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https://dev.mysql.com/doc/refman/5.7/en/performance-schema-events-statements-history-table.html
To set the number of rows per thread explicitly, set the performance_schema_events_statements_history_size system variable at server startup. When the table contains the maximum number of rows for a given thread, the oldest thread row is discarded ... The events_statements_history table contains the N most recent statement events that have ended per ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-events-transactions-history-table.html
To set the number of rows per thread explicitly, set the performance_schema_events_transactions_history_size system variable at server startup. When the table contains the maximum number of rows for a given thread, the oldest thread row is discarded ... The events_transactions_history table contains the N most recent transaction events that have ended per ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-events-waits-history-table.html
To set the number of rows per thread explicitly, set the performance_schema_events_waits_history_size system variable at server startup. When the table contains the maximum number of rows for a given thread, the oldest thread row is discarded when a ... The events_waits_history table contains the N most recent wait events that have ended per ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-change-buffer.html
The purge operation can write disk blocks for a series of index values more efficiently than if each value were written to disk immediately. During this time, disk I/O is increased, which can cause a significant slowdown for disk-bound queries. The ...
https://dev.mysql.com/doc/refman/5.7/en/partitioning-key.html
Partitioning by key is similar to partitioning by hash, except that where hash partitioning employs a user-defined expression, the hashing function for key partitioning is supplied by the MySQL server. NDB Cluster uses MD5() for this purpose; for ...PARTITION BY KEY are similar to those for creating a table that is partitioned by ...
https://dev.mysql.com/doc/refman/5.7/en/optimizing-queries-myisam.html
An update of the following form is very fast: UPDATE tbl_name SET count_col=count_col+1 WHERE key_col=constant; This is very important when you use MySQL storage engines such as MyISAM that has only table-level locking (multiple readers with single ... 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 ...
https://dev.mysql.com/doc/refman/5.7/en/security-options.html
For descriptions of each of these, see Section 5.1.6, “Server Command Options”, and Section 5.1.7, “Server System Variables”. The following table shows mysqld options and system variables that affect security.
https://dev.mysql.com/doc/refman/5.7/en/sys-ps-is-account-enabled.html
Returns YES or NO to indicate whether Performance Schema instrumentation for a given account is enabled. Parameters in_host VARCHAR(60): The host name of the account to check. Example mysql> SELECT sys.ps_is_account_enabled('localhost', 'root'); ...
https://dev.mysql.com/doc/refman/5.7/en/sys-session.html
These views are similar to processlist and x$processlist, but they filter out background processes to display only user sessions. For descriptions of the columns, see Section 26.4.3.22, “The processlist and x$processlist Views”.
https://dev.mysql.com/doc/refman/5.7/en/group-by-modifiers.html
Following each set of rows for a given year, an extra super-aggregate summary row appears showing the total for all countries and products. For any column in the result set with a name that matches any of those names, its value is set to NULL. For ... The GROUP BY clause permits a WITH ROLLUP modifier that causes summary output to include extra rows that represent higher-level (that is, super-aggregate) summary ...