[TINKERPOP-1367] Preserve path history for min() and max()

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.2.0-incubating
• Component/s: process
• Assignee: Unassigned
• Reporter: Jason Plurad
• Created: 12/Jul/16 02:04
• Updated: 02/Mar/18 15:24

Description

Via https://groups.google.com/d/msg/gremlin-users/qZwsvRjw7L4/YyT-s1foBAAJ

gremlin> g.V().outE().as('e').values('weight').path()
==>[v[1], e[9][1-created->3], 0.4]
==>[v[1], e[7][1-knows->2], 0.5]
==>[v[1], e[8][1-knows->4], 1.0]
==>[v[4], e[10][4-created->5], 1.0]
==>[v[4], e[11][4-created->3], 0.4]
==>[v[6], e[12][6-created->3], 0.2]

gremlin> g.V().outE().as('e').values('weight').max().path()
==>[1.0]

Currently all reducing barriers are treated the same (min, max, mean, etc.). But they are indeed different when it comes to path computations. Some of them could preserve the path history, others could not.

For max() and min(), we could preserve the path history. In fact, in this respect, max() and min() would NOT be ReducingBarrierSteps, but in fact be some sort of "barrier" FilterStep.