The view role_usage_grants is meant to identify
   USAGE privileges granted on various kinds of
   objects to a currently enabled role or by a currently enabled role.
   In PostgreSQL, this currently only
   applies to domains, and since domains do not have real privileges
   in PostgreSQL, this view is empty.
   Further information can be found under
   usage_privileges.  In the future, this view may
   contain more useful information.
  
Table 32-25. role_usage_grants Columns
| Name | Data Type | Description | 
|---|
| grantor | sql_identifier | In the future, the name of the role that granted the privilege | 
| grantee | sql_identifier | In the future, the name of the role that the privilege was granted to | 
| object_catalog | sql_identifier | Name of the database containing the object (always the current database) | 
| object_schema | sql_identifier | Name of the schema containing the object | 
| object_name | sql_identifier | Name of the object | 
| object_type | character_data | In the future, the type of the object | 
| privilege_type | character_data | Always USAGE | 
| is_grantable | character_data | YES if the privilege is grantable, NO if not |