From 4d9c20d5d9ea274929af55ed17f5523547f84367 Mon Sep 17 00:00:00 2001
From: Vincent Driessen <vincent@3rdcloud.com>
Date: Mon, 14 Apr 2014 11:26:02 +0200
Subject: [PATCH] Reimplement Queue.empty() in a Lua script.

This makes the .empty() function perform all the computing in Redis
itself, rather than in Python.  This is both atomic, and faster.
---
 rq/queue.py | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/rq/queue.py b/rq/queue.py
index 49d43d7..2f725e3 100644
--- a/rq/queue.py
+++ b/rq/queue.py
@@ -65,10 +65,25 @@ class Queue(object):
 
     def empty(self):
         """Removes all messages on the queue."""
-        job_list = self.get_jobs()
-        self.connection.delete(self.key)
-        for job in job_list:
-            job.cancel()
+        script = b"""
+            local prefix = "rq:job:"
+            local q = KEYS[1]
+            local count = 0
+            while true do
+                local job_id = redis.call("lpop", q)
+                if job_id == false then
+                    break
+                end
+
+                -- Delete the relevant keys
+                redis.call("del", prefix..job_id)
+                redis.call("del", prefix..job_id..":dependents")
+                count = count + 1
+            end
+            return count
+        """
+        script = self.connection.register_script(script)
+        return script(keys=[self.key])
 
     def is_empty(self):
         """Returns whether the current queue is empty."""