Node-RED listen PostgreSQL in real-time - node.js

Question

I need to listen PostgreSQL on changes in real-time with Node-RED.
How can I do this?
I created trigger on new record in the table and notify this to 'changes' channel.
CREATE FUNCTION notify_trigger() RETURNS trigger AS $$
DECLARE
BEGIN
PERFORM pg_notify('changes', TG_TABLE_NAME || ',id,' || NEW.id );
RETURN new;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER watched_table_trigger AFTER INSERT ON users
FOR EACH ROW EXECUTE PROCEDURE notify_trigger();
But I don't know how to listen it from Node-RED. Could you help me please?
Maybe I can do it differently?

Answer 1

Have a look at this previous SO question:
MQTT Client subscribe to PostgreSQL DB Changes
It looks like Postgress supports Python based triggers which could be used to send a MQTT message which Node-RED could easily subscriber to.

Answer 2

I found a good solution for yourself with WebSocket. Look at example below:
var pg = global.get('pg'),
WebSocket = global.get('ws'),
config = {
user: 'user',
password: 'user',
host: 'somehost',
port: 1234,
database: 'somedb'
},
client = new pg.Client(config);
client.connect(function(err) {
if (err) node.error(err);
client.on('notification', function(msg) {
node.send(msg);
});
var query = client.query("LISTEN changes");
});
delete msg._session;
return msg;
Post your solution, I really want to know more ways to solve this.