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https://dev.mysql.com/doc/refman/8.0/en/subquery-optimization.html
Note A limitation on UPDATE and DELETE statements that use a subquery to modify a single table is that the optimizer does not use semijoin or materialization subquery optimizations. As a workaround, try rewriting them as multiple-table UPDATE and ...
https://dev.mysql.com/doc/refman/8.0/en/table-corruption.html
If you have started mysqld with the myisam_recover_options system variable set, MySQL automatically checks and tries to repair MyISAM tables if they are marked as 'not closed properly' or 'crashed'. If this happens, MySQL writes an entry in the ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-online-ddl-performance.html
Session 1: mysql> CREATE TABLE t1 (c1 INT) ENGINE=InnoDB; mysql> START TRANSACTION; mysql> SELECT * FROM t1; The session 1 SELECT statement takes a shared metadata lock on table t1. Online DDL improves several aspects of MySQL operation: ...Reduced ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-innodb-tablestats-table.html
The INNODB_TABLESTATS table provides a view of low-level status information about InnoDB tables. This data is used by the MySQL optimizer to calculate which index to use when querying an InnoDB table. InnoDB tables are represented in this view if ...This information is derived from in-memory data structures rather than data stored on ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-ndb-transid-mysql-connection-map-table.html
For this table to be created, the MySQL Server must be a binary supplied with the NDB Cluster distribution, or one built from the NDB Cluster sources with NDB storage engine support enabled. The ndb_transid_mysql_connection_map table provides a ...
https://dev.mysql.com/doc/refman/8.0/en/optimizing-memory-tables.html
Consider using MEMORY tables for noncritical data that is accessed often, and is read-only or rarely updated. Benchmark your application against equivalent InnoDB or MyISAM tables under a realistic workload, to confirm that any additional ...B-tree ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-columns-extensions-table.html
The COLUMNS_EXTENSIONS table (available as of MySQL 8.0.21) provides information about column attributes defined for primary and secondary storage engines. The COLUMNS_EXTENSIONS table has these columns: TABLE_CATALOG The name of the catalog to ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-connection-control-table-reference.html
Table 28.8 INFORMATION_SCHEMA Connection Control Tables Table Name Description CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS Current number of consecutive failed connection attempts per account .
https://dev.mysql.com/doc/refman/8.0/en/information-schema-firewall-table-reference.html
Table 28.9 INFORMATION_SCHEMA Firewall Tables Table Name Description Deprecated MYSQL_FIREWALL_USERS Firewall in-memory data for account profiles 8.0.26 MYSQL_FIREWALL_WHITELIST Firewall in-memory data for account profile allowlists 8.0.26 .
https://dev.mysql.com/doc/refman/8.0/en/information-schema-thread-pool-table-reference.html
Table 28.7 INFORMATION_SCHEMA Thread Pool Tables Table Name Description TP_THREAD_GROUP_STATE Thread pool thread group states TP_THREAD_GROUP_STATS Thread pool thread group statistics TP_THREAD_STATE Thread pool thread information .