[TINKERPOP-1650] PathRetractionStrategy makes Match steps unsolvable

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.2.3, 3.2.4
• Fix Version/s: 3.2.7, 3.3.1
• Component/s: process
• Assignee: Ted Wilmes
• Reporter: Branden Moore
• Created: 15/Mar/17 19:56
• Updated: 11/Oct/17 19:24
• Resolved: 11/Oct/17 19:24

Description

The `PathRetractionStrategy` can make certain Match() steps "Unsolvable".

This (nonsensical) example demonstrates the issue:

gremlin> g = graph.traversal()
==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]
gremlin> g.V().hasLabel("person").as("perp").match(__.as("a").out("created").as("sw"), __.as("sw").has("lang", "java").as("java")).where("sw", neq("a")).select("perp")
The provided match pattern is unsolvable: [[MatchStartStep(a), VertexStep(OUT,[created],vertex), MatchEndStep(sw)], [MatchStartStep(sw), HasStep([lang.eq(java)]), MatchEndStep(java)], [MatchStartStep(sw), WherePredicateStep(neq(a)), MatchEndStep]]
Type ':help' or ':h' for help.
Display stack trace? [yN]n
gremlin> 

If we remove the `PathRetractionStrategy`, or use `g.withPath()` the match step is solvable, and works fine.

g.withoutStrategies(PathRetractionStrategy).V().hasLabel("person").as("perp").match(__.as("a").out("created").as("sw"), __.as("sw").has("lang", "java").as("java")).where("sw", neq("a")).select("perp")
==>v[1]
==>v[4]
==>v[4]
==>v[6]
gremlin> g.withPath().V().hasLabel("person").as("perp").match(__.as("a").out("created").as("sw"), __.as("sw").has("lang", "java").as("java")).where("sw", neq("a")).select("perp")
==>v[1]
==>v[4]
==>v[4]
==>v[6]
gremlin> 

Issue Links

• links to: GitHub Pull Request #731