Oh, that works perfectly. Awesome! On Thu, 11 Feb 2016 at 01:15 Marko Rodriguez <okramma...@gmail.com> wrote:
> Hi Ran, > > GroupStep in OLTP does use "on the fly"-reduction. > > > https://github.com/apache/incubator-tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/GroupStep.java#L176-L182 > > https://github.com/apache/incubator-tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/ReducingBarrierStep.java#L89-L92 > > That is, if the amount of objects getting grouped becomes to large, a > "midway" reduction takes place. > > Thoughts?, > Marko. > > http://markorodriguez.com > > On Feb 10, 2016, at 10:35 AM, Ran Magen <rma...@gmail.com> wrote: > > > I'm not sure if its relevant for this ticket, but I have another use-case > > for combiners in an OLTP use-case. > > In Unipop (to which I'll hopefully have documentation very soon and be > able > > to share with you guys) we have GroupStep optimizations. But since we can > > have results for the same step coming from different back-ends, we need > > some way to combine them to one result. > > If we had a simple way to combine the results, that would be great. If > not, > > we'll just implement something by ourselves... > > > > On Mon, 8 Feb 2016 at 17:29 Marko A. Rodriguez (JIRA) <j...@apache.org> > > wrote: > > > >> Marko A. Rodriguez created TINKERPOP-1136: > >> --------------------------------------------- > >> > >> Summary: GroupStep OLAP does not combine, only reduces. > >> Key: TINKERPOP-1136 > >> URL: > https://issues.apache.org/jira/browse/TINKERPOP-1136 > >> Project: TinkerPop > >> Issue Type: Improvement > >> Components: process > >> Affects Versions: 3.1.1-incubating > >> Reporter: Marko A. Rodriguez > >> Fix For: 3.2.0-incubating > >> > >> > >> Right now, {{GroupStep}} does not support a combiner. Unfortunately, > this > >> is a necessary consequence of not knowing the semantics of the reduction > >> :|. This is analogous to why Spark has {{reduceByKey}} vs. > {{groupByKey}}. > >> HOWEVER, if a {{Barrier}} is used for reduction in the > {{reduceTraversal}} > >> and that {{Barrier}} is a {{ReducingBarrierStep}}, then a combiner can > be > >> used. I suspect that 99% of the time, the {{Barrier}} is a > >> {{ReducingBarrierStep}}. Once TINKERPOP-1131 is merged, it should be > >> possible to make {{GroupStep}} more intelligent by doing an analysis of > its > >> {{Barrier}}-step. > >> > >> > >> > >> -- > >> This message was sent by Atlassian JIRA > >> (v6.3.4#6332) > >> > >
