Troubleshooting & Understanding What Causes "Lock Wait Timeout Exceeded" Error in MySQL

What Causes “Lock wait timeout exceeded” Error in MySQL?

For those dealing with database administration, the dreaded “Lock wait timeout exceeded” error message is unfortunately a common occurrence. This error means that the two or more queries you are attempting to run have created a deadlock, which can lead to data loss and corrupt databases. This issue can happen when multiple users are trying to access the same table, resulting in chaotic and conflicting queries.

What Exactly Is a Deadlock?

A deadlock is a situation when two or more database query threads are stuck in an endless, mutually exclusive loop. In other words, the queries become locked and none of them can finish out successfully. This is usually caused by user error while writing code, or due to unoptimized queries.

What Causes the Lock Wait Timeout Exceeded Error?

This error occurs when one of the threads involved in the deadlock cannot complete its query within the lock wait timeout. This timeout is set by the MySQL server itself to keep the database from getting stuck in an infinite loop. If the timeout expires, then the most recently executed query will be rolled back (i.e. undone) and the error message is displayed.

How Can I Fix the Lock Wait Timeout Error?

The best way to prevent this error from occurring is to make sure that your SQL queries are properly optimized. You should also ensure that your code is written so that it makes efficient use of indexes and locks on the database tables. Additionally, you can increase the lock wait timeout value, but this may expose you to higher risk of data corruption.