dblink_get_notify() returns setof (notify_name text, be_pid int, extra text) dblink_get_notify(text connname) returns setof (notify_name text, be_pid int, extra text)
    dblink_get_notify retrieves notifications on either
    the unnamed connection, or on a named connection if specified.
    To receive notifications via dblink, LISTEN must
    first be issued, using dblink_exec.
    For details see LISTEN and NOTIFY.
   
SELECT dblink_exec('LISTEN virtual');
 dblink_exec 
-------------
 LISTEN
(1 row)
SELECT * FROM dblink_get_notify();
 notify_name | be_pid | extra
-------------+--------+-------
(0 rows)
NOTIFY virtual;
NOTIFY
SELECT * FROM dblink_get_notify();
 notify_name | be_pid | extra
-------------+--------+-------
 virtual     |   1229 |
(1 row)