如何查看postgresql用户权限

select * from information_schema.table_privileges where grantee='user_name';

select * from information_schema.usage_privileges where grantee='user_name';

select * from information_schema.routine_privileges where grantee='user_name';

create user user_name;

alter user user_name with password '';

alter user user_name with CONNECTION LIMIT  20;#连接数限制