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https://issues.apache.org/jira/browse/TINKERPOP-1254?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ted Wilmes updated TINKERPOP-1254:
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Fix Version/s: 3.2.1
> Support dropping traverser path information when it is no longer needed.
> ------------------------------------------------------------------------
>
> Key: TINKERPOP-1254
> URL: https://issues.apache.org/jira/browse/TINKERPOP-1254
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.1.1-incubating
> Reporter: Marko A. Rodriguez
> Assignee: Ted Wilmes
> Fix For: 3.2.1
>
>
> The most expensive traversals (especially in OLAP) are those that can not be
> "bulked." There are various reasons why two traversers at the same object can
> not be bulked, but the primary reason is {{PATH}} or {{LABELED_PATH}}. That
> is, when the history of the traverser is required, the probability of two
> traversers having the same history is low.
> A key to making traversals more efficient is to do as a much as possible to
> remove historic information from a traverser so it can get bulked. How does
> one do this?
> {code}
> g.V.as('a').out().as('b').out().where(neq('a').and().neq('b')).both().name
> {code}
> The {{LABELED_PATH}} of "a" and "b" are required up to the {{where()}} and at
> which point, at {{both()}}, they are no longer required. It would be smart to
> support:
> {code}
> traverser.dropLabels(Set<String>)
> traverser.dropPath()
> {code}
> We would then, via a {{TraversalOptimizationStrategy}} insert a step between
> {{where()}} and {{both()}} called {{PathPruneStep}} which would be a
> {{SideEffectStep}}. The strategy would know which labels were no longer
> needed (via forward lookahead) and then do:
> {code}
> public class PathPruneStep {
> final Set<String> dropLabels = ...
> final boolean dropPath = ...
> public void sideEffect(final Traverser<S> traverser) {
> final Traverser<S> start = this.starts.next();
> if(this.dropPath) start.dropPath();
> else start.dropLabels(labels);
> }
> }
> {code}
> Again, the more we can prune historic path data no longer needed, the higher
> the probability of bulking. Think about this in terms of {{match()}}.
> {code}
> g.V().match(
> a.out.b,
> b.out.c,
> c.neq.a,
> c.out.b,
> ).select("a")
> {code}
> All we need is "a" at the end. Thus, once a pattern has been passed and no
> future patterns require that label, drop it!
> This idea is related to TINKERPOP-331, but I don't think we should deal with
> manipulating the species. Thus, I think 331 is too "low level."
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