issue#2: Union multiple sorted sets with top K elements returned

[levyfan]

2 Union multiple sorted sets with top K elements returned

See details: https://groups.google.com/forum/#!topic/redis-dev/gTX6Jt2gr3s

Proposed command: ZUNIONMINK k numkeys key [key ...] [WEIGHTS weight [weight ...]] [WITHSCORES] ZUNIONMAXK k numkeys key [key ...] [WEIGHTS weight [weight ...]] [WITHSCORES]

heap.c is a implementation based on Vector. The interface keeps close to std::make_heap, std::pop_heap and std::push_heap.

Tested on redis master(unstable) branch.

[itamarhaber]

@levyfan thank you - reviewing.

[itamarhaber]

@levyfan looks excellent. A few things:

• Naming: I like the min/max but to be aligned with the core API's terminology it makes more sense to use the REV notation, hence ZUNIONTOP and ZUNIONREVTOP would be preferable.
• Your heap-on-vector is textbook and looks :tulip: + :100: points for the test. I think it belongs upstream in the Redis Modules SDK. Would you mind making it into a separate PR there? /cc @dvirsky
• It would be nice to have the README updated :wink:
• I'm thinking of doing ZINTERTOP (and of course ZINTERREVTOP) that is very useful, for example, when you're storing a global leader board and sets of "friends". Unless you beat me to it, your contribution will serve as a great basis for that.

[dvirsky]

@levyfan all in all an excellent PR. we are very excited about it! Are you planning on writing additional modules yourself?

[levyfan]

@dvirsky I am planing to write a feed system just like facebook. Our team all agree that redis is a very good start point. We will write many business codes on redis and we are happy to share our work if it (or some part) could be generalized.

[levyfan]

Hi @itamarhaber , please have a review. And I also create a PR including the heap implementation at https://github.com/RedisLabs/RedisModulesSDK/pull/3

[itamarhaber]

Thanks once again @levyfan - looks awesome!

The only remark I have is that the getkeys-api is declared during command creation but the implementation itself is missing from the command.

[levyfan]

Hi @itamarhaber , I see a TODO at rxsets.c /* TODO: handle this once the getkey-api allows signalling errors */ It is only allowed to return REDISMODULE_OK if it is a getkey-api call, right?

[levyfan]

@itamarhaber I write something like return RedisModule_IsKeysPositionRequest(ctx) ? REDISMODULE_OK : RedisModule_WrongArity(ctx); just as rxsets.c did. Please have a review.

[itamarhaber]

Yep - that's the best I could come up with ;)

Thank you so much, I'm really looking forward to seeing what you and your team will next come up with - merging.

[itamarhaber]

Fixes #2