Syntax
------

IS_FREE_LOCK(str)

Description
-----------

Checks whether the lock named str is free to use (that is, not locked).
Returns 1 if the lock is free (no one is using the lock), 0 if the lock is in
use, and NULL if an error occurs (such as an incorrect argument, like an empty
string or NULL). str is case insensitive.

If the metadata_lock_info plugin is installed, the Information Schema
metadata_lock_info table contains information about locks of this kind (as
well as metadata locks).

Statements using the IS_FREE_LOCK function are not safe for statement-based
replication.

URL: https://mariadb.com/kb/en/is_free_lock/