MySQL Row-Level Locks Explained

The implementation principle of MySQL row level locking is achieved through two ways: lock granularity and lock type.

1. The granularity of locks:
   MySQL’s row-level lock is implemented in the InnoDB storage engine, by default using Next-Key Lock, which locks on index records, including both row records and index records, thus avoiding deadlock problems during concurrent operations. Row-level locking in InnoDB is achieved by locking on the index rather than the entire table, allowing only the necessary rows to be locked during concurrent operations, thus improving performance.
2. There are two types of locks in MySQL at the row level: shared locks (S lock) and exclusive locks (X lock).
3. Shared lock (S-lock): Multiple transactions can hold shared locks simultaneously to ensure the consistency of read operations. Shared locks do not block each other, but are mutually exclusive with exclusive locks.
4. Exclusive lock (X lock): An exclusive lock is a lock that allows only one transaction to hold it at a time. If a transaction holds an exclusive lock, other transactions are unable to hold either a shared lock or an exclusive lock simultaneously. Exclusive locks will block each other until the previous transaction releases the lock.

MySQL’s row-level locking ensures transaction isolation and prevents data inconsistency during concurrent operations. However, it is important to note that excessive row-level locking can lead to performance issues, so when using row-level locking, it is necessary to balance concurrency performance and data consistency.