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https://dev.mysql.com/doc/refman/8.4/en/delete.html
The speed of delete operations may also be affected by factors discussed in Section 10.2.5.3, “Optimizing DELETE Statements”. To reclaim unused space and reduce file sizes, use the OPTIMIZE TABLE statement or the myisamchk utility to reorganize ... DELETE is a DML statement that removes rows from a ...
https://dev.mysql.com/doc/refman/8.4/en/general-thread-states.html
Removing duplicates The query was using SELECT DISTINCT in such a way that MySQL could not optimize away the distinct operation at an early stage. Sorting index The thread is sorting index pages for more efficient access during a MyISAM table ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-online-ddl-operations.html
mysql> SELECT NAME, TOTAL_ROW_VERSIONS FROM INFORMATION_SCHEMA.INNODB_TABLES WHERE NAME LIKE 'test/t1'; +---------+--------------------+ | NAME | TOTAL_ROW_VERSIONS | +---------+--------------------+ | test/t1 | 0 | +---------+--------------------+ ... Online support details, syntax examples, and usage notes for DDL operations are provided under the following topics in this ...
https://dev.mysql.com/doc/refman/8.4/en/partitioning-maintenance.html
Table maintenance of partitioned tables can be accomplished using the statements CHECK TABLE, OPTIMIZE TABLE, ANALYZE TABLE, and REPAIR TABLE, which are supported for partitioned tables. OPTIMIZE PARTITION to reclaim any unused space and to ... A ...
https://dev.mysql.com/doc/internals/en/implementing-info-method.html
Prior to commencing a table scan, the [custom-engine.html#custom-engine-api-reference-info info()] method is called to provide extra table information to the optimizer. The information required by the optimizer is not given through return values ...
https://dev.mysql.com/doc/internals/en/implementing-the-info-method.html
The optimizer requests an update of table information by calling the [custom-engine.html#custom-engine-api-reference-info handler::info()] method. If you cannot provide an accurate number quickly you should set the value to be greater than 1 so ...
https://dev.mysql.com/doc/refman/8.4/en/aggregate-functions.html
SELECT COUNT(*) FROM tbl_name query performance for InnoDB tables is optimized for single-threaded workloads if there are no extra clauses such as WHERE or GROUP BY. InnoDB processes SELECT COUNT(*) statements by traversing the smallest available ...
https://dev.mysql.com/doc/refman/8.4/en/create-table.html
This helps the MySQL optimizer to prioritize which index to use and also more quickly to detect duplicated UNIQUE keys. Table Options Table options are used to optimize the behavior of the table. For more information about the persistent statistics ...| {FULLTEXT | SPATIAL} [INDEX | KEY] [index_name] (key_part,...) [index_option] ...
https://dev.mysql.com/doc/refman/8.4/en/invisible-indexes.html
MySQL supports invisible indexes; that is, indexes that are not used by the optimizer. If an index made invisible actually is needed or used by the optimizer, there are several ways to notice the effect of its absence on queries for the table: ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-option-tables.html
ndb-optimization-delay: Number of milliseconds to wait between processing sets of rows by OPTIMIZE TABLE on NDB tables. ndb_optimized_node_selection: Determines how SQL node chooses cluster data node to use as transaction coordinator. The following ...