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https://dev.mysql.com/doc/refman/5.7/en/innodb-file-defragmenting.html
To speed up index scans, you can periodically perform a “null” ALTER TABLE operation, which causes MySQL to rebuild the table: ALTER TABLE tbl_name ENGINE=INNODB You can also use ALTER TABLE tbl_name FORCE to perform a “null” alter operation ... Random insertions into or deletions from a secondary index can cause the index to become ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-index-types.html
If there is no logical unique and non-null column or set of columns to use a the primary key, add an auto-increment column. If you do not define a PRIMARY KEY for a table, InnoDB uses the first UNIQUE index with all key columns defined as NOT NULL ... Each InnoDB table has a special index called the clustered index that stores row ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-information-schema-files-table.html
FILES columns that are not relevant to InnoDB always return NULL, and are excluded from the query. row *************************** FILE_ID: 0 FILE_NAME: ./ibdata1 FILE_TYPE: TABLESPACE TABLESPACE_NAME: innodb_system FREE_EXTENTS: 0 TOTAL_EXTENTS: 12 ... The Information Schema FILES table provides metadata about all InnoDB tablespace types including file-per-table tablespaces, general tablespaces, the system tablespace, temporary table tablespaces, and undo tablespaces (if ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-transaction-isolation-levels.html
Transaction isolation is one of the foundations of database processing. Isolation is the I in the acronym ACID; the isolation level is the setting that fine-tunes the balance between performance and reliability, consistency, and reproducibility of ...
https://dev.mysql.com/doc/refman/5.7/en/insert-on-duplicate.html
The VALUES() function is meaningful only as an introducer for INSERT statement value lists, or in the ON DUPLICATE KEY UPDATE clause of an INSERT statement, and returns NULL otherwise. If you specify an ON DUPLICATE KEY UPDATE clause and a row to ...
https://dev.mysql.com/doc/refman/5.7/en/keyring-functions-plugin-specific.html
Return value: Returns 1 for success, or NULL and an error for failure. Return value: Returns 1 for success, or NULL and an error for failure. For each keyring plugin-specific function, this section describes its purpose, calling sequence, and ...
https://dev.mysql.com/doc/refman/5.7/en/multiple-tables.html
The pet table keeps track of which pets you have. If you want to record other information about them, such as events in their lives like visits to the vet or when litters are born, you need another table. What should this table look like? It needs ...
https://dev.mysql.com/doc/refman/5.7/en/myisam-ftdump.html
Example: Suppose that the test database contains a table named mytexttable that has the following definition: CREATE TABLE mytexttable ( id INT NOT NULL, txt TEXT NOT NULL, PRIMARY KEY (id), FULLTEXT (txt) ) ENGINE=MyISAM; The index on id is index 0 ...It reads the MyISAM index file directly, so it must be run on the server host where the table is ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-accounts-table.html
This is NULL for an internal thread, or for a user session that failed to authenticate. This is NULL for an internal thread, or for a user session that failed to authenticate. The accounts table contains a row for each account that has connected to ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-atom-molecule-events.html
For example, a row fetch might result in rows like this: Row# EVENT_NAME TIMER_START TIMER_END ---- ---------- ----------- --------- 1 wait/io/file/myisam/dfile 10001 10002 2 wait/io/table/sql/handler 10000 NULL The row fetch causes a file read. In ... For a table I/O event, there are usually two rows in events_waits_current, not ...