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https://issues.apache.org/jira/browse/TINKERPOP-1136?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Marko A. Rodriguez closed TINKERPOP-1136.
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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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