How to implement lock-free and optimistic locking operations on data in MySQL?

How to implement lock-free and optimistic locking operations of data in MySQL?

Overview:
In high-concurrency database applications, locks are a common performance bottleneck. MySQL provides a variety of lock mechanisms to ensure data consistency and concurrency control, but too many lock operations will lead to performance degradation. In order to solve this problem, MySQL introduced lock-free and optimistic locking mechanisms to improve the concurrency performance of the database. This article will introduce how to use lock-free and optimistic locking to operate data in MySQL.

1. Example of lock-free operation:
Lock-free operation refers to achieving concurrent access to the database without using any lock mechanism under certain conditions. In MySQL, lock-free operations can be achieved by using auto-incrementing primary keys and optimistic locking mechanisms.

The sample code is as follows:

-- 创建用户表
CREATE TABLE user (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(100) NOT NULL,
  balance INT NOT NULL
);

-- 插入数据
INSERT INTO user (name, balance)
VALUES ('Alice', 100), ('Bob', 200), ('Charlie', 300);

-- 查询数据
SELECT * FROM user;

-- 无锁化操作示例：Alice向Bob转账100元
BEGIN;
DECLARE @alice_balance INT;
DECLARE @bob_balance INT;
SELECT balance INTO @alice_balance FROM user WHERE name = 'Alice';
SELECT balance INTO @bob_balance FROM user WHERE name = 'Bob';
IF @alice_balance >= 100 THEN
  UPDATE user SET balance = @alice_balance - 100 WHERE name = 'Alice';
  UPDATE user SET balance = @bob_balance + 100 WHERE name = 'Bob';
END IF;
COMMIT;

-- 查询数据
SELECT * FROM user;

The above sample code shows the idea of ​​using lock-free operations to implement concurrent transfers in MySQL. In lock-free operation, we do not use any database lock mechanism, but use optimistic locking mechanism to achieve data consistency and concurrency control.

2. Optimistic lock operation example:
Optimistic lock means that when performing concurrent operations, it is assumed that the data will not conflict, and only checks for conflicts when the data is submitted, and rolls back the transaction. Optimistic locking can be implemented in MySQL by using the version number or timestamp field.

The sample code is as follows:

-- 创建用户表
CREATE TABLE user (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(100) NOT NULL,
  balance INT NOT NULL,
  version INT NOT NULL
);

-- 插入数据
INSERT INTO user (name, balance, version)
VALUES ('Alice', 100, 0), ('Bob', 200, 0), ('Charlie', 300, 0);

-- 查询数据
SELECT * FROM user;

-- 乐观锁操作示例：Alice向Bob转账100元
BEGIN;
DECLARE @alice_id INT;
DECLARE @bob_id INT;
DECLARE @alice_balance INT;
DECLARE @bob_balance INT;
SELECT id INTO @alice_id, balance INTO @alice_balance FROM user WHERE name = 'Alice';
SELECT id INTO @bob_id, balance INTO @bob_balance FROM user WHERE name = 'Bob';
IF @alice_balance >= 100 THEN
  UPDATE user SET balance = @alice_balance - 100, version = version + 1 WHERE id = @alice_id AND version = @alice_version;
  UPDATE user SET balance = @bob_balance + 100, version = version + 1 WHERE id = @bob_id AND version = @bob_version;
END IF;
COMMIT;

-- 查询数据
SELECT * FROM user;

The above sample code shows the idea of ​​using optimistic locking operations to implement concurrent transfers in MySQL. In the optimistic lock operation, we use the version number to control the consistency of the data. If the current version number is inconsistent with the version number when reading, it means that the data has been modified by other transactions and the operation will be rolled back.

Summary:
Lock-free operations and optimistic locking are important means to improve concurrency performance in MySQL. By using lock-free operations and optimistic locking, the performance overhead caused by locks can be reduced and the concurrency performance of the database can be improved. Lock-free operations achieve concurrent access by using auto-increasing primary keys and optimistic locking mechanisms; optimistic locks implement data concurrency control through version numbers or timestamp fields. In practical applications, it is necessary to choose an appropriate concurrency control strategy according to specific scenarios to achieve lock-free data and optimistic lock operations.

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