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https://dev.mysql.com/doc/refman/8.0/en/switchable-optimizations.html
For more information, see Section 10.2.2.5, “Derived Condition Pushdown Optimization” Derived Table Merging Flags derived_merge (default on) Controls merging of derived tables and views into outer query block. The derived_merge flag controls ...
https://dev.mysql.com/doc/refman/8.0/en/tracing-example.html
Next, for every table in the query, we estimate the cost of, and number of records returned by, a table scan or a range access. "resulting_clause_is_simple": true, "resulting_clause": "`test`.`alias1`.`col_int_key`" } /* clause_processing */ }, The ...Now we can examine the trace, whose first column (QUERY), containing the original statement to be traced, is shown here: SELECT * FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE\G *************************** ...
https://dev.mysql.com/doc/refman/8.0/en/view-updatability.html
Some views are updatable and references to them can be used to specify tables to be updated in data change statements. That is, you can use them in statements such as UPDATE, DELETE, or INSERT to update the contents of the underlying table. Derived ...For dependent subqueries in the select list, no data change statements are ...
https://dev.mysql.com/doc/refman/8.0/en/stored-program-restrictions.html
(Bug #16396) References to stored functions, loadable functions, and tables in the ON SCHEDULE clauses of CREATE EVENT and ALTER EVENT statements are not supported. Altering the system tables in the mysql database is not supported and is very likely ...The following statements are not permitted: The locking statements LOCK TABLES and UNLOCK ...Some of the restrictions ...
https://dev.mysql.com/doc/refman/8.0/en/myisam-storage-engine.html
(When an AUTO_INCREMENT column is defined as the last column of a multiple-column index, reuse of values deleted from the top of a sequence does occur.) The AUTO_INCREMENT value can be reset with ALTER TABLE or myisamchk. Table 18.2 MyISAM Storage ... MyISAM is based on the older (and no longer available) ISAM storage engine but has many useful ...
https://dev.mysql.com/doc/refman/8.0/en/optimizing-queries-myisam.html
Some general tips for speeding up queries on MyISAM tables: To help MySQL better optimize queries, use ANALYZE TABLE or run myisamchk --analyze on a table after it has been loaded with data. (For unique indexes, this is always 1.) MySQL uses this ...This updates a value for each index part that indicates the average number of rows that have the same ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-innodb-ft-config-table.html
The INNODB_FT_CONFIG table provides metadata about the FULLTEXT index and associated processing for an InnoDB table. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table ...The values for this column might change, depending on the needs for performance tuning and debugging for InnoDB full-text ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-events-transactions-current-table.html
The table stores one row per thread showing the current status of the thread's most recent monitored transaction event, so there is no system variable for configuring the table size. Other tables that contain transaction event rows are logically ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-prepared-statements-instances-table.html
This is accessed through the MySQL C API and maps onto underlying server commands as shown in the following table. This is accessed using SQL statements and maps onto underlying server commands as shown in the following table. This table enables ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-processlist-table.html
Note If the performance_schema_show_processlist system variable is enabled, the processlist table also serves as the basis for an alternative implementation underlying the SHOW PROCESSLIST statement. As mentioned previously, if the ...For a ... The ...