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https://issues.apache.org/jira/browse/TINKERPOP-2831?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17643561#comment-17643561
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ASF GitHub Bot commented on TINKERPOP-2831:
-------------------------------------------
cole-bq commented on PR #1873:
URL: https://github.com/apache/tinkerpop/pull/1873#issuecomment-1338208731
I would like to take some time to explore an alternative solution to this
issue. The main drawback of switching to FastNoSuchElementException is that it
does not include a stack trace. There are some concerns about the impact of
removing the stack trace from this exception.
The current implementation of hasNext() throws and catches
NoSuchElementException's which gives it the same performance bottleneck you are
trying to avoid. I want to try and speed up hasNext() so that users can check
it before calling next() if they want to avoid the performance penalty
associated with the NoSuchElementException.
I believe that a fast implementation of hasNext() would remove the need for
this PR and would avoid the need to trade better exceptions for better
performance.
> Throw NoSuchElementException frequently which slowers the performance
> ---------------------------------------------------------------------
>
> Key: TINKERPOP-2831
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2831
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.5.4
> Reporter: Redriver
> Priority: Major
> Attachments: Screen Shot 2022-11-24 at 11.35.40.png
>
>
> When I run g.V().label().groupCount() on a huge graph: 600m vertices + 6
> billion edges, the JVM async profiler exposed that the NoSuchElementException
> is a hotspot. In fact, that exception is used to inform the caller that the
> iteration end reached, so the stack trace information is not used. In
> addition, creating a new exception everytime is also not necessary.
> {code:java}
> java.lang.Throwable.fillInStackTrace(Native Method)
> java.lang.Throwable.fillInStackTrace(Throwable.java:783) => holding
> Monitor(java.util.NoSuchElementException@1860956919})
> java.lang.Throwable.<init>(Throwable.java:250)
> java.lang.Exception.<init>(Exception.java:54)
> java.lang.RuntimeException.<init>(RuntimeException.java:51)
> java.util.NoSuchElementException.<init>(NoSuchElementException.java:46)
> org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerGraphIterator.next(TinkerGraphIterator.java:63)
> org.janusgraph.hadoop.formats.util.JanusGraphVertexDeserializer.getOrCreateVertex(JanusGraphVertexDeserializer.java:192)
> org.janusgraph.hadoop.formats.util.JanusGraphVertexDeserializer.readHadoopVertex(JanusGraphVertexDeserializer.java:153)
> org.janusgraph.hadoop.formats.util.HadoopRecordReader.nextKeyValue(HadoopRecordReader.java:69)
> org.apache.spark.rdd.NewHadoopRDD$$anon$1.hasNext(NewHadoopRDD.scala:230)
> org.apache.spark.InterruptibleIterator.hasNext(InterruptibleIterator.scala:37)
> scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:408)
> org.apache.spark.storage.memory.MemoryStore.putIterator(MemoryStore.scala:220)
> org.apache.spark.storage.memory.MemoryStore.putIteratorAsBytes(MemoryStore.scala:348)
> org.apache.spark.storage.BlockManager$$anonfun$doPutIterator$1.apply(BlockManager.scala:1182)
> org.apache.spark.storage.BlockManager$$anonfun$doPutIterator$1.apply(BlockManager.scala:1156)
> org.apache.spark.storage.BlockManager.doPut(BlockManager.scala:1091)
> org.apache.spark.storage.BlockManager.doPutIterator(BlockManager.scala:1156)
> org.apache.spark.storage.BlockManager.getOrElseUpdate(BlockManager.scala:882)
> org.apache.spark.rdd.RDD.getOrCompute(RDD.scala:335)
> org.apache.spark.rdd.RDD.iterator(RDD.scala:286)
> org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:52)
> org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
> org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
> org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:52)
> org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
> org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
> org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:52)
> org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
> org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
> org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:52)
> org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
> org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
> org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:99)
> org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:55)
> org.apache.spark.scheduler.Task.run(Task.scala:121)
> org.apache.spark.executor.Executor$TaskRunner$$anonfun$10.apply(Executor.scala:416)
> org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1360)
> org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:422)
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> java.lang.Thread.run(Thread.java:748)
> {code}
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