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 |
---|---|---|---|---|
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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