Lock wait timeout exceeded; try restarting transaction - How to solve MySQL error: lock wait timeout, try restarting transaction

Title: How to solve MySQL error: lock wait timeout, try to restart the transaction, need specific code examples

Text:

MySQL as a A commonly used relational database management system that is widely used in various types of applications. However, when using MySQL, we may encounter various errors and exceptions. One of the common errors is "Lock wait timeout exceeded; try restarting transaction". This article explains how to solve this problem and provides specific code examples.

1. Cause of lock wait timeout
   In MySQL, a transaction is composed of a series of operations to maintain the consistency and integrity of the database. A transaction usually starts with a BEGIN statement and ends with a COMMIT or ROLLBACK statement. When multiple transactions access the same database resource at the same time, lock competition may occur, causing a transaction to wait for too long for other transactions to release the lock, resulting in a lock wait timeout error.
2. Solution
   In order to solve the "Lock wait timeout exceeded; try restarting transaction" error, we can take the following methods:

2.1 Optimize query statements
In In MySQL, query statements are one of the most commonly used database operations. Optimizing query statements can effectively reduce lock contention problems. You can try to use appropriate indexes, reduce unnecessary JOIN operations, reduce full table scans and other methods to improve query performance, thereby reducing lock waiting time.

2.2 Limit the length of transactions
Longer transactions will increase the time it takes to lock resources, thereby increasing the time other transactions wait for locks. By limiting the length of transactions and dividing transactions into smaller units of operations, lock contention problems can be reduced.

2.3 Improve transaction isolation level
MySQL supports multiple transaction isolation levels, such as Read Uncommitted, Read Committed, Repeatable Read and Serialization (Serializable). Different transaction isolation levels handle lock competition differently. Setting the transaction isolation level to a lower level, such as read uncommitted, can reduce the lock waiting time.

2.4 Increase the lock wait timeout time
In MySQL, the default lock wait timeout time is 50 seconds. If you are in a high-concurrency environment and some operations take a long time to complete, you can avoid the "Lock wait timeout exceeded" error by setting the lock wait timeout. You can use the following SQL statement to set the lock wait timeout to 100 seconds:

SET innodb_lock_wait_timeout = 100;

3. Code example
   The following is a sample code that demonstrates how to handle the "Lock wait timeout exceeded" error in a Java program:

try {
    // 建立数据库连接
    Connection connection = DriverManager.getConnection(url, username, password);
    
    // 开启事务
    connection.setAutoCommit(false);
    
    // 执行数据库操作
    // ...
    
    // 提交事务
    connection.commit();
    
} catch (SQLException e) {
    if (e.getErrorCode() == 1205) { // 锁等待超时错误码为1205
        // 尝试重新启动事务
        // ...
    } else {
        e.printStackTrace();
    }
}

In the above code, we capture the SQL exception and make judgments based on the error code. If the error code is 1205, which is a lock wait timeout error, we can try to restart the transaction.

Summary:

When using MySQL, you may encounter the "Lock wait timeout exceeded; try restarting transaction" error. In order to solve this problem, we can reduce lock competition problems by optimizing query statements, limiting transaction length, improving transaction isolation level, and increasing lock wait timeout. We also provide a Java code example that demonstrates how to handle this error.

I hope this article will be helpful to you and solve the lock waiting timeout problem in MySQL!

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