System tables

There are multiple types of system tables:

• mysql schema: There are mostly real tables stored on TiKV
• information_schema: These tables are generated on request and not stored on disk.
• performance_schema: These tables are generated on request and not stored on disk.
• metrics_schema: These are metrics from Prometheus, not real tables.
• SYS: these are views etc to make performance_schema easier to use.

See also the docs:

• TiDB mysql schema
• TiDB information_schema
• TiDB performance_schema
• TiDB sys schema
• TiDB metrics_schema
• MySQL performance_schema
• MySQL information_schema
• MySQL sys schema
• MySQL mysql schema