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 replication.
 


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