Setting null values

[Philip Graff]

Hi all,

I've noticed that if I try to set a property value as null, I get different behavior depending on when I do it. If I do it following an addV() step - i.e. when I create the Vertex, in this case - then the property is just not set and no error is thrown. However, if I do it on an existing Element, then I get an IllegalStateException from the AddPropertyStep. In the latter case, any properties I set before the one with the null value are actually set, but any after are not. In the former case, all properties without a null value are set. See the example below.

gremlin> graph = TinkerFactory.createModern()

==>tinkergraph[vertices:6 edges:6]

gremlin> g = graph.traversal()

==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]

gremlin> g.V(1).property("x", 1).property("y", null).property("z", 2)

The AddPropertyStep does not have a provided value: AddPropertyStep({key=[y]})

Type ':help' or ':h' for help.

Display stack trace? [yN]N

gremlin> g.V(1).properties()

==>vp[name->marko]

==>vp[x->1]

==>vp[age->29]

gremlin> g.addV("test").property("x", 1).property("y", null).property("z", 2)

==>v[13]

gremlin> g.V(13).properties()

==>vp[x->1]

==>vp[z->2]

gremlin>

I wouldn't expect this to be the desired behavior. Shouldn't setting a property on a new Vertex also throw the IllegalStateException? The fact that it quietly moves on means that I don't know if my property is set or not in a general sense.

Thanks,

Phil 

[Thanos Giannakis]

Hi Phlip,

I have noticed the same issue. Adding a vertex with a null property works, it just ignores the property in the travelsal, but trying to update a property value with null will throw an exception.

I think the desired solution would be, if a property is updated with null, then remove the property. Else you need to detect this in application level and handle it. 

Thanos

[Stephen Mallette]

That's an interesting inconsistency. I guess it has to do with property() being treated as a modulator to addV() and then the AddVertexStep having a different flow of processing than AddPropertyStep.

> I think the desired solution would be, if a property is updated with null, then remove the property. Else you need to detect this in application level and handle it. 

That could be a way to resolve it but I think that rather than institute a major change in behavior we should just have AddVertexStep have similar functionality to AddVertexStep (or the other way around) and keep property removal explicit to drop(). Created an issue:

https://issues.apache.org/jira/browse/TINKERPOP-2099

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