1017 Data Dictionary Tables Data Dictionary Tables These tables comprise the data dictionary, which contains metadata about database objects. For additional information, see Chapter 14,  MySQL Data Dictionary . Important The data dictionary is new in MySQL 8.0. A data dictionary-enabled server entails some general operational differences compared to previous MySQL releases. For details, see Section 14.7, “Data Dictionary Usage Differences” . Also, for upgrades to MySQL 8.0 from MySQL 5.7, the upgrade procedure differs somewhat from previous MySQL releases and requires that you verify the upgrade readiness of your installation by checking specific prerequisites. For more information, see Section 2.11, “Upgrading MySQL” , particularly Section 2.11.5, “Preparing Your Installation for Upgrade” . • catalogs : Catalog information. • character_sets : Information about available character sets. • check_constraints : Information about  CHECK  constraints defined on tables. See Section 13.1.20.6, “CHECK Constraints” . • collations : Information about collations for each character set. •  column_statistics : Histogram statistics for column values. See Section 8.9.6, “Optimizer Statistics” . • column_type_elements : Information about types used by columns. • columns : Information about columns in tables. • dd_properties : A table that identifies data dictionary properties, such as its version. The server uses this to determine whether the data dictionary must be upgraded to a newer version. • events : Information about Event Scheduler events. See Section 25.4, “Using the Event Scheduler” . If the server is started with the  --skip-grant-tables  option, the event scheduler is disabled and events registered in the table do not run. See Section 25.4.2, “Event Scheduler Configuration” . • foreign_keys ,  foreign_key_column_usage : Information about foreign keys. • index_column_usage : Information about columns used by indexes. • index_partitions : Information about partitions used by indexes. • index_stats : Used to store dynamic index statistics generated when  ANALYZE TABLE  is executed. • indexes : Information about table indexes. • innodb_ddl_log : Stores DDL logs for crash-safe DDL operations. • parameter_type_elements : Information about stored procedure and function parameters, and about return values for stored functions. • parameters : Information about stored procedures and functions. See Section 25.2, “Using Stored Routines” . • resource_groups : Information about resource groups. See Section 5.1.16, “Resource Groups” .