Search Results
https://dev.mysql.com/doc/refman/8.4/en/aggregate-functions.html
InnoDB does not keep an internal count of rows in a table because concurrent transactions might “see” different numbers of rows at the same time. SELECT COUNT(*) FROM tbl_name query performance for InnoDB tables is optimized for single-threaded ... This section describes aggregate functions that operate on sets of ...
https://dev.mysql.com/doc/refman/8.4/en/backup-policy.html
This backup operation acquires a global read lock on all tables at the beginning of the dump (using FLUSH TABLES WITH READ LOCK). After that, the dump becomes lock-free and does not disturb reads and writes on the tables. It was assumed earlier that ...A full backup (a snapshot of the data at a point in time) can be done in MySQL with several ...
https://dev.mysql.com/doc/refman/8.4/en/change-replication-filter.html
Names of tables and database not containing any special characters need not be quoted. Values used with REPLICATION_WILD_TABLE and REPLICATION_WILD_IGNORE_TABLE are string expressions, possibly containing (special) wildcard characters, and so must ...Filters set using this statement differ from those set using the server options in two key respects: The statement does not require restarting the server to take effect, only that the replication SQL thread be stopped using STOP REPLICA SQL_THREAD first (and restarted with START REPLICA SQL_THREAD ...
https://dev.mysql.com/doc/refman/8.4/en/create-function-loadable.html
CREATE FUNCTION requires the INSERT privilege for the mysql system schema because it adds a row to the mysql.func system table to register the function. CREATE FUNCTION also adds the function to the Performance Schema user_defined_functions table ...
https://dev.mysql.com/doc/refman/8.4/en/drop-tablespace.html
DROP [UNDO] TABLESPACE tablespace_name This statement drops a tablespace that was previously created using CREATE TABLESPACE. The UNDO keyword must be specified to drop an undo tablespace. Only undo tablespaces created using CREATE UNDO TABLESPACE ...
https://dev.mysql.com/doc/refman/8.4/en/error-log-configuration.html
INSTALL COMPONENT adds the component to the mysql.component table (an InnoDB table), and the components to load at startup are read from this table, which is only accessible after InnoDB is initialized. Note Loading a log component implicitly using ... In MySQL 8.4, error logging uses the MySQL component architecture described at Section 7.5, “MySQL ...
https://dev.mysql.com/doc/refman/8.4/en/lock-instance-for-backup.html
REPAIR TABLE TRUNCATE TABLE, OPTIMIZE TABLE, and account management statements are blocked. LOCK INSTANCE FOR BACKUP permits DDL operations that only affect user-created temporary tables. In effect, files that belong to user-created temporary tables ... LOCK INSTANCE FOR BACKUP UNLOCK INSTANCE LOCK INSTANCE FOR BACKUP acquires an instance-level backup lock that permits DML during an online backup while preventing operations that could result in an inconsistent ...
https://dev.mysql.com/doc/refman/8.4/en/myisamchk-repair-options.html
--correct-checksum Command-Line Format --correct-checksum Correct the checksum information for the table. See also the description of this option under table checking options. For a description of the output format, see Section 6.6.4.5, “Obtaining ...--data-file-length=len, -D len Command-Line Format --data-file-length=len Type Numeric The maximum length of the data file (when re-creating data file when it is ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-pitr.html
Performing point-in-time recovery of NDB Cluster tables with NDB Cluster and NDB Cluster Replication can be accomplished using a native NDB data backup (taken by issuing CREATE BACKUP in the ndb_mgm client) and restoring the ndb_binlog_index table ... Point-in-time recovery—that is, recovery of data changes made since a given point in time—is performed after restoring a full backup that returns the server to its state when the backup was ...
https://dev.mysql.com/doc/refman/8.4/en/optimizing-innodb-ddl-operations.html
Many DDL operations on tables and indexes (CREATE, ALTER, and DROP statements) can be performed online. Online DDL support for adding secondary indexes means that you can generally speed up the process of creating and loading a table and associated ...