Marko A. Rodriguez created TINKERPOP-1136:
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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.
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