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https://dev.mysql.com/doc/refman/8.0/en/explain-output.html
ref_or_null This join type is like ref, but with the addition that MySQL does an extra search for rows that contain NULL values. This means that MySQL reads a row from the first table, then finds a matching row in the second table, and then in the ... The EXPLAIN statement provides information about how MySQL executes ...
https://dev.mysql.com/doc/refman/8.0/en/handler-scope.html
When a condition occurs in a stored program, the server searches for applicable handlers in the current scope (current BEGIN ... If there are no applicable handlers, the search continues outward with the handlers in each successive containing scope ... A stored program may include handlers to be invoked when certain conditions occur within the ...
https://dev.mysql.com/doc/refman/8.0/en/identifier-case-sensitivity.html
This means such names are not case-sensitive in Windows, but are case-sensitive in most varieties of Unix. The lower_case_table_names system variable also affects how the server handles identifier case sensitivity, as described later in this section. The following statement would not work on Unix, because it refers to the alias both as a and as A: mysql> SELECT col_name FROM tbl_name AS a WHERE a.col_name = 1 OR A.col_name = 2; However, this same statement is permitted on ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-innodb-ft-config-table.html
The values for this column might change, depending on the needs for performance tuning and debugging for InnoDB full-text processing. Example mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_CONFIG; +---------------------------+-------------------+ ... The INNODB_FT_CONFIG table provides metadata about the FULLTEXT index and associated processing for an InnoDB ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-innodb-ft-default-stopword-table.html
This is not used if you override the default stopword processing with either the innodb_ft_server_stopword_table or the innodb_ft_user_stopword_table system variable. Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-adaptive-hash.html
Based on the observed pattern of searches, a hash index is built using a prefix of the index key. The adaptive hash index enables InnoDB to perform more like an in-memory database on systems with appropriate combinations of workload and sufficient ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-change-buffer.html
During this time, disk I/O is increased, which can cause a significant slowdown for disk-bound queries. The change buffer is a special data structure that caches changes to secondary index pages when those pages are not in the buffer pool. The ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-index-types.html
InnoDB uses this primary key value to search for the row in the clustered index. How the Clustered Index Speeds Up Queries Accessing a row through the clustered index is fast because the index search leads directly to the page that contains the row ... Each InnoDB table has a special index called the clustered index that stores row ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-locking-reads.html
FOR UPDATE For index records the search encounters, locks the rows and any associated index entries, the same as if you issued an UPDATE statement for those rows. Your application code can ensure referential integrity throughout this sequence of ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-standard-monitor.html
This limit does not apply to output written to server standard error output (stderr). Status This section shows the timestamp, the monitor name, and the number of seconds that per-second averages are based on. SEMAPHORES This section reports threads ... The Lock Monitor is the same as the Standard Monitor except that it includes additional lock ...