How the RELEASE_LOCK() function works in Mariadb?

The RELEASE_LOCK() function in MariaDB is used to release a user-level lock that was acquired with the GET_LOCK() function. This function returns a boolean value (1 or 0) to indicate whether the lock was released.

Syntax

The syntax for the RELEASE_LOCK() function is as follows:

RELEASE_LOCK(str);

Where:

str is the name of the lock to be released. It is a case-insensitive string.

Examples

Example 1: Releasing a lock

The following example shows how to release a lock named my_lock:

RELEASE_LOCK('my_lock');

This will release the lock named my_lock if it was acquired by the current thread. If the lock was not acquired by the current thread, the function will return 0.

Example 2: Releasing a lock that does not exist

The following example shows how to release a lock that does not exist:

RELEASE_LOCK('non_existent_lock');

This will return NULL because the lock named non_existent_lock does not exist.

Example 3: Releasing all locks

The following example shows how to release all locks that are held by the current thread:

RELEASE_ALL_LOCKS();

This will release all locks that are held by the current thread.

The following functions are related to RELEASE_LOCK():

GET_LOCK(): Acquires a user-level lock.
IS_FREE_LOCK(): Checks whether a lock is free.
IS_USED_LOCK(): Checks whether a lock is in use.

Conclusion

The RELEASE_LOCK() function is a useful tool for releasing user-level locks in MariaDB. It is important to use this function to release locks when they are no longer needed to avoid blocking other threads.