Sharing of data table locking mechanism in MySQL

MySQL is a commonly used relational database system. It has the characteristics of high efficiency, stability and strong scalability, and has been widely used in many companies and projects. In MySQL, in order to avoid problems such as dirty reads and phantom reads caused by concurrent data operations, the concept of "lock" is introduced to control data access permissions. This article focuses on explaining the data table locking mechanism in MySQL and how to use it in practical applications to improve the efficiency and security of data access.

Types of locks and usage scenarios

Locks in MySQL can be divided into two categories: row-level locks and table-level locks. Row-level locks only lock the queried rows, and other rows are not affected; table-level locks lock the entire table, and all data operations need to wait for the lock to be released. Depending on the usage scenario, choosing different locking methods can effectively improve system performance.

For situations where you only need to access one or a small amount of data, using row-level locks can better improve concurrency. For example, when performing account login verification, you only need to lock the account record. For scenarios that require batch processing of data, table-level locks can be used to avoid data conflicts between multiple sessions to ensure the correctness and integrity of operations.

Table-level locks in MySQL

Table-level locks are the most basic form of locking in MySQL. Its locking granularity is large and will have a significant performance impact on queries and operations. There are two main table-level locking mechanisms in MySQL: shared locks and exclusive locks.

1. Shared Lock

Shared lock is a locking mechanism used to control concurrent reading. When a shared lock is applied to a data table, it means that other transactions can read the data in the table at the same time without blocking the read operations of other transactions, but it will block the write operations. The usage is as follows:

SELECT * FROM table_name LOCK IN SHARE MODE;

2. Exclusive Lock

Exclusive lock is a locking mechanism used to control concurrent write operations. When an exclusive lock is applied to a data table, the table is locked and other transactions are prohibited from performing any form of read or write operations. Only after the current transaction completes all write operations, other transactions can perform read and write operations again. The usage is as follows:

SELECT * FROM table_name FOR UPDATE;

Advantages and disadvantages of table-level locks

Table-level locks have the following advantages:

• There is only one lock state at the same time, simple and easy to operate accomplish.
• Suitable for locking when batch processing operations on large amounts of data.
• The locking granularity is large and it is easy to handle conflicts of large amounts of data.

However, table-level locks also have the following shortcomings:

• It will cause low system concurrency, especially in read-intensive scenarios.
• It is difficult to cope with the data performance processing of high concurrent writing, and it is easy to cause deadlock and other problems.
• It is easy to cause data operation conflicts and data loss, affecting the correctness and integrity of the data.

Application cases of table-level locks

For the application cases of table-level locks, this article takes the "order status update" operation as an example to illustrate. When multiple transactions update the status of the same order, in order to avoid dirty writes or phantom reads, table-level locks should be used to lock and unlock data to ensure the correctness and integrity of the data. Using the exclusive lock in MySQL, you can perform the following operations:

START TRANSACTION; -- 开启事务
SELECT * FROM orders WHERE order_id = '10001' FOR UPDATE; -- 对某个订单进行排他锁定
-- 其他相关数据的更新操作
COMMIT; -- 提交事务

Such operations can be applied to the processing of orders, inventory, flow and other data, which helps to avoid conflicts in data operations and improve Availability and security of data storage.

Summary

In the MySQL database, the use of locks plays a vital role in the correctness and security of data. For different types of data operation scenarios, different locking mechanism selections can effectively improve the system's concurrent processing capabilities and data security. In daily development, developers should make flexible choices based on actual conditions to ensure the correctness and integrity of data operations, improve the processing efficiency of business performance, and better meet application needs.

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