Merge vertex list in gremlin orientDb

Question

I am a newbie in the graph databases world, and I made a query to get leaves of the tree, and I also have a list of Ids. I want to merge both lists of leaves and remove duplicates in a new one to sum property of each. I cannot merge the first 2 sets of vertex

g.V().hasLabel('Group').has('GroupId','G001').repeat(
    outE().inV()
).emit().hasLabel('User').as('UsersList1')

.V().has('UserId', within('001','002')).as('UsersList2')

.select('UsersList1','UsersList2').dedup().values('petitions').sum().unfold()

Regards

Answer 1

There are several things wrong in your query:

• you call V().has('UserId', within('001','002')) for every user that was found by the first part of the traversal
• the traversal could emit more than just the leafs
• select('UsersList1','UsersList2') creates pairs of users
• values('petitions') tries to access the property petitions of each pair, this will always fail

The correct approach would be:

g.V().has('User', 'UserId', within('001','002')).fold().
  union(unfold(),
        V().has('Group','GroupId','G001').
            repeat(out()).until(hasLabel('User'))).
  dedup().
  values('petitions').sum()