Nice! n+1 is something Hibernate Search has to deal with too, that's why I was interested in the fetch profiles and graph loading in JPA 2.1
On 5 March 2013 17:44, Emmanuel Bernard <emman...@hibernate.org> wrote: > I have implemented a solution that gives an entity based on a tuple. > https://hibernate.onjira.com/browse/OGM-273#comment-50082 > > Note that it does not currently works for MongoDB, but that's waiting > for the dedicated GridDialect method as well as OGM-151. > Also note that I have no idea how that will work for associations. I > suspect some nasty n+1 is happening as best. Worse case, an exception :) > > Emmanuel > > On Tue 2013-03-05 10:30, Emmanuel Bernard wrote: >> We might hope for a stable enough contract on Hibernate Search and >> hope that we won't break serializability between micro or minor >> versions. That will need to be taken into account in the test suite and >> design. >> On the OGM side though, we are not at that level of maturity and we will >> force homogenous Hibernate OGM version across all the cluster. The grid >> will have to go down for upgrades or enforce that no mpa reduce job >> using OGM is used while the version roll out is in process. >> >> Emmanuel >> >> On Mon 2013-03-04 18:30, Sanne Grinovero wrote: >> > Found an example, this is all the code it needs to have a MassIndexer >> > working >> > on top of Infinispan's Map/Reduce: >> > >> > https://github.com/infinispan/infinispan/blob/master/query/src/main/java/org/infinispan/query/impl/massindex/IndexingMapper.java#L40 >> > >> > Note it's initialize method which injects needed components; the >> > implementation is serialized across nodes. >> > >> > Sanne >> > >> > On 4 March 2013 18:26, Sanne Grinovero <sa...@hibernate.org> wrote: >> > > We finished this discussion on IRC, in case someone else was interested: >> > > >> > > <sanne> hum I forgot the first step.. transformation from entry into >> > > entity >> > > <sanne> updated >> > > <sanne> emmanuel, the "hidrate" step is what DavideD is bashing is >> > > head against, but let's assume he finds a workaround and we focus on >> > > the pattern as first step? >> > > <emmanuel> https://gist.github.com/emmanuelbernard/5084039 >> > > <emmanuel> sanne: ^ that's how I would do it if I had an Iterator from >> > > the tuple >> > > <emmanuel> assuming pushToExecutor pushes to whatever concurrent work >> > > mechanism you planned to use on consumes >> > > <emmanuel> Plus I am not folloing exactly how you plan consumes(Entry) >> > > to be executed concurrently >> > > <emmanuel> is that the GridDialect responsibility? >> > > <emmanuel> That looks like a lot of work on the dialect's side >> > > <sanne> emmanuel, imagine the backend is Infinispan and has some large >> > > amount of data per node, plus that each node has its own backend >> > > IndexManager (like and ideal sharding) >> > > <emmanuel> ie pool mgt and cap + queuing >> > > <sanne> then with your approach the iterator needs to fetch data from >> > > all remote nodes, and then enqueue in a local blocking queue which is >> > > returning the data to the original owners >> > > <sanne> but if you skip that step, you can just forward the statless >> > > consumer to each node and have it run on data locality >> > > <emmanuel> I was thinking that if you had the luncene index locally on >> > > each node you would ahve a different impl of the MassIndexer anyways >> > > <emmanuel> that would simply send a command to each local node >> > > <sanne> To answer your question: that would be an optional GridDialect >> > > responsibility. I would endorse a trivial first draft doing a >> > > single-threaded loop. >> > > <emmanuel> and have GridDialect.getDataFor() returnlocal data >> > > <sanne> The "consumes" implementation can be either implemented with a >> > > simple iterator - as in your design - so I don't think it pushes much >> > > complexity to the GridDialect implementor? >> > > <sanne> The benefit of the consumer is that *optionally* it can be >> > > mapped on the Map phase, and that's trivial if your backend supports >> > > Map/Reduce >> > > <emmanuel> sanne: I don't follow that soory >> > > <emmanuel> how does that make it mappable to the Map phase? >> > > <sanne> "public void consume(Entry e) " is a degenerate (simplified) >> > > form of map. >> > > <sanne> mm infinispan IDE crashes at the right moment. >> > > <emmanuel> I thought Map was about *filtering* >> > > <emmanuel> not processing >> > > <sanne> you can decide to accept 100% of values (without filtering), >> > > but actually you might want to filter on the specified tables only. >> > > <sanne> also, the return type doesn't have to match the input type: >> > > hence you define a transformation function, which is inherently >> > > applied in parallel on all matching entries. >> > > <emmanuel> sanne: but then you require the OGM code to be everywhere >> > > (ie on each node of the targetNoSQL >> > > <emmanuel> to eb able to do tuple -> entity >> > > <emmanuel> that's not realistic >> > > <emmanuel> assuming your transform phase is about tuple -> entity and >> > > some HSearch ops >> > > <sanne> yes right >> > > <sanne> but isn;t it worth it? it's optional and much more efficient, >> > > as you avoid transferring any data. >> > > <sanne> btw we often assume all nodes in the grid are equally >> > > configured, so having same apps & libraries deployed. >> > > <emmanuel> sanne: let me try and summarize what I understand >> > > <emmanuel> it's more efficient if you store the Lucene index locally >> > > with the data, and if the grid is written in Java or at least can run >> > > code in Java including libraries and if you distribute the OGM >> > > configuration across the whole grid >> > > <emmanuel> Otherwise, it does not make any difference >> > > <emmanuel> Also the GridDialect implementation need to know if you are >> > > doing this trick to only return local data >> > > <sanne> no there are other drawbacks which get defeated, but minor so >> > > I didn't mention them >> > > <emmanuel> am I right? >> > > <sanne> mainly, you skip the need for the contentions point as there >> > > is no push to a shared blocking queue >> > > <sanne> no the GridDialect doesn't need to know. >> > > <emmanuel> sanne: sure if you can process the code on each node you >> > > avoid the shared blocking queue, at lest until you reach the >> > > IndexManager >> > > <sanne> you'll just forward a simple (standard) M/R task, and it will >> > > need to execute it as always. >> > > <sanne> the IndexManager is parallel ;) >> > > <emmanuel> sanne: parallel on a single node >> > > <sanne> yes, but no contentions points other than the internal >> > > structure of the IW >> > > <emmanuel> I mean updating the index for a given table is better done >> > > on a singlle node >> > > <sanne> IndexWriter >> > > <emmanuel> sorry I meant IndexWriter >> > > <emmanuel> ah but ou mention perfect sharding >> > > <emmanuel> you need cosmological alignment for this shit to happen >> > > <sanne> not if we plan for it :) >> > > <sanne> you might remember the changes to Segments in the ISPN code, >> > > to accomodate index storage consistent with the data locality >> > > <sanne> that's expected in 6.0 >> > > <emmanuel> So gridDialect.getData(Consumer consumer, String.. tables) is >> > > wrong >> > > <emmanuel> it's more gridDialect.getData(ConsumerImpl.class, String... >> > > tables) >> > > <emmanuel> as you ened to send the Comsumer impl >> > > <emmanuel> not simply use it >> > > <sanne> hu, it needs a reference to the current SearchFactory at very >> > > least >> > > <emmanuel> sanne: but you're telling me you send the M/R task >> > > <emmanuel> so you need to send the M/R code as well >> > > <sanne> yes but here we enter Infinspan specific implementation >> > > <sanne> I would register the needed components in Infinispan and use >> > > the ServiceRegistry to look them up remotely >> > > <sanne> not to mention Infinispan could accomodate a custom command for >> > > it >> > > <emmanuel> What I am saying is that you don't pass the Consumer >> > > *instance* tot he grid dialect but rather the impl, no? >> > > <sanne> the impl class definition? >> > > <emmanuel> sanne: you tell me. How do I send M/R code today? >> > > <emmanuel> certainly not an impl instance >> > > <sanne> yes you do >> > > <sanne> JBMar will take care of it, including state. >> > > <sanne> but in this case that would be wrong of course as I don't want >> > > to serialize the whole SearchFactory so I'd use injection and lookup, >> > > but that's a detail of Infinispan. >> > > <sanne> But this shouldn't be MassIndexer specific right? it's good to >> > > expose a general "execute on all" method, and I think accepting >> > > instances would make life easier for most - even though we might need >> > > to document some limitations. >> > > <emmanuel> alright, I guess 'll have to live with a visitor pattern >> > > for a feature that has 5% chance of happening :) >> > > <sanne> I'm going to punch Davide >> > > <sanne> as he's yelling "it's not a visitor" but doesn't have the guts >> > > to write it down :) >> > > <emmanuel> sanne: DavideD 's would have nothing to do about it, that's >> > > requires a lot of config and Infinispan machinery I'm not sure is here >> > > today >> > > <DavideD> :) >> > > <emmanuel> ah >> > > <emmanuel> I don't care how it's called, it's one of those patterns >> > > that make the code harder to follow >> > > <DavideD> I was actually trying to remember the name of the pattern >> > > <sanne> ok now we agree :) >> > > <emmanuel> Obfuscator pattern family >> > > <sanne> very popular among consultants, I don't understand why you >> > > complain :P >> > > <sanne> Anyway, let's wrap up and broaden the horizon: >> > > <emmanuel> ok so we are left with findin to to load a entity from a tuple >> > > <sanne> you don't think it's useful as a general purpose method? >> > > <emmanuel> sanne: wil be for queries >> > > <emmanuel> It's just that it's non obvious >> > > <sanne> Exactly. Also I think lambda methods are getting widely better >> > > known. >> > > <emmanuel> syntactically yes >> > > <emmanuel> VM wise, perf improvements will come later >> > > <sanne> what I mean is that by defining the SPI this way, I don't >> > > expect it to be more complex for the GridDialect implementors, while >> > > we can reuse it for a wider scope of needs. >> > > >> > > --Sanne >> > > >> > > On 4 March 2013 17:02, Emmanuel Bernard <emman...@hibernate.org> wrote: >> > >> >> > >> >> > >> On 4 mars 2013, at 17:39, Sanne Grinovero <sa...@hibernate.org> wrote: >> > >> >> > >>> On 4 March 2013 16:20, Emmanuel Bernard <emman...@hibernate.org> wrote: >> > >>>> I already gave what I knew on how to load an entity from a tuple >> > >>>> (which >> > >>>> isn't much) but we can try and dig together. Something I thought about >> > >>>> is that ORM probably has a mechanism to load an entity from a >> > >>>> resultset >> > >>>> via the query parser. And that probably looks also like the second >> > >>>> half >> > >>>> of OgmLoader.load. We could look at this part and see if we can make >> > >>>> an >> > >>>> OGM version of it. We never had the need before as we never had query >> > >>>> support (the way SQL does it). >> > >>> >> > >>> I would also need to study the ORM code, but to add a high level >> > >>> observation, >> > >>> the methods currently defined by the GridDialect are focusing on >> > >>> loading from well known key instances, >> > >>> there is nothing to makes us able to scan/inspect for all values. >> > >>> >> > >>> In other words: even if we wanted to load keys first, we don't have >> > >>> definitions >> > >>> of functions from raw->primary key instances either. >> > >> >> > >> I understand that. I'm not denying the need for the method. >> > >> >> > >>> >> > >>> >> > >>>> On the visitor vs Iterator approach, I still don't see how >> > >>>> implementing >> > >>>> an Iterator on a map / reduce backend would be harder than the visitor >> > >>>> but maybe I'm missing something. >> > >>>> >> > >>>> class IteratorAsStream { >> > >>>> final Query someMapReduceQuery = ...; >> > >>>> >> > >>>> public Object next() { >> > >>>> if (!someMapReduceQuery.started()) { >> > >>>> // execute and collect results in parallel >> > >>>> someMapReduceQuery.execute(); >> > >>>> } >> > >>>> Object result = someMapReduce.getNextOrBlock(); >> > >>>> return result; >> > >>>> } >> > >>>> } >> > >>> >> > >>> That could work to *load* all entities in parallel, but I'd like to >> > >>> process the entities in parallel as well. >> > >>> And I'd rather not force the GridDialect implementors to write some >> > >>> Hibernate Search specific code, >> > >>> so to break out we need some form of "Execute X on each": a closure or >> > >>> a lambda. >> > >>> >> > >> >> > >> I can't see how the visitor model helps in your processing of entities >> > >> in parallel. To me both approaches are strictly equivalent. Care to >> > >> show some pseudo-code? >> _______________________________________________ >> hibernate-dev mailing list >> hibernate-dev@lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/hibernate-dev _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
