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.
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
help_topic is NULL.
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
gc_delete_range: to record the data to be deleted
GLOBAL_VARIABLES: global system variable table
tidb: to record the version information when TiDB executes