Add support for LISTEN / NOTIFY / RAISE events

New option *Keep listening for notifications*
https://www.postgresql.org/docs/current/sql-listen.html

Author: Alkarex

README.md

@@ -7,6 +7,8 @@ It supports *splitting* the resultset and *backpressure* (flow control), to allo
 
 It supports *parameterized queries* and *multiple queries*.
 
+It supports [`LISTEN`](https://www.postgresql.org/docs/current/sql-listen.html) / [`NOTIFY`](https://www.postgresql.org/docs/current/sql-notify.html) / [`RAISE`](https://www.postgresql.org/docs/current/plpgsql-errors-and-messages.html) events.
+
 ## Outputs
 
 The response (rows) is provided in `msg.payload` as an array.
@@ -19,6 +21,22 @@ See the [underlying documentation](https://node-postgres.com/apis/result) for de
 
 In the case of multiple queries, then `msg.pgsql` is an array.
 
+## Events
+
+If you tick the *Keep listening for notifications* option along with a [`LISTEN`](https://www.postgresql.org/docs/current/sql-listen.html) request (see below),
+you will receive a message for each [`NOTIFY`](https://www.postgresql.org/docs/current/sql-notify.html) event,
+where `msg.channel` is the name of the channel, `msg.payload` is content of the notification, and `msg.processId` indicates the process ID.
+
+```sql
+LISTEN my_topic;
+```
+
+This can be especially useful when combined with a [`TRIGGER`](https://www.postgresql.org/docs/15/sql-createtrigger.html) to be informed of database changes such as new insertions.
+
+See the [underlying documentation](https://node-postgres.com/apis/client#notification) for details.
+
+Likewise, you may get notice messages producted by [`RAISE`](https://www.postgresql.org/docs/current/plpgsql-errors-and-messages.html) as a `msg.notice` message.
+
 ## Inputs
 
 ### SQL query template

locales/en-US/postgresql.html

@@ -16,6 +16,23 @@ <h3>Outputs</h3>
 	</p>
 	<p>In the case of multiple queries, then <code>msg.pgsql</code> is an array.</p>
 
+	<h3>Events</h3>
+	<p>
+		If you tick the <em>Keep listening for notifications</em> option along with a <a href="https://www.postgresql.org/docs/current/sql-listen.html"><code>LISTEN</code></a> request (see below),
+		you will receive a message for each <a href="https://www.postgresql.org/docs/current/sql-notify.html"><code>NOTIFY</code> event,
+		where <code>msg.channel</code> is the name of the channel, <code>msg.payload</code> is content of the notification, and <code>msg.processId</code> indicates the process ID.
+	</p>
+
+<pre>
+LISTEN my_topic;
+</pre>
+
+This can be especially useful when combined with a <a href="https://www.postgresql.org/docs/15/sql-createtrigger.html"><code>TRIGGER</code></a> to be informed of database changes such as new insertions.
+
+See the <a href="https://node-postgres.com/apis/client#notification">underlying documentation</a> for details.
+
+Likewise, you may get notice messages producted by <a href="https://www.postgresql.org/docs/current/plpgsql-errors-and-messages.html"><code>RAISE</code></a> as a <code>msg.notice</code> message.
+
 	<h3>Inputs</h3>
 	<h4>SQL query template</h4>
 	<p>This node uses the <a href="https://github.com/janl/mustache.js">Mustache template system</a> to generate queries based on the message:</p>

locales/en-US/postgresql.json

@@ -15,6 +15,7 @@
 			"server": "Server",
 			"query": "Query",
 			"split": "Split results in multiple messages",
+			"listen": "Keep listening for notifications",
 			"rowsPerMsg": "Number of rows per message"
 		},
 		"placeholder": {