redis script to take atomically N elements from a redis sorted set according to score and limit

take_redis_sorted_set.lua

-- This script allow you to perform the following hypothetical operation in a transaction :
--
-- ZRANGEBYSCORE key min max LIMIT 0 count
-- ZREMRANGEBYSCORE key min max LIMIT 0 count
--
-- LIMIT on ZREMRANGEBYSCORE is not supported at the moment, this script resolve it

local keys = redis.call('zcount', KEYS[1], ARGV[1], ARGV[2]);
local count = math.min(keys, ARGV[3]);
if count == 0 then
  return {};
else
  local result = redis.call('zrange', KEYS[1], 0, count - 1);
  redis.call('zremrangebyrank', KEYS[1], 0, count - 1);
  return result;
end

-- This script can be used in the following way :
-- 
-- EVAL "SCRIPT" 1 key min max limit
--
-- e.g. : EVAL "SCRIPT" 1 mykey -inf 1454320319 100