[TINKERPOP-2340] MatchStep with VertexStep - Neither the sideEffects, map, nor path has a Y-key

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.4.5
• Component/s: process
• Environment: TinkerPop 3.4.5
• Assignee: Unassigned
• Reporter: Anton
• Created: 17/Feb/20 21:30
• Updated: 19/Feb/20 16:51

Description

Using Tinkerpop Modern graph, find all pairs of people who worked on software with the same name, filtering out pairs that would bind X and Y to the same person, using MATCH traversal:

g.V().match(
            __.as("X").out("created").as("Z"),
            __.as("X").V().as("Y").out("created").as("V"),
            __.as("Z").values("name").as("SOFTWARE"),
            __.as("V").values("name").as("SOFTWARE"),
            __.as("X").values("name").as("DEV_X"),
            __.as("Y").values("name").as("DEV_Y")
        ).where("X", P.neq("Y"))
        .select("DEV_X", "DEV_Y", "SOFTWARE")

The above fails with:

java.lang.IllegalArgumentException: Neither the sideEffects, map, nor path has a Y-key: WherePredicateStep(neq(Y))

	at org.apache.tinkerpop.gremlin.process.traversal.step.Scoping.getScopeValue(Scoping.java:124)
	at org.apache.tinkerpop.gremlin.process.traversal.step.filter.WherePredicateStep.setPredicateValues(WherePredicateStep.java:82)
	at org.apache.tinkerpop.gremlin.process.traversal.step.filter.WherePredicateStep.filter(WherePredicateStep.java:103)
	at org.apache.tinkerpop.gremlin.process.traversal.step.filter.FilterStep.processNextStart(FilterStep.java:38)
	at org.apache.tinkerpop.gremlin.process.traversal.step.filter.WherePredicateStep.processNextStart(WherePredicateStep.java:150)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:50)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.MatchStep$MatchEndStep.processNextStart(MatchStep.java:569)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
	at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:197)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.MatchStep.standardAlgorithm(MatchStep.java:371)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.ComputerAwareStep.processNextStart(ComputerAwareStep.java:46)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:50)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.MapStep.processNextStart(MapStep.java:36)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.SelectStep.processNextStart(SelectStep.java:156)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:128)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:38)
	at org.apache.tinkerpop.gremlin.process.traversal.Traversal.fill(Traversal.java:181)
	at org.apache.tinkerpop.gremlin.process.traversal.Traversal.toList(Traversal.java:119)

Adding an extra dedup() step makes it work:

g.V().match(
            __.as("X").out("created").as("Z"),
            __.as("X").V().as("Y").out("created").as("V"),
            __.as("Z").values("name").as("SOFTWARE"),
            __.as("V").values("name").as("SOFTWARE"),
            __.as("X").values("name").as("DEV_X"),
            __.as("Y").values("name").as("DEV_Y")
        ).dedup().where("X", P.neq("Y"))
        .select("DEV_X", "DEV_Y", "SOFTWARE")

returns:

{DEV_X=marko, DEV_Y=josh, SOFTWARE=lop}
{DEV_X=marko, DEV_Y=peter, SOFTWARE=lop}
{DEV_X=josh, DEV_Y=marko, SOFTWARE=lop}
{DEV_X=josh, DEV_Y=peter, SOFTWARE=lop}
{DEV_X=peter, DEV_Y=marko, SOFTWARE=lop}
{DEV_X=peter, DEV_Y=josh, SOFTWARE=lop}

This seems to be related to TINKERPOP-1762.