The view pg_shadow exists for backwards
   compatibility: it emulates a catalog that existed in
   PostgreSQL before version 8.1.
   It shows properties of all roles that are marked as
   rolcanlogin.
  
   The name stems from the fact that this table
   should not be readable by the public since it contains passwords.
   pg_user
   is a publicly readable view on
   pg_shadow that blanks out the password field.
  
Table 43-45. pg_shadow Columns
| Name | Type | References | Description | 
|---|
| usename | name | pg_authid.rolname | User name | 
| usesysid | oid | pg_authid.oid | ID of this user | 
| usecreatedb | bool |  | User may create databases | 
| usesuper | bool |  | User is a superuser | 
| usecatupd | bool |  | User may update system catalogs.  (Even a superuser may not do
       this unless this column is true.) | 
| passwd | text |  | Password (possibly encrypted) | 
| valuntil | abstime |  | Password expiry time (only used for password authentication) | 
| useconfig | text[] |  | Session defaults for run-time configuration variables |