[
https://issues.apache.org/jira/browse/TINKERPOP-887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15622949#comment-15622949
]
ASF GitHub Bot commented on TINKERPOP-887:
------------------------------------------
Github user BrynCooke commented on the issue:
https://github.com/apache/tinkerpop/pull/470
Exactly. It's currently a huge pain to figure out where things have gone
wrong. Without this patch I have to divide and conquer my code every time I hit
a FastNoSuchElementException.
There is no cost to a try/catch block. The construction of the regular
NoSuchElementException is expensive, but should only be thrown on the top level
traversal.
I actually found no significant difference between branches in terms of
performance.
Mine
```
gremlin> graph = TinkerGraph.open()
==>tinkergraph[vertices:0 edges:0]
gremlin> graph.io(gryo()).readGraph('data/grateful-dead.kryo')
==>null
gremlin> h = graph.traversal()
==>graphtraversalsource[tinkergraph[vertices:808 edges:8049], standard]
gremlin> g = graph.traversal().withoutStrategies(LazyBarrierStrategy.class)
==>graphtraversalsource[tinkergraph[vertices:808 edges:8049], standard]
gremlin> clock(100){ h.V().out().out().out().toSet() }
==>3.33155785
gremlin> clock(20){ g.V().out().out().out().toSet() }
==>520.2727724499999
gremlin> clock(20){ g.V().out().flatMap(out()).flatMap(out()).toSet() }
==>903.5254189999999
gremlin> clock(100){ g.V().repeat(out()).times(3).toSet() }
==>1.8392006699999999
gremlin> clock(100){ h.V().count() }
==>0.0069826
gremlin>
```
Master
```
gremlin> graph = TinkerGraph.open()
==>tinkergraph[vertices:0 edges:0]
gremlin> graph.io(gryo()).readGraph('data/grateful-dead.kryo')
==>null
gremlin> h = graph.traversal()
==>graphtraversalsource[tinkergraph[vertices:808 edges:8049], standard]
gremlin> g = graph.traversal().withoutStrategies(LazyBarrierStrategy.class)
==>graphtraversalsource[tinkergraph[vertices:808 edges:8049], standard]
gremlin> clock(100){ h.V().out().out().out().toSet() }
==>3.59260972
gremlin> clock(20){ g.V().out().out().out().toSet() }
==>519.7500263
gremlin> clock(20){ g.V().out().flatMap(out()).flatMap(out()).toSet() }
==>907.32923195
gremlin> clock(100){ g.V().repeat(out()).times(3).toSet() }
==>1.76869779
gremlin> clock(100){ h.V().count() }
==>0.006985369999999999
gremlin>
```
> FastNoSuchElementException hides stack trace in client code
> -----------------------------------------------------------
>
> Key: TINKERPOP-887
> URL: https://issues.apache.org/jira/browse/TINKERPOP-887
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.0.2-incubating
> Reporter: Bryn Cooke
> Assignee: Marko A. Rodriguez
> Priority: Minor
>
> I wrote some code that incorrectly assumed that a Gremlin query would return
> an element, but it didn't. The surprise was that I got no stack trace and
> therefore had no idea where in *my* code I had introduced the error.
> I haven't looked in detail at the TP code, so what comes next is speculation:
> If FastNoSuchElementException is being used in truly exceptional
> circumstances then why is a singleton is used over a normal exception with
> stack trace? It could just as easily be converted to a normal exception.
> If FastNoSuchElementException is being used for control flow then probably it
> shouldn't. Code should check hasNext rather than trying for next and dealing
> with an exceptional result. I'm not sure what the current state of things are
> in the JVM but at least in the past try catch blocks would inhibit
> optimization even without stack traces so this type of code was considered an
> antipattern.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
