[SQL NOTIFY Help] sending NOTIFY to the external program

Hi,
In one of our project we are supposed to send the notifications
regarding any row modifications in a perticular table to the external
application which will be implementing the listen event for the same.
We are using the postgress version 8.0.3.
we have observed that pgNotify structure in "libpq-fe.h" file is
having the following structure;
typedef struct pgNotify
{       char       *relname;            /* notification condition name
*/       int                     be_pid;                 /* process ID of
notifying server process */       char       *extra;                      /* notification
parameter */       /* Fields below here are private to libpq; apps should not use
'em */       struct pgNotify *next;          /* list link */
} PGnotify;
But, by default only relname and be_pid are used.  The technical
document also mentions that extra attribute is not used and by default
it will be null.
Can anybody clarify whether we can pass the primary key value of
the record modified in the extra attribute of this structure?
If not any help regarding the same will be appreciated.

Thanks in Advance,
Ramachandra B.S.


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