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

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

When using a MySQL database, you may sometimes encounter a common error : Lock wait timeout exceeded; try restarting transaction, this error indicates that the transaction wait timeout has expired. This error usually occurs when accessing the database concurrently, because one transaction locks a resource and other transactions cannot obtain the resource, resulting in a timeout.

So how should we solve this problem? Some common solutions are described next, with specific code examples provided.

1. Check transaction concurrency control:
   The root cause of the timeout error is improper transaction concurrency control. In MySQL, transactions can be controlled using statements such as BEGIN and ROLLBACK. When we write transaction code, we should pay attention to the following points:
2. Use the START TRANSACTION statement to start a transaction instead of a simple BEGIN statement.
3. After the transaction ends, use the COMMIT statement to commit the transaction.
4. When dealing with concurrent access, an appropriate locking mechanism should be used, such as SELECT ... FOR UPDATE or SELECT ... LOCK IN SHARE MODE.

The following is a sample code that shows how to use appropriate transaction concurrency control:

START TRANSACTION;
SELECT * FROM table_name WHERE id = some_id FOR UPDATE;
-- 执行一些操作
UPDATE table_name SET column_name = new_value WHERE id = some_id;
COMMIT;

2. Adjust the transaction timeout:
   MySQL's default transaction timeout is 50 seconds. In some special cases, this timeout may need to be adjusted. You can set a new timeout by modifying the configuration file or using SET innodb_lock_wait_timeout = 100;. Note that the timeout is in seconds.

The following is a sample code that shows how to adjust the transaction timeout:

SET innodb_lock_wait_timeout = 100;

3. Reduce the size and complexity of transactions:
   Another common reason is The transaction is too large or complex. If a transaction involves a large number of operations or involves a large amount of data, the chance of the transaction waiting to time out increases. Therefore, we can reduce the probability of timeout errors by reducing the size and complexity of transactions.

The following is a sample code that shows how to reduce the size and complexity of transactions:

-- 逐步拆分大事务
START TRANSACTION;
-- 第一步操作
COMMIT;

START TRANSACTION;
-- 第二步操作
COMMIT;

-- ...
-- 后续操作
COMMIT;

4. Optimize database structures and queries:
   Finally, we should optimize Database structure and query statements to reduce the possibility of transaction wait timeouts. There are some common optimization techniques you can use, such as:
5. Create appropriate indexes to improve query performance.
6. Avoid using full table scan query.
7. Try to reduce cross-table queries.

For transaction wait timeout errors, we can use the tools or command lines provided by MySQL to analyze the performance of queries and tables, and make corresponding optimizations.

To sum up, when we encounter the Lock wait timeout exceeded; try restarting transaction error, we should first check the transaction concurrency control, and then adjust the transaction timeout to reduce the size and complexity, and optimize database structures and queries. By applying these solutions properly, we can avoid the occurrence of MySQL transaction wait timeout errors.

I hope the solutions and code examples provided in this article can help you solve the MySQL transaction wait timeout problem.

The above is the detailed content of Lock wait timeout exceeded; try restarting transaction - How to solve MySQL error: transaction wait timeout. For more information, please follow other related articles on the PHP Chinese website!