[TINKERPOP-1261] Side-effect group().by() can't handle user-defined maps

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.2.0-incubating
• Fix Version/s: 3.2.4
• Component/s: process
• Assignee: Marko A. Rodriguez
• Reporter: Daniel Kuppitz
• Created: 11/Apr/16 19:58
• Updated: 19/Jan/17 17:24
• Resolved: 19/Jan/17 17:24

Description

Side-effect grouping is usually used to add things to an existing map. That no longer works as the group().by() expects all map values to be traversers. Check this:

Normal grouping:

gremlin> g = TinkerFactory.createModern().traversal()
==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]
gremlin> g.V().hasLabel("person").group().by("name").by(out("created").values("name").fold()).next()
==>peter=[lop]
==>vadas=[]
==>josh=[ripple, lop]
==>marko=[lop]

Side-effect grouping:

gremlin> m = ["marko":[]]
==>marko=[]
gremlin> g.withSideEffect("m", m).V().hasLabel("person").group("m").by("name").by(out("created").values("name").fold()).cap("m")
java.util.ArrayList cannot be cast to org.apache.tinkerpop.gremlin.process.traversal.Traversal$Admin
Display stack trace? [yN] y
java.lang.ClassCastException: java.util.ArrayList cannot be cast to org.apache.tinkerpop.gremlin.process.traversal.Traversal$Admin
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.GroupStep$GroupBiOperator.apply(GroupStep.java:217)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.GroupStep$GroupBiOperator.apply(GroupStep.java:171)
	at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversalSideEffects.add(DefaultTraversalSideEffects.java:92)
	at org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect.GroupSideEffectStep.sideEffect(GroupSideEffectStep.java:97)
	at org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect.SideEffectStep.processNextStart(SideEffectStep.java:39)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.hasNext(ExpandableStepIterator.java:42)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.SupplyingBarrierStep.processAllStarts(SupplyingBarrierStep.java:83)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.SupplyingBarrierStep.processNextStart(SupplyingBarrierStep.java:70)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)
	at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:146)
	at org.apache.tinkerpop.gremlin.console.Console$_closure3.doCall(Console.groovy:206)
...