MySQL lock mechanism and its practical application

MySQL locking mechanism and its application

Abstract:
As a relational database management system, MySQL’s locking mechanism plays a crucial role in concurrent access. important role. This article will introduce MySQL's lock mechanism, including lock types, ways to acquire and release locks, and how to use them in practical applications, and provide specific code examples.

1. Introduction
In the case of multiple users accessing the database concurrently, the data consistency and isolation of the database are crucial. In order to ensure the correctness of the data, MySQL uses a locking mechanism. The lock mechanism can prevent multiple users from concurrently modifying the same data and ensure the correctness and consistency of the data. This article will introduce three common lock types: shared lock (Read Lock), exclusive lock (Write Lock) and intention lock (Intention Lock).

2. Types of locks

1. Shared lock (Read Lock):
   Shared lock allows multiple transactions to read the same data at the same time, but does not allow modification of the data . Shared locks can be obtained by using LOCK IN SHARE MODE or FOR SHARE in the query statement.
2. Exclusive lock (Write Lock):
   Exclusive lock only allows one transaction to modify the data, and other transactions cannot read and modify the data. An exclusive lock can be obtained by using FOR UPDATE in the query statement.
3. Intention Lock:
   Intention lock is a lock acquired in advance before acquiring shared locks and exclusive locks to improve concurrency performance.

3. How to acquire and release locks

1. Acquire locks:
   Acquire locks through the GET_LOCK() function, which accepts two Parameters: lock name and timeout. If the lock is acquired successfully, 1 is returned, otherwise 0 is returned.
2. Release the lock:
   Release the lock through the RELEASE_LOCK() function, which accepts one parameter: the name of the lock. If the lock is released successfully, 1 is returned, otherwise 0 is returned.

4. Application of locks

1. Concurrency control:
   In concurrent access, the use of locks can prevent multiple transactions from modifying the same data at the same time, ensuring Data consistency.
2. Database operation process control:
   By acquiring and releasing locks, you can control the process and sequence of database operations.

The specific example code is as follows:

import MySQLdb

# 获取锁
def get_lock(lock_name):
    db = MySQLdb.connect(host='localhost', user='root', password='password', db='test')
    cursor = db.cursor()
    cursor.execute("SELECT GET_LOCK('%s', 10)" % lock_name)
    result = cursor.fetchone()[0]
    if result == 1:
        print("Lock success")
    else:
        print("Lock failure")
    cursor.close()
    db.close()

# 释放锁
def release_lock(lock_name):
    db = MySQLdb.connect(host='localhost', user='root', password='password', db='test')
    cursor = db.cursor()
    cursor.execute("SELECT RELEASE_LOCK('%s')" % lock_name)
    result = cursor.fetchone()[0]
    if result == 1:
        print("Release lock success")
    else:
        print("Release lock failure")
    cursor.close()
    db.close()

# 获取锁
get_lock("my_lock")

# 业务逻辑

# 释放锁
release_lock("my_lock")

5. Summary
MySQL’s locking mechanism plays an important role in concurrent access and can ensure data consistency and isolation. . This article introduces MySQL lock types, how to acquire and release locks, and how to use them in practical applications, and provides specific code examples. In the process of using locks, you need to pay attention to the granularity of the lock and the release of the lock to avoid problems such as deadlock.

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