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@xxxxxxxxxxx
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