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https://dev.mysql.com/doc/refman/8.4/en/estimating-performance.html
For small tables, you can usually find a row in one disk seek (because the index is probably cached). For bigger tables, you can estimate that, using B-tree indexes, you need this many seeks to find a row: log(row_count) / log(index_block_length / 3 ... In most cases, you can estimate query performance by counting disk ...
https://dev.mysql.com/doc/refman/8.4/en/events-metadata.html
To obtain metadata about events: Query the EVENTS table of the INFORMATION_SCHEMA database. Event times can be obtained by selecting from the Information Schema EVENTS table or from SHOW EVENTS, but they are reported as ETZ or STZ values. Value ...
https://dev.mysql.com/doc/refman/8.4/en/faqs-general.html
For the syntax required to perform multiple-table updates, see Section 15.2.17, “UPDATE Statement”; for that required to perform multiple-table deletes, see Section 15.2.2, “DELETE Statement”. A multiple-table insert can be accomplished ...
https://dev.mysql.com/doc/refman/8.4/en/flow-control-functions.html
The default return type of IF() (which may matter when it is stored into a temporary table) is calculated as follows: If expr2 or expr3 produce a string, the result is a string. The second syntax returns the result for the first condition that is ...
https://dev.mysql.com/doc/refman/8.4/en/group-by-functional-dependence.html
The following discussion provides several examples of the ways in which MySQL detects functional dependencies. The examples use this notation: {X} -> {Y} Understand this as “X uniquely determines Y,” which also means that Y is functionally ...
https://dev.mysql.com/doc/refman/8.4/en/group-replication-monitoring.html
These Performance Schema tables display information specific to Group Replication: replication_group_member_stats: See Section 20.4.4, “The replication_group_member_stats Table”. These Performance Schema replication tables also show information ... You can use the MySQL Performance Schema to monitor Group ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-online-ddl-failure-conditions.html
A timeout occurs while waiting for an exclusive lock on the table, which may be needed briefly during the initial and final phases of the DDL operation. The operation takes a long time and concurrent DML modifies the table so much that the size of ... The failure of an online DDL operation is typically due to one of the following conditions: An ALGORITHM clause specifies an algorithm that is not compatible with the particular type of DDL operation or storage ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-performance-midpoint_insertion.html
The goal is to make sure that frequently accessed (“hot”) pages remain in the buffer pool, even as read-ahead and full table scans bring in new blocks that might or might not be accessed afterward. You can control the insertion point in the LRU ... Rather than using a strict LRU algorithm, InnoDB uses a technique to minimize the amount of data that is brought into the buffer pool and never accessed ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-undo-tablespaces.html
Undo tablespaces contain undo logs, which are collections of records containing information about how to undo the latest change by a transaction to a clustered index record. Default undo tablespaces are created at initialization time to provide a ...To handle aggressive growth, the file extension size is doubled if the previous file extension happened less than 0.1 seconds ...
https://dev.mysql.com/doc/refman/8.4/en/install-component.html
INSTALL COMPONENT requires the INSERT privilege for the mysql.component system table because it adds a row to that table to register the component. Specifying PERSIST for any variable in SET silently executes SET PERSIST_ONLY immediately after ...