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https://dev.mysql.com/doc/refman/5.7/en/explain-extended.html
See Section 8.2.2.1, “Optimizing Subqueries, Derived Tables, and View References with Semijoin Transformations”. For SELECT statements, the EXPLAIN statement produces extra (“extended”) information that is not part of EXPLAIN output but can ...
https://dev.mysql.com/doc/refman/5.7/en/faqs-cjk.html
This set of Frequently Asked Questions derives from the experience of MySQL's Support and Development groups in handling many inquiries about CJK (Chinese-Japanese-Korean) issues. What problems should I be aware of when working with the Big5 ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-persistent-stats.html
The persistent optimizer statistics feature improves plan stability by storing statistics to disk and making them persistent across server restarts so that the optimizer is more likely to make consistent choices each time for a given query.
https://dev.mysql.com/doc/refman/5.7/en/innodb-standard-monitor.html
Contention can be due to heavy parallelism of queries or problems in operating system thread scheduling. You can calculate from these numbers how many data file I/O operations your queries currently are doing. The Lock Monitor is the same as the ...
https://dev.mysql.com/doc/refman/5.7/en/internal-temporary-tables.html
Tables created for subquery or semijoin materialization (see Section 8.2.2, “Optimizing Subqueries, Derived Tables, and View References”). For queries that use the SQL_SMALL_RESULT modifier, MySQL uses an in-memory temporary table, unless the ...
https://dev.mysql.com/doc/refman/5.7/en/log-file-maintenance.html
As described in Section 5.4, “MySQL Server Logs”, MySQL Server can create several different log files to help you see what activity is taking place. However, you must clean up these files regularly to ensure that the logs do not take up too ...
https://dev.mysql.com/doc/refman/5.7/en/memory-storage-engine.html
Despite the in-memory processing for MEMORY tables, they are not necessarily faster than InnoDB tables on a busy server, for general-purpose queries, or under a read/write workload. User-Created and Temporary Tables MEMORY table contents are stored ... The MEMORY storage engine (formerly known as HEAP) creates special-purpose tables with contents that are stored in ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-limitations-transactions.html
This issue does not occur for queries that use index or table scans, even against NDB tables having BLOB or TEXT columns. You can help minimize issues with shared read locks by avoiding queries that use unique key lookups that retrieve BLOB or TEXT ... A number of limitations exist in NDB Cluster with regard to the handling of ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-replication-failover.html
In the event that the primary Cluster replication process fails, it is possible to switch over to the secondary replication channel. This means that the ndb_apply_status table contains information for the replica on this host as well as for any ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-commands.html
If you are running with --safe-updates enabled, status also prints the values for the mysql variables that affect your queries. This is useful when you want to log some queries to a file, but not others. mysql sends each SQL statement that you ...