Re: Listen/Notify?

Andrea Gavana ha scritto:
> Hi All,
> 
>     sorry for my newbieness, I really know too little about pysqlite.
> I was wondering if pysqlite supports commands like LISTEN/NOTIFY,
> which I could use to update my GUI when the database "sees" a change
> made by another user. My application is a multiuser graphical
> interface, and I would like to update the GUI based on database
> modifications. The actions I would do are:
> 
> - put an INSERT/UPDATE/DELETE trigger on the table(s) I
>   want to be informed about on change
> - in the trigger send a NOTIFY
> - in the frontend start a new thread which LISTENs to the
>   NOTIFYs sent by the backend
> - when a NOTIFY arrives post an appropriate event into your
>   GUI thread (I usually use wx.CallAfter)
> 
> It is a very good suggestion I got from a wxPython user, and I just
> wanted to know if it is possible to do it with pysqlite (he is using
> PostgreSQL).
> 

SQLite does not support this.
However you can just define a function for sending a packet via UDP to 
registered listeners.

As an example:

_listeners = set()
_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

def register_listener(host, port):
     _listeners.add((host, int(port)))

def send_notify(name):
     packet = struct.pack('!H', len(name)) + name
     for host, port in _listeners:
         _socket.sendto(packet, (host, port))


conn = sqlite.connect(':memory:')
conn.create_function('register_listener', 2, register_listener)
conn.create_function('send_notify', 1, send_notify)



Regards   Manlio Perillo