tinkerpop3: use gremlin to count number of edges beetween all pairs of nodes

Question

I have a multigraph and I am interested in counting the number of edges connecting each pair of nodes; moreover, I would need to get, for each pair of nodes, the maximum value of a certain attribute.

Unfortunately it seems to me we can use .group().by(...) with one attribute only, while I would need to group by inV and outV. In Cypher I would write something like

MATCH (e0: Employee)-[fb: R]-> (e1: Employee)
WITH e0, e1, count(*) AS frequency, min(fb.value) AS min_val
RETURN e0, e1, frequency, min_val

Can anybody help?

Cheers!

Answer 1

Answered on the Gremlin users mailing list, but to close the circle, here's the traversal again:

gremlin> g.V().as("e0").outE("e").as("e").inV().as("e1").select("e0","e","e1").
gremlin>       group().by(select("e0","e1").by("name")).
gremlin>               by(fold().match(__.as("x").count(local).as("freq"),
gremlin>                               __.as("x").unfold().select("e").by("value").max().as("max")).select("freq","max")
gremlin>               ).next()
==>{e0=c, e1=d}={freq=1, max=9}
==>{e0=b, e1=d}={freq=1, max=9}
==>{e0=f, e1=h}={freq=1, max=9}
==>{e0=e, e1=h}={freq=1, max=9}
==>{e0=a, e1=b}={freq=2, max=10000}
==>{e0=b, e1=c}={freq=4, max=4}
==>{e0=e, e1=f}={freq=1, max=9}
==>{e0=f, e1=g}={freq=1, max=9}
==>{e0=a, e1=c}={freq=1, max=9}