Reputation: 3641

Cypher Query in Neo4j Returns 'undefined'

I've built a graph using Neo4j which consists of about 1000 nodes and about 270,000 relationships. The graph is a flight network (airports are nodes, and flights are relationships) so there are many relationships from node to node. I'm sure there are also many cycles in certain queries (I'm not sure if that's a problem). Anyway, certain queries work fine, like these:

start a=node(1), b=node(2) match p=a-[:flys_to*..1]->b return p;
start a=node(1), b=node(2) match p=shortestPath(a-[:flys_to]->b) return p;

But when I try other more complicated queries, there is no friendly error message; it just hangs for about 3 minutes (depending on which two nodes I search between) and returns "Undefined".

One of the queries that hangs looks like this:

start a=node(1), b=node(2) match p=a-[:flys_to*..2]->b return p;

Also, an interesting side note is that when I type the following query, it instantly returns "Undefined":

start a=node(1), b=node(2) match p=a-[:flys_to]->b return p;

Does this make sense, or does anyone have any ideas as to where I might start troubleshooting?

More Info about this Specific Problem

Here's a compressed file of the database: http://www.opensourcebanking.org/neo4j/

I'm running this in a virtual environment over VMware. The host is OSX 10.8.2 and the guest is Windows Server 2012. The JRE is 1.6.0_38. Also, I have auto indexing setup on the node property 'iata', and the relationship property "flys_to".

Here are a few Cypher queries and their related logged messages:

The following query returns 'undefined' almost immediately:

start a=node(353), b=node(295)
match p=a-->b
return p;

And here's what I get in the log:

SEVERE: The exception contained within MappableContainerException could not be mapped to a response, re-throwing to the HTTP container
org.neo4j.helpers.ThisShouldNotHappenError: Developer: Andres claims that: Unexpected traversal state encountered
    at org.neo4j.cypher.internal.pipes.matching.BidirectionalTraversalMatcher$StepCollisionDetector.includePath(BidirectionalTraversalMatcher.scala:101)
    at org.neo4j.kernel.StandardBranchCollisionDetector.evaluate(StandardBranchCollisionDetector.java:74)
    at org.neo4j.kernel.StandardBranchCollisionDetector.evaluate(StandardBranchCollisionDetector.java:37)
    at org.neo4j.kernel.impl.traversal.BidirectionalTraverserIterator.fetchNextOrNull(BidirectionalTraverserIterator.java:157)
    at org.neo4j.kernel.impl.traversal.BidirectionalTraverserIterator.fetchNextOrNull(BidirectionalTraverserIterator.java:41)
    at org.neo4j.helpers.collection.PrefetchingIterator.hasNext(PrefetchingIterator.java:55)
    at scala.collection.JavaConversions$JIteratorWrapper.hasNext(JavaConversions.scala:574)
    at scala.collection.Iterator$$anon$21.hasNext(Iterator.scala:371)
    at scala.collection.Iterator$$anon$21.hasNext(Iterator.scala:371)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at org.neo4j.cypher.internal.ClosingIterator$$anonfun$hasNext$1.apply$mcZ$sp(ClosingIterator.scala:36)
    at org.neo4j.cypher.internal.ClosingIterator$$anonfun$hasNext$1.apply(ClosingIterator.scala:35)
    at org.neo4j.cypher.internal.ClosingIterator$$anonfun$hasNext$1.apply(ClosingIterator.scala:35)
    at org.neo4j.cypher.internal.ClosingIterator.failIfThrows(ClosingIterator.scala:87)
    at org.neo4j.cypher.internal.ClosingIterator.hasNext(ClosingIterator.scala:35)
    at scala.collection.Iterator$class.foreach(Iterator.scala:660)
    at org.neo4j.cypher.internal.ClosingIterator.foreach(ClosingIterator.scala:31)
    at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:48)
    at scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:128)
    at scala.collection.TraversableOnce$class.toList(TraversableOnce.scala:242)
    at org.neo4j.cypher.internal.ClosingIterator.toList(ClosingIterator.scala:31)
    at org.neo4j.cypher.PipeExecutionResult.createTimedResults(PipeExecutionResult.scala:73)
    at org.neo4j.cypher.PipeExecutionResult.dumpToString(PipeExecutionResult.scala:80)
    at org.neo4j.cypher.PipeExecutionResult.dumpToString(PipeExecutionResult.scala:125)
    at org.neo4j.cypher.javacompat.ExecutionResult.dumpToString(ExecutionResult.java:91)
    at org.neo4j.shell.kernel.apps.Start.exec(Start.java:71)
    at org.neo4j.shell.kernel.apps.ReadOnlyGraphDatabaseApp.execute(ReadOnlyGraphDatabaseApp.java:32)
    at org.neo4j.shell.impl.AbstractAppServer.interpretLine(AbstractAppServer.java:115)
    at org.neo4j.shell.kernel.GraphDatabaseShellServer.interpretLine(GraphDatabaseShellServer.java:92)
    at org.neo4j.shell.impl.AbstractClient.evaluate(AbstractClient.java:130)
    at org.neo4j.shell.impl.AbstractClient.evaluate(AbstractClient.java:114)
    at org.neo4j.server.webadmin.console.ShellSession.evaluate(ShellSession.java:101)
    at org.neo4j.server.webadmin.rest.console.ConsoleService.exec(ConsoleService.java:125)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
    at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ResponseOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:205)
    at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
    at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)
    at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
    at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:390)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:943)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

The following query works fine. It returns 426 rows and nothing is logged.

start a=node(353), b=node(295)
match p=a-[:flys_to*..1]->b
return p;

The following query returns 'undefined' after about 10-15 minutes:

start a=node(353), b=node(295)
match p=a-[:flys_to*..2]->b
return p;

Log:

SEVERE: The exception contained within MappableContainerException could not be mapped to a response, re-throwing to the HTTP container
java.lang.OutOfMemoryError: Java heap space
    at org.neo4j.cypher.internal.pipes.matching.AddedHistory.toSeq(History.scala:87)
    at org.neo4j.cypher.internal.pipes.matching.AddedHistory.toMap(History.scala:75)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.isMatchSoFar(PatternMatcher.scala:166)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.org$neo4j$cypher$internal$pipes$matching$PatternMatcher$$traverseNextNodeFromRelationship(PatternMatcher.scala:98)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher$$anonfun$4.apply(PatternMatcher.scala:150)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher$$anonfun$4.apply(PatternMatcher.scala:150)
    at scala.collection.immutable.Stream$$anonfun$map$1.apply(Stream.scala:175)
    at scala.collection.immutable.Stream$$anonfun$map$1.apply(Stream.scala:175)
    at scala.collection.immutable.Stream$Cons.tail(Stream.scala:634)
    at scala.collection.immutable.Stream$Cons.tail(Stream.scala:626)
    at scala.collection.immutable.Stream.foldLeft(Stream.scala:302)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.traverseRelationship(PatternMatcher.scala:150)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.traverseNextSpecificNode(PatternMatcher.scala:61)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.traverseNode(PatternMatcher.scala:72)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.foreach(PatternMatcher.scala:36)
    at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:48)
    at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:99)
    at scala.collection.TraversableOnce$class.toBuffer(TraversableOnce.scala:250)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.toBuffer(PatternMatcher.scala:28)
    at scala.collection.TraversableLike$class.toStream(TraversableLike.scala:571)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.toStream(PatternMatcher.scala:28)
    at scala.collection.TraversableLike$class.toIterator(TraversableLike.scala:570)
    at org.neo4j.cypher.internal.pipes.matching.PatternMatcher.toIterator(PatternMatcher.scala:28)
    at scala.collection.Iterator$$anon$21.hasNext(Iterator.scala:371)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at org.neo4j.cypher.internal.ClosingIterator$$anonfun$hasNext$1.apply$mcZ$sp(ClosingIterator.scala:36)
    at org.neo4j.cypher.internal.ClosingIterator$$anonfun$hasNext$1.apply(ClosingIterator.scala:35)
    at org.neo4j.cypher.internal.ClosingIterator$$anonfun$hasNext$1.apply(ClosingIterator.scala:35)
    at org.neo4j.cypher.internal.ClosingIterator.failIfThrows(ClosingIterator.scala:87)
    at org.neo4j.cypher.internal.ClosingIterator.hasNext(ClosingIterator.scala:35)

Upvotes: 4

Answers (2)

Michael Hunger

Reputation: 41706

For me this returns 426 rows:

start a=node(353), b=node(295)
match p=a-->b
return p;

Upvotes: 0

Michael Hunger

Reputation: 41706

Did you try to use shortestPath or allShortestPaths for your queries?

 start a=node(1), b=node(2) match p=allShortestPaths(a-[:flys_to*..2]->b) return p;


+--------------------------------------------------------------------------------------------------------+
| p                                                                                                      |
+--------------------------------------------------------------------------------------------------------+
| [Node[1]{iata:"ABE"},:flys_to[224044] {},Node[546]{iata:"SFO"},:flys_to[24211] {},Node[2]{iata:"ABI"}] |
| [Node[1]{iata:"ABE"},:flys_to[224044] {},Node[546]{iata:"SFO"},:flys_to[24210] {},Node[2]{iata:"ABI"}] |
....
| [Node[1]{iata:"ABE"},:flys_to[66032] {},Node[146]{iata:"DFW"},:flys_to[1] {},Node[2]{iata:"ABI"}]      |
| [Node[1]{iata:"ABE"},:flys_to[66032] {},Node[146]{iata:"DFW"},:flys_to[0] {},Node[2]{iata:"ABI"}]      |
+--------------------------------------------------------------------------------------------------------+
28 rows
20 ms
 start a=node(1), b=node(2) match p=shortestPath(a-[:flys_to*..2]->b) return p;

+--------------------------------------------------------------------------------------------------------+
| p                                                                                                      |
+--------------------------------------------------------------------------------------------------------+
| [Node[1]{iata:"ABE"},:flys_to[224044] {},Node[546]{iata:"SFO"},:flys_to[24211] {},Node[2]{iata:"ABI"}] |
+--------------------------------------------------------------------------------------------------------+
1 row
1 ms

Upvotes: 0

Cypher Query in Neo4j Returns &#39;undefined&#39;

Answers (2)

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Cypher Query in Neo4j Returns 'undefined'