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https://dev.mysql.com/doc/refman/8.4/en/error-log-event-fields.html
Error events intended for the error log contain a set of fields, each of which consists of a key/value pair. An event field may be classified as core, optional, or user-defined: A core field is set up automatically for error events. However, its ...
https://dev.mysql.com/doc/refman/8.4/en/error-lost-connection.html
Sometimes the “during query” form happens when millions of rows are being sent as part of one or more queries. Usually it indicates network connectivity trouble and you should check the condition of your network if this error occurs frequently.
https://dev.mysql.com/doc/refman/8.4/en/explain-for-connection.html
To obtain the execution plan for an explainable statement executing in a named connection, use this statement: EXPLAIN [options] FOR CONNECTION connection_id; EXPLAIN FOR CONNECTION returns the EXPLAIN information that is currently being used to ...
https://dev.mysql.com/doc/refman/8.4/en/extensions-to-ansi.html
This gives better performance for some very specific, but quite normal queries. MySQL Server supports some extensions that you are not likely to find in other SQL DBMSs. Be warned that if you use them, your code is most likely not portable to other ...
https://dev.mysql.com/doc/refman/8.4/en/federated-usagenotes.html
Queries that fail to use indexes can thus cause poor performance and network overload. The following items indicate features that the FEDERATED storage engine does and does not support: The remote server must be a MySQL server. The remote table that ...
https://dev.mysql.com/doc/refman/8.4/en/full-text-adding-collation.html
Warning User-defined collations are deprecated; you should expect support for them to be removed in a future version of MySQL. The server issues a warning for any use of COLLATE user_defined_collation in an SQL statement; a warning is also issued ...
https://dev.mysql.com/doc/refman/8.4/en/fulltext-fine-tuning.html
Otherwise, queries for the table may yield incorrect results, and modifications to the table causes the server to see the table as corrupt and in need of repair. You can exert more control over full-text searching behavior if you have a MySQL source ...
https://dev.mysql.com/doc/refman/8.4/en/index-extensions.html
InnoDB automatically extends each secondary index by appending the primary key columns to it. Consider this table definition: CREATE TABLE t1 ( i1 INT NOT NULL DEFAULT 0, i2 INT NOT NULL DEFAULT 0, d DATE DEFAULT NULL, PRIMARY KEY (i1, i2), INDEX ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-cached-indexes-table.html
The INNODB_CACHED_INDEXES table reports the number of index pages cached in the InnoDB buffer pool for each index. For related usage information and examples, see Section 17.15.5, “InnoDB INFORMATION_SCHEMA Buffer Pool Tables”. Index ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-ft-index-cache-table.html
The INNODB_FT_INDEX_CACHE table provides token information about newly inserted rows in a FULLTEXT index. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that ...