Unidirected hyper-edges not working as documented

[pluradj]

Reference from janusgraph-users. Related documentation.

It seems like this functionality worked in older Titan releases, but has not been working since Titan 0.9.0-M2. There must not be any JUnit test cases covering this either.

[automathman]

the only info I've found so far about Titan's support was here: https://github.com/thinkaurelius/titan/issues/860 I know that titan did not export them properly to graphson, but it did not seem like a un-fixable problem. Not sure I buy the "incorrect ID's" argument.

In titan 0.5.x this was supported by special methods in TitanRelation Interface, and it's implementing class(es) : setProperty(EdgeLabel label, TitanVertex vertex)

[automathman]

I've found this feature very useful for some of my graph models, because I can update a pointer to a vertex without deleting/adding an edge (avoiding potential cassandra tombstone issues for "hot" data), and in concurrent operations I do not end up with multiple "pointers" as I would with addEdge workflows

[pluradj]

Thanks for the pointer @automathman. Based on that Titan issue, we'll handle this as an enhancement request, as the functionality was dropped in Titan 1.0.

[robertdale]

There are tests for this. It should be verified that they are executing and passing (or not passing).
https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-test/src/main/java/org/janusgraph/graphdb/JanusGraphTest.java#L459

[pluradj]

Those tests define the unidirected edges in the schema, but there aren't any tests actually exercise creating elements using it in the same fashion as described in the documented example.

[robertdale]

Oh, I think I see the confusion I have. I think the title is misleading. Unidirected edges work and there are tests for it [1]. Unidirected edges as hyper-edges (stored in a property) don't work and there is actually a test that should fail for this condition [2].

1. https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-test/src/main/java/org/janusgraph/graphdb/JanusGraphTest.java#L859

2. https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-test/src/main/java/org/janusgraph/graphdb/JanusGraphTest.java#L895

[automathman]

where would I track progress on the "enhancement request" - here? or is there another ticket/issue?

[The-Don-Himself]

I'm also very interested in this and have subscribed to this issue, I think @automathman a possible way to track this issue is to monitor chatter on the JanusGraph developers group and the JanusGraph users group.

I have this daunting feeling that this is really an edge case (but one that sets JanusGraph apart from other Graph DBs) so it might take some time before it moves to the top of the impending features list but I could be wrong. Perhaps @pluradj and @robertdale can shed more light on this.

[pluradj]

@automathman We can continue to track the enhancement request with this issue. For now, all that is being done is removing the documentation that doesn't reflect reality.

I think it might be interesting to hear a perspective from @fppt on hyperedges.