MySQL 8.0 vs 5.7: New Features & Full Migration Guide

1. Introduction

Overview of MySQL

Why Focus on the Differences Between MySQL 5.7 and 8.0

2. Major Differences Between MySQL 5.7 and 8.0 (Beginner Overview)

Changing the Default Character Set

-- Emoji data that may cause an error in MySQL 5.7
INSERT INTO test_table (text_column) VALUES ('😊'); 

New Features Added

1. Enhanced JSON Functionality

• Searching and manipulating JSON data has become more intuitive.
• Example: Easily extract specific values from JSON data. sql SELECT JSON_EXTRACT(json_column, '$.key') FROM test_table;

1. Introduction of Window Functions

• Window functions have been added to streamline data analysis.
• Example: Query to calculate sales ranking for each customer sql SELECT customer_id, sales, RANK() OVER (ORDER BY sales DESC) AS rank FROM sales_table;

Deprecated and Removed Features

• query_cache Removal It has been deprecated to improve performance. Instead, indexing and application-side cache management are recommended.
• Discontinuation of Old Encryption Methods Old authentication methods have been removed to enhance security.

Performance Improvements

• Heatmap-based Index Management: Allows efficient removal of rarely used indexes.
• InnoDB Optimization: Accelerates transaction processing.

-- Index optimization example
ALTER TABLE sales_table ADD INDEX (sales_amount);

3. In‑Depth Look at Differences Between MySQL 5.7 and 8.0 (For Intermediate/Advanced Users)

Details of the Default Character Set

• Character Set Compatibility: When migrating from 5.7 to 8.0, if existing databases use latin1 or other character sets, you need to consider changing the character set during migration.
• Performance Improvements: Using utf8mb4 can make some string comparisons more efficient, but you should verify the performance impact on large databases in advance.

-- Example of changing to utf8mb4
ALTER TABLE sample_table CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Enhanced JSON Features

1. JSON_TABLE function Allows JSON data to be transformed into a tabular format, making it easy to query complex JSON data.

   SELECT * FROM JSON_TABLE(
       '[{"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"}]',
       '$[*]' COLUMNS (
           id INT PATH '$.id',
           name VARCHAR(50) PATH '$.name'
       )
   ) AS jt;

2. Index Optimization Creating indexes on JSON data is now possible, improving query performance.

   CREATE INDEX json_index ON test_table (JSON_EXTRACT(json_column, '$.key'));

Performance and InnoDB Improvements

1. Doublewrite Buffer Introduction Improves data crash resilience and enhances disk I/O efficiency.
2. Persistent Metadata Addition Storing table definitions and index information on disk improves performance after a restart.

-- Example of index optimization
ALTER TABLE sales_table ADD INDEX (sales_amount);

Introduction of Window Functions

• Calculate cumulative sales per customer
• Compute rankings and positions

SELECT customer_id, sales, SUM(sales) OVER (PARTITION BY customer_id ORDER BY sales_date) AS cumulative_sales
FROM sales_table;

Deprecated Features and Migration Considerations

• Removed Features
• query_cache: Removed to improve performance.
• Old authentication methods: Deprecated to enhance security.
• Migration Considerations
• You need to identify queries or applications that use deprecated features in advance and consider alternatives.

4. Migration Considerations

Checking Compatibility

1. Changes to Reserved Words MySQL 8.0 adds new reserved words that may conflict with existing column or table names. You need to check and rename them in advance. Example: GROUPS and WINDOW became reserved words in 8.0.

   -- Example rename to avoid issues
   ALTER TABLE example_table RENAME COLUMN groups TO user_groups;

2. Use of Deprecated Features Queries or settings that worked in 5.7 may be deprecated or removed in 8.0. For example, query_cache has been removed in 8.0. Consider using application-level caching as an alternative.
3. Changes to Character Set and Collation MySQL 8.0 changes the default character set to utf8mb4. If existing tables use latin1 or other character sets, compatibility issues may arise during migration.

   -- Example of changing character set
   ALTER TABLE my_table CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Importance of Data Backups

• Using mysqldump

  mysqldump -u root -p --all-databases > backup.sql

• Physical backup (using tools like Percona XtraBackup).

Testing in a Test Environment

1. Data Restore Restore the backup in the test environment and simulate the migration.
2. Application Verification After migration, verify that the application works correctly on MySQL 8.0, paying particular attention to SQL query compatibility and performance.
3. Load Testing Conduct load testing on the migrated database, simulating real traffic to identify performance bottlenecks.

Planning the Migration

1. Current State Analysis

• Understand the current MySQL environment’s configuration and usage.
• Check for deprecated features and reserved word conflicts.

1. Preparing Migration Tools

• Use MySQL’s official mysql_upgrade tool to smoothly upgrade the database.

1. Phased Migration

• First perform the migration in a development environment, then move to staging, and finally to production.

1. Post-Migration Optimization

• Rebuild indexes and perform performance tuning.

   ANALYZE TABLE my_table;
   OPTIMIZE TABLE my_table;

Troubleshooting

1. Check Error Logs Review MySQL logs to pinpoint the cause of errors.

   tail -f /var/log/mysql/error.log

2. Use Compatibility Settings In MySQL 8.0, you can temporarily change sql_mode to ensure compatibility.

   SET sql_mode='NO_ENGINE_SUBSTITUTION';

3. Leverage Official Documentation Consult MySQL’s upgrade guide and FAQ for solutions.

5. Migration Procedure Guide

Migration Preparation

1. Check the current version Check the current MySQL version before migration. This helps with using the mysql_upgrade tool and verifying compatibility.

   mysql --version

2. Check for deprecated features Identify deprecated features and settings that could affect the migration. Create a list using the official “MySQL 8.0 Upgrade Guide”.
3. Data backup Obtain a full backup to keep the data safe. Recommended methods are as follows:

• mysqldump command use: bash mysqldump -u root -p --all-databases > backup.sql
• Physical backup (using Percona XtraBackup, etc.).

Migration Steps

1. Install MySQL 8.0 Install MySQL 8.0 on the target server. Installation steps vary by OS; the following is an example for Ubuntu:

   sudo apt update
   sudo apt install mysql-server

2. Verify configuration files Check the my.cnf (or my.ini) file and update the settings.

• Remove deprecated options
• Set the new character set (utf8mb4)

   [mysqld]
   character-set-server=utf8mb4
   collation-server=utf8mb4_unicode_ci

3. Import data Import the data using the backup file you obtained.

   mysql -u root -p < backup.sql

4. Run the mysql_upgrade tool After upgrading to MySQL 8.0, run the mysql_upgrade tool to update the databases to the latest format.

   mysql_upgrade -u root -p

Post-Migration Optimization

1. Rebuild indexes Rebuild indexes to optimize for the new InnoDB engine.

   ALTER TABLE table_name ENGINE=InnoDB;

2. Check query performance After migration, test the main queries used by the application and adjust indexes or settings as needed.

   EXPLAIN SELECT * FROM table_name WHERE column_name = 'value';

3. Monitor logs For several days after migration, monitor error logs and slow query logs to detect issues early.

   tail -f /var/log/mysql/error.log

Testing and Validation

1. Verify application functionality Ensure the application runs correctly and all queries behave as expected.
2. Load testing Conduct load tests that simulate real traffic to evaluate performance and stability.
3. Check data integrity After migrating from 5.7 to 8.0, verify that data is retained correctly. Pay special attention to issues related to character sets and collations.

Troubleshooting Measures

1. Restore from backup If the issue cannot be resolved, consider restoring the backup to revert to the previous environment.
2. Consult official support Use MySQL’s official upgrade guide and support resources to find solutions.
3. Share error details Posting error information on forums or developer communities can help you obtain solutions.

6. FAQ (Frequently Asked Questions)

• MySQL 8.0 offers improved security and performance.
• New features (e.g., enhanced JSON capabilities and window functions) improve development efficiency.
• With MySQL 5.7’s support ending, you can reduce security risks.

Q3: Will data compatibility be maintained during migration?

• If the character set uses latin1 or an older collation, there is a risk of garbled text after migration.
• If you are using deprecated or removed features, errors or unexpected behavior may occur.

Q5: How much time does migration take?

• Database size (larger data volumes take more time).
• Server performance and network speed.
• Time for testing in a test environment and handling issues.

Q6: What are the key changes in MySQL 8.0 that require special attention?

• The default character set has changed to utf8mb4, which may cause character set issues during migration.
• query_cache has been removed, and the caching configuration method has changed.
• New reserved words (e.g., GROUPS and WINDOW) have been added, which may cause conflicts with existing tables or queries.

Q7: Can performance degrade after migration?

• Improper index configuration.
• Inefficient queries that become apparent after migration.
• New settings that are not optimized.

Q8: What security enhancements does MySQL 8.0 have?

• Enhanced authentication method: caching_sha2_password is now the default, raising the security level.
• Expanded data encryption: InnoDB tablespace encryption has been introduced.
• Login attempt limits: You can set a limit on failed login attempts, adding a mechanism to prevent unauthorized access.

Q9: Should you outsource the migration to MySQL 8.0?

7. Summary

Benefits of Migrating to MySQL 8.0

1. Improved Performance

• Optimizations in the new InnoDB engine have significantly improved transaction processing and query execution speed.

1. Addition of New Features

• Enhanced JSON capabilities and the introduction of window functions streamline data manipulation and analysis.
• Changing the default character set to utf8mb4 makes internationalization easier.

1. Enhanced Security

• Strengthened authentication methods and encryption features improve security.

Things to Watch Out for During Migration

• Check for Deprecated and Removed Features
• Verify items such as query_cache and old authentication methods that could affect the migration.
• Character Set Issues
• If you are using latin1 or other character sets, you may encounter garbled text after migration. Switching to an appropriate character set is necessary.
• Testing in a Staging Environment
• Before applying changes to production, simulate the migration in a test environment to resolve potential issues in advance.

Key Points for a Successful Migration

1. Thorough Preparation

• Analyze the current database state to identify incompatibilities and potential issues.
• Take backups and verify the restore procedures.

1. Migrate Incrementally

• Proceed with migration from test to staging to production environments, addressing issues at each stage.

1. Post-Migration Optimization

• Rebuild indexes and adjust settings to maximize database performance after migration.

Future Outlook