Information Functions Checks whether the lock named  str  is in use (that is, locked). If so, it returns the connection identifier of the client session that holds the lock. Otherwise, it returns  NULL . This function is unsafe for statement-based replication. A warning is logged if you use this function when binlog_format  is set to  STATEMENT . Releases all named locks held by the current session and returns the number of locks released (0 if there were none) This function is unsafe for statement-based replication. A warning is logged if you use this function when binlog_format  is set to  STATEMENT . Releases the lock named by the string  str  that was obtained with  GET_LOCK() . Returns  1  if the lock was released,  0  if the lock was not established by this thread (in which case the lock is not released), and  NULL  if the named lock did not exist. The lock does not exist if it was never obtained by a call to GET_LOCK()  or if it has previously been released. The  DO  statement is convenient to use with  RELEASE_LOCK() . See Section 13.2.3, “DO Statement” . This function is unsafe for statement-based replication. A warning is logged if you use this function when binlog_format  is set to  STATEMENT . 2279 Name Description BENCHMARK() Repeatedly execute an expression CHARSET() Return the character set of the argument COERCIBILITY() Return the collation coercibility value of the string argument COLLATION() Return the collation of the string argument CONNECTION_ID() Return the connection ID (thread ID) for the connection CURRENT_ROLE() Return the current active roles CURRENT_USER() ,  CURRENT_USER The authenticated user name and host name DATABASE() Return the default (current) database name FOUND_ROWS() For a SELECT with a LIMIT clause, the number of rows that would be returned were there no LIMIT clause ICU_VERSION() ICU library version LAST_INSERT_ID() Value of the AUTOINCREMENT column for the last INSERT ROLES_GRAPHML() Return a GraphML document representing memory role subgraphs Table 12.20 Information Functions 12.16 Information Functions • RELEASE_LOCK( str • RELEASE_ALL_LOCKS()