mysql Schema

The mysql schema contains TiDB system tables. The design is similar to the mysql schema in MySQL, where tables such as mysql.user can be edited directly. It also contains a number of tables which are extensions to MySQL.

Grant system tables

These system tables contain grant information about user accounts and their privileges:

• user: user accounts, global privileges, and other non-privilege columns
• db: database-level privileges
• tables_priv: table-level privileges
• columns_priv: column-level privileges

Server-side help system tables

Currently, the help_topic is NULL.

Statistics system tables

• stats_buckets: the buckets of statistics
• stats_histograms: the histograms of statistics
• stats_meta: the meta information of tables, such as the total number of rows and updated rows
• analyze_jobs: the ongoing statistics collection tasks and the history task records within the last 7 days

GC worker system tables

• gc_delete_range: to record the data to be deleted

System tables related to cached tables

• table_cache_meta stores the metadata of cached tables.

Miscellaneous system tables

• GLOBAL_VARIABLES: global system variable table

• tidb: to record the version information when TiDB executes bootstrap