[jira] [Closed] (TINKERPOP-1136) GroupStep OLAP does not combine, only reduces.

["Marko A. Rodriguez (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TINKERPOP-1136?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Marko A. Rodriguez closed TINKERPOP-1136.
-----------------------------------------
       Resolution: Duplicate
         Assignee: Marko A. Rodriguez
    Fix Version/s:     (was: 3.2.0-incubating)

TINKERPOP-1225 is the same thing and is currently in VOTE for 3.2.0.

> 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
>            Assignee: Marko A. Rodriguez
>
> 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.



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