J
JanusGraph•3mo ago
Tsung

Adding an edge to a non-existent vertex creates a shell vertex

Hi, I recently noticed an odd behaviour when using the Java Janusgraph library (version 1.1.0) to add edges. Adding an edge from an existing vertex S, to a non-existing vertex T, will automatically create an empty shell vertex for T. Is this an intended and reliable behavior that is documented somewhere? Simplified example: 
var transaction = graph.buildTransaction().start(); // graph is a StandardJanusGraph
var g = transaction.traversal();
g.inject(1).addE(edgeLabel).from(V("ExistingVertexId")).to(V("MissingVertexId")).iterate();
transaction.commit();
var transaction = graph.buildTransaction().start(); // graph is a StandardJanusGraph
var g = transaction.traversal();
g.inject(1).addE(edgeLabel).from(V("ExistingVertexId")).to(V("MissingVertexId")).iterate();
transaction.commit();
This creates a shell vertex with the label vertex and no properties, which I can see from the gremlin console: 
gremlin> g.V("MissingVertexId").label()
==>vertex
gremlin> g.V("MissingVertexId").valueMap()
==>[]
gremlin> g.V("MissingVertexId").label()
==>vertex
gremlin> g.V("MissingVertexId").valueMap()
==>[]
Other observations: - Trying to add an edge through the gremlin console in the same way fails with an error about the non-existing target vertex - Adding the missing vertex later using the Java library successfully adds the label and properties to the vertex, and preserves the previously-added edge Thanks in advance!
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