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https://issues.apache.org/jira/browse/TINKERPOP-1335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15327452#comment-15327452
]
Marko A. Rodriguez commented on TINKERPOP-1335:
-----------------------------------------------
Note that I just confirmed via a test case with {{GryoInputFormat}} that the
wrong answer is produced by {{SparkGraphComputer}}. This is good as now we can
isolate this to TinkerPop solely and can test it in our test suite without the
need for Spark Server infrastructure.
> OLAP queries potentially fail for certain match()/select() query patterns
> -------------------------------------------------------------------------
>
> Key: TINKERPOP-1335
> URL: https://issues.apache.org/jira/browse/TINKERPOP-1335
> Project: TinkerPop
> Issue Type: Bug
> Components: hadoop, process
> Affects Versions: 3.2.0-incubating
> Reporter: Daniel Kuppitz
> Assignee: Marko A. Rodriguez
>
> There are certain queries that return wrong results when executed via
> {{SparkGraphComputer}}. After testing a few queries I would say that the
> problematic query pattern is a {{match()}} / {{select()}} combo.
> For example (Grateful Dead graph):
> {code}
> gremlin> g.V().hasLabel("song").match(
> __.as("a").values("name").as("name"),
> __.as("a").values("performances").as("performances")
> ).select("name","performances").count()
> ==>0
> {code}
> If {{count()}} is replaced by {{program()}}, the whole thing is going to
> throw exceptions. However, if we select {{a}} instead of {{name}} and
> {{performances}}, we get correct result. Likewise, if we remove the
> {{select()}} or just rewrite the {{match()}} part, everything works as
> expected. The simplest query to reproduce the erroneous behavior is this one:
> {code}
> g.V().match(__.as("a").values("name").as("name")).select("name").count()
> {code}
> The tests were done using a real Spark Server. I didn't try to use Spark in
> local mode or Giraph. I did try {{TinkerGraphComputer}}, which worked fine.
> Here's an actual stacktrace that shows were to find the root of all evil:
> {noformat}
> ERROR 2016-06-09 21:24:25,988 Logging.scala:95 -
> org.apache.spark.executor.Executor: Exception in task 0.2 in stage 119.0 (TID
> 307)
> java.lang.IllegalStateException: The host of the object is unknown:
> {a=v[{~label=Comment, member_id=2034, community_id=1676454656}], content=ok,
> length=2}:java.util.LinkedHashMap
> at
> org.apache.tinkerpop.gremlin.process.computer.traversal.WorkerExecutor.getHostingVertex(WorkerExecutor.java:242)
> ~[gremlin-core-3.2.1-20160601-aa673db1.jar:3.2.1-20160601-aa673db1]
> at
> org.apache.tinkerpop.gremlin.process.computer.traversal.WorkerExecutor.lambda$drainStep$262(WorkerExecutor.java:220)
> ~[gremlin-core-3.2.1-20160601-aa673db1.jar:3.2.1-20160601-aa673db1]
> at
> org.apache.tinkerpop.gremlin.process.computer.traversal.WorkerExecutor$$Lambda$113/1202183304.accept(Unknown
> Source) ~[na:na]
> at java.util.Iterator.forEachRemaining(Iterator.java:116) ~[na:1.8.0_40]
> at
> org.apache.tinkerpop.gremlin.process.computer.traversal.WorkerExecutor.drainStep(WorkerExecutor.java:215)
> ~[gremlin-core-3.2.1-20160601-aa673db1.jar:3.2.1-20160601-aa673db1]
> at
> org.apache.tinkerpop.gremlin.process.computer.traversal.WorkerExecutor.execute(WorkerExecutor.java:146)
> ~[gremlin-core-3.2.1-20160601-aa673db1.jar:3.2.1-20160601-aa673db1]
> at
> org.apache.tinkerpop.gremlin.process.computer.traversal.TraversalVertexProgram.execute(TraversalVertexProgram.java:285)
> ~[gremlin-core-3.2.1-20160601-aa673db1.jar:3.2.1-20160601-aa673db1]
> at
> org.apache.tinkerpop.gremlin.spark.process.computer.SparkExecutor.lambda$null$9(SparkExecutor.java:111)
> ~[spark-gremlin-3.2.1-20160601-aa673db1.jar:3.2.1-20160601-aa673db1]
> at
> org.apache.tinkerpop.gremlin.spark.process.computer.SparkExecutor$$Lambda$92/910806192.apply(Unknown
> Source) ~[na:na]
> at
> org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils$3.next(IteratorUtils.java:247)
> ~[gremlin-core-3.2.1-20160601-aa673db1.jar:3.2.1-20160601-aa673db1]
> at
> scala.collection.convert.Wrappers$JIteratorWrapper.next(Wrappers.scala:42)
> ~[scala-library-2.10.6.jar:na]
> at scala.collection.Iterator$$anon$14.hasNext(Iterator.scala:389)
> ~[scala-library-2.10.6.jar:na]
> at scala.collection.Iterator$$anon$13.hasNext(Iterator.scala:371)
> ~[scala-library-2.10.6.jar:na]
> at
> org.apache.spark.util.collection.ExternalSorter.insertAll(ExternalSorter.scala:189)
> ~[spark-core_2.10-1.6.1.2.jar:1.6.1.2]
> at
> org.apache.spark.shuffle.sort.SortShuffleWriter.write(SortShuffleWriter.scala:64)
> ~[spark-core_2.10-1.6.1.2.jar:1.6.1.2]
> at
> org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:73)
> ~[spark-core_2.10-1.6.1.2.jar:1.6.1.2]
> at
> org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
> ~[spark-core_2.10-1.6.1.2.jar:1.6.1.2]
> at org.apache.spark.scheduler.Task.run(Task.scala:89)
> ~[spark-core_2.10-1.6.1.2.jar:1.6.1.2]
> at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:214)
> ~[spark-core_2.10-1.6.1.2.jar:1.6.1.2]
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> [na:1.8.0_40]
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> [na:1.8.0_40]
> at java.lang.Thread.run(Thread.java:745) [na:1.8.0_40]
> {noformat}
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