I'm a total newbie with NoSQL DBs in general, and with Couchbase in
particular. My main document type is a Session type. A Session document has
a startDate, an endDate and an owner field.
Several sessions can be owned by the same user. A session is closed if it
has an endDate. On one given device, a given user can only open a Session
if it doesn't already have one open. But they can open a session on another
device, which means I can have several open sessions in my database for any
given owner. I want to retrieve the most recently open session for a given
owner. I'm pretty sure it can be done with a clever map/reduce view, but
I'm sill confused about how it works. Here is what I started doing in
Objective-C:
[[database viewNamed:@"openByOwner"] setMapBlock:^(NSDictionary *doc,
CBLMapEmitBlock emit) { if([doc[@"type"] isEqualToString:@"session"] &&
doc[@"endDate"] == nil){ emit(doc[@"owner"], doc); }}
reduceBlock:^id(NSArray *keys, NSArray *values, BOOL rereduce) { return
nil;} version:@"1.0"];
With this I think I can filter my documents to get only open sessions, but
how should I proceed to get only the one with the biggest start date for
each owner in my query?
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