## 1. Pre-Upgrade Checklist
1. Backup Data
- Ensure all data is backed up to prevent data loss.
```
mysqldump -u root -p --all-databases > all_databases_backup.sql
```
- Alternatively, use a physical backup tool like `xtrabackup` for large databases.
2. Verify Current MySQL Version
- Check the current version.
```
mysql -u root -p -e "SELECT VERSION();"
```
3. Check System Requirements
- Confirm the operating system and hardware meet MySQL 8.0 requirements.
- Ensure sufficient disk space and memory are available.
4. Review Incompatible Changes
- Review the [MySQL documentation](https://dev.mysql.com/doc/refman/8.0/en/upgrading-from-previous-series.html) for detailed incompatible changes.
- Identify deprecated features in MySQL 5.x that may not be supported in 8.0.
5. Stop Applications
- Stop or pause any dependent applications to avoid conflicts during the upgrade.
```
sudo systemctl stop application-service-name
```
6. Check and Fix Table Compatibility
- Ensure all tables use `InnoDB` or compatible storage engines.
```
mysql -u root -p -e "SELECT TABLE_NAME, ENGINE FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'your_database';"
```
## 2. Upgrade Steps
1. Download and Install MySQL 8
- Update the package index.
```
sudo apt-get update
```
- Install MySQL 8.
```
sudo apt-get install mysql-server-8.0
```
- Ensure the correct version of MySQL 8.0 is selected.
2. Stop MySQL Service
- Stop the MySQL service.
```
sudo systemctl stop mysql
```
3. Backup Configuration Files
- Backup `my.cnf` or other configuration files.
```
sudo cp /etc/mysql/my.cnf /etc/mysql/my.cnf.bak
```
- Note any custom configurations that might need adjustment for MySQL 8.0.
4. Upgrade Data Files
- Run the `mysql_upgrade` tool to ensure compatibility.
```
sudo mysql_upgrade -u root -p
```
- Restart the MySQL service.
```
sudo systemctl start mysql
```
## 3. Post-Upgrade Checklist
1. Verify MySQL Version
- Confirm the upgrade was successful.
```
mysql -u root -p -e "SELECT VERSION();"
```
2. Check Databases
- Verify that all databases are intact and accessible.
```
mysql -u root -p -e "SHOW DATABASES;"
```
3. Review Log Files
- Check the MySQL error log for any warnings or errors.
```
sudo tail -f /var/log/mysql/error.log
```
4. Test Applications
- Restart applications and test database connections.
- Run application-specific test cases to identify any issues.
5. Run Integrity and Performance Checks
- Run data integrity checks.
```
mysqlcheck -u root -p --all-databases
```
- Perform performance tests to ensure optimal performance.
6. Review User Permissions
- Verify that user permissions and roles are functioning as expected.
```
mysql -u root -p -e "SELECT user, host FROM mysql.user;"
```
- Update any user accounts that might require new privileges.
7. Update Configurations
- Adjust configuration parameters for optimal performance:
- `innodb_buffer_pool_size`
- Ensure `query_cache_size` is disabled (deprecated in MySQL 8.0).
8. Optimize Database Performance
- Rebuild indexes and optimize tables.
```
mysql -u root -p -e "OPTIMIZE TABLE table_name;"
```
- Update statistics for better query performance.
```
ANALYZE TABLE table_name;
```
## Final Notes
- Update Client Tools: Ensure MySQL client tools and libraries are updated to versions that support MySQL 8.
- Monitor Performance: Continuously monitor server performance and apply tuning as needed.
- Documentation: Keep a log of all changes made during the upgrade process for future reference.