[TINKERPOP-2499] PathRetractionStrategy returns inconsistent results when match() is not detected as the final step

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Done
• Affects Version/s: 3.4.9
• Fix Version/s: 3.5.0
• Component/s: process
• Labels: breaking
• Assignee: Stephen Mallette
• Reporter: Stephen Mallette
• Created: 31/Dec/20 18:52
• Updated: 22/Jan/21 16:42
• Resolved: 22/Jan/21 16:42

Description

This issue comes from TINKERPOP-2481 where it was originally noted that perhaps IdentityRemovalStrategy had something to do with the following:

gremlin> g.V().match(__.as("a").out("knows").as("b")).identity()
==>[]
==>[]
gremlin> g.withStrategies(IdentityRemovalStrategy.instance()).V().match(__.as("a").out("knows").as("b")).identity()
==>[a:v[1],b:v[2]]
==>[a:v[1],b:v[4]]
gremlin> g.withoutStrategies(PathRetractionStrategy).V().match(__.as("a").out("knows").as("b")).identity()
==>[a:v[1],b:v[2]]
==>[a:v[1],b:v[4]]
gremlin> g.V().match(__.as("a").out("knows").as("b")).unfold()
gremlin> g.V().match(__.as("a").out("knows").as("b")).unfold().path()
==>[v[1],v[1],v[2],[a:v[1],b:v[2]],a=v[1]]
==>[v[1],v[1],v[2],[a:v[1],b:v[2]],b=v[2]]
==>[v[1],v[1],v[4],[a:v[1],b:v[4]],a=v[1]]
==>[v[1],v[1],v[4],[a:v[1],b:v[4]],b=v[4]]

but it is not a good idea to fix the behavior of one strategy by way of another so PathRetractionStrategy needs to get a bit smarter.