Tinkerpop 3.1.1 OLAP (Spark) Gremlin error on filter query: The properties of an adjacent vertex can not be read or updated

[Jen]

Hi,

I am trying to do a filter query in OLAP (Spark) Gremlin which uses a filter where I'm trying to read a vertex property and getting an error. On the Grateful Dead example graph, I'm trying to filter song vertices such that songs are kept which are not covers or are not sung by Garcia or Weir. I've written the query like this:

gremlin> g.V().hasLabel('song').filter(has('songType',without('cover')).or().match(

    __.as('songV').out('sungBy').as('sungV'),

    __.as('sungV').values('name').as('artistName')).

select('artistName').where(without('Garcia','Weir')))

I use the match statement to allow traversals beyond the local star graph. And I get the exception (full stack trace is below) java.lang.UnsupportedOperationException: The properties of an adjacent vertex can not be read or updated. 

Is this related to https://issues.apache.org/jira/browse/TINKERPOP-691? Is this a bug in Tinkerpop, or am I writing my query wrong? If it's a bug, is there any workaround for OLAP TP 3.1.1?

-Jen

Stack trace:

java.lang.UnsupportedOperationException: The properties of an adjacent vertex can not be read or updated

        at org.apache.tinkerpop.gremlin.process.computer.GraphComputer$Exceptions.adjacentVertexPropertiesCanNotBeReadOrUpdated(GraphComputer.java:202)

        at org.apache.tinkerpop.gremlin.process.computer.util.ComputerGraph$ComputerAdjacentVertex.properties(ComputerGraph.java:471)

        at org.apache.tinkerpop.gremlin.structure.Element.values(Element.java:107)

        at org.apache.tinkerpop.gremlin.process.traversal.step.map.PropertiesStep.flatMap(PropertiesStep.java:50)

        at org.apache.tinkerpop.gremlin.process.traversal.step.map.FlatMapStep.processNextStart(FlatMapStep.java:47)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:54)

        at org.apache.tinkerpop.gremlin.process.traversal.step.map.MatchStep$MatchEndStep.processNextStart(MatchStep.java:460)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)

        at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:147)

        at org.apache.tinkerpop.gremlin.process.traversal.step.map.MatchStep.standardAlgorithm(MatchStep.java:313)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.ComputerAwareStep.processNextStart(ComputerAwareStep.java:47)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:54)

        at org.apache.tinkerpop.gremlin.process.traversal.step.map.MapStep.processNextStart(MapStep.java:36)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)

        at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:147)

        at org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil.test(TraversalUtil.java:84)

        at org.apache.tinkerpop.gremlin.process.traversal.step.filter.OrStep.processNextStart(OrStep.java:41)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)

        at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:147)

        at org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil.test(TraversalUtil.java:84)

        at org.apache.tinkerpop.gremlin.process.traversal.step.filter.TraversalFilterStep.filter(TraversalFilterStep.java:46)

        at org.apache.tinkerpop.gremlin.process.traversal.step.filter.FilterStep.processNextStart(FilterStep.java:38)

        at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)

        at java.util.Iterator.forEachRemaining(Iterator.java:115)

        at org.apache.tinkerpop.gremlin.process.computer.traversal.TraverserExecutor.lambda$execute$337(TraverserExecutor.java:83)

        at java.lang.Iterable.forEach(Iterable.java:75)

        at org.apache.tinkerpop.gremlin.process.computer.traversal.TraverserExecutor.execute(TraverserExecutor.java:80)

        at org.apache.tinkerpop.gremlin.process.computer.traversal.TraversalVertexProgram.execute(TraversalVertexProgram.java:166)

        at org.apache.tinkerpop.gremlin.spark.process.computer.SparkExecutor.lambda$null$17(SparkExecutor.java:92)

        at org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils$3.next(IteratorUtils.java:232)

        at scala.collection.convert.Wrappers$JIteratorWrapper.next(Wrappers.scala:42)

        at scala.collection.Iterator$$anon$13.hasNext(Iterator.scala:371)

        at org.apache.spark.util.collection.ExternalSorter.insertAll(ExternalSorter.scala:209)

        at org.apache.spark.shuffle.sort.SortShuffleWriter.write(SortShuffleWriter.scala:73)

        at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:73)

        at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)

        at org.apache.spark.scheduler.Task.run(Task.scala:88)

        at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:214)

        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

        at java.lang.Thread.run(Thread.java:745)

[Daniel Kuppitz]

Hi Jen,

am I writing my query wrong?

Yes. The query is bad for OLAP, because a local traversal traverses past the local star-graph. The problem here is that the match() step is already nested (local traversal) and you're trying to traverse out() and access the property "artistName" of the adjacent vertex.

Here's what I would do:

g.V().hasLabel("song").as("song").choose(has("songType", neq("cover")),
    identity(), out("sungBy")).
  where(hasLabel("song").or().has("name", without("Garcia","Weir"))).
  select("song").dedup()

There's also a match()-only solution, but it would require that there's always at least one "sungBy" edge for every song. Also note that you could make your query work, if you would know the id of Garcia and Weir upfront.

Cheers,

Daniel

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[Marko Rodriguez]

Hello,

Can one of you make a ticket in JIRA for the simplest traversal that exposes this problem? The compiler should have picked up that you were leaving the star graph and thrown a compile-time exception. In other words, this shouldn't have been a runtime exception.

Thanks,

Marko.

http://markorodriguez.com

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[Daniel Kuppitz]

Done.

https://issues.apache.org/jira/browse/TINKERPOP-1323

Cheers,

Daniel

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[Marko Rodriguez]

Fixed.

https://github.com/apache/incubator-tinkerpop/commit/9c56fa3a93ff1979373c681337c335de396ad916

This is in master/. The problem is that MatchStep traversals are not isolated like union() or coalesce()… instead, they will be concatenated in some arbitrary order. Thus, match() is much like RepeatStep (save that in repeat(), its the same traversal being concatenated with itself). Therefore, in TraversalHelper.isLocalStarGraph(), the same logic I use for RepeatStep should also apply to MatchStep. Simple fix. I added the failing test case and now your get a compile-time instead of a runtime error.

Enjoy,

Marko.

http://markorodriguez.com

To view this discussion on the web visit https://groups.google.com/d/msgid/gremlin-users/CA%2Bf9seUMrfHjuSSLQdfiXaskWXu6SF7y3tTX92qhNN-URiHL-w%40mail.gmail.com.

[Jen]

Great, thanks for your help, Marko and Daniel. The query Daniel suggested works great for me and glad to hear the error message is fixed too!

Thanks,

Jen