Notification EXTRA data

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sql-notify.html :


Higher-level mechanisms can be built by using tables in the database
to pass additional data (beyond a mere notification name) from notifier
to listener(s).

How ?


root2=> select * from pg_listener ;
 relname | listenerpid | notification
---------+-------------+--------------
 aaa     |         723 |            0
(1 row)


grep -5  "typedef struct pgNotify" /usr/local/include/libpq-fe.h

typedef struct pgNotify
{
        char       *relname;           /* notification condition name */
        int           be_pid;              /* process ID of server process
*/
        char       *extra;                /* notification parameter */
} PGnotify;



I need to insert "extra" data - uid, ...

 PGnotify   *notify;
 notify->extra;

........
Thanks