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https://dev.mysql.com/doc/refman/8.0/en/subquery-optimization-with-exists.html
This is a problem because many real world subqueries become very slow unless the equality can be pushed down. For multiple-table subqueries, execution of NULL IN (SELECT ...) is particularly slow because the join optimizer does not optimize for the ...WHERE subquery_where) MySQL evaluates queries “from outside to inside.” That is, it first obtains the value of the outer expression outer_expr, and then runs the subquery and captures the rows that it ...
https://dev.mysql.com/doc/refman/8.0/en/mysqldump.html
Use this option, which is available from MySQL 8.0.30, if you want to increase the time allowed for queries from mysqldump before they are logged to the slow query log file. With large data sizes, even if the backup step takes a reasonable time, ...
https://dev.mysql.com/doc/refman/8.0/en/mysqladmin.html
Slow queries The number of queries that have taken more than long_query_time seconds. Following the flush-logs command, you can provide a space-separated list of one or more of the following log types: binary, engine, error, general, relay, slow.
https://dev.mysql.com/doc/refman/8.0/en/information-schema-optimization.html
To write queries for these tables most efficiently, use the following general guidelines: Try to query only INFORMATION_SCHEMA tables that are views on data dictionary tables. Note Comparison behavior for database and table names in ... Applications ...
https://dev.mysql.com/doc/refman/8.0/en/limit-optimization.html
If you need only a specified number of rows from a result set, use a LIMIT clause in the query, rather than fetching the whole result set and throwing away the extra data. MySQL sometimes optimizes a query that has a LIMIT row_count clause and no ...
https://dev.mysql.com/doc/refman/8.0/en/upgrade-binary-package.html
Then perform another slow shutdown of the 5.7 server and start the MySQL 8.0 server to try again. This section describes how to upgrade MySQL binary and package-based installations on Unix/Linux. In-Place Upgrade Logical Upgrade MySQL Cluster ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-optimization.html
To write queries for these tables most efficiently, take advantage of their indexes. Tables that do not are those that normally contain few rows or are unlikely to be queried frequently. Applications that monitor databases may make frequent use of ...
https://dev.mysql.com/doc/refman/8.0/en/execution-plan-information.html
Depending on the details of your tables, columns, indexes, and the conditions in your WHERE clause, the MySQL optimizer considers many techniques to efficiently perform the lookups involved in an SQL query. A query on a huge table can be performed ...
https://dev.mysql.com/doc/refman/8.0/en/controlling-optimizer.html
MySQL provides optimizer control through system variables that affect how query plans are evaluated, switchable optimizations, optimizer and index hints, and the optimizer cost model. The server maintains histogram statistics about column values in ...
https://dev.mysql.com/doc/refman/8.0/en/estimating-performance.html
The preceding discussion does not mean that your application performance slowly degenerates by log N. As long as everything is cached by the OS or the MySQL server, things become only marginally slower as the table gets bigger. After the data gets ... In most cases, you can estimate query performance by counting disk ...