Deep understanding of "mysql"

MySQL has a complex architecture and architecture, which describe the organizational structure and working principles of MySQL from different perspectives.

1. MySQL architecture

MySQL's architecture is mainly a layered design, including the following three levels:

1. Client layer: Responsible for interacting with users, processing user requests, and passing requests to the server layer. The client includes multiple components such as a connection manager, a command dispatcher, and a query cache.

2. Server layer: Responsible for responding to client requests and returning data to the client. It includes multiple components such as data parser, query optimizer, storage engine interface, etc. The storage engine can be selected according to needs.

3. Storage engine layer: Responsible for storing and retrieving data. MySQL's architecture allows developers to customize the storage engine for the needs of specific applications.

2. MySQL architecture

MySQL's architecture mainly consists of three parts: application layer, MySQL service layer, and storage engine layer.

1. Application layer: This layer is the top layer of the entire architecture, including the application client, application software logic and other components, and is a layer directly facing users. In this layer, applications can use the API provided by MySQL (such as c, Python, PHP, etc.) to directly access the MySQL database.

2. MySQL service layer: This layer is the core of the entire architecture and is the main processing center responsible for functions such as data management and query processing. The MySQL service layer includes multiple components such as connectors, analyzers, optimizers, and executors, which work together to complete the parsing, optimization, and execution of SQL statements.

3. Storage engine layer: The storage engine layer is the component responsible for data storage and retrieval. They implement basic table operations (such as addition, deletion, modification, and query), and provide advanced functions such as transaction processing, concurrency control, and indexing. MySQL provides a variety of storage engines, such as MyISAM, InnoDB, Memory, etc.

In short, the architecture and architecture of MySQL are designed to better realize the functions of MySQL and improve its performance. Among them, the architecture mainly focuses on the hierarchical organizational structure of MySQL and the interactive relationship between each layer, while the architecture mainly focuses on the overall design ideas and patterns of MySQL.

While MySQL's architecture and architecture have some similarities, they are not exactly the same concepts. Architecture is the basis for the design and development of computer systems. It mainly refers to the parts of a computer system and how these parts work together. Architecture, on the other hand, focuses more on design ideas and patterns, involving higher-level abstractions and architectural styles. Therefore, although MySQL architecture and architecture are related, it is still important to understand their differences.

"Architecture" can be translated as "architecture" in English, and "architecture" can be translated as "structure" or "framework". These terms may differ slightly depending on the context, but are generally used interchangeably. In the official MySQL documentation, officials prefer to use the word "architecture" to describe the overall architecture and architecture of MySQL.

MySQL as a whole still has a CS architecture, which is composed of two parts: client and server. Here we mainly analyze the server-side architecture. The server side can be roughly divided into two parts: Server layer and storage engine layer (the functions of the two are somewhat similar to the Service layer and the relationship with the DAO layer in daily development, and can be compared and understood).

The Server layer is the core part of MySQL and is mainly responsible for connection management, security verification, query parsing and optimization, caching, built-in functions and other services. These include components such as connectors, query caches, analyzers, optimizers, and executors.

The storage engine layer is mainly responsible for data storage and retrieval, that is, storing data into files and managing indexes. MySQL comes with a variety of storage engines, such as InnoDB, MyISAM, Memory, etc. Each storage engine has its own characteristics and application scenarios.

Okay, that’s the introduction to the architecture. For the sake of easy classification and clear memory, let’s classify it into three layers for the time being and introduce the following content.

The MySQL client layer mainly consists of three modules: connector, query cache and analyzer.

• Connector: The connector is used to connect to the MySQL server, process client requests and complete identity authentication. When a client initiates a connection request to the MySQL server, the connector checks connection parameters, authenticates identity, creates threads, etc. The connector is also responsible for managing the connection pool to improve database access efficiency.
• Query Cache: Query Cache is used to cache SELECT query results to improve query performance. When the client sends a SELECT query request, MySQL will first query the query cache. If the query results have been cached, the results will be returned directly. The disadvantage of the query cache is that it is only effective when the table data does not change frequently, and it takes up a lot of memory. Therefore, in high concurrency situations, it is recommended to disable the query cache.
• Analyzer (Parser): The analyzer is used to parse SQL statements. When the client sends a SQL statement to MySQL, the analyzer is responsible for parsing the statement structure, identifying keywords, checking for syntax errors, generating execution plans, etc. The analyzer is an important part of MySQL, which directly affects the performance and effect of SQL queries.

In addition to these components, the client layer also provides some other functions, such as character set conversion, security verification, SSL encryption, asynchronous IO, etc. MySQL client supports multiple programming languages ​​and technologies, including C, C++, Java, Python, etc. Each programming language and technology has a corresponding client library (Connector).

The MySQL service layer is the core component of the MySQL database management system and mainly includes the following functions:

• Storage Engine: MySQL database management system supports multiple storage engines, such as InnoDB, MyISAM, etc. Each engine has different characteristics and applicable scenarios. The storage engine is responsible for storing data on disk in a specific format and providing CRUD (add, delete, modify, query) operations on data.
• Query Optimizer: The query optimizer is one of the core functions of MySQL. It is responsible for analyzing SQL query statements and generating optimal execution plans. The query optimizer will help users improve query efficiency as much as possible while ensuring that the query is correct.
• Logging Module: The logging module is used to record database operation information and error information, including binary logs, error logs, query logs, etc. The log module can help administrators quickly discover and solve database failures and performance problems.
• Security and Authentication: MySQL supports multiple authentication methods, such as password authentication, SSL/TLS encryption, plug-in authentication, etc. The security authentication module is responsible for protecting the data security and user privacy of the MySQL database.
• Backup and Recovery: Backup and recovery are a very important part of MySQL database management. MySQL provides a variety of backup methods, such as physical backup, logical backup, etc., to meet the backup needs of different scenarios. At the same time, MySQL also provides a variety of data recovery tools and technologies to help administrators quickly recover data.
• Replication: MySQL's replication technology can implement master-slave replication, multi-master replication and other scenarios to improve data availability and application read performance. The replication function supports asynchronous and semi-synchronous replication modes.

Above the service layer is the client layer. Clients can use MySQL Connectors in various programming languages ​​to connect and access data in the MySQL database.

MySQL's storage engine layer specifically includes the following functions:

• Supports multiple storage engines: MySQL uses a plug-in storage engine and supports multiple storage engines, such as InnoDB, MyISAM, etc.
• For tables rather than libraries: The storage engine is for tables rather than for libraries (different tables in a library can use different storage engines).
• Shielding storage engine differences: The server communicates with the storage engine through API to shield the differences between different storage engines.
• Data operations: The storage engine is responsible for storing data on disk in a specific format and providing CRUD (add, delete, modify, query) operations on data.

Specifically, the InnoDB storage engine supports advanced features such as transactions, row-level locks, and foreign key constraints, and is suitable for highly concurrent data writing and reading scenarios; while the MyISAM storage engine is suitable for large-scale query data sets, such as data warehouses. wait. In addition, there are other storage engines, such as Memory, CSV, Blackhole, etc., each with different characteristics and application scenarios.

MySQL is one of the most widely used relational database management systems currently, with powerful functions and stable performance. MySQL mainly includes the following mechanisms :

1. Storage engine mechanism: MySQL supports multiple storage engines, such as InnoDB, MyISAM, etc. Each storage engine has its own characteristics and applicable scenarios.

2. Lock mechanism: MySQL's concurrency control mechanism is responsible for managing concurrent access of multiple transactions in the database to avoid data inconsistency.

3. Transaction mechanism: MySQL supports the ACID characteristics of transactions, and can control the submission and rollback of transactions through BEGIN, COMMIT and ROLLBACK statements.

4. Query optimizer mechanism: MySQL's query optimizer can select the optimal execution plan based on the complexity of the SQL statement and the distribution of data.

5. Memory management mechanism: MySQL uses the buffer pool to reduce the number of disk I/O operations and improve data reading and writing efficiency. It also has dedicated threads to manage the data cached in the buffer pool.

6. Backup and recovery mechanism: MySQL provides a variety of backup and recovery methods, such as mysqldump, binary log, etc., which can meet the backup needs in different scenarios.

7. Security mechanism: MySQL provides many security mechanisms, such as user management, permission control, etc., to ensure the security of the database.

8. Partitioning mechanism: MySQL supports partitioned tables, which can divide a large table into several small tables for storage to improve data retrieval efficiency.

9. Logging mechanism: MySQL uses binary logs and error logs to record system operating status and exception information to facilitate later troubleshooting and fault recovery.

Please refer to books for details

"MySQL Technology Insider: InnoDB Storage Engine" is a classic book that provides an in-depth introduction to the InnoDB storage engine of the MySQL database, with very comprehensive coverage. The following is the table of contents for the first edition of the book (twenty-six chapters in total):

Part I InnoDB storage engine

1. InnoDB storage engine overview

2. Architecture

3. Threads and concurrency control

4. Lock analysis

5. Index data structure

6. Indexes in Mysql and InnoDB

7. InnoDB transactions

8. transaction isolation level

9. MVCC: multi-version concurrency control

10. MVCC implementation of InnoDB

11. insert buffer

12. Adaptive hash index

13. InnoDB internal architecture

14. InnoDB disk I/O

15. InnoDB cache structure

16. InnoDB cache management

17. InnoDB instances and tablespaces

Part II High Availability, Backup and Recovery

1. Backup and recovery

2. Database and tablespace backup

3. Log basics

4. InnoDB redo log

5. InnoDB undo log

6. InnoDB Debugging Tips

Part III Tools

1. InnoDB monitoring tools

2. InnoDB performance tuning

3. Other storage engines and summary

Note: This book has been published for many years, and the content may be lagging behind and may not be completely consistent with the latest version of the current MySQL database.

There is also a book related to tuning high performance

The following is the table of contents of "High Performance MySQL (Third Edition)" (23 chapters in total):

Part I MySQL Basics

• Chapter 1 MySQL Architecture and History
• Chapter 2 Benchmark Testing and Benchmark Testing Tools
• Chapter 3 Schema and Data Type Optimization

Part II Query performance optimization

• Chapter 4 Index Optimization
• Chapter 5 Query Performance Optimization
• Chapter 6 Advanced Query Optimization
• Chapter 7 Concurrency Control

Part III Advanced Features

• Chapter 8 Storage Engine Optimization
• Chapter 9 Mass Data Processing Optimization
• Chapter 10 Locks and Transactions
• Chapter 11 MySQL Replication
• Chapter 12 MySQL Partitioning

Part IV Server Performance Optimization

• Chapter 13 Optimizing Server Parameters
• Chapter 14 Advanced Configuration
• Chapter 15 MySQL Performance Monitoring
• Chapter 16 Diagnosing MySQL Performance Problems

Part V High Availability

• Chapter 17 MySQL Replication
• Chapter 18. MySQL Cluster
• Chapter 19 MySQL High Availability
• Chapter 20 Scalable Architecture

Part VI full text index

• Chapter 21 Full text index

Part VII Application Design

• Chapter 22 Stored Procedures and Functions
• Chapter 23 PHP and MySQL

Note: This book has been published for many years, and the content may be lagging behind and may not be completely consistent with the latest version of the current MySQL database.