# Epic Travel & Expeditions - MongoDB to MySQL Migration Guide

## Overview
This guide helps you migrate the Epic Travel & Expeditions application from MongoDB to MySQL for cPanel deployment.

## Key Differences

### Database Structure
- **MongoDB**: Document-based, collections, flexible schema
- **MySQL**: Table-based, structured schema, relationships

### Data Type Mapping
| MongoDB | MySQL |
|---------|-------|
| _id (ObjectId) | id VARCHAR(36) - UUID |
| String | VARCHAR or TEXT |
| Number | INT, DECIMAL, NUMERIC |
| Date | DATETIME |
| Array | JSON column |
| Object | JSON column |

## Migration Steps

### 1. Export Data from MongoDB

```bash
# Export destinations
mongoexport --db=test_database --collection=destinations --out=destinations.json

# Export specials
mongoexport --db=test_database --collection=specials --out=specials.json

# Export admin_users
mongoexport --db=test_database --collection=admin_users --out=admin_users.json

# Export contacts
mongoexport --db=test_database --collection=contacts --out=contacts.json

# Export newsletter_subscribers
mongoexport --db=test_database --collection=newsletter_subscribers --out=newsletter.json
```

### 2. Transform Data for MySQL

MongoDB documents need to be transformed to match MySQL schema:

**MongoDB Document:**
```json
{
  "_id": {"$oid": "507f1f77bcf86cd799439011"},
  "name": "Paris",
  "rating": 4.9
}
```

**MySQL INSERT:**
```sql
INSERT INTO destinations (id, name, rating) 
VALUES ('507f1f77bcf86cd799439011', 'Paris', 4.9);
```

### 3. Code Changes Required

#### Backend Changes

**Old (MongoDB with Motor):**
```python
from motor.motor_asyncio import AsyncIOMotorClient

client = AsyncIOMotorClient(mongo_url)
db = client[os.environ['DB_NAME']]

# Query
destinations = await db.destinations.find().to_list(100)
```

**New (MySQL with SQLAlchemy):**
```python
from sqlalchemy.orm import Session
from database import SessionLocal, Destination

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()

# Query
destinations = db.query(Destination).limit(100).all()
```

#### API Route Changes

**Old (Async MongoDB):**
```python
@router.get("/destinations")
async def get_destinations():
    destinations = await db.destinations.find().to_list(100)
    return destinations
```

**New (Sync MySQL):**
```python
@router.get("/destinations")
def get_destinations(db: Session = Depends(get_db)):
    destinations = db.query(Destination).limit(100).all()
    return destinations
```

### 4. Environment Variables

**Old (.env for MongoDB):**
```env
MONGO_URL=mongodb://localhost:27017
DB_NAME=test_database
```

**New (.env for MySQL):**
```env
MYSQL_HOST=localhost
MYSQL_PORT=3306
MYSQL_DATABASE=epic_travel
MYSQL_USER=dbuser
MYSQL_PASSWORD=password
```

### 5. Dependencies

**Remove:**
```
motor==3.3.1
pymongo==4.5.0
```

**Add:**
```
PyMySQL>=1.1.0
SQLAlchemy>=2.0.23
```

## Automated Migration Script

```python
#!/usr/bin/env python3
"""
Migrate data from MongoDB to MySQL
"""
from pymongo import MongoClient
from sqlalchemy.orm import Session
from database import engine, SessionLocal, Destination, Special
import uuid

def migrate_destinations():
    # Connect to MongoDB
    mongo_client = MongoClient('mongodb://localhost:27017')
    mongo_db = mongo_client['test_database']
    
    # Connect to MySQL
    mysql_db = SessionLocal()
    
    try:
        # Get all destinations from MongoDB
        mongo_destinations = mongo_db.destinations.find()
        
        for doc in mongo_destinations:
            # Transform MongoDB document to SQLAlchemy model
            destination = Destination(
                id=str(doc.get('id', uuid.uuid4())),
                name=doc['name'],
                location=doc['location'],
                description=doc['description'],
                image=doc['image'],
                category=doc['category'],
                rating=float(doc['rating']),
                price=float(doc['price']),
                currency=doc.get('currency', 'USD'),
                created_at=doc.get('created_at')
            )
            mysql_db.add(destination)
        
        mysql_db.commit()
        print(f"Migrated {mongo_destinations.count()} destinations")
        
    except Exception as e:
        mysql_db.rollback()
        print(f"Error: {e}")
    finally:
        mysql_db.close()
        mongo_client.close()

if __name__ == "__main__":
    migrate_destinations()
```

## Testing Migration

### 1. Compare Counts
```sql
-- MySQL
SELECT COUNT(*) FROM destinations;
SELECT COUNT(*) FROM specials;
SELECT COUNT(*) FROM admin_users;
```

```javascript
// MongoDB
db.destinations.count()
db.specials.count()
db.admin_users.count()
```

### 2. Sample Data Verification
```sql
-- Check a specific destination
SELECT * FROM destinations WHERE name = 'Paris';
```

### 3. Test Relationships
```sql
-- Check specials with destinations
SELECT d.name, s.discount, s.end_date
FROM destinations d
JOIN specials s ON d.id = s.destination_id;
```

## Performance Considerations

### Indexing
MySQL indexes are already defined in schema:
- Primary keys on id columns
- Indexes on frequently queried columns (name, location, category, email)
- Foreign keys for relationships

### Connection Pooling
SQLAlchemy provides built-in connection pooling:
```python
engine = create_engine(
    DATABASE_URL,
    pool_size=10,
    max_overflow=20,
    pool_recycle=3600
)
```

### Query Optimization
- Use LIMIT for pagination
- Use indexes for WHERE clauses
- Use JOIN instead of multiple queries
- Cache frequently accessed data

## Rollback Plan

If migration fails:
1. Keep MongoDB running alongside MySQL initially
2. Test thoroughly before switching
3. Keep MongoDB backups for 30 days
4. Have both versions of code ready

## Post-Migration Checklist

- [ ] All collections migrated to tables
- [ ] Data counts match between MongoDB and MySQL
- [ ] All relationships working correctly
- [ ] Authentication still working
- [ ] API endpoints returning correct data
- [ ] Frontend displaying data correctly
- [ ] Image uploads working
- [ ] Admin dashboard functional
- [ ] Contact forms saving to MySQL
- [ ] Newsletter subscriptions working

## Common Issues

### Issue: Date format differences
**Solution:** Convert MongoDB ISODate to MySQL DATETIME
```python
created_at = datetime.fromisoformat(doc['created_at'])
```

### Issue: JSON array in specials.highlights
**Solution:** MySQL JSON column handles this automatically
```python
highlights = json.dumps(['item1', 'item2'])  # Store as JSON string
highlights = json.loads(row.highlights)      # Retrieve and parse
```

### Issue: UUID vs ObjectId
**Solution:** Use UUID strings in MySQL
```python
import uuid
id = str(uuid.uuid4())
```

## Support

For migration assistance:
- Check logs for specific errors
- Verify MySQL credentials
- Test database connection independently
- Review SQLAlchemy documentation
- Contact: advisor@epictravelexpeditions.com
