Add listening_channels method.

James William Pye · James William Pye · commit 94b88505438d · 2010-02-17T17:02:28.000-07:00
diff --git a/postgresql/api.py b/postgresql/api.py
@@ -1035,6 +1035,12 @@ def unlisten(self, *channels) -> None:
 		Equivalent to issuing "UNLISTEN <x>" for x in channels.
 		"""
 
+	@abstractmethod
+	def listening_channels(self) -> ["channel name", ...]:
+		"""
+		Return an *iterator* to all the channels currently being listened to.
+		"""
+
 class SocketFactory(object):
 	@propertydoc
 	@abstractproperty
diff --git a/postgresql/driver/pq3.py b/postgresql/driver/pq3.py
@@ -2247,12 +2247,28 @@ def notify(self, channel, payload = None,
 				channel.replace('"', '""'),
 			))
 
-	def listen(self, *channels):
-		qstr = ';'.join(('LISTEN ' + x.replace('"', '""') for x in channels))
+	def listening_channels(self):
+		if self.version_info[:2] > (8,4):
+			return self.sys.listening_channels()
+		else:
+			return self.sys.listening_relations()
+
+	def listen(self, *channels, len = len):
+		qstr = ''
+		for x in channels:
+			# XXX: hardcoded identifier length?
+			if len(x) > 63:
+				raise ValueError("channel name too long: " + x)
+			qstr += '; LISTEN ' + x.replace('"', '""')
 		return self.execute(qstr)
 
-	def unlisten(self, *channels):
-		qstr = ';'.join(('UNLISTEN ' + x.replace('"', '""') for x in channels))
+	def unlisten(self, *channels, len = len):
+		qstr = ''
+		for x in channels:
+			# XXX: hardcoded identifier length?
+			if len(x) > 63:
+				raise ValueError("channel name too long: " + x)
+			qstr += '; UNLISTEN ' + x.replace('"', '""')
 		return self.execute(qstr)
 
 	def __init__(self, connector, *args, **kw):
diff --git a/postgresql/lib/libsys.sql b/postgresql/lib/libsys.sql
@@ -1,5 +1,5 @@
 ##
-# libsys.sql
+# libsys.sql - SQL to support driver features
 ##
 -- Queries for dealing with the PostgreSQL catalogs for supporting the driver.
 
@@ -161,3 +161,11 @@ SELECT pg_reload_conf()
 
 [languages:transient:column]
 SELECT lanname FROM pg_catalog.pg_language
+
+[listening_channels:transient:column]
+SELECT channel FROM pg_catalog.pg_listening_channels() AS x(channel)
+
+[listening_relations:transient:column]
+-- listening_relations: old version of listening_channels.
+SELECT relname as channel FROM pg_catalog.pg_listener
+WHERE listenerpid = pg_catalog.pg_backend_pid();
diff --git a/postgresql/test/test_driver.py b/postgresql/test/test_driver.py
@@ -1479,6 +1479,9 @@ def testNotify(self):
 		self.db.notify('foo')
 		self.db.execute('')
 		self.failUnlessEqual(self.db._notifies, [])
+		# Invoke an error to show that listen() is all or none.
+		self.failUnlessRaises(Exception, self.db.listen, 'doesntexist', 'x'*64)
+		self.failUnless('doesntexist' not in self.db.listening_channels())
 
 if __name__ == '__main__':
 	unittest.main()
