[
https://issues.apache.org/jira/browse/TINKERPOP-967?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16510966#comment-16510966
]
ASF GitHub Bot commented on TINKERPOP-967:
------------------------------------------
Github user GCHQResearcher1337 commented on a diff in the pull request:
https://github.com/apache/tinkerpop/pull/876#discussion_r195046349
--- Diff:
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/RepeatTest.java
---
@@ -386,5 +456,26 @@ public void
g_V_hasXname_markoX_repeatXoutE_inV_simplePathX_untilXhasXname_rippl
public Traversal<Vertex, Path>
get_g_V_hasXloop_name_loopX_repeatXinX_timesX5X_path_by_name() {
return
g.V().has("loops","name","loop").repeat(__.in()).times(5).path().by("name");
}
+
+ @Override
+ public Traversal<Vertex, Path>
get_g_V_repeatXout_repeatXoutX_timesX1XX_timesX1X_limitX1X_path_by_name() {
+ // NB We need to prevent the RepeatUnrollStrategy from
applying to properly exercise this test as this traversal can be simplified
--- End diff --
Thanks @spmallette I wanted to do something like this but hadn't spotted
these tests. While writing some tests I've noticed that when
RepeatUnrollStrategy is applied from the inside out, adding a barrier step onto
the end:
repeat(a.repeat(b).times(1)).times(1) -> repeat(a.b.barrier).times(1)
repeat(a.b.barrier).times(1) -> a.b.barrier.barrier
eg
```
gremlin> g.V().repeat(out().repeat(out()).times(1)).times(1).explain()
==>Traversal Explanation
===========================================================================================================================================================================================================================
Original Traversal [GraphStep(vertex,[]),
RepeatStep([VertexStep(OUT,vertex), RepeatStep([VertexStep(OUT,vertex),
RepeatEndStep],until(loops(1)),emit(false)),
RepeatEndStep],until(loops(1)),emit(false))]
ConnectiveStrategy [D] [GraphStep(vertex,[]),
RepeatStep([VertexStep(OUT,vertex), RepeatStep([VertexStep(OUT,vertex),
RepeatEndStep],until(loops(1)),emit(false)),
RepeatEndStep],until(loops(1)),emit(false))]
MatchPredicateStrategy [O] [GraphStep(vertex,[]),
RepeatStep([VertexStep(OUT,vertex), RepeatStep([VertexStep(OUT,vertex),
RepeatEndStep],until(loops(1)),emit(false)),
RepeatEndStep],until(loops(1)),emit(false))]
FilterRankingStrategy [O] [GraphStep(vertex,[]),
RepeatStep([VertexStep(OUT,vertex), RepeatStep([VertexStep(OUT,vertex),
RepeatEndStep],until(loops(1)),emit(false)),
RepeatEndStep],until(loops(1)),emit(false))]
InlineFilterStrategy [O] [GraphStep(vertex,[]),
RepeatStep([VertexStep(OUT,vertex), RepeatStep([VertexStep(OUT,vertex),
RepeatEndStep],until(loops(1)),emit(false)),
RepeatEndStep],until(loops(1)),emit(false))]
IncidentToAdjacentStrategy [O] [GraphStep(vertex,[]),
RepeatStep([VertexStep(OUT,vertex), RepeatStep([VertexStep(OUT,vertex),
RepeatEndStep],until(loops(1)),emit(false)),
RepeatEndStep],until(loops(1)),emit(false))]
AdjacentToIncidentStrategy [O] [GraphStep(vertex,[]),
RepeatStep([VertexStep(OUT,vertex), RepeatStep([VertexStep(OUT,vertex),
RepeatEndStep],until(loops(1)),emit(false)),
RepeatEndStep],until(loops(1)),emit(false))]
RepeatUnrollStrategy [O] [GraphStep(vertex,[]),
VertexStep(OUT,vertex), VertexStep(OUT,vertex), NoOpBarrierStep(2500),
NoOpBarrierStep(2500)]
CountStrategy [O] [GraphStep(vertex,[]),
VertexStep(OUT,vertex), VertexStep(OUT,vertex), NoOpBarrierStep(2500),
NoOpBarrierStep(2500)]
PathRetractionStrategy [O] [GraphStep(vertex,[]),
VertexStep(OUT,vertex), VertexStep(OUT,vertex), NoOpBarrierStep(2500),
NoOpBarrierStep(2500)]
LazyBarrierStrategy [O] [GraphStep(vertex,[]),
VertexStep(OUT,vertex), NoOpBarrierStep(2500), VertexStep(OUT,vertex),
NoOpBarrierStep(2500), NoOpBarrierStep(2500)]
TinkerGraphCountStrategy [P] [GraphStep(vertex,[]),
VertexStep(OUT,vertex), NoOpBarrierStep(2500), VertexStep(OUT,vertex),
NoOpBarrierStep(2500), NoOpBarrierStep(2500)]
TinkerGraphStepStrategy [P] [TinkerGraphStep(vertex,[]),
VertexStep(OUT,vertex), NoOpBarrierStep(2500), VertexStep(OUT,vertex),
NoOpBarrierStep(2500), NoOpBarrierStep(2500)]
ProfileStrategy [F] [TinkerGraphStep(vertex,[]),
VertexStep(OUT,vertex), NoOpBarrierStep(2500), VertexStep(OUT,vertex),
NoOpBarrierStep(2500), NoOpBarrierStep(2500)]
StandardVerificationStrategy [V] [TinkerGraphStep(vertex,[]),
VertexStep(OUT,vertex), NoOpBarrierStep(2500), VertexStep(OUT,vertex),
NoOpBarrierStep(2500), NoOpBarrierStep(2500)]
Final Traversal [TinkerGraphStep(vertex,[]),
VertexStep(OUT,vertex), NoOpBarrierStep(2500), VertexStep(OUT,vertex),
NoOpBarrierStep(2500), NoOpBarrierStep(2500)]
```
Do you think it's ok to leave multiple barrier steps at the end? I could
add an extra check that we aren't inserting a barrier after a barrier here -
but this could interfere with a barrier added by a user?
https://github.com/apache/tinkerpop/blob/d3b6a340dbb9c89355c40089a5c083dc0dbd4c5b/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/optimization/RepeatUnrollStrategy.java#L72
> Support nested-repeat() structures
> ----------------------------------
>
> Key: TINKERPOP-967
> URL: https://issues.apache.org/jira/browse/TINKERPOP-967
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.1.0-incubating
> Reporter: Marko A. Rodriguez
> Assignee: Marko A. Rodriguez
> Priority: Major
>
> All the internal plumbing is staged for this to happen, we just haven't gone
> all the way. In short, a {{NESTED_LOOP}} traverser has an internal
> {{loopStack}} where {{repeat(repeat())}} will have a {{loopStack}} of two.
> The {{it.loops()}} checks of the internal repeat will always check the top of
> the stack and when its done repeating will delete its counter off the top of
> the stack.
> [~dkuppitz]'s work on {{LoopStep}} will be backwards compatible. In
> {{RepeatStep}} we will support:
> {code}
> repeat('a',out('knows').repeat('b',out('parent')))
> {code}
> and thus, things like {{loops('a')}} as well as {{times('a',2)}}. Note that
> naming the loop stack will be a super rare case as most people will just
> assume standard nested looping semantics with a push/pop stack.
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