To be more precise, by pagination I'm referring to methods QueryBuilder.startOffset/maxResults. Since our remote protocol are stateless we would need to re-execute the query to fetch the next page. That leads to the same problem of approximation.
On 03/11/2014 03:11 PM, Adrian Nistor wrote: > I think that technical trickiness is also required for implementing > pagination, and would probably also suffer from same > limitations/approximations. > Should we remove pagination too from the api? > > On 03/11/2014 10:47 AM, Sanne Grinovero wrote: >> On 10 March 2014 17:09, Mircea Markus <mmar...@redhat.com> wrote: >>> On Mar 10, 2014, at 15:12, Sanne Grinovero <sa...@infinispan.org> wrote: >>> >>>> Ok you make some good points, and I've no doubts of it being useful. >>>> >>>> My only concern is that this could slow us down significantly in >>>> providing other features which might be even more useful or pressing. >>>> You have to pick your battles and be wise on where to spend energy >>>> first. >>>> >>>> Considering that it's easier to add methods than to remove them, what >>>> would you think of marking this as experimental for now? >>>> I'd prefer to see the non-indexed query engine delivered first; this >>>> sounds like being a stone on the critical path so it might be wise to >>>> have the option to drop the requirement from a first implementation. >>>> Definitely you're right that we should then implement "some" COUNT >>>> strategy, I'm just not comfortable in committing on this one yet. >>> I can imagine a lot of users emulating this by simply iterating over the >>> entries in the result set. Even if we do just that and document it as slow, >>> I think it's still worth exposing this somewhere. >> I'm not questioning it to be useful. But the implementation is tricky, >> for example simply iterating would require a global (and distributed) >> lock to be accurate. >> Otherwise we can only document it as an approximation, and worst is we >> can't even estimate an error margin: under steady load it would >> probably be a reasonable estimation, but there are corner cases in >> which you can get off by several orders of magnitude. >> Among others, your assumptions would need to include: >> - no nodes failing (no state transfers happening) >> - no write spikes (probably one of the best reasons to deploy >> infinispan is to be able to absorb spikes) >> - no wild churning across datastore/cachestores >> - expirations happening in a homogeneus pattern (this entirely >> depends on the use case) >> >> Also there is no way to make this work in the context of a >> transaction, as it would pretty much violate any promise of repeatable >> read properties. >> >> So the question is, if a user would still consider it useful after >> (hopefully) understanding all the attached strings. >> >> In other contexts we discussed the need for Infinispan to provide >> something like a snapshot capability based on TOA. If we had that, we >> could implement a count operation on top of it. >> >> Sanne >> _______________________________________________ >> infinispan-dev mailing list >> infinispan-dev@lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/infinispan-dev > _______________________________________________ > infinispan-dev mailing list > infinispan-dev@lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev _______________________________________________ infinispan-dev mailing list infinispan-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev