How to get both edge and vertex properties?

[kyeljmd]

After looking at the library I could not seem to find an example on How to get both edge and vertex properties in one query? is this possible with the current implementation?

[mpollmeier]

you could use as/select as demonstrated in https://github.com/mpollmeier/gremlin-scala/blob/master/gremlin-scala/src/test/scala/gremlin/scala/SelectSpec.scala#L77

Note though that select.by doesn't work yet, there's an open PR that almost works: #241

[kyeljmd]

@mpollmeier I tried to follow one of the examples on the SelectSpec. So I came up with something like this.

val itm = g.V.has(KeyValue(TripModel.ID, id)).as("a").outE().as("e").select.head

Whenever I try to print out the value
println(itm)

I always end up with a value like this.

e[{~label=includes, ~out_vertex={~label=trip, tripId=465760a0-073d-46a5-ab1e-debdb86de5b2}, ~in_vertex={~label=business, businessId=cf8c84c6-0fa4-4482-839d-19d9fa8ceb52}, ~local_id=1b214ce0-0141-11e9-b27f-6d2c86545d91}][{~label=trip, tripId=465760a0-073d-46a5-ab1e-debdb86de5b2}-includes->{~label=business, businessId=cf8c84c6-0fa4-4482-839d-19d9fa8ceb52}]

I have also tried something similar to one of the test spec which is this one.

val itm = g.V.has(KeyValue(TripModel.ID, id)).as("a").outE().as("e").select.head._1

The resulting code from above throws this exception

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[ClassCastException: org.apache.tinkerpop.gremlin.structure.util.detached.DetachedEdge cannot be cast to scala.Tuple2]] at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:251) at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:178) at play.core.server.AkkaHttpServer$$anonfun$1.applyOrElse(AkkaHttpServer.scala:363) at play.core.server.AkkaHttpServer$$anonfun$1.applyOrElse(AkkaHttpServer.scala:361) at scala.concurrent.Future.$anonfun$recoverWith$1(Future.scala:413) at scala.concurrent.impl.Promise.$anonfun$transformWith$1(Promise.scala:37) at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60) at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:55) at akka.dispatch.BatchingExecutor$BlockableBatch.$anonfun$run$1(BatchingExecutor.scala:91) at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12) Caused by: java.lang.ClassCastException: org.apache.tinkerpop.gremlin.structure.util.detached.DetachedEdge cannot be cast to scala.Tuple2 at service.TripService.getTrip(TripService.scala:41) at controllers.trip.TripController.$anonfun$getTrip$1(TripController.scala:21) at play.api.mvc.ActionBuilder.$anonfun$apply$11(Action.scala:363) at scala.Function1.$anonfun$andThen$1(Function1.scala:52) at play.api.mvc.ActionBuilderImpl.invokeBlock(Action.scala:482) at play.api.mvc.ActionBuilderImpl.invokeBlock(Action.scala:480) at play.api.mvc.ActionBuilder$$anon$9.invokeBlock(Action.scala:331) at play.api.mvc.ActionBuilder$$anon$9.invokeBlock(Action.scala:326) at play.api.mvc.ActionBuilder$$anon$2.apply(Action.scala:419) at play.api.mvc.Action.$anonfun$apply$2(Action.scala:96)

Is there anything I have been doing wrong?

[mpollmeier]

This works with Tinkergraph (haven't tested with a remote graph):

import gremlin.scala._
import org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerFactory

implicit val graph = TinkerFactory.createModern.asScala
val g = graph.traversal

val vLabel = StepLabel[Vertex]()
val propLabel1 = StepLabel[java.util.Map[String, Object]]()
val propLabel2 = StepLabel[java.util.Map[String, Object]]()
val trav = g.V.as(vLabel).valueMap().as(propLabel1).select(vLabel).outE.valueMap().as(propLabel2)
trav.select((propLabel1, propLabel2)).toList
// List[(java.util.Map[String,Object], java.util.Map[String,Object])] = List(({name=[marko], age=[29]},{weight=0.4}), ({name=[marko], age=[29]},{weight=0.5}), ({name=[marko], age=[29]},{weight=1.0}), ({name=[josh], age=[32]},{weight=1.0}), ({name=[josh], age=[32]},{weight=0.4}), ({name=[peter], age=[35]},{weight=0.2}))

Otherwise I guess it's better to run two queries (one for vertices, one for edges) and combine at the client.

[kyeljmd]

Thanks @mpollmeier We have tried that approach but it's quite hard to the marshalling for it. We ended up performing another query just to retrieve the other properties that we have needed.