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https://dev.mysql.com/doc/refman/8.4/en/subquery-materialization.html
The optimizer may index the table with a hash index to make lookups fast and inexpensive. The index contains unique values to eliminate duplicates and make the table smaller. MySQL can also apply subquery materialization to a single-table UPDATE or ... The optimizer uses materialization to enable more efficient subquery ...
https://dev.mysql.com/doc/mysql-cluster-manager/8.4/en/mcm-attribute-tables-mysqld.html
ndb-deferred-constraints: Specifies that constraint checks on unique indexes (where these are supported) should be deferred until commit time. ndb-log-empty-epochs: When enabled, causes epochs in which there were no changes to be written to ...
https://dev.mysql.com/doc/refman/8.4/en/adding-collation.html
The MySQL 8.4 server issues a warning for any use of COLLATE user_defined_collation in an SQL statement; a warning is also issued when the server is started with --collation-server set equal to the name of a user-defined collation. Note If you ...
https://dev.mysql.com/doc/refman/8.4/en/charset-configuration.html
To determine which collations are available for each character set, use the SHOW COLLATION statement or query the INFORMATION_SCHEMA COLLATIONS table. The MySQL server has a compiled-in default character set and collation. To change these defaults, ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-ft-default-stopword-table.html
The INNODB_FT_DEFAULT_STOPWORD table holds a list of stopwords that are used by default when creating a FULLTEXT index on InnoDB tables. For related usage information and examples, see Section 17.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-tablestats-table.html
This data is used by the MySQL optimizer to calculate which index to use when querying an InnoDB table. Table statistics are updated only for DELETE or UPDATE operations that modify indexed columns. Statistics are not updated by operations that ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-deadlocks-handling.html
That is because these operations are not really “atomic”; they automatically set locks on the (possibly several) index records of the row inserted or deleted. For example, organize database operations into functions within your application, or ... This section builds on the conceptual information about deadlocks in Section 17.7.5.2, “Deadlock ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-online-ddl-limitations.html
The following limitations apply to online DDL operations: The table is copied when creating an index on a TEMPORARY TABLE. When running an in-place online DDL operation, the thread that runs the ALTER TABLE statement applies an online log of DML ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-recovery.html
You can use the CHECK TABLE statement to check whether a table is corrupt, although CHECK TABLE naturally cannot detect every possible kind of corruption. When encountering index tree corruption, InnoDB writes a corruption flag to the redo log, ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-events-waits-current-table.html
The events_waits_current table has these indexes: Primary key on (THREAD_ID, EVENT_ID) TRUNCATE TABLE is permitted for the events_waits_current table. The table stores one row per thread showing the current status of the thread's most recent ...