CODEWITHSUNDEEP
graph-databasesgremlingremlin-servergremlinpython
alexyichu
alexyichu

Reputation: 3612

How do I find vertices without particular edges from a particular vertex in Gremlin?

I am using python to run my gremlin queries, for which I am still getting used to / learning. Let's say I have vertex labels A and B, and there can be an edge from A to B called abEdge. I can find B vertices that have such edges from a particular A vertex with:

g.V()\
    .hasLabel("A")\
    .has("uid", uid)\  # uid is from a variable
    .outE("abEdge")\
    .inV()\
    .toList()

But how would I go about finding B vertices that have no such edges from a particular A vertex?

My instinct is to try the following:

# Find B edges without an incoming edge from a particular A vertex
gremlin.V()\
    .hasLabel("B")\
    .where(__.not_(inE("abEdge").from_(
        V()\
        .hasLabel("A")\
        .has("uid", uid)
    )))\
    .next()

And that results in a bad query (Not sure where yet), I'm still reading up on Gremlin, but I am also under time contraints so here I am asking. If anyone can help but just using groovy syntax that is fine too as it's not too bad to convert between the two.

Any explanations would be helpful too as I am still learning this technology.

Update

I guess if this were a real-life question, and related to this website. We could ask (A=Person, B=Programming-Language, and abEdge=knows):

Which programming languages does particular person A not know?

Upvotes: 2

Views: 463

Answers (1)

stephen mallette
stephen mallette

Reputation: 46206

It looks like you almost had the answer:

g.V().hasLabel("B"). \
  filter(__.not_(__.in_('abEdge').has("A","uid",uid))). \
  toList()

I prefer filter() when using just a single Traversal argument, but I think you could replace with where() if you liked.

Upvotes: 2

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