how can i write the query on gremlin console to return the pair vertices these have the parallel edge?

Question

I like to transform this cypher query to gremlin.

(n:Person)-[:friend]->(t:Person)-[:friend]->(n:Person)

Thanks

Answer 1

Using the air-routes data set, one way to do this is to use the cyclicPath step as follows.

gremlin> g.V('44').outE().inV().outE().inV().cyclicPath().path()
==>[v[44],e[5019][44-route->8],v[8],e[3975][8-route->44],v[44]]
==>[v[44],e[5020][44-route->13],v[13],e[4158][13-route->44],v[44]]
==>[v[44],e[5021][44-route->20],v[20],e[4387][20-route->44],v[44]]


gremlin> g.V('44').outE().inV().outE().inV().cyclicPath().path().by('code').by()
==>[SAF,e[5019][44-route->8],DFW,e[3975][8-route->44],SAF]
==>[SAF,e[5020][44-route->13],LAX,e[4158][13-route->44],SAF]
==>[SAF,e[5021][44-route->20],PHX,e[4387][20-route->44],SAF]
==>[SAF,e[5022][44-route->31],DEN,e[4736][31-route->44],SAF]
==>[v[44],e[5022][44-route->31],v[31],e[4736][31-route->44],v[44]]
   

Or if you just want the edge IDs

gremlin> g.V('44').outE().inV().outE().inV().cyclicPath().path().by('code').by(id)
==>[SAF,5019,DFW,3975,SAF]
==>[SAF,5020,LAX,4158,SAF]
==>[SAF,5021,PHX,4387,SAF]
==>[SAF,5022,DEN,4736,SAF]  

Another way to write this query involves a where step

gremlin> g.V('44').as('a').outE().inV().outE().inV().where(eq('a')).path().by('code').by()
==>[SAF,e[5019][44-route->8],DFW,e[3975][8-route->44],SAF]
==>[SAF,e[5020][44-route->13],LAX,e[4158][13-route->44],SAF]
==>[SAF,e[5021][44-route->20],PHX,e[4387][20-route->44],SAF]
==>[SAF,e[5022][44-route->31],DEN,e[4736][31-route->44],SAF]