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https://dev.mysql.com/doc/refman/8.4/en/merge-table-problems.html
The following are known problems with MERGE tables: MERGE child tables are locked through the parent table. If the parent is a temporary table, it is not locked, and thus the child tables are also not locked; this means that parallel use of the ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-online-operations.html
The mysqld on which the copying ALTER TABLE statement is issued takes a metadata lock, but this is in effect only on that mysqld. Regardless of the algorithm used, the mysqld takes a Global Schema Lock (GSL) while executing ALTER TABLE; this ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-programs-ndb-select-all.html
Possible values for lock_type are: 0: Read lock 1: Read lock with hold 2: Exclusive read lock There is no default value for this option. ndb_select_all prints all rows from an NDB table to stdout. Usage ndb_select_all -c connection_string tbl_name ...
https://dev.mysql.com/doc/refman/8.4/en/mysqlcheck.html
Each table is locked and therefore unavailable to other sessions while it is being processed, although for check operations, the table is locked with a READ lock only (see Section 15.3.6, “LOCK TABLES and UNLOCK TABLES Statements”, for more ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-mutex-instances-table.html
LOCKED_BY_THREAD_ID When a thread currently has a mutex locked, LOCKED_BY_THREAD_ID is the THREAD_ID of the locking thread, otherwise it is NULL. The mutex_instances table has these indexes: Primary key on (OBJECT_INSTANCE_BEGIN) Index on (NAME) ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-tp-thread-state-table.html
Otherwise, the thread is blocked by a call to thd_wait_begin() and the value specifies the type of wait. ACCUMULATED_EXEC_TIME: The wall clock time spent processing queries by the server. The tp_thread_state table has one row per thread created by ...
https://dev.mysql.com/doc/refman/8.4/en/show-engine.html
Note InnoDB mutexes and rwlocks can also be monitored using Performance Schema tables. For rwlocks, the Name field reports the source file where the rwlock is implemented, and the line number in the file where the rwlock is created. SHOW ENGINE ...
https://dev.mysql.com/doc/refman/8.4/en/storage-engines.html
row *************************** Engine: InnoDB Support: DEFAULT Comment: Supports transactions, row-level locking, and foreign keys Transactions: YES XA: YES Savepoints: YES *************************** 3. InnoDB row-level locking (without escalation ... Storage engines are MySQL components that handle the SQL operations for different table ...
https://dev.mysql.com/doc/refman/8.4/en/stored-program-restrictions.html
The following statements are not permitted: The locking statements LOCK TABLES and UNLOCK TABLES. Also, the same local variable name can be used in nested blocks. A local variable in an inner block takes precedence over a local variable in an outer ...Some of the restrictions noted here apply to all stored routines; that is, both to stored procedures and stored ...
https://dev.mysql.com/doc/refman/8.4/en/thread-pool-operation.html
To ensure that no thread group becomes blocked by stalled statements, the thread pool has a background thread that regularly monitors thread group states. A statement becomes blocked if it encounters a disk I/O operation or a user level lock (row ...