PostgreSQL PG_AUTHID View

 PG_AUTHID is views its contains information about rolename and user password,user password validity,user connection limit and  Role automatically inherits privileges of roles it is a member of,detailed information about user and privilege management.

Name	Type	Description
rolname	name	Role name
rolsuper	bool	Role has superuser privileges
rolinherit	bool	Role automatically inherits privileges of roles it is a member of
rolcreaterole	bool	Role can create more roles
rolcreatedb	bool	Role can create databases
rolcatupdate	bool	Role can update system catalogs directly. (Even a superuser cannot do this unless this column is true)
rolcanlogin	bool	Role can log in. That is, this role can be given as the initial session authorization identifier
rolreplication	bool	Role is a replication role. That is, this role can initiate streaming replication and set/unset the system backup mode usingpg_start_backup and pg_stop_backup
rolconnlimit	int4	For roles that can log in, this sets maximum number of concurrent connections this role can make. -1 means no limit.
rolpassword	text	Password (possibly encrypted); null if none. If the password is encrypted, this column will begin with the string md5 followed by a 32-character hexadecimal MD5 hash. The MD5 hash will be of the user's password concatenated to their user name. For example, if user joe has password xyzzy, PostgreSQL will store the md5 hash of xyzzyjoe. A password that does not follow that format is assumed to be unencrypted.
rolvaliduntil	timestamptz	Password expiry time (only used for password authentication); null if no expiration

Examples

--create the unencrypted user 

postgres=# create user u2 WITH UNENCRYPTED PASSWORD 'u2';
CREATE ROLE

--create the user with password validation time

postgres=# CREATE USER u3 WITH PASSWORD 'u3' VALID UNTIL '2017-06-06';
CREATE ROLE

--Describe the pg_authid view

postgres=# \d  pg_authid
             Table "pg_catalog.pg_authid"
     Column     |           Type           | Modifiers 
----------------+--------------------------+-----------
 rolname        | name                     | not null
 rolsuper       | boolean                  | not null
 rolinherit     | boolean                  | not null
 rolcreaterole  | boolean                  | not null
 rolcreatedb    | boolean                  | not null
 rolcatupdate   | boolean                  | not null
 rolcanlogin    | boolean                  | not null
 rolreplication | boolean                  | not null
 rolconnlimit   | integer                  | not null
 rolpassword    | text                     | 
 rolvaliduntil  | timestamp with time zone | 
Indexes:
    "pg_authid_oid_index" UNIQUE, btree (oid), tablespace "pg_global"
    "pg_authid_rolname_index" UNIQUE, btree (rolname), tablespace "pg_global"
Tablespace: "pg_global" 

--list the user and show the users password and password validatation time

postgres=# select rolname,rolpassword,rolvaliduntil from pg_authid;                      
 rolname  |             rolpassword             |     rolvaliduntil      
----------+-------------------------------------+------------------------
 postgres | md505ea766c2bc9e19f34b66114ace97598 | 
 rep      | md5df2c887bcb2c49b903aa33bdbc5c2984 | 
 u1       |                                     | 
 u2       | u2                                  | 
 u3       | md5dad1ef51b879799793dc38d714b97063 | 2017-06-06 00:00:00-04
(5 rows)