I'm puzzled by all the answers, because to me the question is not clear. Just like Robert says: different uses have different requirements on the behavior of counters.
So what are you looking for and why do things like DatastoreService.allocateIds or MemcacheService.increment not work for you? On another note: Brewer's CAP theorem is interesting reading material. Might provide you some background on Nick's comments (and some other features GAE is claimed to lack compared to SQL databases, including difference between strong consistent vs eventually consistent) On 19 mrt, 17:06, Jeff Schnitzer <[email protected]> wrote: > On Fri, Mar 18, 2011 at 6:10 PM, Barry Hunter <[email protected]> wrote: > > > At least some can answer count queries using just index scans - ie > > doesnt touch the actual data. Can get close to that with keys_only - > > which persumably is just what the index contains - and counting the > > rows, but it still requires transfer of all keys to the application (I > > think anyway) just to be discarded. > > This is what PreparedQuery.countEntities() does. It doesn't transfer > keys to the application, but it's still an O(N) operation. > > Jeff -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
