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https://dev.mysql.com/doc/refman/8.0/en/replication-semisync-interface.html
These settings help as the number of replicas increases, because contention for locks can slow down performance. When you install the source and replica plugins for semisynchronous replication (see Section 19.4.10.1, “Installing Semisynchronous ...
https://dev.mysql.com/doc/refman/8.0/en/replication-snapshot-method.html
Assuming the above exceptions do not apply to your database, use the cold backup technique to obtain a reliable binary snapshot of InnoDB tables: do a slow shutdown of the MySQL Server, then copy the data files manually. If the source database ...
https://dev.mysql.com/doc/refman/8.0/en/upgrade-troubleshooting.html
After the errors are fixed, perform a slow shutdown (by setting innodb_fast_shutdown=0) before attempting the upgrade again. A schema mismatch in a MySQL 5.7 instance between the .frm file of a table and the InnoDB data dictionary can cause an ...
https://dev.mysql.com/doc/refman/8.0/en/windows-testing.html
In this case, start mysqld with the skip_name_resolve system variable enabled and use only localhost and IP addresses in the Host column of the MySQL grant tables. (Be sure that an account exists that specifies an IP address or you may not be able ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-nutshell.html
The InnoDB memcached plugin supports multiple get operations (fetching multiple key-value pairs in a single memcached query) and range queries. On high concurrency systems, deadlock detection can cause a slowdown when numerous threads wait for the ... This section summarizes what has been added to, deprecated in, and removed from MySQL ...
https://dev.mysql.com/doc/refman/8.0/en/optimizer-hints.html
Changes to this variable affect execution of all subsequent queries; to affect one query differently from another, it is necessary to change optimizer_switch before each one. If subqueries subq1 and subq2 are converted to semijoins, tables t4@subq1 ... One means of control over optimizer strategies is to set the optimizer_switch system variable (see Section 10.9.2, “Switchable ...
https://dev.mysql.com/doc/refman/8.0/en/explain-output.html
select_type Value JSON Name Meaning SIMPLE None Simple SELECT (not using UNION or subqueries) PRIMARY None Outermost SELECT UNION None Second or later SELECT statement in a UNION DEPENDENT UNION dependent (true) Second or later SELECT statement in a ... The EXPLAIN statement provides information about how MySQL executes ...
https://dev.mysql.com/doc/refman/8.0/en/mysqlslap.html
Run all the load statements, then run all the queries in the query file with five clients (five times each): mysqlslap --concurrency=5 --iterations=5 --query=query.sql --create=create.sql --delimiter=";" mysqlslap supports the following options, ...
https://dev.mysql.com/doc/refman/8.0/en/set-operations.html
With the optional ALL keyword, duplicate-row removal does not occur and the result includes all matching rows from all queries in the union. Result Set Column Names and Data Types Set Operations with TABLE and VALUES Statements Set Operations using ...
https://dev.mysql.com/doc/refman/8.0/en/derived-table-optimization.html
(For an example, see Section 10.2.2.2, “Optimizing Subqueries with Materialization”.) If merging would result in an outer query block that references more than 61 base tables, the optimizer chooses materialization instead. Even for queries that ...The optimizer handles derived tables, view references, and common table expressions the same way: It avoids unnecessary materialization whenever possible, which enables pushing down conditions from the outer query to derived tables and produces more efficient execution ...