postgres=# \dg
                                                              List of roles
 Role name |                                                    Attributes                                                    | Member of
-----------+------------------------------------------------------------------------------------------------------------------+-----------
 itsm      | Create DB, Cannot login                                                                                          | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}

postgres=# drop role itsm;
ERROR:  role "itsm" cannot be dropped because some objects depend on it
DETAIL:  1 object in database itsm

postgres=# select datname,usename,state,count(*)
   from pg_stat_activity
   group by datname,usename,state order by 4 desc;

 datname  | usename | state  | count
----------+---------+--------+-------
 postgres | omm     | active |     3
 postgres | omm     | idle   |     2
 itsm     | omm     | active |     1
(3 rows)

--检查表属主
select relname,relnamespace,relkind from pg_class
  where relowner=(select oid from pg_roles where rolname='itsm')
  order by 3 desc;

--检查用户的系统权限
SELECT * FROM pg_roles WHERE rolname='itsm';

--检查用户的表权限
select * from information_schema.table_privileges
  where grantee='itsm';

--检查用户的usage权限
select * from information_schema.usage_privileges
  where grantee='itsm';

--检查用户在存储过程函数的执行权限
select * from information_schema.routine_privileges
  where grantee='itsm';

--检查用户在表的列上的权限
select * from information_schema.column_privileges
  where grantee='itsm';

--检查用户自定义类型上授予的USAGE权限
select * from information_schema.udt_privileges
  where grantee='itsm';

postgres=# revoke all on database itsm from itsm;
REVOKE
postgres=# \c itsm
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "itsm" as user "omm".
itsm=# drop user itsm;
DROP ROLE