System metadatabase

This topic describes how to view the exclusive metadata of your CelerData cluster via system-defined views.

Each CelerData cluster maintains a database sys, which contains several read-only, system-defined views. These metadata views provide a unified, easy-to-use interface that allows you to have an overall insight into the privilege structure, object dependencies, and other information within your CelerData cluster.

View metadata information via sys

You can view the exclusive metadata information within a CelerData cluster by querying the content of views in sys.

The following example checks the privileges granted to user-defined roles by querying the view grants_to_roles.

MySQL > SELECT * FROM sys.grants_to_roles LIMIT 5\G
*************************** 1. row ***************************
        GRANTEE: role_test
 OBJECT_CATALOG: default_catalog
OBJECT_DATABASE: db_test
    OBJECT_NAME: tbl1
    OBJECT_TYPE: TABLE
 PRIVILEGE_TYPE: SELECT, ALTER
   IS_GRANTABLE: NO
*************************** 2. row ***************************
        GRANTEE: role_test
 OBJECT_CATALOG: default_catalog
OBJECT_DATABASE: db_test
    OBJECT_NAME: tbl2
    OBJECT_TYPE: TABLE
 PRIVILEGE_TYPE: SELECT
   IS_GRANTABLE: YES
*************************** 3. row ***************************
        GRANTEE: role_test
 OBJECT_CATALOG: default_catalog
OBJECT_DATABASE: db_test
    OBJECT_NAME: mv_test
    OBJECT_TYPE: MATERIALIZED VIEW
 PRIVILEGE_TYPE: SELECT
   IS_GRANTABLE: YES
*************************** 4. row ***************************
        GRANTEE: role_test
 OBJECT_CATALOG: NULL
OBJECT_DATABASE: NULL
    OBJECT_NAME: NULL
    OBJECT_TYPE: SYSTEM
 PRIVILEGE_TYPE: CREATE RESOURCE GROUP
   IS_GRANTABLE: NO

Views in sys

sys contains the following metadata views:

View	Description
grants_to_roles	Records the information of privileges that are granted to user-defined roles.
grants_to_users	Records the information of privileges that are granted to users.
role_edges	Records the grantees of roles.
object_dependencies	Records the dependency relationship of asynchronous materialized views.
policy_references	Records the application information of the Masking Policy and Row Access Policy.

NOTE

As per their scenarios of applications, views in sys are only accessible to some admin roles by default. Depending on your specific needs, you can grant other users the SELECT privilege on these views.