Understanding MySQL Lock Deadlocks

Issue:
A MySQL table with 5,000,000 rows is prone to deadlocks due to parallel Perl processes updating it. The deadlock error occurs when updating a specific row.

Cause:
Deadlocks occur when two or more transactions attempt to acquire locks on the same row in a conflicting manner. In this case, the multiple processes using a_lock on file_table attempt to access the same row concurrently.

Solution:

1. Understanding the Lock Wait Timeout:
The error message suggests restarting the transaction. This refers to the lock wait timeout. By default, MySQL waits indefinitely for a lock to be acquired. You can set it to a shorter timeout period to automatically handle and retry deadlocks.

2. Handling Deadlocks:
Handle deadlocks by implementing logic in your code to retry failed queries. You can use try/catch blocks to detect the deadlock error and automatically re-execute the query.

3. Optimization Strategies:
To reduce the likelihood of deadlocks, consider the following optimizations:

• Tune the database to reduce contention on specific rows or columns.
• Optimize your queries to minimize the number of table scans and index seeks.
• Use smaller and more frequent transaction blocks to release locks sooner.
• Consider using a different storage engine, such as MyISAM, which does not support row-level locking.

4. Recommended Resources:
For further information, refer to the following resources:

• MySQL Manual: https://dev.mysql.com/doc/refman/8.0/en/deadlocks.html