Reverse dependency mapping should be a set instead of a list.

rq/job.py

@@ -424,14 +424,14 @@ class Job(object):
     def register_dependency(self):
         """Jobs may have a waitlist. Jobs in this waitlist are enqueued
         only if the dependency job is successfully performed. We maintain this
-        waitlist in Redis, with key that looks something like:
+        waitlist in a Redis set, with key that looks something like:
             
-            rq:job:job_id:waitlist = ['job_id_1', 'job_id_2']
+            rq:job:job_id:waitlist = {'job_id_1', 'job_id_2'}
         
         This method puts the job on it's dependency's waitlist.
         """
         # TODO: This can probably be pipelined
-        self.connection.rpush(Job.waitlist_key_for(self._dependency_id), self.id)
+        self.connection.sadd(Job.waitlist_key_for(self._dependency_id), self.id)
 
     def __str__(self):
         return '<Job %s: %s>' % (self.id, self.description)

rq/queue.py

@@ -247,7 +247,7 @@ class Queue(object):
         """Enqueues all jobs in the waitlist and clears it"""
         # TODO: can probably be pipelined
         while True:
-            job_id = as_text(self.connection.lpop(job.waitlist_key))
+            job_id = as_text(self.connection.spop(job.waitlist_key))
             if job_id is None:
                 break
             waitlisted_job = Job.fetch(job_id, connection=self.connection)

tests/test_job.py

@@ -289,4 +289,4 @@ class TestJob(RQTestCase):
         job._dependency_id = 'id'
         job.save()
         job.register_dependency()
-        self.assertEqual(as_text(self.testconn.lpop('rq:job:id:waitlist')), job.id)
+        self.assertEqual(as_text(self.testconn.spop('rq:job:id:waitlist')), job.id)

tests/test_queue.py

@@ -304,7 +304,7 @@ class TestQueue(RQTestCase):
         # After waitlist is enqueued, job_1 and job_2 should be in queue
         self.assertEqual(q.job_ids, [])
         q.enqueue_waitlist(parent_job)
-        self.assertEqual(q.job_ids, [job_1.id, job_2.id])
+        self.assertEqual(set(q.job_ids), set([job_1.id, job_2.id]))
         self.assertFalse(self.testconn.exists(parent_job.waitlist_key))
 
     def test_enqueue_job_with_dependency(self):