Search Results
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-foreign-cols-table.html
The INNODB_FOREIGN_COLS table provides status information about InnoDB foreign key columns. The INNODB_FOREIGN_COLS table has these columns: ID The foreign key index associated with this index key field; the same value as INNODB_FOREIGN.ID. For ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-ft-config-table.html
The INNODB_FT_CONFIG table has these columns: KEY The name designating an item of metadata for an InnoDB table containing a FULLTEXT index. The values for this column might change, depending on the needs for performance tuning and debugging for ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-optimization.html
Selecting columns or using retrieval conditions for dynamic metadata along with static metadata adds overhead to process the dynamic metadata. Some INFORMATION_SCHEMA tables contain columns that provide table statistics: STATISTICS.CARDINALITY ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-locking.html
For example, SELECT c1 FROM t WHERE c1 BETWEEN 10 and 20 FOR UPDATE; prevents other transactions from inserting a value of 15 into column t.c1, whether or not there was already any such value in the column, because the gaps between all existing ...
https://dev.mysql.com/doc/refman/8.4/en/memory-use.html
For each concurrent thread, a table structure, column structures for each column, and a buffer of size 3 * N are allocated (where N is the maximum row length, not counting BLOB columns). A BLOB column requires five to eight bytes plus the length of ... MySQL allocates buffers and caches to improve performance of database ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-mutex-instances-table.html
The mutex_instances table has these columns: NAME The instrument name associated with the mutex. The OBJECT_INSTANCE_BEGIN column is a property that uniquely identifies the mutex. When a thread attempts to lock a mutex, the events_waits_current ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-replication-applier-status-by-coordinator-table.html
The replication_applier_status_by_coordinator table has these columns: CHANNEL_NAME The replication channel which this row is displaying. Issuing RESET BINARY LOGS AND GTIDS or RESET REPLICA resets the values shown in these columns. All error codes ... For a multithreaded replica, the replica uses multiple worker threads and a coordinator thread to manage them, and this table shows the status of the coordinator ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-setup-instruments-table.html
This column can be modified, although setting ENABLED has no effect for instruments that have already been created. This column can be modified, although setting TIMED has no effect for instruments that have already been created. For example, memory ... The setup_instruments table lists classes of instrumented objects for which events can be collected: mysql> SELECT * FROM performance_schema.setup_instruments\G ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-setup-threads-table.html
row *************************** NAME: thread/sql/event_scheduler ENABLED: YES HISTORY: YES PROPERTIES: singleton VOLATILITY: 0 DOCUMENTATION: NULL The setup_threads table has these columns: NAME The instrument name. This column can be modified, ...
https://dev.mysql.com/doc/refman/8.4/en/primary-key-optimization.html
The primary key for a table represents the column or set of columns that you use in your most vital queries. With the InnoDB storage engine, the table data is physically organized to do ultra-fast lookups and sorts based on the primary key column ...Query performance benefits from the NOT NULL optimization, because it cannot include any NULL ...