Looking for a copy set command (or alternative) in Redis

Question

I'm a newcomer to Redis and I'm looking for some specific help around sets. To give some background: I'm building a web-app which consists of a large number of card decks which each have a set of individual cards with unique ids. I want users to have a set of 5 cards drawn for them at random from a specific deck.

My plan is to have all of the card ids of a given deck stored as a set in Redis; then I want to use the SPOP function to draw individual cards and remove them from the set so that they are not drawn again within that hand. It would seem to make sense to do this by copying the deck's 'master set' of card IDs into a new temporary set, performing the popping on the copy and then deleting the copied set when I'm done.

But: I can't find any Redis function to command a set copy - the closest thing I can see would be to also create an empty set and then 'join' the empty set and the 'master copy' of the set into a new (if temporary) set with SUNIONSTORE, but that seems hacky. I suppose an alternative would be to copy the set items out into my 'host language' (node.js) and then manually insert the items back into a new Redis set, but this also seems clunky. There's probably a better third option that I haven't even thought of.

Am I doing something wrong - am I not 'getting' Redis, or is the command-set still a bit immature?

Answer 1

redis> sadd mydeck 1 (integer) 1 redis> sadd mydeck 2 (integer) 1 redis> sadd mydeck 3 (integer) 1 redis> smembers mydeck 1) "1" 2) "2" 3) "3" redis> sunionstore tempdeck mydeck (integer) 3 redis> smembers mydeck 1) "1" 2) "2" 3) "3" redis> smembers tempdeck 1) "1" 2) "2" 3) "3" 

Have fun with Redis! Salvatore