How to get multiple vertices/edges in a single gremlin query?

0
votes

I am in a situation where I need to get two different types of vertices using a single query. For example, assume that the graph has the following structure :

Node("User")--Edge("is_member")-->Node("Membership")--Edge("is_member")-->Node("Group")

Assume that the nodes have the following properties:

  1. Membership
    • status
    • date
  2. Group
    • name
    • date
    • type

Now, I need to get all the Membership nodes that a user is_member of, along with the corresponding Group's name. How do I write a Gremlin query for this?

I am using the Bulbs framework. How do I store the result in a python object?

1
titangremlinbulbs
Are you sure that you need a Node for 'Membership'? … to me that rather sounds like a type of edge. You can also have properties on edges. – Faber
@Faber I felt that adding membership as a node could help me later to make interesting relations like, liking the fact that a user is a member of a group, commenting on it, etc. – Kevin

1 Answers

1
votes

The following query gives you for user u1 a map with key = Membership-Nodes and value = list of group names of the key membership node:

m=[:];u1.out('is_member').groupBy(m){it}{it.out('is_member').name}

Output is:

gremlin> m
==>v[m1]=[group1]
==>v[m2]=[group2, group3]

Here the used sample graph:

g = new TinkerGraph()
u1 = g.addVertex('u1')
u2 = g.addVertex('u2')
m1 = g.addVertex('m1')
m2 = g.addVertex('m2')
g1 = g.addVertex('g1')
g2 = g.addVertex('g2')
g3 = g.addVertex('g3')

g.addEdge(u1, m1, 'is_member')
g.addEdge(u1, m2, 'is_member')
g.addEdge(u2, m2, 'is_member')
g.addEdge(m1, g1, 'is_member')
g.addEdge(m2, g2, 'is_member')
g.addEdge(m2, g3, 'is_member')

g1.name = 'group1'
g2.name = 'group2'
g3.name = 'group3'

See also: How do I write a sub-query?

(tested with gremlin2)