Performance Schema metadata_locks Table

MariaDB starting with 10.5.2

The metadata_locks table was introduced in MariaDB 10.5.2.

The metadata_locks table contains metadata lock information.

To enable metadata lock instrumention, at runtime:

UPDATE performance_schema.setup_instruments SET enabled='YES', timed='YES' 
  WHERE name LIKE 'wait/lock/metadata%';

or in the configuration file:

performance-schema-instrument='wait/lock/metadata/sql/mdl=ON'

The table is by default autosized, but the size can be configured with the performance_schema_max_metadata_locks system variabe.

The table is read-only, and TRUNCATE TABLE cannot be used to empty the table.

The table contains the following columns:

Field	Type	Null	Default	Description
Field	Type	Null	Default	Description
OBJECT_TYPE	varchar(64)	NO	NULL	Object type. One of BACKUP, COMMIT, EVENT, FUNCTION, GLOBAL, LOCKING SERVICE, PROCEDURE, SCHEMA, TABLE, TABLESPACE, TRIGGER (unused) or USER LEVEL LOCK.
OBJECT_SCHEMA	varchar(64)	YES	NULL	Object schema.
OBJECT_NAME	varchar(64)	YES	NULL	Object name.
OBJECT_INSTANCE_BEGIN	bigint(20) unsigned	NO	NULL	Address in memory of the instrumented object.
LOCK_TYPE	varchar(32)	NO	NULL	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	varchar(32)	NO	NULL	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	varchar(32)	NO	NULL	Lock status. One of GRANTED, KILLED, PENDING, POST_RELEASE_NOTIFY, PRE_ACQUIRE_NOTIFY, TIMEOUT or VICTIM.
SOURCE	varchar(64)	YES	NULL	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	bigint(20) unsigned	YES	NULL	Thread that requested the lock.
OWNER_EVENT_ID	bigint(20) unsigned	YES	NULL	Event that requested the lock.

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