Comment by _benedict | Hacker News Reader

Comment by _benedict | Hacker News Reader

Parent Full thread

It will exist next year. Cassandra is getting HA ACID transactions (depending how you define C; we won't be getting foreign key constraints by then) that will be fast. Typically as fast (in latency terms) as a normal eventually consistent operation. Depending on the read/write balance and complexity, they may even result in a reduction in cluster resource utilisation. For many workloads there will be additional costs, but it remains to be discovered exactly how much. I hope it will be on that sort of scale.

>It also has some, terribly slow, lightweight transactions

FWIW, LWTs are much (2x) faster in 4.1 (which has been very slowly making its way out the door for a while now... the project is mostly already more focused on 4.2, so pushing 4.1 out the door is tortuous for procedural reasons)

cool, good to know. There's still the relational vs. no-relational question though for many use cases but having better transactions opens the door for more use cases.

Right with real transaction you could maintain your own index if you really need them.

And to have good performance you should never join entity that have distinct partition key. Otherwise you end up reading too much data over the network.

I’m honestly very happy Cassandra will get real transaction. But i still need to understand the proposed design. Will it be possible to have serializability when doing Range scan query?

> when doing range scan query

Yes, but probably not initially. The design supports them, it’s just not very pressing to implement since most users today use hash partitioners. There will be a lot of avenues in which to improve transactions after they are delivered and it is hard to predict what will get the investment when.

Proper global indexes are likely to follow on the heels of transactions, as they solve most of the problem. Though transactions being one-shot and needing to declare partition-keys upfront means there’s some optimistic concurrency control required. Interactive transactions supporting pessimistic concurrency and without needing to declare the involved keys will also hopefully follow, at which point indexes are very trivial, but the same caveat as above applies.

Yes, Cassandra will still not be suitable for all workloads.

Reply on news.ycombinator.com