MySQL如何避免死锁（mysql死锁）

Deadlocks are a common problem in large database systems that protect concurrent accesses. A deadlock occurs when multiple threads try to acquire locks on the same resources in different orders. When this happens, all involved threads become stuck in an endless cycle, each waiting for the others to release their locks. As a result, the system hangs and can crash if not handled properly.

MySQL provides several methods to avoid deadlocks. First, you can use the InnoDB lock table Monitor, which shows the threads currently locking and waiting for resources. By monitoring this table, you can detect the presence of a potential deadlock and take the necessary steps to solve it.

In addition, you can use the SET sql_wait_timeout command to set a timeout limit on transactions. This allows MySQL to simply terminate transactions if they take too long to finish, thus preventing a potential deadlock.

Finally, you can break up transactions that require multiple locks into smaller pieces. This allows MySQL to lock one resource at a time, thus avoiding any potential blockers.

Example

For example, let’s say that we have two transactions, A and B, that want to acquire locks on two different rows in the same table:

Transaction A:

locking row 1

Transaction B:

locking row 2

Normally, these two transactions will block each other and cause a deadlock. However, if we break up each transaction into two parts, we can avoid this problem:

Transaction A:

locking row 1

Transaction B:

locking row 1

locking row 2

By breaking up each transaction, MySQL can acquire each lock one at a time, thus avoiding a potential deadlock.

In summary, deadlocks can be a serious problem in large databases. Fortunately, MySQL provides several methods to avoid them, such as monitoring the lock table, setting a timeout limit, and breaking up long transactions into smaller pieces. By implementing these strategies, you can ensure that your database will stay functional and reliable.