I posted the following email a couple of days ago and I didn't get any responses. Makes me wonder, does anyone on this list know/use Secondary Indexes? They seem to me like a pretty big feature and it's a bit disappointing to not be able to get a documentation on it.
I think the Cassandra committers are doing a heck of a job adding all these cool functionalities but the documenting side doesn't really keep up. Jonathan Ellis's blog post on Secondary Indexes only scratches the surface of the topic, and if you consider that the whole point of using Cassandra is scalability, there isn't a single mention of how Secondary Indexes scale!!! (This same thing applies to Counters too)
I'm not trying to be a complainer, but as someone new to this community, I hope you guys take my comments as productive criticism.
I just read Jonathan Ellis' great post on Secondary Indexes (http://www.datastax.com/dev/blog/whats-new-cassandra-07-secondary-indexes) and I was wondering where I can find a bit more info on them. I would like to know:
1) Are there in limitations beside the hash properties (no between queries)? Like size or memory, etc?
2) Are there distributed? If so, how does that work? How are there stored on the nodes?
3) When you write a new row, when/how does the index get updated? What I would like to know is the atomicity of the operation, is the "index write" part of the "row write"?
4) Is there a difference between creating a secondary index vs creating an "index" CF manually such as "users_by_country"?