CompareAndUpdateScript.java

    public static String script = "" +
            "local key = KEYS[1]" +
            "local field = ARGV[1]" +
            "local value = ARGV[2]" +
            "local op = ARGV[3]" +
            "local current = redis.call('hget', key, field)" +
            "if (current == null) then " +
            "    redis.call('hset', key, field, value)" +
            "elseif op == '>' then" +
            "  if tonumber(value) > tonumber(current) then" +
            "    redis.call('hset', key, field, value)" +
            "  end " +
            "elseif op == '<' then" +
            "  if tonumber(value) < tonumber(current) then" +
            "    redis.call('hset', key, field, value)" +
            "  end " +
            "end ";