Issue 1:
see https://groups.google.com/forum/?fromgroups=#!topic/neo4j/CjKNqI5WGhE for context.

I constantly encounter a strange problem when running a relatively simple query on Linux based machines while on Windows 7 I have no problems at all (both from neo4j-shell and from Python using py2neo).

I have a database with 7762 nodes and 20730 relationships. I have an index on node property 'venueID'. There are 817 nodes with node property 'venueID:2826' and 1233 nodes wirh 'venueID:2611' (for all the other values of this node property there are few nodes). I created the database using py2neo both on Windows and Linux.

If I run the following query

START a=node:my_nodes('venueID:2611'), b=node:my_nodes('venueID:2826')
MATCH a-->b
RETURN count(a)

on Windows 7 with Java version 1.7.0_09 using neo4j versions 1.8, 1.9.M01, 1.7.2 I get an answer within 15000ms;

on Debian-based server (Linux 2.6.32-5-amd64) with Java version 1.6.0-18 using stable neo4j version 1.8 as well as 1.9-SNAPSHOT and 1.9.M02 I constantly get an error

"ServerError: Error occurred in server thread; nested exception is:

org.neo4j.helpers.ThisShouldNotHappenError: Developer: Andres claims that: Unexpected traversal state encountered"

In the console log when using 1.9-SNAPSHOT I see the following message

11:18:32.807 [535102763@qtp-423265228-2] ERROR org.mortbay.log - /db/data/cypher

org.neo4j.helpers.ThisShouldNotHappenError: Developer: Andres claims that: Unexpected traversal state encountered

at org.neo4j.cypher.internal.pipes.matching.BidirectionalTraversalMatcher$StepCollisionDetector.includePath(Bidirect$

at org.neo4j.kernel.StandardBranchCollisionDetector.evaluate(StandardBranchCollisionDetector.java:74) ~[neo4j-kernel$

at org.neo4j.kernel.StandardBranchCollisionDetector.evaluate(StandardBranchCollisionDetector.java:37) ~[neo4j-kernel$

at org.neo4j.kernel.impl.traversal.BidirectionalTraverserIterator.fetchNextOrNull(BidirectionalTraverserIterator.jav$

at org.neo4j.kernel.impl.traversal.BidirectionalTraverserIterator.fetchNextOrNull(BidirectionalTraverserIterator.jav$

at org.neo4j.helpers.collection.PrefetchingIterator.hasNext(PrefetchingIterator.java:55) ~[neo4j-kernel-1.9-SNAPSHOT$

at scala.collection.JavaConversions$JIteratorWrapper.hasNext(JavaConversions.scala:574) ~[scala-library-2.9.1-1.jar:$

at scala.collection.Iterator$$anon$21.hasNext(Iterator.scala:371) ~[scala-library-2.9.1-1.jar:na]

at scala.collection.Iterator$$anon$21.hasNext(Iterator.scala:371) ~[scala-library-2.9.1-1.jar:na]

at scala.collection.Iterator$class.foreach(Iterator.scala:660) ~[scala-library-2.9.1-1.jar:na]

at scala.collection.Iterator$$anon$21.foreach(Iterator.scala:368) ~[scala-library-2.9.1-1.jar:na]

at org.neo4j.cypher.internal.pipes.EagerAggregationPipe.createResults(EagerAggregationPipe.scala:76) ~[neo4j-cypher-$

at org.neo4j.cypher.internal.pipes.ColumnFilterPipe.createResults(ColumnFilterPipe.scala:37) ~[neo4j-cypher-1.9-SNAP$

at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl$$anonfun$6.apply(ExecutionPlanImpl.scala:127) ~[neo4j-c$

at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl$$anonfun$6.apply(ExecutionPlanImpl.scala:125) ~[neo4j-c$

at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl.execute(ExecutionPlanImpl.scala:33) ~[neo4j-cypher-1.9-$

at org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:59) ~[neo4j-cypher-1.9-SNAPSHOT.jar:1.9-SNAPSHOT]

at org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:63) ~[neo4j-cypher-1.9-SNAPSHOT.jar:1.9-SNAPSHOT]

at org.neo4j.cypher.javacompat.ExecutionEngine.execute(ExecutionEngine.java:79) ~[neo4j-cypher-1.9-SNAPSHOT.jar:1.9-

When I change the node properties for which I query to the ones which do not exist in the database, the query executes with no problem.

I tried it out also on virtual Linux Mint installed inside my Windows 7, but I get the same error as on the server.

Could anyone provide a hint what might be wrong?

Issue 2:
see http://console.neo4j.org/?id=258d6g for an example, and http://stackoverflow.com/questions/13970033/returning-all-relationships-for-a-list-of-nodes for the discussion on this.