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select * from performance_schema.metadata_locks;
select * from performance_schema.metadata_locks
where object_name='foo';
OBJECT_TYPE OBJECT_SCHEMA OBJECT_NAME OBJECT_INSTANCE_BEGIN LOCK_TYPE LOCK_DURATION LOCK_STATUS SOURCE OWNER_THREAD_ID OWNER_EVENT_ID
insert into performance_schema.metadata_locks
set object_name='FOO', owner_thread_id=1;
ERROR 42000: INSERT command denied to user 'root'@'localhost' for table `performance_schema`.`metadata_locks`
update performance_schema.metadata_locks
set owner_thread_id=12 where object_name='foo';
ERROR 42000: UPDATE command denied to user 'root'@'localhost' for table `performance_schema`.`metadata_locks`
delete from performance_schema.metadata_locks;
ERROR 42000: DELETE command denied to user 'root'@'localhost' for table `performance_schema`.`metadata_locks`
delete from performance_schema.metadata_locks
where timer_name='CYCLE';
ERROR 42000: DELETE command denied to user 'root'@'localhost' for table `performance_schema`.`metadata_locks`
LOCK TABLES performance_schema.metadata_locks READ;
ERROR 42000: SELECT, LOCK TABLES command denied to user 'root'@'localhost' for table `performance_schema`.`metadata_locks`
UNLOCK TABLES;
LOCK TABLES performance_schema.metadata_locks WRITE;
ERROR 42000: SELECT, LOCK TABLES command denied to user 'root'@'localhost' for table `performance_schema`.`metadata_locks`
UNLOCK TABLES;
#
# MDEV-25325 column_comment for performance_schema tables
#
select column_name, column_comment
from information_schema.columns
where table_schema='performance_schema' and table_name='metadata_locks';
column_name column_comment
OBJECT_TYPE Object type. One of BACKUP, COMMIT, EVENT, FUNCTION, GLOBAL, LOCKING SERVICE, PROCEDURE, SCHEMA, TABLE, TABLESPACE, TRIGGER (unused) or USER LEVEL LOCK.
OBJECT_SCHEMA Object schema.
OBJECT_NAME Object name.
OBJECT_INSTANCE_BEGIN Address in memory of the instrumented object.
LOCK_TYPE Lock type. One of BACKUP_FTWRL1, BACKUP_START, BACKUP_TRANS_DML, EXCLUSIVE, INTENTION_EXCLUSIVE, SHARED, SHARED_HIGH_PRIO, SHARED_NO_READ_WRITE, SHARED_NO_WRITE, SHARED_READ, SHARED_UPGRADABLE or SHARED_WRITE.
LOCK_DURATION Lock duration. One of EXPLICIT (locks released by explicit action, for example a global lock acquired with FLUSH TABLES WITH READ LOCK) , STATEMENT (locks implicitly released at statement end) or TRANSACTION (locks implicitly released at transaction end).
LOCK_STATUS Lock status. One of GRANTED, KILLED, PENDING, POST_RELEASE_NOTIFY, PRE_ACQUIRE_NOTIFY, TIMEOUT or VICTIM.
SOURCE Source file containing the instrumented code that produced the event, as well as the line number where the instrumentation occurred. This allows one to examine the source code involved.
OWNER_THREAD_ID Thread that requested the lock.
OWNER_EVENT_ID Event that requested the lock.
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