On 07/24/2016 03:31 AM, Mehran Ziadloo wrote:
> I'm sorry, you are right. Let me rephrase that.
>
> What I meant was that the notifications are received by the client
> connections
> as if it was generated within their corresponding database (let's name the
> database with a client connection listening to it; DB_C), then a
> notification
> generated by a NOTIFY command within DB_X like this:
>
> pg_notify_db('DB_C', some_channel, 'payload');
>
> can be heard by the client. Of course, the client needs to know which
> database
> has sent the notification but I think we can skip that part since we can
> easily
> include database name in the notification's payload if necessary.
>
> That was one of the two solutions. The other one is like this:
>
> pg_notify_all(some_channel, 'payload');
>
> And this one sends the notification to all of the client connections,
> regardless of which database they are connected/listening to.
>
> I hope it makes sense now.
>
>
As to how to start writing an extension:
https://www.postgresql.org/docs/9.5/static/extend-extensions.html
As to how NOTIFY/LISTEN works:
https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/commands/async.c;h=beef574076c257db0a868b39a946565185f6c53e;hb=ba37ac217791dfdf2b327c4b75e7083b6b03a2f5
--
Adrian Klaver
adrian.klaver@aklaver.com