would redis support plugins?

[GoogleCodeExporter]

Redis is an outstanding storage solution. High performance, atomic operations, 
data structures, replication, etc. 

But it does not support transactions very well. The MULTI/EXEC mechanism is too 
simple. It cannot handle complex situations. Data structures support is 
somewhat limited.

I think, supporting complex operations and data structures with plugins may be 
a better way, like stored procedures in RDB.

Actually, I'm working on this feature now. 

Any comments?

Original issue reported on code.google.com by everwa...@gmail.com on 18 Aug 2010 at 3:06

[GoogleCodeExporter]

First of all, the Redis "transaction" mechanism is simple because we only want 
it to execute multiple commands atomically. It sure would be possible to 
implement some kind of rollback, but this comes at a huge performance penalty, 
which is exactly why this is *not* supported.

The idea of a plugin system was proposed earlier this year and led to some 
discussion that you can read here: 
http://groups.google.com/group/redis-db/browse_thread/thread/923504bf13eec521/dd
2e82275a30ac3a

Can you elaborate on why you think that "data structures support" is limited?

Original comment by pcnoordh...@gmail.com on 18 Aug 2010 at 10:42

[GoogleCodeExporter]

pcnoordhuis, thanks for your comment. I have read the discussion on Google 
groups.

Redis supports some basic data structures. But in some situations, we need 
complex data structure server. For example, we have a user queue, push user id 
in, and pop from queue head. User id should not be duplicated in the queue. 
Currently, we write our own data structure server combined set and list. Find 
in the set, then push to the queue if not found. We cannot use redis set and 
list due to concurrent access issue.

If Redis supports plugins, or script, this could be easy to solve. But script 
cannot handle more complex data structures.

Original comment by everwa...@gmail.com on 18 Aug 2010 at 1:44

[GoogleCodeExporter]

Couldn't a single, sorted set be used in this instance? Score would be a 
timestamp; multi zrem zadd to "push", and multi zrange zremrangebyrank to 
pop... 

Original comment by matthewr...@comcast.net on 21 Aug 2010 at 3:05

[GoogleCodeExporter]

Thanks for your comments. I did not make clear. We have operations to move user 
in the queue, such as move forward/backward, move to head/tail. I have read the 
redis command reference carefully. It seems not able to do such operations 
atomically.

Original comment by everwa...@gmail.com on 25 Aug 2010 at 7:01

[GoogleCodeExporter]

Performing those operations on lists is slow, generally O(n) where n is the 
length of the list (or really, the position in the list that your item is).  
You can use a zset to offer O(log(n)) performance for all of your operations, 
but you need to implement a lock (which can be done in Redis) to make it work 
correctly.  Ask on the mailing list about how you would go about implementing 
your operations on a zset if you aren't able to figure it out.

Original comment by josiah.c...@gmail.com on 25 Aug 2010 at 7:31