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https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html
In general, you should try to avoid using an ON DUPLICATE KEY UPDATE clause on tables with multiple unique indexes. It is possible to use IGNORE with ON DUPLICATE KEY UPDATE in an INSERT statement, but this may not behave as you expect when ... If ...
https://dev.mysql.com/doc/refman/8.0/en/change-replication-source-to.html
This option prevents the replication applier from taking actions such as creating temporary tables and executing LOAD DATA INFILE requests, which increases the security of the channel. OFF: The replica sets sql_require_primary_key = OFF; no ...If ...
https://dev.mysql.com/doc/refman/8.0/en/sql-prepared-statements.html
To create a test case that reproduces a problem with prepared statements, so that you can file a bug report. If you create a prepared statement within a stored routine, it is not deallocated when the stored routine ends. To guard against too many ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-optimization.html
To see whether a given Performance Schema table has indexes and what they are, use SHOW INDEX or SHOW CREATE TABLE: mysql> SHOW INDEX FROM performance_schema.accounts\G *************************** 1. row *************************** Table: accounts ... Applications that monitor databases may make frequent use of Performance Schema ...For example, include a WHERE clause that ...
https://dev.mysql.com/doc/refman/8.0/en/index-condition-pushdown-optimization.html
Index Condition Pushdown (ICP) is an optimization for the case where MySQL retrieves rows from a table using an index. Without ICP, the storage engine traverses the index to locate rows in the base table and returns them to the MySQL server which ...With ICP enabled, and if parts of the WHERE condition can be evaluated by using only columns from the index, the MySQL server pushes this part of the WHERE condition down to the storage ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-memcached-troubleshoot.html
loose-daemon_memcached_option='-c 64' To troubleshoot problems where the memcached daemon is unable to store or retrieve InnoDB table data, encode the -vvv memcached option in the daemon_memcached_option configuration parameter in the MySQL ... This ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-limitations-limits.html
Memory consumed when data is inserted into an NDB table is not automatically recovered when deleted, as it is with other storage engines. Instead, the following rules hold true: A DELETE statement on an NDB table makes the memory formerly used by ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-standard-monitor.html
The contents include the statement that failed as well as information about the constraint that failed and the referenced and referencing tables. The Lock Monitor is the same as the Standard Monitor except that it includes additional lock ...
https://dev.mysql.com/doc/refman/8.0/en/replication-options-gtids.html
Only statements that can be logged using GTID safe statements can be logged when enforce_gtid_consistency is set to ON, so the operations listed here cannot be used with this option: CREATE TEMPORARY TABLE or DROP TEMPORARY TABLE statements inside ...There is an exception that nontransactional DML is allowed in the same transaction or in the same statement as transactional DML, if all nontransactional tables are ...
https://dev.mysql.com/doc/refman/8.0/en/condition-filtering.html
In join processing, prefix rows are those rows passed from one table in a join to the next. In general, the optimizer attempts to put tables with low prefix counts early in the join order to keep the number of row combinations from increasing ...