The total number of locks exceeds the lock table size - How to solve MySQL error: The number of locks exceeds the lock table size

How to solve MySQL error: The number of locks exceeds the lock table size, specific code examples are needed

When using MySQL for data operations, we often encounter various error message. One of them is "The total number of locks exceeds the lock table size", meaning the number of locks exceeds the lock table size. So what causes this error and how to solve it?

First, let’s take a look at the locking mechanism in MySQL. MySQL uses various types of locks to control access and modification of data in the database. According to the scope of the lock, locks can be divided into table-level locks and row-level locks. Table-level locks lock the entire table, while row-level locks lock one or more rows in the table.

When multiple transactions perform concurrent operations at the same time, lock conflicts will occur. When a transaction needs to acquire a lock to access data, if the lock is occupied by other transactions, a wait will occur. When the number of waiting transactions exceeds the lock table size defined in MySQL, the error "The total number of locks exceeds the lock table size" will occur.

To solve this error, there are several methods:

1. Increase the lock table size

It can be increased by modifying the configuration file in MySQL Lock table size. Open the MySQL configuration file my.cnf and add the following configuration under [mysqld]:

lock-tables = <value>

Among them, indicates the lock table size you want to set. Typically, this value can be set to a larger integer, such as 100000.

2. Optimizing query statements

Sometimes, lock conflicts are caused by insufficient optimization of query statements. You can find out areas that need optimization by checking the execution plan of the query statement. You can use the EXPLAIN keyword provided by MySQL to view the execution plan of the query statement.

For example, if your query statement is similar to:

SELECT * FROM table WHERE column = <value> FOR UPDATE;

, you can try changing it to:

SELECT * FROM table WHERE column = <value>;

This can avoid locking the entire table.

3. Reduce the transaction isolation level

The transaction isolation level in MySQL is divided into read uncommitted (read uncommitted), read committed (read committed), and repeatable read ( repeatable read) and serializable. Higher isolation levels cause the lock table size to increase.

If your application does not have high requirements for data consistency, you can try lowering the transaction isolation level. You can set the isolation level to read committed by using the following statement:

SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;

This can reduce the probability of lock conflicts.

4. Decompose large transactions

If your business logic requires large transaction operations, a large number of locks may be generated. You can try to split a large transaction into multiple small transactions to reduce the probability of lock conflicts.

The above are some common solutions. You can choose the method that suits you according to the specific situation. Below we use a code example to demonstrate how to solve this error.

Suppose the following query statement appears in your code:

cursor.execute("SELECT * FROM table WHERE column = %s FOR UPDATE", (value,))

You can change it to:

cursor.execute("SELECT * FROM table WHERE column = %s", (value,))

This way you can avoid locking the entire table.

To sum up, when MySQL reports an error "The total number of locks exceeds the lock table size", we can increase the lock table size, optimize query statements, lower the transaction isolation level and decompose large transactions. to solve this problem. Of course, specific solutions need to be determined based on the actual situation. Hope this article can help you solve this problem.

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