Overview

Apache Doris cluster has multiple built-in system databases to store metadata information about the Doris system itself.

information_schema

All tables under the information_schema database are virtual tables and do not have physical entities. These system tables contain metadata about the Doris cluster and all its database objects, including databases, tables, columns, permissions, etc. They also include functional status information like Workload Group, Task, etc.

There is an information_schema database under each Catalog, containing metadata only for the corresponding Catalog's databases and tables.

All tables in the information_schema database are read-only, and users cannot modify, drop, or create tables in this database.

By default, all users have read permissions for all tables in this database, but the query results will vary based on the user's actual permission. For example, if User A only has permissions for db1.table1, querying the information_schema.tables table will only return information related to db1.table1.

mysql

All tables under the mysql database are virtual tables and do not have physical entities. These system tables contain information such as permissions and are mainly used for MySQL ecosystem compatibility.

There is a mysql database under each Catalog, but the content of tables is identical.

All tables in the mysql database are read-only, and users cannot modify, delete, or create tables in this database.

__internal_schema

All tables under the __internal_schema database are actual tables in Doris, stored similarly to user-created data tables. When a Doris cluster is created, all system tables under this database are automatically created.

By default, common users have read-only permissions for tables in this database. However, once granted, they can modify, delete, or create tables under this database.