[TINKERPOP-1994] LazyBarrierStrategy fully responsible for barrier() additions

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Done
• Affects Version/s: 3.2.9
• Fix Version/s: 3.5.0, 3.4.11
• Component/s: process
• Assignee: Stephen Mallette
• Reporter: Stephen Mallette
• Created: 02/Jul/18 19:10
• Updated: 16/Mar/21 00:05
• Resolved: 16/Mar/21 00:05

Description

As it stands, LazyBarrierStrategy, RepeatUnrollStrategy and PathRetractionStrategy (others??) add barrier() steps as needed - for example:

gremlin> g.V().repeat(out().barrier()).times(2).explain()
==>Traversal Explanation
===============================================================================================================================================================================================
Original Traversal                 [GraphStep(vertex,[]), RepeatStep([VertexStep(OUT,vertex), NoOpBarrierStep, RepeatEndStep],until(loops(2)),emit(false))]

ConnectiveStrategy           [D]   [GraphStep(vertex,[]), RepeatStep([VertexStep(OUT,vertex), NoOpBarrierStep, RepeatEndStep],until(loops(2)),emit(false))]
MatchPredicateStrategy       [O]   [GraphStep(vertex,[]), RepeatStep([VertexStep(OUT,vertex), NoOpBarrierStep, RepeatEndStep],until(loops(2)),emit(false))]
FilterRankingStrategy        [O]   [GraphStep(vertex,[]), RepeatStep([VertexStep(OUT,vertex), NoOpBarrierStep, RepeatEndStep],until(loops(2)),emit(false))]
InlineFilterStrategy         [O]   [GraphStep(vertex,[]), RepeatStep([VertexStep(OUT,vertex), NoOpBarrierStep, RepeatEndStep],until(loops(2)),emit(false))]
IncidentToAdjacentStrategy   [O]   [GraphStep(vertex,[]), RepeatStep([VertexStep(OUT,vertex), NoOpBarrierStep, RepeatEndStep],until(loops(2)),emit(false))]
RepeatUnrollStrategy         [O]   [GraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
PathRetractionStrategy       [O]   [GraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
AdjacentToIncidentStrategy   [O]   [GraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
CountStrategy                [O]   [GraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
LazyBarrierStrategy          [O]   [GraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
TinkerGraphCountStrategy     [P]   [GraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
TinkerGraphStepStrategy      [P]   [TinkerGraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
ProfileStrategy              [F]   [TinkerGraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]
StandardVerificationStrategy [V]   [TinkerGraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]

Final Traversal                    [TinkerGraphStep(vertex,[]), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500), VertexStep(OUT,vertex), NoOpBarrierStep, NoOpBarrierStep(2500)]

We should centralize the logic for this in LazyBarrierStrategy and remove it from other strategies. By keeping the logic in a single place we can (1) ensure the best implementation - note in the above example, we're getting extra barrier() steps (2) users can be assured that removing the single LazyBarrierStrategy will remove all automated barrier() applications.

This isn't a breaking change, but it could change traversal behavior I suppose - perhaps this goes just to 3.4.0.......

Issue Links

• is duplicated by: TINKERPOP-2004 LazyBarrierStrategy should be the only strategy that adds barriers