version** - Know what version you're on

---

## Schema Version History

| Version | Description | Date |
|---------|-------------|------|
| 0 | Initial schema (may have sire/dam columns) | - |
| 1 | Migrated to parents table | March 2026 |
| 2 | Added litter_id column | March 2026 |

---

## Summary

✅ **Migrations run automatically on every startup**  
✅ **No manual intervention needed**  
✅ **Data is preserved during migrations**  
✅ **Schema is validated after migrations**  
✅ **Works with Docker and standalone**  
✅ **Fresh installs get correct schema**  
✅ **Old installs are automatically upgraded**  

**The "no such column: sire" error is now fixed automatically!** 🎉