Norio Akagi created TINKERPOP-2971:
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             Summary: having order() before fold() omits an empty list in 
GroupStep's value traversal
                 Key: TINKERPOP-2971
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2971
             Project: TinkerPop
          Issue Type: Bug
          Components: tinkergraph
    Affects Versions: 3.6.4
            Reporter: Norio Akagi


Using the modern graph,
{code:java}
gremlin> g.V().group().by().by(out().fold())
==>[v[1]:[v[3],v[2],v[4]],v[2]:[],v[3]:[],v[4]:[v[5],v[3]],v[5]:[],v[6]:[v[3]]]{code}
{{out().fold()}} produces an empty list when there is no solution for {{out()}} 
in a value traversal of GroupStep. However if I put {{order()}} those empty 
lists are gone.
{code:java}
gremlin> g.V().group().by().by(out().order().fold())
==>[v[1]:[v[2],v[3],v[4]],v[4]:[v[3],v[5]],v[6]:[v[3]]]{code}
I think this is not an expected behavior. 

I don't see the similar effect in by() itself
{code:java}
gremlin> g.V().as("a").select("a").by(out().fold())
==>[v[3],v[2],v[4]]
==>[]
==>[]
==>[v[5],v[3]]
==>[]
==>[v[3]]{code}
{code:java}

gremlin> g.V().as("a").select("a").by(out().order().fold())
==>[v[2],v[3],v[4]]
==>[]
==>[]
==>[v[3],v[5]]
==>[]
==>[v[3]]{code}
So likely this is GroupStep specific issue. We need to investigate how this 
occurs and fix if needed.



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