Sparql-gremlin 工具不使用索引

Question

我使用 sparql-gremlin 3.4.0 和 janusgraph 0.3.1。在顶点属性 'iri' 上创建索引后，gremlin 查询立即给出结果。相反，如果我在 sparql 中执行相同的查询，它不会使用任何索引。在下面的示例中，我使用 force-index 选项来避免扫描查询。

有什么建议吗？

Answer 1

可能有两个问题需要考虑：(1) TinkerPop 没有将该查询适当地优化到 JanusGraph 可以轻松使用索引的状态，或者 (2) JanusGraph 没有优化要使用的查询的某些方面索引。对于后一种情况，JanusGraph 必须很好地优化 match() 步骤以使用索引，因为这是 sparql-gremlin 在其翻译过程中使用的核心步骤。我很确定它不会那样做。对于前一种情况，JanusGraph 可能依赖于 TinkerPop 将 match() 转换为更易于使用的东西 - 在您的示例中，希望 JanusGraph 能够处理您编写的最初测试查询 - g.V().has('iri', ...)。我认为 explain() 会告诉你那里发生了什么，就像我用 TinkerGraph 测试你的示例的变体时对我所做的那样：

gremlin> s.sparql("SELECT ?x WHERE { ?x v:name 'marko' }").explain()
==>Traversal Explanation
===========================================================================================================================================================================================
Original Traversal                 [InjectStep([SELECT ?x WHERE { ?x v:name 'marko' }])]

ConnectiveStrategy           [D]   [InjectStep([SELECT ?x WHERE { ?x v:name 'marko' }])]
SparqlStrategy               [D]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
MatchPredicateStrategy       [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
FilterRankingStrategy        [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
EarlyLimitStrategy           [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
InlineFilterStrategy         [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
IncidentToAdjacentStrategy   [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
AdjacentToIncidentStrategy   [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
RepeatUnrollStrategy         [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
CountStrategy                [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
PathRetractionStrategy       [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
LazyBarrierStrategy          [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
TinkerGraphCountStrategy     [P]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
TinkerGraphStepStrategy      [P]   [TinkerGraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
ProfileStrategy              [F]   [TinkerGraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]
StandardVerificationStrategy [V]   [TinkerGraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]

Final Traversal                    [TinkerGraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(x), PropertiesStep([name],value), IsStep(eq(marko)), MatchEndStep]]), SelectOneStep(last,x)]

不太好。

因此，解决方案的选项是：

JanusGraph 需要更好地优化 match() 以处理此类查询或
TinkerPop 标准遍历策略应该更擅长将此类查询转换为更通用的模式或
sparql-gremlin 应该编译成与现有遍历策略更匹配的 Gremlin

关于最后一点，请注意如果 sparql-gremlin 生成此 match() 查询会发生什么情况：

gremlin> g.V().match(__.as('a').has('person','name','marko')).select('a').values('name').explain()
==>Traversal Explanation
==========================================================================================================================================================================================================
Original Traversal                 [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(a), HasStep([~label.eq(person), name.eq(marko)]), MatchEndStep]]), SelectOneStep(last,a), PropertiesStep([name],v
                                      alue)]

ConnectiveStrategy           [D]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(a), HasStep([~label.eq(person), name.eq(marko)]), MatchEndStep]]), SelectOneStep(last,a), PropertiesStep([name],v
                                      alue)]
MatchPredicateStrategy       [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(a), HasStep([~label.eq(person), name.eq(marko)]), MatchEndStep]]), SelectOneStep(last,a), PropertiesStep([name],v
                                      alue)]
FilterRankingStrategy        [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(a), HasStep([~label.eq(person), name.eq(marko)]), MatchEndStep]]), SelectOneStep(last,a), PropertiesStep([name],v
                                      alue)]
EarlyLimitStrategy           [O]   [GraphStep(vertex,[]), MatchStep(AND,[[MatchStartStep(a), HasStep([~label.eq(person), name.eq(marko)]), MatchEndStep]]), SelectOneStep(last,a), PropertiesStep([name],v
                                      alue)]
InlineFilterStrategy         [O]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), PropertiesStep([name],value)]
IncidentToAdjacentStrategy   [O]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), PropertiesStep([name],value)]
AdjacentToIncidentStrategy   [O]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), PropertiesStep([name],value)]
RepeatUnrollStrategy         [O]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), PropertiesStep([name],value)]
CountStrategy                [O]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), PropertiesStep([name],value)]
PathRetractionStrategy       [O]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), NoOpBarrierStep(2500), PropertiesStep([name],value)]
LazyBarrierStrategy          [O]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), NoOpBarrierStep(2500), PropertiesStep([name],value)]
TinkerGraphCountStrategy     [P]   [GraphStep(vertex,[]), HasStep([~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), NoOpBarrierStep(2500), PropertiesStep([name],value)]
TinkerGraphStepStrategy      [P]   [TinkerGraphStep(vertex,[~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), NoOpBarrierStep(2500), PropertiesStep([name],value)]
ProfileStrategy              [F]   [TinkerGraphStep(vertex,[~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), NoOpBarrierStep(2500), PropertiesStep([name],value)]
StandardVerificationStrategy [V]   [TinkerGraphStep(vertex,[~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), NoOpBarrierStep(2500), PropertiesStep([name],value)]

Final Traversal                    [TinkerGraphStep(vertex,[~label.eq(person), name.eq(marko)])@[a], SelectOneStep(last,a), NoOpBarrierStep(2500), PropertiesStep([name],value)]

好多了。所以，我倾向于认为这是 TinkerPop 需要解决的一个普遍问题，它涉及最后两点的某种组合。当然，如果 JanusGraph 可以进一步优化 match() 就好了。 None of this当然是你问题的解决方案，但它至少应该解释发生了什么以及问题出在哪里。我创建了 TINKERPOP-2325 以供进一步讨论和跟踪。

Sparql-gremlin 工具不使用索引

Sparql-gremlin tool don't use indexes

sparql

gremlin

tinkerpop

tinkerpop3

janusgraph